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Design of a Continuous Blowdown Facility for Hypersonic Research

Permanent Link: http://ufdc.ufl.edu/UFE0045050/00001

Material Information

Title: Design of a Continuous Blowdown Facility for Hypersonic Research
Physical Description: 1 online resource (96 p.)
Language: english
Creator: Djerekarov, Jivko O
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2012

Subjects

Subjects / Keywords: blowdown -- facility -- hypersonic -- scramjet
Mechanical and Aerospace Engineering -- Dissertations, Academic -- UF
Genre: Aerospace Engineering thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Ground based experimental facilities for hypersonic flight simulation have an important role in the understanding of internal and external aerodynamics in the hypersonic flight regime. Given the large energy needed to generate flight conditions, facilities are often of short duration operation, namely several milliseconds. This is not sufficient to reproduce all processes present in hypersonic vehicle operation. Continuous flow ground test facilities include arc-heated facilities, vitiated heaters, and non-vitiated heater facilities. Among these, non-vitiated heaters have the unique advantage of raising the enthalpy of the working gas without the introduction of contaminants as seen in the other methods of heating. The focus of this work is to describe the design and construction of a non-vitiated heater ground test facility for external and internal hypersonic research.   The non-vitiated heater was designed for a maximum temperature of 1300 K, or Mach 5 enthalpy simulation. The facility uses electrically heated coils to heat the working gas (air) passing through the core. The facility has been heavily insulated with alumina to minimize heat losses to the surroundings and provide additional structural support. Power for the non-vitiated heater is supplied via a1.2 MW external power transformer.   A second stage vitiation heater is added to raise the simulation to Mach 6 flight enthalpy. It allows for back to back experiments under vitiated and non-vitiated conditions as well as capability for higher enthalpy simulations. The vitiation heater stage uses hydrogen-air combustion to heat the working gas. Oxygen replenishment is used to keep the correct mole fraction in the test gas. With the vitiated heater, the facility is capable of producing temperatures up to 1800 K corresponding to Mach 6 enthalpy. Continuous air flow to the facility is supplied by two air compressors capable of producing a total mass flow rate of 1.5 kg/s.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Jivko O Djerekarov.
Thesis: Thesis (M.S.)--University of Florida, 2012.
Local: Adviser: Segal, Corin.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2012
System ID: UFE0045050:00001

Permanent Link: http://ufdc.ufl.edu/UFE0045050/00001

Material Information

Title: Design of a Continuous Blowdown Facility for Hypersonic Research
Physical Description: 1 online resource (96 p.)
Language: english
Creator: Djerekarov, Jivko O
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2012

Subjects

Subjects / Keywords: blowdown -- facility -- hypersonic -- scramjet
Mechanical and Aerospace Engineering -- Dissertations, Academic -- UF
Genre: Aerospace Engineering thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Ground based experimental facilities for hypersonic flight simulation have an important role in the understanding of internal and external aerodynamics in the hypersonic flight regime. Given the large energy needed to generate flight conditions, facilities are often of short duration operation, namely several milliseconds. This is not sufficient to reproduce all processes present in hypersonic vehicle operation. Continuous flow ground test facilities include arc-heated facilities, vitiated heaters, and non-vitiated heater facilities. Among these, non-vitiated heaters have the unique advantage of raising the enthalpy of the working gas without the introduction of contaminants as seen in the other methods of heating. The focus of this work is to describe the design and construction of a non-vitiated heater ground test facility for external and internal hypersonic research.   The non-vitiated heater was designed for a maximum temperature of 1300 K, or Mach 5 enthalpy simulation. The facility uses electrically heated coils to heat the working gas (air) passing through the core. The facility has been heavily insulated with alumina to minimize heat losses to the surroundings and provide additional structural support. Power for the non-vitiated heater is supplied via a1.2 MW external power transformer.   A second stage vitiation heater is added to raise the simulation to Mach 6 flight enthalpy. It allows for back to back experiments under vitiated and non-vitiated conditions as well as capability for higher enthalpy simulations. The vitiation heater stage uses hydrogen-air combustion to heat the working gas. Oxygen replenishment is used to keep the correct mole fraction in the test gas. With the vitiated heater, the facility is capable of producing temperatures up to 1800 K corresponding to Mach 6 enthalpy. Continuous air flow to the facility is supplied by two air compressors capable of producing a total mass flow rate of 1.5 kg/s.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Jivko O Djerekarov.
Thesis: Thesis (M.S.)--University of Florida, 2012.
Local: Adviser: Segal, Corin.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2012
System ID: UFE0045050:00001


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1 DESIGN OF A CONTINUOUS BLOWDOWN FACILITY FOR HYPERSONIC RESEARCH By JIVKO DJEREKAROV A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MAST ER OF SCIENCE UNIVERSITY OF FLORIDA 2012

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2 2012 Jivko Djerekarov

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3 To Kalina and my Family

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4 ACKNOWLEDGMENTS I thank Dr. Corin Segal for his guidance and for presenting me with this education and research opportunity. I thank my family for t heir love and support and I thank all my colleagues in the combustion and propulsion lab who assisted me in my studies and research challenges.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF TABLES ................................ ................................ ................................ ............ 7 LIST OF FIGURES ................................ ................................ ................................ .......... 8 ABSTRACT ................................ ................................ ................................ ................... 11 CHAPTER 1 GROUND BASED HYPERSONIC TEST FACILITIES ................................ ............ 13 Introduction ................................ ................................ ................................ ............. 13 Long Duration Test Facilities ................................ ................................ .................. 15 Arc Heated Facilities ................................ ................................ ........................ 15 Combustion Heaters ................................ ................................ ......................... 19 Non vitiated Heaters ................................ ................................ ......................... 19 Short Duration Facilities ................................ ................................ .......................... 22 Gas Driven Shock Tunnels ................................ ................................ ............... 22 Detonation Dri ven Shock Tunnels ................................ ................................ .... 23 Piston driven shock tunnels ................................ ................................ .............. 24 Summary ................................ ................................ ................................ ................ 25 2 NON VITIATED HEATER ................................ ................................ ....................... 27 Facility Design ................................ ................................ ................................ ........ 27 Electric Heater Construction ................................ ................................ ................... 30 Facility Wiring and Silicon Control Rectifier (SCR) ................................ ........... 32 SCR basic operation principle ................................ ................................ .......... 33 Insulation ................................ ................................ ................................ ................ 34 Enclosure ................................ ................................ ................................ ................ 38 Facility Heat Transfer Analysis ................................ ................................ ............... 41 3 SECOND STAGE VITIATION HEATER ................................ ................................ 45 Design Parameters ................................ ................................ ................................ 45 Second Stage Heater Instrumentation ................................ ................................ .... 46 Bell mouth Design ................................ ................................ ................................ .. 54 4 DATA MEASUREMENT AND FACILITY CONTROLLER ................................ ....... 58 Data Collection Set Up ................................ ................................ ........................... 58 LabVIEW Controller ................................ ................................ ................................ 62 Control Logic ................................ ................................ ................................ .... 62

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6 Electric Heater Safety Features ................................ ................................ ........ 68 5 ELECTRIC HEATER PERFORMANCE EVALUATION ................................ .......... 70 Introduction ................................ ................................ ................................ ............. 70 Experimental Set Up ................................ ................................ ............................... 70 Non Vitiated Heater Performance ................................ ................................ .... 70 Examples of Possible Studies ................................ ................................ .......... 77 APPENDIX A HEATER DRAWINGS ................................ ................................ ............................. 80 B CONTROL PROGRAM ................................ ................................ ........................... 82 C BELLMOUTH ................................ ................................ ................................ .......... 91 L IST OF REFERENCES ................................ ................................ ............................... 94 BIOGRAPHICAL SKETCH ................................ ................................ ............................ 96

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7 LIST OF TABLES Table page 2 1 Stainless steel 310 material p roperties ................................ ............................... 31 2 2 Heater insulation material p roperties ................................ ................................ .. 35 2 3 He ater alumina insulation p arts ................................ ................................ .......... 36 2 4 Enclosure components and s pecifications ................................ .......................... 40 3 1 Second stage heater component s pecifications ................................ ................. 47 3 2 Electronic control panel l egend ................................ ................................ ........... 49 3 3 Relay ECP connection l egend ................................ ................................ ........... 54 3 4 Material properties for T hermeez 7020 ceramic p utty ................................ ........ 57 4 1 List of t ransducers ................................ ................................ .............................. 60 4 2 Thermocouple c onnection Legend ................................ ................................ ..... 61 5 1 Examples of possible internal flow test conditions ................................ .............. 78 5 2 Examples of possible externall flow test conditions ................................ ............ 79

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8 LIST OF F IGURES Figure page 1 1 Supersonic wind tunnel ground test facilities flight envelopes. ........................... 14 1 2 Arc facility configurati ons ................................ ................................ .................... 18 1 3 NASA Glenn Hypersonic Test Facility ................................ ................................ 21 1 4 T5 free piston tunnel at GALCIT ................................ ................................ ......... 25 2 1 Heater facilit y diagram ................................ ................................ ........................ 29 2 2 Non Vitiated Heater with second stage heater assembly. ................................ .. 31 2 3 Wiring schematic of electric heater ................................ ................................ ..... 33 2 4 Phase angle control diagram ................................ ................................ .............. 34 2 5 Coil Insulation Construction ................................ ................................ ................ 37 2 6 Analytical results of insulation sizing ................................ ................................ .. 38 2 7 Heater Enclosure ................................ ................................ ................................ 39 2 8 Stagnation pr essure vs. theoretical exit stagnation temperature ........................ 42 2 9 Rayleigh flow prediction for exit coil Mach. ................................ ......................... 43 2 10 Mass flow rate de pendence on pressure and heat addition. .............................. 44 3 1 Combustion chamber asse mbly ................................ ................................ ......... 46 3 2 Hydrogen and Oxygen Combustion Chamber supply lines. ............................... 47 3 3 Electronic Control Panel (ECP) ................................ ................................ .......... 50 3 4 Wiring connection diagram of main second stage control components .............. 51 3 5 Electronic Control Panel Wiring Diagram. ................................ .......................... 52 3 6 Relay Distribution Box Numbering Legend ................................ ......................... 53 3 7 Bell Mouth mold design. ................................ ................................ ..................... 55 3 8 Bottom and Top Isometric Views of the bell mouth casing. ................................ 55 3 9 Bell mouth bolting assembly for cast forming. ................................ .................... 56

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9 3 10 Combustion chamber and bell mouth assembly. ................................ ................ 57 4 1 Thermocouple and pressure tr ansducer physical location diagram .................... 59 4 2 Dat a acquisition component diagram ................................ ................................ 60 4 3 Plot of control input voltage to the SCR ................................ .............................. 63 4 4 Logic Chart of voltage control operation. ................................ ............................ 64 4 5 Front panel view of the heater control program. ................................ ................. 67 4 6 Circuit diagram of pressure switch wiring ................................ ........................... 69 5 1 Facility peak performance data ................................ ................................ ........... 72 5 2 Current response data ................................ ................................ ........................ 73 5 3 Predicted and measured SCR output voltage values ................................ ......... 74 5 4 Maximum temperature test at high current values ................................ .............. 75 5 5 Non vi tiated heater calibration curve ................................ ................................ .. 76 A 1 Non Vitiated Heater ................................ ................................ ............................ 80 A 2 Non Vitiated Heater Resistance Heating Coils ................................ ................... 81 B 1 Frame 1 of program frame sequence. ................................ ................................ 82 B 2 Sequence Fr ame 2. ................................ ................................ ............................ 83 B 3 Current Measurement Sub VI. ................................ ................................ ............ 84 B 4 Third program sequence frame. ................................ ................................ ......... 85 B 5 Fourth program sequence frame ................................ ................................ ........ 86 B 6 Sixth sequence frame. ................................ ................................ ........................ 87 B 7 Manual control mode program components. ................................ ...................... 88 B 8 Automatic control mode program components. ................................ .................. 89 B 9 Final sequence frame, data recording structure. ................................ ................ 90 C 1 Bellmouth ................................ ................................ ................................ ........... 91 C 2 Bellmouth mold ................................ ................................ ................................ ... 92

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10 C 3 Bellmouth molding base ................................ ................................ ..................... 93

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11 Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master Of Science DESIGN OF A CONTINUOUS BLOWDOWN FACILITY FOR HYPERSONIC RES EARCH By Jivko Djerekarov December 2012 Chair: Corin Segal Major: Aerospace Engineering Ground based experimental facilities for hypersonic flight simulation have an important role in the understanding of internal and external aerodynamics in the hypers onic flight regime. Given the large energy needed to generate flight conditions, facilities are often of short duration operation, namely several milliseconds. This is not sufficient to reproduce all processes present in hypersonic vehicle operation. Conti nuous flow ground test facilities include arc heated facilities, vitiated heaters, and non vitiated heater facilities. Among these, non vitiated heaters have the unique advantage of raising the enthalpy of the working gas without the introduction of contam inants as seen in the other methods of heating. The focus of this work is to describe the design and construction of a non vitiated heater ground test facility for external and internal hypersonic research. The non vitiated heater was designed for a maxi mum temperature of 1300 K, or Mach 5 enthalpy simulation. The facility uses electrically heated coils to heat the working gas (air) passing through the core. The facility has been heavily insulated with alumina to minimize heat losses to the surroundings a nd provide additional structural

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12 support. Power for the non vitiated heater is supplied via a1.2 MW external power transformer. A second stage vitiation heater is added to raise the simulation to Mach 6 flight enthalpy. It allows for back to back experime nts under vitiated and non vitiated conditions as well as capability for higher enthalpy simulations. The vitiation heater stage uses hydrogen air combustion to heat the working gas. Oxygen replenishment is used to keep the correct mole fraction in the tes t gas. With the vitiated heater, the facility is capable of producing temperatures up to 1800 K corresponding to Mach 6 enthalpy. Continuous air flow to the facility is supplied by two air compressors capable of producing a total mass flow rate of 1.5 kg/s

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13 CHAPTER 1 GROUND BASED HYPERSO NIC TEST FACILITIES Introduction The present work is focused on the construction and design of a non vitiated, electrically heated, hypersonic ground test facility at the University of Florida Combustion and Propulsion L aboratory. The facility is a continuous blow down wind tunnel capable of Mach 2 to 6.5 enthalpy simulation. Few ground based facilities are capable of non vitiated hypersonic combustion simulation, mainly due to the high power and cost requirement for such installation. Hypersonic research is important for future military and civilian applications. Military hypersonic applications include ballistic missiles, affordable and reliable space access vehicles, and other synergetic combinations with broad range of fuel options [ 2 ] Civilian applications include atmospheric reentry vehicles, and affordable space access. It is not possible to duplicate all aerodynamic and thermal effects encountered in the hypersonic flight regime within one test facility. Instead a variety of ground based facilities exist, each capturing a particular area of hypersonic flow. Figure 1 1 [ 1 ] shows the respective test trajectories of a variety of ground based test facilities. Also indicated is the performance of the hypersonic tunnel facility discussed in this document. The dynamic pressure boundaries for hypersonic flight between 0.25 and 1 atm are shown in the figure as well as suggested hypersonic flight corridors. The present chapter gives a brief overview of the different techniq ues used for ground based hypersonic simulation.

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14 Figure 1 1. Supersonic wind tunnel ground test facilities flight envelopes. Shows the flight Mach number limits of general types of facilities. The region between the dynamic pressures q=0.25atm and q=1at m bounds the range of optimized scramjet operation. Also shown are the experimental scramjet flight tests of the X 43 and Kholod. (Reprinted by permission from Segal, Corin. The Scramjet Engine Process and Characteristics, Cambridge University Press, New Y ork, 2009 )

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15 Long Duration Test Facilities Hypersonic ground based test facilities may be separated into two broad categories: short and long duration facilities. Short duration facilities mainly consist of shock tubes and shock tunnels. Long duration f acilities are generally continuous and blow down wind tunnels with test times on the order of seconds to minutes, allowing for Reynolds, Prandtl, and Mach number simulations. Long duration facilities designed for simulation of supersonic combustion are cha racterized by the method by which the test gas is pre h eated. This can be either done with electric arc, combustion, or electrical resistance non vitiated heating Arc Heated Facilities Arc heated facilities first came into use in the late 1950 s to meet d emands for research into atmospheric reentry and hypersonic missiles. Arc heated facilities are unique in their ability to reproduce thermal environments simulating flight from Mach 8 to 20 for long exposure periods required for thermo structural validatio n survivability of materials. [ 3 ] Arc heaters utilize conductive, convective, and radiative heat transfer from a high voltage DC electric arc discharge to a gas column momentarily constrained within a cooled plenum section. The heated gas ranges from 3,000 to 10,000 K and can be discharged continuously on the order of several minutes. This gives arc heaters the ability to simulate flight regimes ranging from Mach 8 to Mach 20 enthalpy. Arc heaters are categorized by the method of stabilizing the arc. The thr ee most common methods are vortex stabilized arcs, magnetically stabilized arcs, and segmented arcs Figure 1 2 shows a general schematic of each type.

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16 Vortex stabilized arc s are the simplest type of arc heaters. The heater utilize s a swirl chamber where t he working gas is injected. A strong gas swirl is generated inside the arc c hamber, providing arc stability [ 3 ] The swirl of the arc column may be augmented by the use of magnetic spin coils at the anode and cathode to ensure radial distribution of the hig h heat flux zone at the arc electrode contact site [ 3 ] Magnetically stabilized arc heaters utilize a center axis anode discharging to the outer wall of the heater, which serves as the cathode. Arc column stability is provided by external magnetic coils wra pped around the heater plenum, which rotate the arc termination on the column. For this configuration, the working gas may be injected upstream of the main axis arc as it is not used for arc stabilization [ 3 ] Segmented or constricted arc heaters are the mo st advanced type and most widely used in modern hypersonic facilities. The operating principle of the segmented arc heater is based on a combination of the vortex and magnetically stabilized arcs. A modular, segmented plenum chamber, or constrictor, with an electrode at each end is used to sustain high voltage electric discharge. The working fluid is injected at the segmented interfaces, which provides several unique advantages: i. Film cooling at the wall contributes to segment survivability ii. Enhanced local electrical resistivity of the gas column results at the plenum wall, minimizing chance of arc breakdown at mid plenum segments. iii. Injected air serves as vortex stabilizer of the gas column. Additionally, the segmented or constricted arc heater design gives t he a bility to regulate the length of the arc discharge. This is possible thanks to the individual plenum segments serving as ballast resistors of specified impedance to be applied at individual

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17 wall segments, thus maintaining optimum voltage distribution a long the plenum length [ 3 ] The SCIROCCO 70 MW Plasma Wind Tunnel in Italy is the largest constricted arc heater in the world [ 4 ] The wind tunnel was constructed for development and testing of well characterized thermal protection systems [ 4 ] The facility has a 2 meter diameter exit nozzle. The tunnel is capable of providing stagnation temperature operational range between 2,000 and 10,000 K while maintaining an average total pressure between 1 and 17 bar. This allows the simulation of conditions up to Mach 12. Disadvantages of arc heaters are the cost and complexity associated especially with the segmented type heaters. Additionally, electrode erosion causes contamination of the flow, which affects the accuracy of the simulations.

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18 Figure 1 2 Arc facil ity configurations. A is a vortex stabilized arc B is the magnetic stabilized arc and C is the segmented arc configuration. ( Adapted from Smith, D.M., 314 )

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19 Combustion Heaters Combustion heaters inject fuel such as Hydrogen or a hydrocarbon into the air stream and ignite the mixture to raise the temperature of the working gas. Hydrocarbons are capable of achieving total enthalpy of around Mach 7, while the use of Hydrogen allows for even higher en thalpies [ 1 ] Combustion heaters are well suited for a laboratory setting as they are compact and can produce relatively high total temperatures. The use of combustion as a heating mechanism presents some undesired effects and challenges for simulation. The burning of fuel within the working gas to increase the fluid temperature introduces combustion products into the mixture. Further, the Oxygen quantity in the working gas is altered due to the process of burning, which requires an Oxygen replenishing syste m to keep the correct mole fraction of 21 % for air. The combustion products introduced to the gas include water vapor, an undesired effect for simulation of high altitude environments where the air is very dry. Additionally, the contaminated test gas passe s through a converging diverging nozzle prior to the test section. The drop in static temperature through the nozzle may cause condensation, which can rust the nozzle surface and further contaminate the flow. Non vitiated Heaters Non vitiated heaters are u nique in that the total enthalpy is increased without contamination of the working gas. This type of heating may be achieved by passing the working gas over an electrically heated core or by using a graphite storage heater as is done in the NASA Glenn Hype rsonic Tunnel Facility (HTF) [ 5 ] Storage heaters are pre heated before transferring heat to the working fluid. The graphite storage heater on the NASA HTF is used to pre heat pure nitrogen to a temperature above the desired test temperature before mixing w ith ambient

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20 temperature oxygen to achieve the desired molar composition of air. The graphite core is heated through induction from electric current produced by a 3 MW power supply [ 5 ] The graphite core is shown in Figure1 3. The storage heater is 12.2 mete rs tall and 3 meters in diameter. The core is heated slowly at the rate of 28 K per hour to minimize thermal stresses to the graphite. The maximum temperature is on the order of 2800 K and is achieved over 100 hours of pre heating [ 5 ] .Once the nitrogen is a t the desired temperature, the working gas is sent through a domed test chamber with a diameter of 7.6 meters with a thrust stand capable of handling a test article up to 7260 kg [ 5 ]

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21 Figure 1 3. NASA Glenn Hypersonic Test Facility (A) and Graphite storag e heater (B) ( Adopted from Wokie M.R. and Willis B.P. 478 )

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22 Short Duration Facilities Short duration facilities are shock tunnels that have test run times on the order of milliseconds. Shock tunnels produce a shock wave moving through a high pressure reservoir to create very high temperatures and pressures in the nozzle plenum [ 7 ] Use of this method allows for simulation of Mach 20 flight velocities. Reynolds and Prandtl numbers cannot be simulated due to the time scale limitation. Shock tunnels are characterized by the driver method. Driver methods include gas driven, detonation driven, and piston driven shock tubes Gas Driven Shock Tunnels Gas driven shock tunnels typically use a light driver gas such as helium or hydrogen, which is pressurized and heated to specified conditions prior to diaphragm rupture. Specified temperature of the driver gas may be achieved through an electric heater or through deflagrat ion combustion heating. In the electric heating method, the driver gas is heated internally or externally to temperatures up to 500 K prior to diaphragm rupture [ 6 ] Deflagration combustion heating of the driver gas is typically achieved by use of a stoich iometric mixture of hydrogen and oxygen in helium driver gas. There are significant problems with stability of the combustion due to the difficulty in maintaining deflagrative burning at high pressures, especially for post combustion pressure above 40 MPa, thus limiting the maximum driver pressure [ 6 ] Further, due to the possibility of detonation in the pressure vessel, it must be able to withstand pressures that are 5 times higher than that of deflagration [ 6 ]

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23 Detonation Driven Shock Tunnels Detonation dr iven shock tunnels use the detonative mode of combustion to heat the driver gas similarly to deflagration combustion heating method. Two approaches have been developed for using detonation waves in shock tunnels: upstream running detonation (URD) and downs tream running detonation (DRD). The main difference between the two methods is the direction of the detonation induced velocity relative to the primary shock propagation [ 6 ] The URD driver method initiates the detonation at the primary diaphragm. The res ulting Chapman Jouguet (C J) wave is allowed to travel upstream, while the tail of the detonation, which consists of a uniform region of high pressure, is used to drive the incident shock downstream through the tunnel [ 6 ] The advantage of using such a driv er is that constant driver conditions are maintained until the arrival of the reflected C J wave. The challenges of using URD are that the upstream running C J wave creates significant overpressures at the breech end of the tunnel. Additionally, some of th e energy in the detonation wave is wasted due to it being set in motion in the upstream direction (thus, creating a longer path for the wave to travel). The DRD driver method initiates the detonation at the breech of the high pressure chamber, creating a downstream motion of the detonation wave. The diaphragm separating the high and low pressure gases is ruptured by the detonation wave and the combustion products drive the incident shock. In this method the kinetic energy of the detonation induced gas vel ocity is used to drive the incident shock, giving a higher pressure and thermal performance. The disadvantage of using this technique is that the forward running wave is susceptible to flow unsteadiness caused by the decaying flow field behind the detonati on [ 6 ] The DRD driver method was selected for

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24 requiring only the addition of a modest combustible gas handling system 6 Piston driven shock tunnels Piston driven shock tunnel s use a heavy free flying piston to rapidly compress a light driver gas. At the designated pressure the diaphragm separating the high and low pressure chambers of the tube ruptures, producing a shock wave. The free piston offers the greatest performance an d operational flexibility of the driver methods discussed in this chapter [ 6 ] This is due to the high pressure differential that can be achieved by such a method. Problems with using this driver method include the relatively small volume of the compressed gas resulting in rapid decay of the shock tube performance. An example of a piston driven shock tube is the T5 facility in the Graduate Aeronautical Laboratories at the California Institute of Technology (GALCIT) shown in Figure 1 4. The facility is capab le of flows of air or nitrogen up to specific enthalpy of 25 MJ/kg, pressures of 100 MPa, and reservoir temperatures of 10,000 K. The driver gas is compressed adiabatically to pressures on the order of 1300 atm by use of a free piston. The shock tube is 12 m long and 9 cm in diameter, filled with a helium argon gas mixture [ 8 ] The test gas is separated from the test section by a thin diaphragm. The test section and the dump tank are evacuated before a test. The piston is accelerated by the use of high press ure gas stored in the high pressure reservoir up to speeds in excess of 300 m/s. The piston motion compresses the driver gas until the primary diaphragm bursts, creating a shock wave propagating downstream into the shock tube at speeds ranging from 2 to 5 km/s. The incident shock is reflected off the end wall, bursting the secondary diaphragm, and the stationary gas

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25 behind it reaches high temperature and pressure. Test times are on the order of 1 to 2 ms [ 8 ] Figure 1 4. T5 free piston tunnel at GALCIT (Re printed with permission from Segal, Corin. The Scramjet Engine Process and Characteristics, Cambridge University Press, New York, 2009 ) Summary Research in the area of hypersonics is important for military and civilian applications. Ground based test faci lities are important for the development of new technology in this area. Test installations are categorized into short and long duration facilities depending on the test run timescales. Long duration facilities are capable of simulating Mach, Reynolds, an d Prandtl number flow parameters, but are limited by flow rate. They are characterized by the method of pre heating the working gas and are split into arc heated, combustion heated, and electrically heated non vitiated tunnels. Short duration facilities ar e capable of simulating very high Mach numbers, but are limited in terms of test run duration. Short duration facilities are shock tunnels consisting of a high pressure driver gas and a low pressure test gas. Mach number simulation is achieved

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26 by shock wav e compression. Facilities are characterized by the driver method: gas driven, detonation/deflagration, and piston driven shock tunnels. The following chapters will focus on the design of the non vitiated, electrically heated, hypersonic tunnel facility a t University of Florida. The work is focused on the facility design, data acquisition system, and preliminary test run data.

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27 CHAPTER 2 NON VITIATED HEATER Facility Design One way to raise the working fluid enthalpy without altering its chemical compositio n is by electric resistance heating implemented in a non vitiated heater. This chapter focuses on the design and characteristics of the non vitiated heater facility currently in use at the University of Florida. Described are the structural composition, th ermal insulation, and thermal analysis of the heater. Described are the structural composition, thermal insulation, and thermal analysis of the heater. The non vitiated heater facility raises the stagnation enthalpy of the working fluid (air) by means of resistive coils through whose core passes the fluid to be heated. Regulated current of up to 1200 Ampere at variable voltage (max 480 VAC) is conducted through the coils, raising their temperature due to Ohmic dissipation. The fluid in the coils' core ab sorbs the heat by means of forced convective heat transfer. The facility is powered through an external transformer with a current limit of 1200 Amperes. Power control is achieved through a Silicon Controlled Rectifier (SCR) unit. The electric heater can a chieve a maximum stagnation temperature of 1100 K at a flow rate of 180 g/s. Figure 2 1 shows a schematic of the facility. Two compressors with maximum flow rate output of 1.25 kg/s supply air to a compressed air storage tank with maximum holding pressure of 1550 kPa (225 psi). From the storage tank, compressed air is channeled to the non vitiated heater, where the stagnation temperature of the air is raised through conduction and convection. The heated air is then passed through the second stage vitiation heater prior to being channeled to the test section via a

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28 converging diverging nozzle. The vitiation heater is used for test conditions where the electric heater alone cannot provide the necessary enthalpy raise of the fluid or for tests requiring water i njection. Hydrogen Air combustion is used to raise the temperature of the gas to 1800 K. Oxygen enrichment is added to the working gas prior to entry of the first stage heater via oxygen supply tanks to keep the correct mole fraction ratio after combustion in the second stage heater. Detailed description of the vitiated heater and its components is given in Chapter 3.

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29 Figure 2 1. Heater facility diagram with the second stage vitiation heater. Second stage heater uses hydrogen as fuel and oxygen replen ishment.

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30 Electric Heater Construction The non vitiated heater is made from stainless steel 310 alloy. The material was chosen based on its service temperature, price, and availability [ 1 ] Properties for the material are given in Table 2 1. The facility c onsists of cold and hot collector reservoirs connected by six, 2.54 cm (1.0 in.) outer diameter and 3.18 mm (0.125 in.) thick, stainless steel coils. The coils are 1300 cm (511.8 in.) in length molded into shape and welded at the hot and cold collector fla nges. Pressurized air stagnates in the cold collector before being channeled through the electrically heated coils to the hot collector reservoir. From the hot collector the air is channeled to the second stage heater and supersonic nozzle. Figure 2 2 show s a CAD model of the heater. Listed are the heater component specifications: C old collector : 244 cm ( 96 in .) long with 11.43 cm ( 4.5 in .) diameter and 3.18 mm (1/8 in .) thickness. Hot collector: 17.15 cm (6.75 in.) diameter with 3.18 mm (1/8 in.) thicknes s and length of 215.9 cm ( 85 in .) Coils: length of 1300 cm (511.8 in.), inner diameter 1.91 cm (0.75 in.), outer diameter 2.54 cm (1.0 in.), twist angle 8. Flanges are 1.91 cm (0.75 in.) thick with outer radius of 29.26 cm (11.25 in.). The Flanges are a ssembled together using 1.27 cm (1/2 in.) stainless steel 310 bolts. A ceramic sleeve is used to insulate the bolts in order to prevent electrical shorting between the coils and the hot and cold collectors. Zircar alumina gaskets are used to seal the top a nd bottom flanges of the heater. The gasket material is chosen for its high service temperature. P roperties are given in Table 2 3

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31 Table 2 1. Stainless Steel 310 Material Properties Material Stainless Steel 310 Thermal Conductivity (W/m K) @ 373 K 14.2 m) 780 Melting Point (K) 1728 85% MP (K) 1469 Max Service Temp (K) 1423 Coefficient of Thermal expansion (m/m/C) @ 0 873 K 19.1 Tensile Strength, Ultimate (MPa) 620 Tensile Strength, Yield (MPa) 310 Elastic Modu lus (GPa) 200 Source: www.Matweb.com Figure 2 2. Non Vitiated Heater with second stage heater assembly. Second Stage Vitiated Heater Cold Collector Hot Collector Current Conducting Coils

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32 Facility Wiring and Silicon Control Rectifier (SCR) The heater is powered by a 1200 Ampere 480 VAC ext ernal transformer. Power from the transformer is regulated through a Clark Power Systems SCR unit. The electric heater is connected to the SCR through an electrical Delta connection as shown in Figure 2 3. Power is divided into three legs with two coils pe r leg. The SCR controller is current limited. Voltage to the facility depends on the coil resistance. Coil resistance is resistivity given in Table 2 the material resistivity, L is the length and A is the cross sectional area of the material. Given the coil resistance, the voltage through the facility is calculated based on the equations for Delta wiring connection as follows: The phase current and voltage are measured at the input side of the delta, while the line current and voltage are what is seen by the heater at each leg (two coils). At the maximum line current of 1200 A, the power of the facility is 144 kW (48 kW per leg) and the voltage i s 70 v olts. It should be noted that the resistance through one leg is obtained

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33 Figure 2 3. Wiring schematic of electric heater SCR basic operation principle ction is to regulate the amount of current sent to the electric heater. The main power transformer supplies 3 phase, 480 VAC at 60 Hz. Each SCR leg (3 total for 3 phase) carries a 60 Hz signal. Each leg has two SCR switches. An SCR switch allows current fl ow in one direction only, hence two switches are needed to accommodate for the direction change in alternating current. Once a switch is closed, it stays closed until the current direction changes. Power modulation is achieved via phase angle control, that is, SCR switches are closed at a precise time to allow only the desired portion of power to travel to the load as seen in Figure 2 4. The phase controller takes a 2 5 VDC input signal from an NI USB 6255 data acquisition card (Chapter 4).

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34 Figure 2 4. Ph ase angle control diagram. Source: www.mcgoff bethune.com Insulation To minimize heat loss, the facility is thermally insulated. The heater coils are insulated using solid Zircar alumina silica type AXL The ho t collector and flanges are insulated with Zircar Type ASB 2300 blanket insulation Table 2 2 shows the ceramic insulation parts used for the heater. The insulation arrangement can be seen in Figure 2 5. The insulation pieces are glued together with Zircar Alumina Silica cement Type AS CEM (Table 2 3). The material was chosen based on a heater prototype design The prototype heater consisted of a single stainless steel 310 pipe of 9.525 mm (0.375 in.) outer diameter and 6.985 mm (0.275 in.) inner diameter. The prototype was scaled to produce a mass flow rate ratio of 1:25 with the actual heater with the pipe dimensions chosen to maintain equivalent Reynolds numbers. The computational heat transfer

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35 results shown in Figure 2 6 were obtained using thermal resis tance calculation approach for a radial, multilayer medium. A detailed description and analysis of the prototype and insulation are given in reference [ 1 ] Based on these results, an air gap of 6.35 mm (0.25 in.) between the coils and the alumina insulatio n is allowed for increased optimal thermal insulation. Figure 2 6 [ 1 ] shows the external insulation temperature at varying air gaps from the prototype heater design The insulation assembly and design for the non vitiated heater are described below: Large a lumina semi cylinders are glued together with Zircar Alumina Silica cement Type AS CEM around the coils as shown in Figure 2 5. A second cylinder is constructed on top of the first one. The base of the top cylinder is glued to the bottom cylinder. An alumi na coil spacer is installed on top of the large cylinders. The spacer serves to structurally support the coils and prevent them from touching due to deformation. Contact between coils during operation is prohibitive as it will short the electrical circuit. After the first spacer, the male and female alumina cylinders are installed. This construction allows for the insulation to slide (stretch) during coil expansion at high temperatures (see Heat Transfer Analysis for details on coil elongation). The small a lumina cylinders are installed after the top spacer (see Figure 2 5). The curved portions of the coils are insulated using the arched alumina pieces. The arched pieces are similarly glued together around the coils. Table 2 2 Heater Insulation Material Pro perties Material Attribute Attribute Value Zircar Solid Alumina Insulation Type AXL Composition Bulk density Thermal conductivity Maximum Service Temperature Flexural Strength Compressive Strength Al 2 O 3 (38 %), SiO 2 (62 %) 0.28 gm/cc 0.22 W/m K @1373 K 15 33 K 0.17 MPa 0.05 MPa Alumina Silica Blanket ASB 2300 Composition Maximum Service Temperature Al 2 O 3 (47 %), SiO 2 (49 %), Oxides (2 %) 1533 K

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36 Table 2 3 Heater Alumina Insulation Parts Part Part Description Large Alumina Semi Cylind er Inner Diameter: 10.16 cm (4 in.) Outer Diameter: 15.24 cm (6 in.) Total Length: 60.96 cm (24 in.) Female Alumina Semi Cylinder Inner Diameter: 10.16 cm (4 in.) Outer Diameter: 15.24 cm (6in.) Total Length: 60.96 cm (24 in.) Cu taway: Inner Diameter: 12.70 cm (5 in.) Outer Diameter: 15.24 cm (6 in.) Length: 15.24 cm (6 in.) Alumina Coil Spacer Diameter: 15.24 cm (6 in.) Thickness: 6.03 cm (2.375 in.) Cut Depth: 4.45 cm (1.75 in.) Cut Radius: 1.27 cm (0.50 in .) Small Alumina Semi Cylinder Inner Diameter: 3.56 cm (1.40 in.) Outer Diameter: 8.64 cm (3.40 in.) Length: 30.48 cm (12 in.) Arched Alumina Insulation Piece Curvature radius: 35.56 cm (14 in.) Thickness: 3.81 cm (1.5 in .) Depth: 8.89 cm (3.5 in.) Cutaway curvature thickness depth

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37 Figure 2 5. Coil Insulation Construction Alumina Large Semi Cylinders Alumina Coil Spacer Female Alumina Semi Cylinders Male Alumina Semi Cylinders Small Alumina Semi Cylinders Arched alumina Piec es

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38 Figure 2 6 Analytical results of insulation sizing comparing insulation thickness and composite insulation with varying internal diameter. Heat loss and surfac e temperature decrease with increasing insulation thickness and internal diameter of insulation. Analysis completed for a tube temperature of 1300K. Enclosure For safety reasons and to add to the thermal insulation, the entire electric heater is enclosed in a thermally insulated aluminum frame box. The box consists of light aluminum panels with 3.81 cm (1.5 in.) thick fiberglass insulation panels glued to the side facing the heater. Large 215.9 x 99.06 cm (85 x 39 in.) panels are used on the longitudinal sides of the heater. Small 129.54 x 99.06 cm (51 x 39 in.) panels are used on the transverse side. The total height of the box is 396.24 cm (156 in.) with a total length of 215.9 cm (85 in.) and width of 129.54 cm (51 in.). The box is built around the

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39 heat er by mechanically bolting panels on top of each other. A schematic of the enclosure is shown in Figure 2 7. This design allows for easy assembly. Additionally, repairs may be made by removal of individual panels, without requiring the disassembly of the e ntire box. Table 2 4 gives the panel and insulation padding specification. panel and insulation padding specification. Figure 2 7. Heater Enclosure. Fans installed on the top panel of the enclosure are used for cooling.

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40 Table 2 4 Enclosure Components a nd Specifications Part Specifications Large Aluminium Panel Large Aluminium Panel Dimensions: Thickness: 3.175 mm (0.125 in.) Length: 215.9 cm (85 in.) Height: 99.06 cm (39 in.) Small Aluminium Panel Small Aluminium Panel Dimensions: Thickness: 3.175 mm (0.125 in.) Length: 129.54 cm (51 in.) Height: 99.06 cm (39 in.) Fiberglass Insulation Panel High Temperature Rigid Fiberglass Insulation Properties: Temperature Range: 18 to 230 C (0 to 450 F) Heat Flow Rate (K Factor) @ 297 K (75 F): 0.23 Density: Medium: 48 kg/m 3 (3 lbs./ft 3 ); High: 96 kg/m 3 (6 lbs/ft 3 ) Length: 121.92 cm (48 in.) Width: 60.96 cm (24 in.) Thickness: 3.81 cm (1.5 in.) Density: Medium: 48 kg/m 3 (3 lbs./ft 3 ); High: 96 kg/m 3 (6 lbs/ft 3 ) Length: 121.92 cm (48 in.) Width: 60.96 cm (24 in.) Thickness: 3.81 cm (1.5 in.)

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41 Facility Heat Transfer Analysis The purpose of this section is to go through a first order analysis of the expected stagnation temperatures at varying mass flo w rates. Analyzed is the coil wall temperature and coil elongation. Rayleigh flow analysis of the air flow through the coils is also discussed. At maximum power, the expected maximum coil temperature is 1300 K. At this temperature the material is expected to experience elongation due to heating. The expected coil elongation may be predicted using the following relation: 310, the mean coefficient of thermal expansion is 19.1 m/m/C (Table 2 1). This corresponds to a maximum coil elongation of 25 cm, or 1.91 % of the total coil length. The co il insulation structure (Figure 2 5) is designed to give a maximum of 30.5 cm (12 the coils are anchored to the facility enclosure with high temperature Kevlar tape. This gives the heater added structural support and stability. Heat is added to the flow flow ing fluid by heat exchange with the walls of the coils. One dimensional flow with heat addition or Rayleigh flow calculation technique can be used to approximate the stagnation temperature of the flow at the exit of the coils as well as the pressure drop due to heating of the coils. The stagnation temperature raise through a single coil can be calculated for different mass flow rates using the energy equation below For the analysis, air is assumed as ideal gas with a constant specific heat of 1000 J/kg K.

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42 The predicted exit stagnation temperatures at the various facility power settings are given as a function of stagnation pressure and mass flow rate in Figure 2 8 Figure 2 8 Stagnation pressure vs. theoretical exit stagnation temperature at various facility power settings. The exit coil Mach number and stagnation pressure loss can be calculated by using the following Rayleigh flow relations from Anderson dern Compressible Flow. The star condition is referenced to flow properties at the thermal choking point. Entrance Mach number into the coils is M = 0.2. The exit Mach number is presented in

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43 Figure 2 9 as a function of the total pressure. The predic ted exit Mach number is 0.45 at the highest heat input of 169 kW. This result shows that thermal choking is not an issue in mass flow calculations for the facility. Pressure loss in the tubes due to heating varies between 1 and 2 psi (0.07 and 0.14 atm.) a t the maximum predicted heat input. Additional pressure losses are due to friction in the pipes. These losses are estimated to less than 5 psi based on previous work. The supply pressure is considerably higher than the operational pressure, hence these los ses are negligible. Figure 2 9 Rayleigh flow prediction for exit coil Mach number as a function of stagnation pressure at various facility power settings. Mass flow calculations are performed at a choke plate installed after the hot collector for perf ormance evaluation purposes. The choke plate has a throat diameter of 3.56 cm (1.4 in.). The flow can be considered sonic at the throat as long as the ratio

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44 between the stagnation and static pressure at the throat are above 1.89 as dictated by the isentrop ic relation given below. As static pressure measurements at the throat are not performed, the total pressure can be compared to the ambient exit pressure. From this first order analysis it can be deduced that flow will be choked at the throat at stagnati on pressures above 28 psia (1.9 atm.). The mass flow rate can then be calculated iteratively using the compressible flow relations. Figure 2 9 shows the relation between mass flow rate and stagnation pressure. From the above relations it is seen that m ass flow rate depends on the total pressure of the flow as well as stagnation temperature or heat addition. Figure 2 10 Mass flow rate dependence on pressure and heat addition.

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45 CHAPTER 3 SECOND STAGE VITIATI ON HEATER Design Parameters A second stage v itiation heater will allow for a further stagnation temperature raise of the air coming into the facility test section. In the complete facility configuration, this heater will be added atop the first stage electric heater (i.e. no choke plate). The second stage heater uses combustion heating to achieve temperature raise. Hydrogen will be used as the fuel to react with the air according to the following reaction; The oxygen consumed in the combustion will be replenished by adding extra oxygen to the air s tream prior to combustion, hence the governing reaction becomes such that the replenishing O 2 mole fraction is 21 %. By design, the second stage heater will achieve stagnation temperatures of up to 1800 K and allow for simulation of Mach 6.5 enthalpy. Th e combustion chamber is ma de of Zircar ceramic 15.24 cm (6 in.) inner diameter 2.54 cm (1 in.) thick cylinder seated in a stainless steel tube as shown in Figure 3 1. A plasma torch will be used as igniter for combustion of the incoming air and hydrogen m ixture Sali Cylinder Specifications : Composition: Al 2 O 3 80%; SiO 2 20% Maximum service temperature: Continuous 1800 C (3292 F), Intermittent 1830 (3326 F) Melting Point: 1870 C (3392 F)

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46 Figure 3 1. Combustion chamber assembly. Igniter i s inserted on the side of the combustion chamber (not shown in drawing). Second Stage Heater Instrumentation Figure 3 2 shows a schematic of the Hydrogen and Oxygen supply system of the second stage heater as well as the supply set up for the future test section. Table 3 1 gives a component specification list of the set up. The system features Hydrogen fuel and Oxygen replenishment supply lines for the vitiation heater as well as two Hydrogen supply lines for the test section. The entire system is purged w ith nitrogen after operation to prevent storage of combustibles in the supply lines. Zircar Sali cylinder for thermal insulation.

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47 Figure 3 2. Hydrogen and Oxygen Combustion Chamber supply lines. Table 3 1. Second Stage Heater Component Specifications Component Brand Specifications Pneumatic Actuat ed Regulator (PAR) TESCOM 44 1300 SERIES Inlet Pressure: 3750 psig (25.85 MPa) Outlet Pressure Range: 0 300 psig (0 2 MPa) Electronic Controller (EC) TESCOM ER 3000 SERIES Input: 0.5 5.5 VDC analog Output: 0 300 psig (0 2 MPa) H 2 or O 2 Feedback: 0.5 5.5 VDC analog Solenoid Valve (SV) (H 2 line) ASCO Red Hat II Power: 17.1 Watt Pressure: 5 300 psig (34.46 kPa 2 Mpa) Pipe Diameter: 1/2 inch (12.7 mm) Input: 115 VAC Solenoid Valve (SV) (O 2 line) ASCO Red Hat II Power: 10.1 Watt Pressure: 200 psig (1.3 8 Mpa) Pipe Diameter: 3/8 inch (9.525 mm) Input: 115 VAC Flowmeter (FM) (H 2 lines) Omega

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48 Hydrogen supply and Oxygen supply are directly controlled from an Electronic Control Panel (ECP) shown in Figure 3 3. 12 VDC signals from the ECP energize LY Series 12 VDC relays which energize high voltage circuits necessary for powering equipment for the second stage. Figure 3 4 shows the connection scheme between the electronic Control Panel, Relay, and Solenoid Valve used to control Hydrogen supply to the second stage heater. The ECP wiring diagram is shown in Figure 3 5. Listed are the functions and operation principle of all ECP components: Key Switch activates control panel. The key switch is connected in series to all other devices on the control panel as sh own in the panel wiring diagram (Figure 3 5). A standard 230T power supply is used to power the control panel lights as well as the relays (see Figure 3 4). A nitrogen purge switch energizes the solenoid valve for system purge. This clears all plumbing fro m Oxygen/Hydrogen gas. Test section controls include two Hydrogen fuel switches for even distribution in the test section (two Hydrogen ports). The ignition switch is for flame holding tests, and is used to ignite the Hydrogen air gas mixture in the test s ection. Available are liquid fuel switches (for use with JP 8, JP 10, etc) if such studies are required for future experiments. Liquid fuel lines are not installed on the facility, but wiring is available for such a system. Liquid fuel is to be sprayed in the test section. The liquid ON switch serves to send fuel to the system, usually performed using solenoid valve. In the second position, Nitrogen gas is used to purge the liquid fuel system The Liquid Bypass switch connects to a relay which can be used to energize a solenoid valve for fuel bypass configuration, such that fuel will be circulated but not sprayed in the test chamber. Liquid to test section switch opens the fuel spray port on the test section. It should be noted that the plumbing for the liqui d fuel system is currently not installed; the electrical circuit stops at the Relay box, where connections are to be made as required for the future test configuration. Second stage heater controls for Hydrogen and Oxygen are available. Hydrogen and Oxygen Solenoid valves are energized through the corresponding relays (see Figure 3 6 and Table 3 3 ). The Igniter switch fires the igniter for Hydrogen Air combustion in the heater. Three spring loaded TESCOM pressure regulators are available on the control pane l. Regulators 1 and 2 are used in tandem with the Pneumatic Actuated Tescom Pressure regulators for the Hydrogen supply to ports 1 and 2 of the test

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49 section. The third pressure regulator is to be used for the liquid fuel lines pressure control. Hydrogen an d Oxygen to the Second Stage Heater are controlled using ER 3000 TESCOM electronic controllers connected with TESCOM Pneumatic Actuated Pressure Regulators. The ER 3000 will be software controlled using 0.5 5. 5 V analog signal output proportional to the desired pressure output. Table 3 2 Electronic Control Panel Legend Panel Number Function 1 Key Switch (activate panel) 2 Nitrogen Purge 3 Test Section (T/S) Ignition 4 T/S Hydrogen (port 1) 5 T/S Hydrogen (port 2) 6 Liquid Fuel Bypass/Liquid Fuel t o T/S 7 Liquid Fuel ON 8 Nitrogen Purge (liquid fuel system) 9 Second Stage Heater Hydrogen Supply 10 Second Stage Heater Oxygen Supply 11 unassigned Regulator 1 Test Section Hydrogen (port 1) Regulator 2 Test Section Hydrogen (port 2) Regulator 3 Liquid Fuel Pressure Display Liquid Fuel Pressure Indication

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50 Figure 3 3. Electronic Control Panel (ECP) Test Section Control s Second Stage Heater Controls Liquid Fuel Controls 1 2 3 4 5 6 7 8 9 10 1 1 Regulator 1 Regulator 2 Regulator 3 Display

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51 Figure 3 4. Wiring connection diagram of main second stage control components: panel (ECP), Relay, Solenoid Valve. NOTE: pow er supply provides 12 VDC signal to power electronic control panel (ECP) as well as power signal to the relay

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52 Figure 3 5. Electronic Control Panel Wiring Diagram.

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53 Figure 3 6. Relay Distribution Box Numbering Legend

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54 Table 3 3 Relay ECP Connection Leg end. Note: ECP refers to Electronic Control Panel. Relay Number ECP Switch Number Function/Solenoid 1 2 N 2 Purge 2 6 (Down Position) Liquid Fuel ON 3 7 (Down Position) Liquid Fuel Bypass 4 6 (Up Position) N 2 Purge (Test Section Fuel Lines) 5 7 (Up Pos ition) Liquid Fuel To Test Section 6 5 H 2 Test Section Port 2 7 4 H 2 Test Section Port 1 8 3 Test Section Ignition 9 11 (Up Position) Not Assigned 10 Not Assigned Not Assigned 11 10 Heater Ignition 12 9 O 2 Heater Replenishment Supply 13 8 H 2 Heater Fuel Supply 14 Not Assigned Not Assigned 15 Not Assigned Not Assigned Bell mouth Design Hot air coming from the first and second stage heater is channeled to a converging diverging nozzle in order to accelerate the flow to supersonic speeds. The tran sition from the pipe to the nozzle is achieved by using an adequately sized bell mouth, allowing for smooth transition of the flow from the circular 6 inch diameter pipe of the combustion chamber to a 5.08 x 2.54 cm (2 x 1 in.) rectangular nozzle entrance. To achieve such a transition, the bell mouth has a mold design. The mold can be made of plastic or any other easily formed material. The mold geometry is shown in Figure 3 7. A stainless steel casing for the bell mouth is made with rectangular cuts as sho wn in Figure 3 8. To produce the desired transition geometry, the casing is placed on top of the mold and the air gap is filled with ceramic putty. To shape the cast appropriately, the casing and bell mouth mold are bolted to a circular plate once the cera mic putty is inserted. An assembled view of the casing, mold, and bottom plate is shown in Figure 3 9.

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55 Figure 3 7. Bell Mouth mold design. Figure 3 8. Bottom and Top Isometric Views of the bell mouth casing. Nozzle facing side Combustion Chamber side

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56 Figure 3 9. Bell mouth bolting assembly for cast forming. Listed below are the materials and the procedure for creating the bell mouth: The casing is of stainless steel 310. It is 2.5 inches (6.35 cm) high with diameter of 11.25 inches (28.575 cm). The casing may be made of two parts, a n 11.25 inch diameter 1 inch (2.54 cm) thick stainless steel 310 plate and a 1.5 inch (3.81 cm) square solid with 6 inch (15.24 cm) side. The material is the same as the bottom plate. The two are welded together and the inside cavity is machined consequent ly. Detailed drawings are seen in Appendix C. The mold is of plastic, 6 inch diameter on the combustion chamber side and 2 by 1 inch square on the nozzle entrance with total thickness of 2.5 inches. The curvature radius is 3.4 inches (8.636 cm). Two positi oning pins are used for the molding assembly to keep the mold secure. The cast is shaped of Thermeez 7020 Ceramic Putty chosen for its hig h service temperature. Table 3 4 shows the properties of the Putty. Gaps to be filled with Ceramic Putty Mold support plate

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57 The mold support plate is made of 310 stainless st eel (other material may be used if desired). Holes are drilled on the face for the mold position pins. Table 3 4 Material properties for Thermeez 7020 Ceramic Putty Thermeez 7020 Ceramic Putty Properties Maximum Service Temperature 2033 K (3200 F) Com pressive Strength 10.342 MPa (1500 psi) The properly formed bell mouth is bolted to the combustion chamber assembly as shown in Figure 3 10. Figure 3 10. Combustion chamber and bell mouth assembly. Zircar ceramic gasket

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58 CHAPTER 4 DATA MEASUREMENT AND FACILITY CONTROLLER Data Collection Set Up Temperature, pressure, current, and voltage data are measured for monitoring of the test conditions as well as for safety reasons. Temperature readings are obtained using K type thermocouples. Temperature is measured at 37%, 88%, a nd 100% coil length for each coil. Temperature across each Flange weld is also measured. Stagnation temperature is measured after the choke plate positioned at the exit of the hot collector. Stagnation pressure measurement is done at the cold collector. Fi gure 4 1 shows the physical location of temperature and pressure sensors on the heater. Data acquisition (DAQ) is accomplished through National Instruments (NI) DAQ cards and NI Labview TM software. Thermocouple readouts are processed through the NI SCXI 1 000 chassis loaded with the NI SCXI 1100 module and SCXI 1303 accessory card. The data is processed through the Labview TM software as described in the Labview TM Controller section of this chapter The stagnation pressure is recorded through the NI USB 62 55 DAQ card. A data acquisition component diagram is shown in Figure 4 2. The transducers in operation are listed in Table 4 1.

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59 Figure 4 1. Thermocouple and pressure transducer physical location diagram. Stagnation temperature is measured immediately do wnstream of the choke plate. Acceptable Usage Described below is the connection set up of the Data Acquisition System: Temperature Measurements are done at the heater coils (37%, 88%, 100 % coil length), flange welds, and hot collector stagnation point. K type insulated, shielded thermocouples are used to prevent interference from the facility voltage. Thermocouple wiring is distributed using a thermocouple bus at the facility box. The Connection points between thermocouple bus and Data Acquisition Board a re listed in Table 4 2. Additionally, temperature data is recorded in the SCR box for safety reasons. Thermocouple outputs are read through the SCXI 1000 coupled with the SCXI 1100 Multiplexer Amplifier and the SCXI 1301 terminal block. The stagnation Pre ssure is recorded at the cold collector. A PX309 300, 0 300 psi pressure transducer is used. The transducer produces a 0 5V signal proportional to the pressure measurement. This output signal is connected to the USB 6255 data acquisition board. The SCXI 10 00 chassis connects to the PC through a PCI GPIB card. The NI USB 6255 uses a USB connection to interface with LabVIEW. A DELL Quad Core 2 processor computer is used for data processing and control.

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60 Figure 4 2. Data acquisition component diagram. Table 4 1. List of Transducers Component Facility Location Data Acquisition Board Location Specifications Thermocouple Heater Coils/Flanges/Stagnation NI SCXI 1000 through SCXI 1100 and 1300 accessories K Type, insulated Pressure Transducer Cold Collector NI USB 6255 Model: PX309 300A5V Output Signal: 0 5 V proportional Pressure: 0 300 psig

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61 Table 4 2. Thermocouple Connection Legend Facility Location Facility Bus Number SCXI channel number LabVIEW array number Stagnation N/A 1 0 Coil 1, 100 % 4 24 25 C oil 2, 100 % 9 28 20 Coil 3, 100 % 14 3 1 Coil 4, 100 % 19 4 2 Coil 5, 100 % 24 5 3 Coil 6, 100 % 29 6 4 Coil 1, 88 % 3 10 7 Coil 2, 88 % 8 11 8 Coil 3, 88 % 13 12 9 Coil 4, 88 % 18 13 10 Coil 5, 88 % 23 14 11 Coil 6, 88 % 28 15 12 Coil 1, 37 % 0 27 14 Coil 2, 37 % 5 18 15 Coil 3, 37 % 10 19 16 Coil 4, 37 % 15 20 17 Coil 5, 37 % 20 21 18 Coil 6, 37 % 25 22 19 Flange 1, Weld Top 34 8 26 Flange 1, Weld Bottom 30 9 27 Flange 2, Weld Top 35 25 21 Flange 2, Weld Bottom 31 6 5 Flange 3, Weld Top 36 26 22 Flange 3, Weld Bottom 32 7 6 SCR Box Temperature 1 N/A 29 23 SCR Box Temperature 2 N/A 30 24 Cold Flange Temperature 30 16 13

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62 Lab view Controller The Labview TM controller program serves to monitor and record temperature, pressure, and voltage readouts from the facility and SCR unit as well as to send control signal to the SCR in order to regulate the power sent out to the facility. The program is structured as a while loop containing a sequence frame program design. Each sequence frame executes a series of functions before the next set of tasks can be completed in the next frame. Control Logic A proportional controller is used to control the power sent to the Electric Heater through the SCR. Temperature and Pressure data is read in the first sequence frames of the controller. Based on the data the controller regulates the amount of power to be sent to the facility. Power to the facility passes through the SCR, which takes a 0 5V analog signal from the NI USB 6255 analog output channel. Figure 4 3 shows a plot of output power to the facility vs. input signal. Two Control modes are available manual and automatic. The manual control mode allows for direct user control of the analog output voltage signal to the SCR. The automatic mode uses temperature data and user input constraints to regulate stagnation temperature increase to the desired parameters. Figure 4 4 gives a logic schematic of the two control modes.

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63 Figure 4 3. Plot of control input voltage to the SCR vs. electric heater pow er consumption. A polynomial fit approximation shows the approximate data fit and equation, where P is power in kW and V is input voltage in VDC.

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64 Figure 4 4. Logic Chart of voltage control operation.

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65 The controller program screenshots are found in Append ix B. The essential primary functions and operation logic of each sequence structure and program feature are described below. Labview TM sequence structures are labeled from 0 to n. S equence 0: Extraction of temperature data from the SCXI modules. Data is extracted in an array containing samples from each temperature sensor. SCXI array numbering correspondence with sensor location is given in Table 4 2. Data is extracted using a Labview TM sub program (DAQ assistant). Temperature is extracted in a Labview T M dynamic data format and converted to array data format. Stagnation Temperature slope is calculated over 10 loops by storing stagnation temperatures in an array and extrapolating the difference in relation to timing information, also stored in an array. A vailable is a feature for a reference slope line on the stagnation temperature graphical indicator ( see Figure 4 5 ) for visual comparison between desired and actual temperature slope. Sequence 1: Current from the SCR is measured using MAGNALAB CT 2000 1500 current transformers. The current transformers send out a 0 1V signal proportional to the measured current. The signal is read in the USB 6255 data acquisition board. Three current transformer probes are used in the SCR, one for each of the three legs. Cu rrent and RMS voltage from the transformers are extracted in sequence 1. The calibration equations for each current transformer are as follows: Sequence 2: Maximum temperature is extracted from the temperature meas urement array. The physical location of the maximum temperature probe is displayed on the front panel. Sequence 3: Stagnation p re ssure data is extracted using the DAQ assistant sub vi (sub program). Additionally, voltage is read from the SCR controller cir cuit. This voltage feedback is used to indicate if the analog output pressure switch circuit is closed. A more detailed overview of the circuit is given in the Safety Features Section of this chapter. Sequence 4: Temperature difference is calculated acro welds. The adequate safety limit is 50 C as per AEI engineering commission recommendations.

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66 Sequence 5: Temperatures are checked against the safety limit (1200 K). If temperatures are above the limit, voltage output to the SCR contr oller is reduced to 90 % of indicated value. Sequence 6: This program sequence contains the voltage output control logic. Logic schematic of the controller is shown in Figure 4 4. Two modes of operation are available: manual and automatic. Both control mod e algorithms pass through several safety checks before voltage is sent out to the SCR. An Emergency Stop button on the front panel zeros output voltage from the controller. Additionally the power ON/OFF switch can be used to zero output voltage. No more th an 5 VDC output signal may be fed to the SCR. This ensures that SCR will not draw more than 1200 Amperes from the external transformer, which is fused for 1200 Ampere maximum current. The Automatic Controller outputs voltage based on the voltage output equ ation, where V new refers to the updated voltage value and V old refers to the last update value. T goal is a manual input parameter dictating the desired stagnation temperature to achieve. T stagnation is the current stagnation temperature value and T max is the safety limit temperature for the facility (default is 1200 K). An outside timing while loop structure creates a waiting period of 10 program loops (approximately 10 seconds) before an update is allowed for the voltage. This time delay compensates for the metal. A 30 K dead zone is implemented in the control logic to allow for temperature overshoot at lower stagnation temperature operation. The manual controller is much simpler in nature. A 0 5 V control slider on the front panel dictates the output voltage to the SCR. In the event of overheating (temperature above the safety limit), the output value is reduced to 90 % of the control input value. When switching from manual mode to automatic mod e, the initial voltage output of the automatic controller will be the last input voltage value of the manual controller. This is not so when switching from automatic to manual control mode, thus care must be taken to adjust the voltage slider value so as n ot to cause a sudden voltage increase, which can cause equipment damage at the external power source transformer. Sequence 7: Temperature, pressure, timing, and voltage output data is saved to an external spreadsheet for analysis.

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67 Fi gure 4 5. Front panel view of the heater control program. Stagnation temperature graphical display. Manual Voltage Control Slider Camera screens for facility monitoring Current Transformers indication Emergency Stop Button Coil Temperature Indicators Pres sure Switch Status Indicator

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68 Electric Heater Safety Features The electric heater facility has hardware and software safety features designed to prevent accidents. They are described as follows. Hardware Emergency Power Discon nect Circuit Breaker: the most important safety device, the Emergency Disconnect Circuit Breaker shuts down power to the heater by physically disconnecting the SCR from the external transformer power source. SCR fuses: the SCR is fused to 1600 ampere curre nt with four HINODE 660GH 400 fuses at each leg. Pressure Switch: The purpose of the pressure switch is to ensure that the heater cannot be powered without air running through the system. Since air is the main cooling source for the coils, applying power without it may overheat and melt facility components. The pressure switch closes the analog output signal circuit from the NI USB 6255 card to the SCR controller. Feedback is sent to the controller to indicate whether the switch is open or closed. The swit ch is set to close at 22 psia air pressure. Figure 4 6 shows the circuit diagram for the switch. Software Emergency Stop Button: Power to the facility is cut by bringing the voltage output from the NI USB 6255 to the SCR to zero. Over Current protection: The output voltage to the SCR is limited to 5 Volts, corresponding to 1200 Amperes of current output. This ensures the current output does not exceed the output limit of the external transformer. Thermal Safety : Voltage output to the SCR is reduced to 90 % if any of the temperature sensors exceed the safety limit of 1200 K.

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69 Figure 4 6. Circuit diagram of pressure switch wiring

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70 CHAPTER 5 ELECTRIC HEATER PERF ORMANCE EVALUATION Introduction The electric heater performance was evaluated by conducting sev eral tests of the facility. The test focus was to determine the operational limit of the facility as well as demonstrate safe operation. These test data are described in detail in the following paragraphs. The facility was commissioned in May 2012 by Affil iated Engineers Inc. (AEI) based on the successful demonstration of the test criteria described in this chapter. Experimental Set Up For the performance evaluation of the non vitiated heater, the second stage is replaced by a dummy steel pipe of 16.19 cm (6.375 in.) inner diameter with 3.18 mm (1/8 in.) thickness. Between the pipe and the elbow exit of the facility, a choke plate is installed with 3.56 cm (1.4 in.) diameter throat. The choke plate allows for flow rate calculation using the methods describe d in Chapter 2. Non Vitiated Heater Performance The facility performance was evaluated by conducting a maximum temperature test at an intermediate pressure of 40 psia. Power to the facility was increased incrementally to prevent power surges at the exter nal power transformer. Figure 5 1 A. shows experimental results of the facility performance evaluation. Temperature was recorded at 37%, 88%, and 100% along all coils with stagnation pressure data and control voltage signal sent to the SCR. Other facility measured parameters include temperature at electric connections and across weldings for long term safe operation

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71 monitoring. Figure 5 1 B shows the corresponding current data recorded at each leg of the facility. The current and control voltage drops show n in the data are indicative of safety equipment shut off tests. It should be noted that mass flow rate changes with pressure and temperature due to the effect on density. Thus, at 2000 seconds the mass flow rate is 0.4 kg/s but drops to 0.37 kg/s at the peak stagnation temperature value. The maximum temperature achieved was 860 K, which is well above the theoretical predictions in the thermal analysis of chapter 2. Performance may be further improved by an increase in the coil resistance value, which woul d allow for higher power dissipation through the heater. Figure 5 2 shows a collection of data points gathered from preliminary tests. The data is indicative of the correlation between control input signal to the SCR and the output current through the hea ter coils. Current measurements were performed using a FLUKE 376 TRUE RMS Clamp Meter attached to one of the load legs in the SCR. Figure 5 3 indicates correlation between the voltage input signal to the SCR and the SCR output voltage to the heater. Test r esults for current values exceeding 1200 A are shown in Figure 5 4. The test shown was performed to evaluate maximum power performance at medium pressure values. The curves shown in Figures 5 2 and 5 3 combined can be used to predict the power dissipated t hrough the non vitiated heater using the methods described in Chapter 2. A collection of steady state data is shown in Figure 5 5. The data is a collection of steady state stagnation temperature points from several preliminary tests. The majority of prelim inary testing was done at a medium stagnation pressure setting of 40 psia as

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72 reflected by the data. The results show the temperature trend at varying power and pressure settings. A. B. Figure 5 1. Facility peak performance data. (A) Coil and stagna tion temperatures with respect to control voltage, power, and pressure are shown. (B) Corresponding output current through each leg with respect to time

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73 Figure 5 2. Current response data. Shown is the correspondence between current output to the facili ty measured experimentally using a hand held current measuring device and the DAQ output voltage signal to the SCR. The data shown in the figure is an aggregate of 13 individual performance tests of the facility.

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74 Figure 5 3. Predicted and measured SCR output voltage values vs. DAQ voltage signal to the SCR. Voltage divider measurements were performed using a resistor circuit read through the LabVIEW as described in Chapter 4.

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75 Figure 5 4. Maximum temperature test at high current values. For the above results the maximum current value is 1353 Amperes at 74 Volts. The 0 5 VDC control voltage signal to the SCR is shown on the secondary vertical axis.

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76 Figure 5 5. Non vitiated heater calibration curve. Shown is steady state stagnation temperature data versus voltage signal to the SCR. The data is aggregate of several preliminary heater test runs.

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77 Examples of Possible Studies This section will discuss the possible study operational conditions that can be achieved using the facility discussed here. Two categories of tests may be performed: internal flow and external flow. Internal flow tests are used for simulation of supersonic combustion while external flow tests are mainly concerned supersonic aerodynamics. Internal hypersonic flow testing is pract ical in studying scramjet combustor designs. For such experiments, a Mach 2 nozzle can be incorporated after the second stage heater of the facility. Such a set up will allow for simulation of the physical Mach number typically seen in a scramjet combustor The heaters are incorporated to simulate the flow enthalpy for a hypersonic vehicle. Table 5 1 shows several example study scenarios for internal flow simulation. Test section sizing is dependent on the nozzle exit area required to reach the desired Mach number at a given mass flow rate. Water vitiation is mole fraction calculations with STANJAN software based on the governing reaction equations shown in Chapter 4. External flow aerodynamic tests generally require a larger test section in order to preven t wall boundary layer interactions and to achieve high physical Mach number of the flow. Additionally, larger test sections naturally allow for a larger model size, required for accurate Reynolds and Prandtl number simulation. Table 5 2 shows possible exte rnal flow test scenarios.

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78 Table 5 1. Examples of possible internal flow test conditions T stag (K) Mach Mass Flow (kg/s) Test Section Cross section (cm 2 ) Test Duration Non Vitiated 1 st stage only 1300 2 0.66 18 Continuous With 3% water vitiation** (in the 2 nd stage) 1350 2 0.72 20 Continuous With 8% water vitiation** 1700 2 0.72 22.6 Continuous With 14% water vitiation** 1350 2 1.4 38.5 Continuous With 15% water vitiation** 1800 2.5 0.85 42.5 Continuous *compressors max. output: 1.5 kg/s **vi tiation from 300 K produces: 15% mole faction of water to reach 1300K, 25% to reach 1800K.

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79 Table 5 2. Examples of possible externall flow test conditions T stag (K) Mach Mass Flow (kg/s) Test Section Cross section (cm 2 ) Test Duration Non Vitiate d 1 st stage only 950 4 0.5 90 Continuous With 3% water vitiation** (in the 2 nd stage) 1350 5 0.45 232 Continuous With 8% water vitiation** 950 4 0.85 161 Continuous With 14% water vitiation** 1350 5 0.88 438 Continuous With 15% water vitiation** 181 0 5 0.88 310 Continuous *compressors max. output: 1.5 kg/s **vitiation from 300 K produces: 15% mole faction of water to reach 1300K, 25% to reach 1800K.

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80 APPENDIX A HEATER DRAWINGS Figure A 1. Non Vitiated Heater

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81 Figure A 2. Non Vitiated He ater Resistance Heating Coils

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82 APPENDIX B CONTROL PROGRAM Figure B 1. Frame 1 of program frame sequence.

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83 Figure B 2. Sequence Frame 2 of control program. Sub VI diagram is shown in Figure B 3.

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84 Figure B 3. Current Measurement Sub VI.

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85 Figure B 4. Third program sequence frame.

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86 Figure B 5. Fourth program sequence frame. Voltage signal from the pressure switch is compared with 0.05 to account for noise in the lines, which would cause the pressure switch LED to turn ON even if there is no volt age to the SCR controller.

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87 F igure B 6. Sixth sequence frame, voltage reduction factor structure.

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88 Figure B 7. Manual control mode program components.

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89 Figure B 8. Automatic control mode program components.

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90 Figure B 9. Final sequence frame, da ta recording structure.

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91 APPENDIX C BELLMOUTH Figure C 1. Bellmouth

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92 Fi gure C 2. Bellmouth mold

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93 Fi gure C 3. Bellmouth molding base

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94 LIST OF REFERENCES [1] Blot, A. (2009), Design of a Non Vitiated Heater Ground Test Facility for Supersonic Combustion Published M.S. Thesis, University of Florida [2] 198, 2002, pp 1 15 [3] 314 [4] Russo, G., De Fillippis, F., Borrelli SCIROCCO 70 AIAA Journal, vol. 198, 2002, pp 315 351 [5] Tunnel F acility l. 198, 2002, pp 427 478 [6] Chue, R. S. M., Tsai, C. Facility at GASL A Dual Mode, Dual Driver Reflected Shock/Expansion 71 [7] ciples of Hypersonic Test Facility 27 [8] Segal Corin, The Scramjet Eng ine Process and Characteristics, Cambridge University Press, New York, 2009 [9] Turns, Stephen R., An Introduction to Combustion: Concepts and Applications, 2 nd ed., McGraw Hill, Singapore, 2000 [10] Anderson, John D., JR. Hypersonic and High Temperature Gas Dynamics, McGraw Hill, New York 1989 [11] rd ed., McGraw Hill, New York, 2003 [12] Liepman, H. W. and Roshko, A., Elements of Gas Dynamics, John Wiley & Sons, Inc., New York, 1957 [13] Incropera, Frank P., DeWitt, David P., Bergmann, Theodore L., and Lavine Adrienne S., Fundamentals of Heat and Mass Transfer, 6 th ed., John Wiley & Sons, Inc., Asia, 2007 [14] Glassman, Irvin, Combustion, 3 rd ed., Academic Press, Inc., California, 1996

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95 [15] Engineering: Data and Resources Web Site: http://www.pwrengineering.com/data.htm

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96 BIOGRAPHICAL SKETCH Jivko Djerekarov was born in 1987 in the city of Smolian, Bulgaria. At the age of 13 he moves to live in Miami, Florida with his family. The following year he pursues hi s interests in engineering by building a simple wind tunnel for drag measurements. The project wins him a third place in the school science fair. During high school, Jivko attends a three year program at George T. Baker Aviation School, specializing in air frame structures and systems. In 2006, he is admitted to the University of Florida. He purs ues a double degree program in aerospace and mechanical e ngineering. Jivko successfully completes his Bachelor of Science degrees in 2010. sonic aerodynamics and propulsion lead him to volunteer at the Combustion and Propulsion Laboratory at the University of Florida under the supervision and guidance of Dr. Corin Segal. In 2010 he is admitted to the UF graduate program in thermal sciences an d fluid d ynamics. He continues to work with Dr. Corin Segal at the Combustion and Propulsion Laboratory in the pursuit of a Master of Science in A erospace E ngineering. His research efforts focus on the completion of the Non Vitiated Heater Facility at the University of Florida. Under the guidance and support of Dr. Segal, Jivko takes the project from its design to its successful commissioning in May 2012. Aft er graduation Jivko plans on pursuing a career in engineering and looks forward to the next challenge.