超声速燃烧与高超声速推进

俞刚; 范学军

doi:10.6052/1000-0992-13-037

超声速燃烧与高超声速推进

doi: 10.6052/1000-0992-13-037

俞刚^,,
范学军

中国科学院力学研究所高温气体动力学国家重点实验室, 北京 100190

详细信息

作者简介:
俞刚,1938年出生于上海.1961年毕业于天津南开大学数学力学系,同年分配到中国科学院力学研究所工作.先后从事过爆炸力学、气动激光研究.1980和90年代初赴美国芝加哥西北大学、西雅图华盛顿大学以及普林斯顿大学从事燃烧、气流混合和激光诊断技术研究.1992年回国后从事超声速燃烧研究.1995年被聘为研究员,2003年退休.

通讯作者:
俞刚

中图分类号: V231.1
计量
- 文章访问数: 3327
- HTML全文浏览量: 473
- PDF下载量: 2950
- 被引次数: 0
出版历程
- 收稿日期: 2013-05-29
- 修回日期: 2013-09-09
- 刊出日期: 2013-09-25

Supersonic combustion and hypersonic propulsion

YU Gong^,,
FAN Xuejun

State Key Laboratory of High-Temperature Gas Dynamics, Institute of Mechanics, Chinese Academy of Science, Beijing 100190, China

More Information

Corresponding author: YU Gong

摘要

摘要: 50 多年的努力和曲折经历证明了超声速燃烧冲压发动机概念的可行性. 本文对影响超燃冲压发动机技术成熟的主要因素作了扼要的分析. 高超声速推进的首要问题是净推力, 利用超声速燃烧获得推力遇到各种实际问题的制约, 它们往往互相牵制. 几次飞行试验表明高超声速飞行需要的发动机净推力仍差强人意, 液体碳氢燃料(煤油) 超燃冲压发动机在飞行马赫数5 上下的加速和模态转换过程, 成为高超声速吸气式推进继续发展的瓶颈. 研究表明, 利用吸热碳氢燃料不仅是发动机冷却的需要也是提高发动机推力和性能的关键举措, 燃料吸热后物性改变对燃烧性能的附加贡献对超燃冲压发动机的净推力至关重要.当前, 实验模拟技术和测量技术相对地落后, 无法对环境、尺寸和试验时间做到完全的模拟. 计算流体动力学(Computational Fluid Dynamics, CFD) 逐渐成为除实验以外唯一可用的工具, 然而, 超声速燃烧的数值模拟遇到湍流和化学反应动力学的双重困难. 影响对发动机的性能作正确可靠的评估.提出双模态超燃冲压发动机模态转换、吸热碳氢燃料主动冷却燃料催化裂解与超声速燃烧耦合、燃烧稳定性、实验模拟技术与装置、内流场特性和发动机性能测量、数值模拟中的湍流模型、煤油替代燃料及简化机理等研究前沿课题, 和未来5~10 年重点发展方向的建议.
- 超声速燃烧 /
- 高超声速推进 /
- 超燃冲压发动机 /
- 吸热碳氢燃料 /
- 燃烧稳定性 /
- 模态转换
Abstract: After the long and strenuous efforts covering more than 50 years and the tortuous experiences, feasibility of the scramjet concept has finally been proven. In this paper, the main factors influencing the technical maturity of the scramjet engine are briefly analysed. A matter of utmost concern for this new type of air-breathing engine is the net thrust. The production of engine thrust using supersonic combustion encountered a number of practical requirements which were often found to contradict each other. Several flight tests showed that the net engine thrust was still not as good as expected. The acceleration capability and mode transition of scramjet with liquid hydrocarbon fuels (kerosene) operating at flight Mach numbers about 5 has become the bottleneck preventing scramjet engine from continuing development. Research showed that the use of endothermic hydrocarbon fuels is not only necessary for engine cooling but also a critical measure for improving engine thrust and performance. Changes of thermo-physical-chemical characteristics of endothermic fuels during heat absorption make additional contributions to the combustion performance which is essential to the scramjet net thrust. Currently, the technology of experimental simulation and measurement is still lagging behind the needs. The complete duplication or true similarity of atmospheric flight environment, engine size and test duration remains impossible. Therefore, computational fluid dynamics (CFD) has become an important tool besides experiment. However, numerical simulation of supersonic combustion encountered challenges which come from both turbulence and chemical kinetics as well as their interaction. It will inevitably affect the proper assessment of the engine performance. Several frontiers of research in this developing field are pointed out: mode transition in the dual-mode scramjet, active cooling by endothermic hydrocarbon fuel with catalytic cracking coupled with supersonic combustion, combustion stability, experimental simulation and development of test facilities, measurements of the inner flow-field characteristics and engine performance, turbulence modeling, kerosene surrogate fuels and reduced chemical kinetic mechanisms, and so on. Also, directions for future research efforts are proposed and suggestions for the next 5-10 years are given.
- supersonic combustion /
- hypersonic propulsion /
- scramjet /
- endothermic hydrocarbon fuel /
- combustion stability /
- mode transition

HTML全文

参考文献(106)

[1]	Anderson G, Kumar A, Erdos J. 1990. Progress in hypersonic combustion technology with computation and experiment. AIAA 1990-5254.
[2]	Baker R T K. 1996. Coking problems associated with hydrocarbon conversion processes, ACS, Division of Fuel Chemistry, 41: 521-524.
[3]	Ben-Yakar A, Hanson R K. 2001. Cavity flame-holders for ignition and flame stabilization in scramjet: An overview, Journal of Propulsion and Power, 17: 869-877.
[4]	Bezuidenhout J J, Schetz J A, Walker D G. 2001. Heat flux determination using surface and backface temperature histories and inverse methods. AIAA 2001-3530.
[5]	Billig F S. 1988. Combustion processes in supersonic flow. Journal of Propulsion and Power, 4: 209-216.
[6]	Brandstetter A, Rocci Denis S, Kau H-P, Rist D. 2002. Experimental investigation of supersonic combustor with strut injector. AIAA 2002-5242.
[7]	Chen J Y. 2011. Development for reduced mechanism for numerical modeling of turbulent combustion. in: Proceedings of the Numerical Aspects of Reduction in Chemical Kinetics. Marne, France: Sept.
[8]	Choi J J, Menon S. 2009. Large eddy simulation of cavity-stabilized supersonic combustion. AIAA 2009-5383.
[9]	Choi J Y, Y V, Ma F H, Won S H, Jeung I S. 2007. Detached eddy simulation dynamics in scramjet combustion. AIAA 2007-5027.
[10]	Colket M B, Spadaccini L J. 2001. Scramjet fuels autoignition study. Journal of Propulsion and Power, 17: 315-323.
[11]	Curran E T, Murthy S N B. 2001. Scramjet Propulsion. Reston: AIAA 2000 Cutmark E, Schadow K C, Parr T P, Parr D M, Wilson K J. 1989. Combustion enhancement by axial vortices. Journal of Propulsion and Power, 5: 555-560.
[12]	Daguat P, Cathonnet C. 2006. The ignition, oxidation, and combustion of kerosene: A review of experimental and kinetic modeling. Progress in Energy and Combustion Science, 32: 48-92.
[13]	Dooley S, Won S H, Heyne J, Farouk T I, Ju Y G, Dryer F L, Kumar K, Hui X, Sung C J, Wang H W et al. 2012. The experimental evaluation of a methodology for surrogate fuel formulation to emulate gas phase combustion kinetics phenomena. Combustion and Flame, 159: 1444-1466.
[14]	Drummond J P. 1991. Mixing enhancement of reacting parallel fuel jets in a supersonic combustor. AIAA Paper, 1991-1914.
[15]	Edwards T. 2003. Liquid fuel and propellant for aerospace propulsion: 1903-2003. Journal of Propulsion and Power, 19: 1089-1107.
[16]	Edwards T. 1996. Research in Hydrocarbon Fuels for Hypersonics.
[17]	Erik Axdahl, Ajay Kumar. 2012. Study of forebody injection and mixing with application to hypervelocity airbreathing propulsion. AIAA Paper, 2012-3924.
[18]	Falempin F, Serre L. 2002. LEA flight test program-A first step towards an operational application of high-speed airbreathing propulsion. AIAA 2002-5249.
[19]	Fan X J, G Li, J G, Yue L J, Zhang, X Y, Sung C J. 2007a. Effects of entry conditions on cracked kerosene-fueled supersonic combustor performance. Combustion Science and Technology, 179: 2199-2217.
[20]	Fan X J, Yu G, Li J G, Lu X N, Sung C J. 2007b. Performance of supersonic model combustors with distributed injection of supercritical kerosene. AIAA 2007-5406.
[21]	Fan X J, Yu G, Li J G, Lu X N, Sung C J. 2006. Catalytic cracking of supercritical aviation kerosene. AIAA 2006-4868.
[22]	Fan X J, Yu G, Li J G, Lu X N, Zhang X Y, Sung C J. 2007c. Combustion and ignition of thermally cracked kerosene in supersonic model combustors. Journal of Propulsion and Power, 23:317-324.
[23]	Fan X J, Yu G, Li J G, Zhang X Y, Sung C J. 2004. Performance of a supersonic model combustor using vaporized kerosene injection. AIAA 2004-3485.
[24]	Fan X J, Yu G, Li, J G. 2005. Flow rate analyses and calibrations of kerosene cracking for supersonic combustion. AIAA 2005-3555.
[25]	Fan X J, Zhong F Q, Yu G, Li J G, Sung C J. 2009. Catalytic cracking and heat sink capacity of aviation kerosene under supercritical conditions. Journal of Propulsion and Power, 25: 1226-1232.
[26]	Fan X, Zhong F Q, Yu G, Li J G, Sung C J. 2008. Catalytic cracking of china No.3 aviation kerosene under supercritical conditions. AIAA 2008-5130.
[27]	Ferri A, Libby P A, Zakkay V. 1962. Theoretical and Experimental Investigation of Supersonic Combustion. NewYork: Polytechnicinst of Brooklyn.
[28]	Fetterhoff T, Bancroft S, Burfitt W, Hawkins W, Schulz R. 2009. Enabling technologies for an integrated approach to high speed/hypersonic systems test. AIAA 2009-7271.
[29]	Fuller R P, Wu P-K, Nejad A S, Schetz J A. 1998. Comparison of physical and aerodynamic ramps as fuel injectors in supersonic flow. Journal of Propulsion and Power, 14:135-145.
[30]	Garrard D, Seely J, Abel L. 2006. An analysis of alternatives to provide a varying Mach number test capability at APTU. AIAA 2006-8044.
[31]	Genin F, Menon S. 2004. LES of supersonic combustion of hydrocarbon spray in a scramjet. AIAA 2004-4132.
[32]	Georgiadis N J, Yoder Dennis A, Vyas M A, Engblom William. 2011. Status of turbulence modeling for hypersonic propulsion flowpaths. AIAA 2011-5917.
[33]	Goldfeld M, Nestoulia R, Falempin F. 2002. The direct measurement of friction in the boundary layer at supersonic flow velocities. AIAA Paper, 2001-1769.
[34]	Goyne C P, McDaniel J C, Krauss R H, Whitehurst W B. 2007. Test gas vitiation effects in a dual-mode scramjet combustor. Journal of Propulsion and Power, 23: 559-565.
[35]	Gruber M, Carter C, Ryan M, Rieker G B, Jeffries J B, Hanson R K, Liu J W, Mathur T. 2008. Laser-base measurements of OH, temperature, and water vapor concentration in a hydrocarbon-fueled scramjet. AIAA 2008-5070.
[36]	Guy Norris. 2013. High speed strike weapon to build on X-51 flight. Aviation Week & Space Technology.
[37]	Guy Norris. 2011. X-51A scramjet fails on second attempt. Aviation Week & Space Technology.
[38]	Heiser W H, Pratt D T. 1994. Hypersonic Airbreathing Propulsion, Washington D C, AIAA Education.
[39]	Huang H, Sobel D R, Spadaccini L J. 2002. Endothermic heat-sink of hydrocarbon fuels for scramjet cooling. AIAA 2002-3871.
[40]	Ianovsky L S, Sosounov V A, Shikhman, Y M. 1993. Endothermic fuels for hypersonic aviation. in: Proceedings on Fuels and Combustion Technology for Advanced Aircraft Engines. Fiuggi, Italy: AGARD. May, 1993: 1-8.
[41]	Jacobsen L S, Gallimore S D, Schetz J A, O'Brien W F. 2001. An integrated aeroramp-injector/plasma-igniter for hydrocarbon fuels in a supersonic flow. I Experimental studies of the geometric configuration. AIAA 2001-1766.
[42]	JANNAF Airbreathing Propulsion Subcommittee Meeting, CPIA Publ. 654, 1: 17--26. Chemical Propulsion Information Agency, Laurel, MD.
[43]	Jensen J, Braendlein B. 1996. Review of the Marqardt dual mode Mach 8 sramjet development. AIAA 96-3037.
[44]	Johansen C T, McRae C D, Danehy P M, Gallo E, Cantu L, Magnotti G, Cutler A D, Rockwell R D, Goyne C P, McDaniel J C. 2012. OH PLIF visualization of the UVa supersonic combustion experiment: Configuration A. AIAA 2012-2887.
[45]	Jonathan S G, Kenneth U Yu. 2012. Experimental characterization of isolator shock train propation. AIAA 2012-5891.
[46]	Kay I W. 1992. Hydrocarbon-fueled ramjet/scramjet technology program: Phase 2 extension final. NASA, 1-7794.
[47]	Kay I W, Peschke W T, Guile R N. 1992. Hydrocarbon-fueled scramjet combustor investigation. Journal of Propulsion and Power, 8: 507-512.
[48]	Kirchhartz R M, Mee D J, Stalker R J. 2008. Skin friction drag with boundary layer combustion in a circular combustor. AIAA 2008-2589.
[49]	Ladeinde F, Alabi K, Ladeinde T, Davis D, Satchell M, Baurle R A. 2010. CFD enhancements for supersonic combustion simulation with VULCAN. AIAA 2010-6876.
[50]	Lander H, Nixon A C. 1971. Endothermic fuels for hypersonic vehicles. Journal of Aircraft, 8: 200-207.
[51]	Law C K, Sung C J, Wang H, Lu T F. 2002. Development of comprehensive detailed and reduced reaction mechanisms for combustion modeling. AIAA Paper 41: 1629-1646.
[52]	Le D B, Goyne C P, Krauss R H. 2008. Shock train leading-edge detection in a dual-mode scramjet. Journal of Propulsion and Power, 24: 1035-1041.
[53]	Li F, Yu X L, Gu H B, Zhao Y, Lin M, Chen L H, Chang X Y. 2011. Simultaneous measurements of multiple flow parameters for scramjet characterization using tunable diode-laser sensors. Applied Optics, 50: 6697-6707.
[54]	Li J G, Yu G, Zhang Y, Li Y, Qian D X. 1997. Experimental studies on self-ignition of hydrogen/air supersonic combustion. Journal of Propulsion and Power, 13: 538-542.
[55]	Li J, M F H, Yang V, Lin K C, Jackson T A. 2007. A comprehensive study of ignition transient in an ethylene-fueled scramjet combustor. AIAA 2007-5025.
[56]	Li L, Wang J, Fan X J. 2012. Development of integrated high temperature sensor for simultaneous measurement of wall heat flux and temperature. Review of Scientific Instruments, 83: 074901.
[57]	Lin K C, Tam C J, Eklund D R Jackson K R, Jackson T A. 2006. Effect of temperature and heat transfer on shock train structures inside constant-area isolators. AIAA 2006-817.
[58]	Lin K C, Tam C J, Jackson K R, Eklund D R, Jackson T A. 2006. Characterization of shock train structures inside constant-area isolator of model scramjet combustor. AIAA 2006-816.
[59]	Lindstedt R P, Maurice L Q. 2000. Detailed chemical-kinetic model for aviation fuels. Journal of Propulsion and Power, 16: 187-195.
[60]	Mathur T, Eklund D, Jackson T, Gruber M, Powell O, Donbar J. 2001. Post-test analysis of flush-wall fuel injection experiments in a scramjet combustor. AIAA 2001-3197.
[61]	Maurice L, Edwards T, Griffiths J. 2000. Liquid hydrocarbon fuels for hypersonic propulsion. Scramjet propulsion, Reston, VA, American Institute of Aeronautics and Astronautics, Inc., 2000, 757-822.
[62]	Mawid M A, Park T W, Sekar B. Arana C. 2004. Importance of surrogate JP-8/Jet-A fuel in detailed chemical kinetics development. AIAA Paper, 2004-4207.
[63]	McClinton C R, Anderson G Y. 1980. Evaluation of bulk calorimeter and heat balance for determination of supersonic combustor efficiency. Washington D C, NASA Scientific and Technical Information Branch.
[64]	Mehravaran K, Afshari A, Jaberi F A. 2011. Large eddy simulation of turbulent combustion via filtered mass density function. AIAA 2011-5745.
[65]	Melissa A C, Darius D S, O'Brien W F, Schetz J A. 2003. Operation of a plasma torch for supersonic combustion application with a simulated cracked JP-7 feedstock. AIAA 2003-6935.
[66]	Mercier R, McClinton C. 2003. Hypersonic propulsion-transforming the future of flight. AIAA 2003-2732.
[67]	Micka D J, Driscoll J F. 2009. Combustion characteristics of a dual-mode scramjet combustor with cavity cavity flameholder. Proceedings of the Combustion Institute, 32: 2397-2404.
[68]	Micka D J, Driscoll J F. 2008. Reaction zone imaging in a dual-mode scramjet combustor using CH-PLIF. AIAA 2008-5071.
[69]	Montgomery P A Garrard Doug. 2005. Test and evaluation of hypersonic aeropropulsion systems along flight trajectories in a time-varying flight environment. AIAA 2005-3900.
[70]	Morrison C Q, Campbell R L, Edelman R B, Jaul W K. 1997. Hydrocarbon fueled dual-mode ramjet/sramjet concept evaluation. ISABE, 1997-7053.
[71]	Murthy S N B, Curran E T. 1991. High-Speed Flight Propulsion Systems. Washington D. C.: AIAA.
[72]	Nedungadi A, Van Wie D M. 2004. Understanding isolator performance operating in the separation-shock mode. AIAA 2004-3832% Norris R B. 2001. Freejet test of the AFRL HySET scramjet engine model at Mach 6.5 and 4.5. {AIAA Paper, 2001-3196.
[73]	O'Byrne S, Danehy P M, Tedder S A, Culter A D. 2007. Dual-pump coherent anti-stokes Raman Scattering measurements in a supersonic combustor. AIAA Journal, 45: 922-933.
[74]	Peebles C. 2011. Eleven Seconds into the Unknown: A History of the Hyper-X Program. Reston, AIAA.
[75]	Peebles C. 2008. Road to Mach 10: Lessons Learned From the X-43a Flight Research Program. Reston, AIAA. Rasmussen C C, Driscoll J F. 2008. Blow out of flames in high-speed airflow: critical damkohler number. AIAA. 2008-4571.
[76]	Rasmussen C C, Driscoll J F, Hsu K-Y, Carter C D, Gruber M R, Donbar J M. 2004. Blowout limits of supersonic cavity-stabilized flame. AIAA 2004-3660.
[77]	Rasmussen C C, Driscoll J F, Hsu K-Y, Donbar J M, Gruber M R, Carter C D. 2005. Stability limits of cavity-stabilized flames in supersonic flow. in: Proceedings of the Combustion Institute. 30: 2825-2833.
[78]	Rhode M N, DeLoach R. 2005. Hypersonic wind tunnel calibration using the modern design of experiments. AIAA 2005-4274.
[79]	Riggins D W, McClinton C R. 1991. Analysis of losses in supersonic mixing and reaction flows. AIAA 1991-2266.
[80]	Seiner J M, Dash S M, Kenzakowski D C. 2001. Historical survey on enhanced mixing in scramjet engine. Journal of Propulsion and Power, 17: 1273-1286.
[81]	Smith C, Garrard D, Frank J. 2006. The future and way forward for the aerodynamic and propulsion test unit. AIAA 2006-8049.
[82]	Sullins G A. 1993. Demonstration of mode transition in a scramjet combustor journal of propulsion and power. Journal of Propulsion and Power, 9: 515-520.
[83]	Sung C J, Li J G, Yu G, Law C K. 1999. Chemical kinetics and self-ignition in a model supersonic hydrogen-air combustor. AIAA Journal, 37:208-214.
[84]	Thakur A, Segal C. 2004. Flameholding analyses in supersonic flow. AIAA 2004-3831.
[85]	Tishkoff J M, Drummond J P, Edwards T, Nejad A S. 1997. Future direction of supersonic combustion research: Air Force/NASA workshop on supersonic combustion. AIAA Paper, 1997-1017.
[86]	Tomioka S, Izumikawa M, Kouchi T, Matsuo A, Hirano K. 2007. New injector geometry for penetration enhancement of perpendicular jet into supersonic flow. AIAA 2007-5028.
[87]	Violi A, Yan S, Eddings E G, Sarofim A F, Granata S, Faravelli T, Ranzi E. 2002. Experimental formulation and kinetic model for JP-8 surrogate mixtures. Combustion Science and Technology, 174: 399-417.
[88]	Vyas M A, Engblim W A, Georgiadis N J, Trefny C J, Bhagwandin V A. 2010. Numerical simulation of vitiation effect on a hydrogen-fueled dual mode scramjet. AIAA 2010-1127.
[89]	Weber R J, MacKay J S. 1958. An Analysis of Ramjet Engines Using Supersonic Combustion. Washington D C, National Advisory Committee for Aeronautics.
[90]	Wickham D T, Alptekin G O, Engel J R, Karpuk M K. 1999. Additives to reduce coking in endothermic heat exchangers. AIAA 1999-2215.
[91]	Wiese D E. 1992. Thermal management of hypersonic aircraft using noncryogenic fuels. SAE Transactions, 100: 1313.
[92]	Yang S R, Zhao J R, Sung C J, Yu G. 1999. Multiplex CARS measurement in supersonic H-2/air combustion. Applied Physics B, 68: 257-265.
[93]	Yu G, Fan X J, Li J G, Yue L J, Zhang X Y, Sung C J. 2006. Experimental study on combustion of thermally-cracked kerosene in model supersonic combustors. AIAA Paper 2006-4514.
[94]	Yu G, Fan X J, Li J G, Zhang X Y, Sung C J. 2005. Assessment of supersonic combustor performance through the use of vaporized kerosene injection. AIAA 2005-3399.
[95]	Yu G, Fan X, Li J G, Zhang X Y, Yue L J, Sung C J. 2005. Characterization of a supersonic model combustor with partially-cracked kerosene. AIAA 2005-3714.
[96]	Yu G, Li J G, Chang X Y, Chen L H, Sung C J. 2003. Fuel injection and flame stabilization in a liquid-kerosene-fueled supersonic combustor. Journal of Propulsion and Power. 19: 885-893.
[97]	Yu G, Li J G, Chang X Y, Chen L H, Sung C J. 2001. Investigation on combustion characteristics of kerosene-hydrogen dual fuel in a supersonic combustor. Journal of Propulsion and Power, 17: 1262-1272.
[98]	Yu G, Li J G, Chang X Y. 2003. Investigation of vaporized kerosene injection in a supersonic model combustor. AIAA 2003-6938.
[99]	Yu G, Li J G, Yue L J, Zhao J R, Zhang X Y. 2002. Characterization of kerosene combustion in supersonic flow using effervescent atomization. AIAA 2002-5225.
[100]	Yu G, Li J G, Zhang X Y, Chen L H, Sung C J. 2000. Investigation on combustion characteristics of kerosene-hydrogen dual fuel in a supersonic combustor. AIAA 2000-3620.
[101]	Yu G, Li J G, Zhang X Y, Sung C J. 2006. Investigation of vaporized kerosene injection and combustion in a supersonic model combustor. AIAA 2003-6938.
[102]	Yu G, Li J G, Zhang X, Chen L, Han B, Sung C J. 2002. Experimental investigation on flame holding mechanism and combustion performance in hydrogen-fueled supersonic combustor. Combustion Science and Technology, 174: 1-27.
[103]	Yu G, Li J G, Zhao J R, Yue L J, Chang X Y, Sung C J. 2005. An experimental study of kerosene combustion in a supersonic model combustor using effervescent atomization. in: Proceedings of the Combustion Institute, 30: 2859-2866.
[104]	Zhong F Q, Fan X J, Yu G, Li J G, Sung C J. 2010. Performance of supersonic model combustors with staged injection of supercritical aviation kerosene. Acta Mechanica Sinica, 26: 661-668.
[105]	Zhong F Q, Fan X J, Yu G, Li J G, Sung C J. 2008. Heat transfer of aviation kerosene at supercritical conditions. Journal of the Thermophysics and Heat Transfer, 23: 543-550.
[106]	Zhong F Q, Fan X J, Yu G, Li J G. 2009. Thermal cracking of aviation kerosene for scramjet applications. Sci China Ser E-Tech Sci, 52:2644-2652.