Numerical simulation of horizontal fuel injection in supersonic air flow and investigation of the effect of the geometric shape of the wedge surface on mixing performance
Subject Areas : Journal of Simulation and Analysis of Novel Technologies in Mechanical Engineering
Mojtaba Zahedzadeh
1
,
َAshkan Ghafouri
2
*
1 - PhD Student, Department of Mechanical Engineering, Ahv.C., Islamic Azad University, Ahvaz, Iran
2 - Associate Professor, Department of Mechanical Engineering, Ahv.C., Islamic Azad University, Ahvaz, Iran
Keywords: Transverse injection, Supersonic flow, Mixing efficiency, Total pressure loss, Scramjet engine.,
Abstract :
One common method for fuel injection in scramjet engines is transverse fuel injection into a supersonic airflow. Given the extremely high air velocities and very short fuel residence time within the scramjet combustor, achieving efficient fuel-air mixing at these high speeds is a critical challenge. Consequently, research into fuel injection and dispersion is a pivotal aspect of scramjet engine design. This study numerically investigates transverse fuel injection into a supersonic airflow. This was achieved by solving the Reynolds-Averaged Navier-Stokes (RANS) equations coupled with the ideal gas equation of state and a two-equation turbulence model . Furthermore, the impact of three distinct fuel injection wedge surface geometries – flat, wavy, and serrated – was examined. Key parameters, including mixing efficiency and total pressure loss, were calculated and compared for these three configurations. The results demonstrate that the wedge surface geometry directly influences fuel injection performance. Specifically, the serrated wedge yielded the highest mixing efficiency (approximately 14.7%) compared to the flat (9%) and wavy (13.4%) wedges, primarily due to the generation of controlled disturbances. However, this increase in efficiency comes at the cost of elevated total pressure loss, reaching 8.4% for the serrated wedge. The numerical model was validated by comparing simulation results with experimental data, showing good agreement. This study indicates that optimal selection of the wedge geometry can establish a suitable balance between mixing efficiency and pressure loss in scramjet combustor design. The findings of this research can serve as a foundation for improving fuel injection system design in supersonic flow applications.
[1] Curran, E. T. (2001). Scramjet engines: The first forty years. Journal of Propulsion and Power, 17(6), 1138–1148.
[2] Lee, G. S., & Lee, T. (2024). Design and analysis of an ideal scramjet flowpath. Physics of Fluids, 36(3). [3] Voland, R. T., Huebner, L. D., & McClinton, C. R. (2006). X-43A hypersonic vehicle technology development. Acta Astronautica, 59(1–5), 181–191.
[4] Harsha, P., et al. (2005). X-43A vehicle design and manufacture. In AIAA/CIRA 13th International Space Planes and Hypersonics Systems and Technologies Conference.
[5] Wikipedia contributors. (n.d.). Wikipedia. Retrieved September 29, 2025, from https://www.wikipedia.org/.
[6] Hank, J., Murphy, J., & Mutzman, R. (2008). The X-51A scramjet engine flight demonstration program. In 15th AIAA International Space Planes and Hypersonic Systems and Technologies Conference. [7] Norris, G. (2013). X-51A waverider achieves hypersonic goal on final flight. Aviation Week, 2.
[8] Bendett, S., et al. (2021). Advanced military technology in Russia. Chatham House.
[9] Karnozov, V. (2020). Hypersonic Zircon missile from Russia now deployed to the Pacific. Asia-Pacific Defence Reporter, 46(3).
[10] Davy, J. J., et al. (2016). Skylon space plane. International Journal of Engineering and Science, 6(4), 71–77.
[11] Longstaff, R., & Bond, A. (2011). The SKYLON project. In 17th AIAA International Space Planes and Hypersonic Systems and Technologies Conference.
[12] Cau, R. (2024). Characterisation and simulation of reusable single-stage-to-orbit vehicles ascent phase during conceptual design. Politecnico di Torino.
[13] Anderson, J. D. (1989). Hypersonic and high temperature gas dynamics. AIAA.
[14] Rodriguez, D., et al. (2025). Conceptual design and optimization of a scramjet with ablative thermal protection. In AIAA AVIATION FORUM AND ASCEND 2025.
[15] Musielak, D., et al. (2022). Scramjet propulsion: A practical introduction. Wiley.
[16] Liu, Q., Baccarella, D., & Lee, T. (2020). Review of combustion stabilization for hypersonic airbreathing propulsion. Progress in Aerospace Sciences, 119, 100636.
[17] Heiser, W. H., & Pratt, D. T. (1994). Hypersonic airbreathing propulsion. AIAA.
[18] Urzay, J. (2018). Supersonic combustion in air-breathing propulsion systems for hypersonic flight. Annual Review of Fluid Mechanics, 50(1), 593–627.
[19] Tandon, R., et al. (2006). Ultra high temperature ceramics for hypersonic vehicle applications. Sandia National Laboratories (SNL), No. SAND2006-2925.
[20] Segal, C. (2009). The scramjet engine: Processes and characteristics (Vol. 25). Cambridge University Press.
[21] Ahmad, M. (2025). Advancements in the design and development of scramjet engine: An overview. International Journal of Aerospace System Science and Engineering, 1(2), 95–132.
[22] Liu, Y., et al. (2023). Microstructure and ablation mechanism of C/C-ZrC-SiC composite in the solid scramjet plumes environment. Materials Characterization, 198, 112754.
[23] Liu, G., et al. (2022). Effect of pre-swirl nozzle closure modes on unsteady flow and heat transfer characteristics in a pre-swirl system of aero-engine. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, 236(4), 685–703.
[24] Sodja, J. (2007). Turbulence models in CFD (pp. 1–18). University of Ljubljana.
[25] Cerminara, A., et al. (2025). Transpiration cooling in hypersonic flow and mutual effect on turbulent transition and cooling performance. Physics of Fluids, 37(2).
[26] Brune, A., et al. (2015). Variable transpiration cooling effectiveness in laminar and turbulent flows for hypersonic vehicles. AIAA Journal, 53(1), 176–189.
[27] Lin, T., & Bywater, R. (1982). Turbulence models for high-speed, rough-wall boundary layers. AIAA Journal, 20(3), 325–333.
[28] Tian, G. (2023). Active flow control and its applications in supersonic boundary layer. In Boundary Layer Flows—Advances in Experimentation, Modelling and Simulation. IntechOpen.
[29] Delnero, J., et al. (2012). Active flow control upon cavities at low Reynolds numbers. In 6th AIAA Flow Control Conference.
[30] Le Clainche, S., et al. (2023). Improving aircraft performance using machine learning: A review. Aerospace Science and Technology, 138, 108354.
[31] Ahuja, V., & Hartfield, R. (2009). Optimization of fuel-air mixing for a swept ramp scramjet combustor geometry using CFD and a genetic algorithm. In 45th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit.
[32] Fureby, C., et al. (2025). Large-eddy simulation of supersonic combustion in a Mach 2 cavity model scramjet combustor. AIAA Journal, 63(1), 219–232.
[33] Burdette, G., Lander, H., & McCoy, J. (1978). High-energy fuels for cruise missiles. Journal of Energy, 2(5), 289–292.
[34] Martel, C. R. (1987). Military jet fuels, 1944–1987. Aero Propulsion Laboratory, Air Force Wright Aeronautical Laboratories, Air Force Systems Command, United States Air Force.
[35] Li, F., et al. (2013). Plasma-assisted ignition for a kerosene fueled scramjet at Mach 1.8. Aerospace Science and Technology, 28(1), 72–78.
[36] Anderson, C. D., & Schetz, J. A. (2005). Liquid-fuel aeroramp injector for scramjets. Journal of Propulsion and Power, 21(2), 371–374.
[37] Edwards, T. (2002). “Kerosene” fuels for aerospace propulsion—Composition and properties. In 38th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit.
[38] Killi, S., & Injeti, G. (2024). Feasibility of integrating cryogenic propulsion for next generation missiles for enhanced range, stealth and strategic capabilities. Acceleron Aerospace Journal, 3(7), 764–784.
[39] Brewer, G. D. (2017). Hydrogen aircraft technology. Routledge.
[40] Clarke, J., et al. (2023). Cryogenic hydrogen jet and flame for clean energy applications: Progress and challenges. Energies, 16(11), 4411.
[41] Abdelhameed, E., Okamoto, K., & Watanabe, Y. (2024). Numerical study on hydrogen mixing for different scramjet engine combustion chamber configurations. In International Exchange and Innovation Conference on Engineering & Sciences.
[42] Alff, F., et al. (1994). Supersonic combustion of hydrogen/air in a scramjet combustion chamber.
[43] Mohammad, A. K., et al. (2022). Assessing the sustainability of liquid hydrogen for future hypersonic aerospace flight. Aerospace, 9(12), 801.
[44] Choubey, G., et al. (2020). Hydrogen fuel in scramjet engines—a brief review. International Journal of Hydrogen Energy, 45(33), 16799–16815.
[45] Jin, Y., et al. (2021). Effect of nano-sized aluminum additive on wall heat transfer characteristics of the liquid-fueled scramjet engine. Applied Thermal Engineering, 197, 117387.
[46] Küçükosman, R., Yontar, A. A., & Ocakoglu, K. (2022). Nanoparticle additive fuels: Atomization, combustion and fuel characteristics. Journal of Analytical and Applied Pyrolysis, 165, 105575.
[47] Xiong, Y., et al. (2020). Influence of water injection on performance of scramjet engine. Energy, 201, 117477.
[48] Sislian, J., & Schumacher, J. (1999). Fuel/air mixing enhancement by cantilevered ramp injectors in hypersonic flows. In 14th ISABE International Symposium on Air Breathing Engines, Florence, Italy.
[49] Choubey, G., et al. (2021). Numerical investigation on mixing improvement mechanism of transverse injection based scramjet combustor. Acta Astronautica, 188, 426–437.
[50] Aravind, S., & Kumar, R. (2019). Supersonic combustion of hydrogen using an improved strut injection scheme. International Journal of Hydrogen Energy, 44(12), 6257–6270.
[51] Sislian, J. P., et al. (2000). Incomplete mixing and off-design effects on shock-induced combustion ramjet performance. Journal of Propulsion and Power, 16(1), 41–48.
[52] Bordoloi, N., et al. (2021). A review on the flame holding mechanisms used for the development of scramjet engines. Materials Today: Proceedings, 45, 7023–7030.
[53] Cao, R., & Yu, D. (2021). Parametric performance analysis of multiple reheat cycle for hydrogen fueled scramjet with multi-staged fuel injection. Thermophysics and Aeromechanics, 28(4), 583–594.
[54] Northam, G. B., et al. (1992). Evaluation of parallel injector configurations for Mach 2 combustion. Journal of Propulsion and Power, 8(2), 491–499.
[55] Rasheed, I., & Mishra, D. P. (2023). Supersonic combustor with parallel injection. In International Conference on Mechanical Engineering. Springer.
[56] Li, Z., et al. (2020). Influence of backward-facing step on the mixing efficiency of multi microjets at supersonic flow. Acta Astronautica, 175, 37–44.
[57] Vincent-Randonnier, A., Mallart-Martinez, N., & Labaune, J. (2024). Design of a plasma-assisted injector: Principle, characterization and application to supersonic combustion of hydrogen. International Journal of Hydrogen Energy, 88, 1410–1421.
[58] Verma, T., et al. (2025). Optimizing scramjet performance: Impact of curved strut walls on shockwave dynamics and fuel-air mixing. In AIAA SCITECH 2025 Forum.
[59] Atci, M., et al. (2025). Influence of cavity and ramp layout on combustion performance in a strut-based scramjet combustor. International Journal of Engine Research, 26(6), 915–933.
[60] Wendt, M., & Stalker, R. (1996). Transverse and parallel injection of hydrogen with supersonic combustion in a shock tunnel. Shock Waves, 6, 53–59.
[61] Sullins, G., Anderson, J., & Drummond, J. (1982). Numerical investigation of supersonic base flow with parallel injection. In 3rd Joint Thermophysics, Fluids, Plasma and Heat Transfer Conference.
[62] Oevermann, M. (2000). Numerical investigation of turbulent hydrogen combustion in a scramjet using flamelet modeling. Aerospace Science and Technology, 4(7), 463–480.
[63] Glawe, D., et al. (1994). Parallel fuel injection from the base of an extended strut into supersonic flow.
[64] Chenault, C. F., Beran, P. S., & Bowersox, R. D. (1999). Numerical investigation of supersonic injection using a Reynolds-stress turbulence model. AIAA Journal, 37(10), 1257–1269.
[65] Murty, M. C., Chakraborty, D., & Mishal, R. (2010). Numerical simulation of supersonic combustion with parallel injection of hydrogen fuel. Defence Science Journal, 60(5).
[66] Antony Athithan, A., & Jeyakumar, S. (2025). Reacting flow characteristics of wall-mounted ramps in strut-injection scramjet combustors under varying hydrogen jet pressures. Journal of Applied Fluid Mechanics, 18(4), 850–863.
[67] Zhou, Y., et al. (2024). Experiments investigation on atomization characteristics of a liquid jet in a supersonic combustor. Physics of Fluids, 36(4).
[68] Kumar, R., & Ghosh, A. (2025). Instability of isolator shocks to fuel flow rate modulations in a strut-stabilised scramjet combustor. The Aeronautical Journal, 129(1331), 42–62.
[69] Waidmann, W., et al. (1996). Supersonic combustion of hydrogen/air in a scramjet combustion chamber. Space Technology, 15, 421–429.
[70] Wilcox, D. C. (2006). Turbulence modeling for CFD. DCW Industries.
[71] Viti, V., Schetz, J., & Neel, R. (2005). Comparison of first and second order turbulence models for a jet/3D ramp combination in supersonic flow. In 43rd AIAA Aerospace Sciences Meeting and Exhibit.
[72] Mathieu, J., & Scott, J. (2000). An introduction to turbulent flow. Cambridge University Press.
[73] Shojaeefard, M. H., & M.T. (2012). An introduction to turbulent flows and its modeling. Tehran, Iran: Iran University of Science and Technology Press.
[74] Ansys, Inc. (2021). ANSYS FLUENT theory guide. Canonsburg, PA.
[75] Li, L.-q., Huang, W., & Yan, L. (2017). Mixing augmentation induced by a vortex generator located upstream of the transverse gaseous jet in supersonic flows. Aerospace Science and Technology, 68, 77–89.
[76] Zhao, M., et al. (2019). Large eddy simulation of transverse single/double jet in supersonic crossflow. Aerospace Science and Technology, 89, 31–45.
[77] Nair, P. P., Suryan, A., & Narayanan, V. (2024). Effect of upstream injection and pylon downstream of the cavity on the mixing characteristics. Physics of Fluids, 36(2).
[78] Malozemov, V., Omel'Chenko, A., & Uskov, V. (1998). The minimization of the total pressure loss accompanying the breakdown of a supersonic flow. Journal of Applied Mathematics and Mechanics, 62(6), 939–944.