Optimization of oxygen-kerosene gas generator mixing processes

Arkhipov P.A., Bulat P.V., Renev M.E. Optimization of oxygen-kerosene gas generator mixing processes. Scientific and Technical Journal of Information Technologies, Mechanics and Optics, 2026, vol. 26, no. 3, pp. 597–606 (in Russian). doi: 10.17586/2226-1494-2026-26-3-597-606

The study presents optimization results aimed at improving fuel–oxidizer mixing while preserving the operational characteristics of a liquid rocket engine combustion chamber. Traditional chamber design methods described in classic textbooks are based on semi-empirical procedures intended primarily for high-thrust engines delivering several tens of tons of thrust. There is now a growing demand for commercial launch vehicles of the light and ultralight classes. Given the tight size, mass, and energy budgets of small liquid engines, particular attention is paid to the compactness and reliability of injector assemblies. The work addresses the design and optimization of the injector head to achieve optimal mixing at a standoff from the injector faceplate sufficient to minimize its thermal load. Computational fluid dynamics is applied with combustion, heat transfer, species transport, and radiation. To account for the liquid phases of oxygen and kerosene and to represent their velocities in the injectors correctly, a pseudo-gas equation of state is used. Injector throttling characteristics are computed in ANSYS. Global parametric optimization (particle swarm method) is performed over injector angles, diameters, and layout. “NASA CEA” equilibrium calculations are used to validate output parameters. The developed optimization technique reduces combustion chamber dimensions by nearly a factor of two. Combining computational fluid dynamics of mixing and combustion with optimization algorithms enables preliminary design optimization before prototype fabrication, thereby lowering development and manufacturing costs. Compared with common approaches — parametric sweeps, gradient optimization based on simplified correlations, design of experiments, and manual tuning through test campaigns — the method relies on coupled flow and heat-transfer calculations with a fast pseudo-gas model and automatic selection of injector geometry by criteria of mixture uniformity and combustion stability. This reduces the number of physical iterations, improves spray uniformity, and lowers thermal stresses on components. Application areas of the suggested method: injector heads for small- and medium-thrust liquid engines, gas generators, and ignition chambers of test stands. Prospects of the method: accounting for unsteady oscillations and acoustics, optimization under uncertainties, integration of additive manufacturing constraints, and automated channel synthesis.

1. Melkumov T.M., Melik-Pashayev N.I., Chistyakov P.G., Shiukov A.G. Rocket Engines. Moscow, Mashinostroenie Publ., 1976. 400 p. (in Russian)

2. Dobrovolsky M. Liquid Rocket Engines: Fundamentals of Design. Moscow, Bauman Moscow State Technical University Publ, 2016, 460 p. (in Russian)

3. Radhakrishnan K., Ha D.H., Lee H.J. Effect of multicoaxial injectors on nitrogen film cooling in a GCH4/GO2 thrust chamber for small-scale methane rocket engines: a CFD study. Aerospace, 2024, vol. 11, no. 9, pp. 744. doi: 10.3390/aerospace11090744

4. Zhuravlev V.Y., Manokhina E.S., Tolstopiatov M.I. Design and testing of injectors manufactured using additive technologies for a low-thrust liquid rocket engine. Siberian Aerospace Journal, 2025, vol. 26, no. 1, pp. 83–93. doi: 10.31772/2712-8970-2025-26-1-83-93

5. Liu J., Zhang S., Wei J., Haidn O.J. Numerical study of film cooling in single-element injector gaseous CH4/O2 rocket engine with coupled wall function. AIP Advances, 2024, vol. 14, no. 3, pp. 035330. doi: 10.1063/5.0178273

6. Yasuda K., Nakata D., Uchiumi M., Okada K., Imai R. Fundamental study on injector flow characteristics of self-pressurizing fluid for small rocket engines. Journal of Fluids Engineering, 2021, vol. 143, no. 2, pp. 021307. doi: 10.1115/1.4048688

7. Xie Y., Zhang J., Sun M., Wu J., Li P., An B., et al. Review on spray characteristics of liquid–liquid injectors in liquid rocket engines. Physics of Fluids, 2024, vol. 36, no. 9, pp. 091302. doi: 10.1063/5.0223894

8. Adams N.A., Schröder W., Radespiel R., Haidn O.J., Sattelmayer T., Stemmer C., Weigand B. Future space-transport-system components under high thermal and mechanical loads. results from the DFG collaborative research center TRR40. Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 2021, vol. 146, 419 p. doi: 10.1007/978-3-030-53847-7

9. Boccaletto L., Dussauge J.-P. High-performance rocket nozzle concept. Journal of Propulsion and Power, 2010, vol. 26, no. 5, pp. 969–979. doi: 10.2514/1.48904

10. Farmer R., Cheng G., Chen Y.-S., Garcia R. CFD simulation of liquid rocket engine injectors. Rocket Combustion Modeling, 2001.

11. Shi J., Hui Z., Zhou L., Wang Z., Liu Y. A Numerical investigation of film cooling under the effects of different adverse pressure gradients. Aerospace, 2024, vol. 11, no. 5, pp. 365. doi: 10.3390/aerospace11050365

12. Zhang X., Qiao W., Gao Q., Zhang D., Yang L., Fu Q. Experimental study on the dynamic characteristics of gas-centered swirl coaxial injector under varying ambient pressure. Aerospace, 2023, vol. 10, no. 3, pp. 257. doi: 10.3390/aerospace10030257

13. Bulat P.V., Musteikis A.I., Prodan N.V., Renev M.E., Volkov K.N. Simulation of intra-chamber processes in a low-thrust rocket engine with a hydrogen-air mixture and counterflow cooling. Acta Astronautica, 2024, vol. 225, pp. 243–251. doi: 10.1016/j.actaastro.2024.09.029

14. Bösenhofer M., Wartha E.-M., Jordan C., Harasek M. The Eddy dissipation concept—analysis of different fine structure treatments for classical combustion. Energies, 2018, vol. 11, no. 7, pp. 1902. doi: 10.3390/en11071902

15. Wang T.-S. Thermophysics characterization of kerosene combustion. Journal of Thermophysics and Heat Transfer, 2001, vol. 15, no. 2, pp. 140–147. doi: 10.2514/2.6602

16. Ghanbari M., Ahmadi M., Lashanizadegan A. A comparison between Peng-Robinson and Soave-Redlich-Kwong cubic equations of state from modification perspective. Cryogenics, 2017, vol. 84, pp. 13–19. doi: 10.1016/j.cryogenics.2017.04.001

17. Soave G.S. Estimation of the critical constants of heavy hydrocarbons for their treatment by the Soave–Redlich–Kwong equation of state. Fluid Phase Equilibria, 1998, vol. 143, no. 1–2, pp. 29–39. doi: 10.1016/s0378-3812(97)00307-5

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License