Numerical Investigation of Combustion in a Gaseous Bipropellant Rocket Engine

Bipropellant rocket engines remain central to space exploration and the advancement of propulsion technology, offering the high performance and operational flexibility required for both launch vehicles and in-space applications. The growing shift toward sustainable, environmentally friendly propellants has intensified research into the precise modeling and understanding of combustion processes. In this scenario, small-scale rocket engines have proven to be indispensable research tools, providing cost-effective and adaptable platforms to investigate complex combustion phenomena and injector configurations while maintaining the fundamental physical characteristics of full-scale systems. Within this scope, a modular 200N-class bipropellant rocket engine platform, utilizing gaseous oxygen and methane as its baseline propellants, has been designed, developed, and manufactured. To characterize the internal combustion dynamics of this system, an extensive numerical campaign was performed. A three-dimensional Reynolds-Averaged Navier-Stokes (RANS) Computational Fluid Dynamics (CFD) model, employing a non-premixed flamelet formulation and the Shear Stress Transport (SST) turbulence model, was developed and subsequently validated against established reference data from the literature. The simulation results demonstrate strong agreement with existing studies regarding global performance parameters and primary combustion features. This validated 3D framework was then implemented as the primary numerical tool for analyzing the combustion process within the 200N-class engine. Specifically, the influence of injector design was examined while maintaining a constant chamber geometry, enabling a detailed evaluation of how propellant mixing affects flame structure, thermal distribution, and overall engine efficiency. The findings confirm that high-fidelity 3D simulations are not only essential for model validation but are also critical for conducting the detailed flow analysis and performance trend assessments required to optimize small-scale bipropellant propulsion systems.