CFD Analysis of the Combustion of Hydrogen in a Simulated Two Dimensional Scramjet Engine

Abstract

The purpose of this research is to accurately simulate combustion in a scramjet engine using a CFD (Computational Fluid Dynamics) software package called Fluent and to validate the results with existing experimental data from NASA Langley Research Center[1]. The use of a particular engine characteristic called compression ramp injection was used to increase the mixing of air and fuel inside the combustion duct as well as provide the necessary compression of the fuel/air mixture. The duct length and other pertinent dimensions were also determined by published data from NASA [1]. The engine model used is relatively small and, at this stage, can be thought of as a two dimensional combustor duct rather than a true engine. The scope of this project involves the simultaneous calculations and analysis of both combustion and high-speed compressible flow. Thermodynamic data was used to create hydrogen fuel in a Fluent module called prePDF (probability density function), which calculates the look-up tables and chemical reactions for the fuel. Non-premixed combustion at Mach 2 was carried out using various equivalence ratios, (ratio of actual fuel/air mixture to stoichiometric fuel/air mixture) ranging from .4 to 1.4. The basic characteristics of the numerical model are as follows: steady state; non-premixed combustion; hydrogen fuel PDF model with 4 species; k-epsilon viscous model. Results of the numerical analysis include a comparison of combustion efficiencies for various equivalence ratios to the combustion efficiencies and equivalence ratios obtained by NASA in their experimental ground test facility at Langley Research Center [1].