Numerical Simulation of Mixing and Combustion of a Hydrogen Fueled Scramjet combustor using Strut Injectors

A major problem in supersonic combustion is the short residence time of the fluid inside the combustor due to high flow velocities. Thus techniques for mixing enhancement have to be used to achieve a fast and efficient fuel-air mixing. In the present project work, different types of strut fuel injectors are investigated numerically, mainly strut with circular injector, strut with planer injector and strut with alternating wedge injector. The combustor and strut dimensions are same as DLR Scramjet model. It consists of a divergent channel with a flame – holding, wedge shaped structure in the middle of the flow field from the base of which hydrogen is injected. Study of mixing and combustion enhancement has been performed for a Mach 2 and Fuel (hydrogen) is injected at supersonic speed of Mach 1. The simulations have been performed using FLUENT. Standard k-? model has been used for modeling turbulence and single step finite rate chemistry has been used for modeling the H2-Air kinetics. k- ? model is based on a finite volume discretization of the continuity, momentum, energy equations. Numerically predicted profiles of static pressure, axial velocity, turbulent kinetic energy and static temperature for both non-reacting as well as reacting flows are compared with each other models. For the purpose of validation, the k-? results are compared with experimental data. In addition, qualitative comparisons are also made between predicted and measured shadowgraph images. It was found that mixing and combustion with a less flow-disturbing strut was considerably worse than those with a more flow-disturbing strut. Additionally, changes are caused within the shock-wave/expansion wave pattern at the injector exit that has an important influence on loss in total pressure