Numerical simulation of scramjet combustion

Abstract: This thesis work has been carried out partly in conjunction with the
Institute of Propulsion Technology of the German Aerospace Center,
DLR, in Cologne, Germany. The subject is simulation of fluid flow and
hydrogen combustion in a so-called scramjet engine. Scramjet is an
acronym for Supersonic Combustion Ramjet, a novel type of propulsion
device, interesting primarily for potential spaceflight applications. The
aim is to give an indication of how fluid flow and fuel combustion
proceed when both mixing and combustion are carried out at supersonic
speeds, and to provide a validation of two different solver packages for
fluid dynamical problems.

In this study, Reynolds-averaged Navier-Stokes models (RANS) have
been used to examine supersonic flow and combustion in a model
scramjet combustion chamber. The RANS-model is based on a finite
volume discretization of the continuity, momentum, energy and mixture
fraction equations. The configuration used is a model of a laboratory
scramjet combustor at the Institute for Space Propulsion at DLR. 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. Three different operational cases with varying degree of
complexity have been investigated. For the purpose of validation of the
simulation models the results are systematically compared with
experimental data for temperature, velocity and pressure at certain cross-
sections in the combustion chamber. Qualitative comparisons are also
made between the simulated flow fields and experimental schlieren and
shadowgraph fields.

The simulation codes used are ANSYS CFX and a solver program for
fluid dynamics and combustion chemistry developed by my supervisor at
DLR. Each simulation model is capable of predicting both the cold
supersonic flow and the reacting flow fields reasonably well, with some
quantitative inconsistencies for both models. Moreover, during the work
a previously undiscovered deficiency in the non-commercial code is
found, which leads to an appreciated improvement of the program.