Session: 04-10 Combustion V

Submission Number: 178057

Weak Extinction Limits of a Bluff Body Stabilised Flame With Low Momentum Ratio Liquid Fuel 

Bluff body wake stabilised combustion systems are used in aerospace gas turbine engines for thrust augmentation. Weak extinction performance in high Mach number flow is an important criterion in the design of these systems, along with total pressure loss, temperature profile, flame spreading, thrust augmentation ratio, and ignition performance. The Volvo equilateral triangle flame stabiliser has been the subject of a large body of experimental and numerical research including evaluating weak extinction limits, typically with premixed gaseous fuel. Current architectures use liquid kerosene injected upstream of the bluff body flameholder, but design constraints and increasing gas temperature have led to the injection moving closer to the flame holder resulting in increased coupling between the liquid fuel and the bluff body flame. At weak extinction, the momentum ratio of the jet in cross flow fuel injection is reduced providing a severely non-uniform fuel mixture. Existing correlations and stability envelopes are not suitable for predicting the stability envelope under these conditions. This paper presents weak extinction measurements of the Volvo triangular flame stabiliser fuelled from an upstream low momentum ratio fuel injector with liquid kerosene, but not sufficiently far upstream to fully premix. Weak extinction measurements are presented for two blockage ratios in a vitiated air stream at 600K and 800K inlet temperature up to a Mach number of 0.35. These data are compared to previous measurements taken with premixed gas to demonstrate the influence of using heterogeneous liquid fuel. Visible light imaging is compared with OH and CH chemiluminescence at a range of conditions demonstrating that fuel placement is far from premixed in this case and that a scaling of fuel distribution with bluff body width and fuel air ratio exists. At weak extinction, the fuel was shown to be concentrated within the bluff body recirculation zone. A modified chemical, evaporation and mixing time scale model was able to accurately predict the weak extinction of kerosene and propane fuelled combustors by accounting for the heterogeneous fuel placement offering a significant improvement to established correlations.

Presenting Author: Thomas Walker Loughborough University

Presenting Author Biography: Thomas is a senior research associate in the National Centre for Combustion and Aerothermal Technology at Loughborough University, UK. His research is focused on the aerothermal, heat transfer and combustion processes in aerospace gas turbine engines. His current work is measurement of combustion processes in high mach number, vitiated air streams.

Authors:

Thomas Walker Loughborough University
A. Duncan Walker Loughborough University
Jon Carrotte Loughborough University