Experimental Investigation of Self Sustained Lean Premixed Prevaporized Combustion Instabilities by Phase Averaged Laser Diagnostic Techniques.

Combustion;Aerospace Engineering;Engineering;Aerospace Engineering

Temme, Jacob Edwin GerkenIhme, Matthias ;

University of Michigan

关键词: Combustion;    Aerospace Engineering;    Engineering;    Aerospace Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/95931/temme_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Interest in NOX pollution reduction has led to novel combustion techniques includingLean Premixed Prevaporized (LPP) combustion. However, LPP combustionis inherently prone to instabilities which can lead to gas turbine engine blowout andengine component failure. While these instabilities previously have been studied insimple laboratory burners, there is a need to show the connection between these labscales and the instabilities that occur when a realistic, commercial LPP multi-swirlfuel injector is operated with Jet-A fuel at elevated pressures, temperatures andmass flow rates (such as in the present study). In order to investigate the combustioninstabilities in an LPP combustor, a realistic test rig was modified to test twosimilar commercial LPP fuel injectors using liquid Jet-A fuel at high pressures andhigh pre-heat temperatures. Three groups of instabilities were identified based onthe frequency of the pressure oscillations in the combustion chamber: high frequency(>250 Hz), low frequency (50-200 Hz), and very low frequency (<50 Hz). The lowfrequency and very low frequency oscillations were further investigated through theuse of simultaneous high speed video and pressure data. Additionally, the flow fieldduring the low frequency instability was measured through phase averaged particleimage velocimetry (PIV). These results show that the flame has a large scale responseat both types of frequencies. The low frequency instability was determined to be aHelmholtz bulk mode due to equivalence ratio oscillations from the oscillating airflow through the injector. The very low frequency instability was determined to bea flashback / blowout phenomenon near the lean blowout limit. A mathematicalmodel was proposed which predicts the frequency of the very low frequency instability.The findings of this thesis with regard to the source of combustion instabilitiesprovide data which can guide future studies in this area and designs of advanced,low polluting gas turbines.