Experimental study of unsteady heat release in an unstable single element Lean Direct Injection (LDI) gas turbine combustor
Abstract
In an effort to curb emissions from gas turbine engines, many low emission engine concepts have been developed. Among the most promising of these is the LDI (Lean Direct Injection). These systems operate at relatively low equivalence ratios close to blowout and are prone to instabilities. Combustion instabilities can reduce the life of the combustor by causing large pressure fluctuations and enhanced heat release to the walls of the combustor and reduce the efficiency of the engines. The understanding of combustion instabilities is vital to the implementation of such systems. Combustion instabilities are studied in an self-excited single element gas turbine combustor that uses an LDI element for fuel injection at elevetaed chamber pressures. The LDI combustor uses a swirler to ensure mixing of the air and the fuel and expansion of the swirl through a pressure swirl venturi to create a swirl stabilized flame. This project aims to study the heat release modes that occur in the combustor through measurement of light emissions from the flame using photodiodes that are sensitive to wavelengths of light produced by the flame. These are used along with high frequency pressure transducers. The focus is on the flame behavior in the diverging section of the venturi where the swirl is expanded and the flame starts since optic access cannot be obtained in this section. The use of photodiodes also facilitates the study of hydrodynamic modes that occur in the combustor alongside the thermoacoustics. A section which could accommodate the photodiodes was designed and installed on the LDI test rig in the Gas Turbine Cell at Maurice J Zucrow Propulsion Labs at Purdue University. The combustor was tested with this section and dynamic data was obtained from the pressure transducers and the photodiodes for a range of inlet air temperatures and range of equivalence ratios for each inlet air temperature. The dominant instability modes in both sets of data were analyzed and are presented in this document. The dominant heat release modes share similarities but often differ from the dominant pressure modes observed. The data also indicated the presence of azimuthal modes and suggested the presence of a PVC (precessing vortex core) although a definite PVC mode was not picked up by the photodiode data. Overall, the testing was successful and the heat release modes could be analyzed from the photodiode data but a complete picture could not be obtained due to noise and heating issues in the photodiodes which limited the amount of data that could be obtained.
Degree
M.S.M.E.
Advisors
Lucht, Purdue University.
Subject Area
Aerospace engineering|Mechanical engineering|Sustainability
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.