Effect of the Unmixedness of Unburned Gases on the Pressure Fluctuations in a Dump Combustor

Abstract

Combustion instability is a serious obstacle for the lean premixed combustion of gas turbines and can even cause fatal damage to the combustor and the entire system. Thus, enhanced understanding of the mechanisms of combustion instability is necessary for designing and operating gas turbine combustors. In this study, in order to elucidate the instability phenomena, an experimental study was conducted in a rearward-step dump combustor with LPG and air. The fuel supply conditions and the mixing distances ( L fuel) between fuel and air are used as experimental parameters to examine the effects of fuel modulation and unmixedness. The fluctuations of pressure, heat release, and equivalence ratio were measured by a piezoelectric pressure sensor and a high speed intensified charge coupled device (ICCD) camera, respectively. The unmixedness was measured by acetone laser induced fluorescence (LIF) at nonreacting flow because of stratification of the fuel in air. Various combustion modes occurred in accordance with...