RANS simulation of a gas turbine combustor with complex geometry is performed. The turbulence is modelled using a two-equation approach. The scalar mixing and combustion is modelled using a flamelet based approach for partially premixed combustion. In this approach transport equations to described scalar mixing and reacting fields and their statistical interactions are solved along with standard conservation equations. The boundary conditions are specified using measured values. The computed spatial variations of averaged temperature and dry mole fractions of various scalars, including CO and NOx, compared quite well with measured values. The results of this combustion model are compared to the eddy-dissipation-concept (EDC) model commonly used for gas turbine combustion calculation and this comparison showed that the results of partially premixed combustion model is improved considerably.

Combustion oscillation of a self excited combustion-acoustic phenomenon occurs inside the gas turbine combustor. In general, excessive pressure fluctuation of combustion oscillation may impair the gas turbine engine operation and may result in hardware damages. Therefore, combustion oscillation has been one of the problems of the gas turbine development. In this paper, for predicting combustionacoustic instability on the designing stage, we have developed one-dimensional linear instability analysis method and verified the analysis accuracy by premixed combustor laboratory tests. The phase lag between combustion dynamics and acoustic system is considered to affect whether combustion acts to destabilize the whole system. Heat release fluctuation is considered to be influenced from fuel/air ratio fluctuation, which generates at fuel nozzle position and flows to combustion region. Its advection delay time is one of the important parameters in the instability. Further, even if heat source itself is steady, the heat release can fluctuate because gas flow rate fluctuates acoustically, and as results, combustion-acoustic instable can occur. At this mechanism, the flame position and the reaction delay time have important roles. By theoretical discussions and laboratory verifications, we conclude that analysis models of this paper have captured the basic framework needed to predict combustion-acoustic instability.

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