Modeling syngas combustion performance of a can combustor with rotating casing for an innovative micro gas turbine

Abstract

This paper presents the numerical study of the casing rotation effects on the combustion performance of an innovative micro gas turbine for H2/CO syngas fuels. The study was conducted by a computational model consisting of three-dimension compressible k-ε realizable turbulent flow model and presumed probability density function (PPDF) for combustion process invoking a laminar flamelet assumption generated by detailed chemical kinetics from GRI 3.0. The rotating effects on the combustion characteristics of the can combustor were investigated with methane and two different syngas compositions. The two typical compositions of syngas were specified as H2-rich (H2/CO = 4 by molar ratio) and equal molar (H2/CO = 1) syngas. For methane combustion, when the casing was stationary, high-temperature flame stabilized in the core region, but it shrank and moved towards the wall of the combustor due to centrifugal effect as the casing started to rotate. As syngas was substituted for methane at the same fuel flow rate, the high-temperature flame then stabilized along the wall of the combustor. When casing rotated, pattern factor and exit temperature of the combustor increased, but the lower heating value of the syngas fuel caused a power shortage. In order to maintain the same thermal load, the fuel flow rate of the syngas was raised. Consequently, the high-temperature flame was pushed downstream due to increased fuel injection velocity. As a result, pattern factor rises, indicating severe temperature fluctuations at exit of the combustor. The design of the can combustor was then modified to better accommodation for syngas combustion application in the micro gas turbine.