Analysis and design of a can combustor

Abstract

A Can combustor is a feature of gas turbine engine. Prediction of the performance of combustor becomes an integral part for the development of efficient combustor. Primary design objectives are to bum the fuel efficiently, keep the wall temperature as low as possible and minimize emissions such as NOx, Unburnt Hydrocarbon, etc. Some of the parameters that controls the performances of a combustor are fuel/air ratio, degree of turbulence, geometry of the primary air, flow rate of secondary air, etc. Efficient burning depends on how well the fuel and air are mixed before ignition which in tum depends on the degree of turbulence. To keep the wall temperature as low as possible, excess air with higher volume plays an important role, which affects the burning and the process becomes further complicated. To enhance the turbulence, different air injection patterns of primary air inlet are studied and the effect of secondary air injection is investigated. Some theoretical aspects are investigated using different reaction steps and ways of heat transfer. Fluent, a CFD software, is used for the simulation of the combustor applying k-c model for turbulence computation and eddy-dissipation model for studying reaction dynamics. Investigation revealed some important features of the performance of a Can combustor. Investigation revealed that increasing the angle of rotation of primary air inlet and percentage of excess air could reduce wall temperature as well as increase NOx production. It is found that injection of secondary air inlet reduces the wall temperature significantly. Applying the secondary air inlet in different position together reduces wall temperature more effectively along with efficient burning of methane in the combustor. It is also found that wall temperature was drastically reduced when radiation heat transfer is off and variation of reaction steps makes a very little effect on the performance.