Evaluation of mass flowrate through an axial gas turbine stage using different computational methods

Abstract

Mass flowrate is very important, as it determines the frontal area, volume, size, and weight of the engine, and consequently, the momentum drag at certain flight conditions, specific fuel consumption, and the aircraft total loading. The mass flowrate is also needed to determine the shaft power and the thrust power developed by the engine when the specific work output is obtained. Different computational methods have been used in this research to find out their relative accuracy in determining the mass flow passing through an already designed, but not built, stage. The methods employed are free vortex variation of density using approximate scheme including mean radius, arithmetic average density, and numerical integration using the trapezoidal and Simpson's rule. Moreover, closed-form integration (theoretical) with free vortex, linear variation, and parabolic variation of density along the height of the blade was considered. The arithmetic average method was found to give the highest accuracy. The mean-radius method is the least accurate but the simplest. Hence, it is advised to be used especially in quick estimates. The difference in accuracy is not so great to justify using tedious and time-consuming methods.