The effect of variable gas property on axial turbine performance

Industrial gas turbine flow has been evaluated by using computational fluid dynamics with a variable gas property model. The study of a three-stage turbine model has revealed some considerable variable gas property effects on the engine performance. When the gas properties are made constant with respect to the first blade row conditions, the exit total temperature has been over-predicted by about 15 Kelvin. There is also an over-prediction of turbine power output of 0.6%. Simulations using a constant averaged gas property or the fixed value at the last blade row both over-predict the mass flow rate by 0.5% and 1% respectively. The predicted efficiency from the various simulations is found to be less influenced than the parameters discussed above, with a difference of merely 0.25%. The findings suggest that it is necessary to include the variable gas property effect in 3D calculations of practical industrial gas turbine flow.