The Effect of Turbine Blade Cooling on the Cycle Efficiency of Gas Turbine Power Cycles

A thermodynamic cycle analysis computer code for the performance prediction of cooled gas turbines has been used to calculate the efficiency of plants with varying combustor outlet temperature, compressor pressure ratio, and turbomachinery polytropic efficiency. It is shown that the polytropic efficiency exerts a major influence on the optimum operating point of cooled gas turbines: for moderate turbomachinery efficiency the search for enhanced combustor outlet temperature is shown to be logical, but for high turbomachinery efficiency this is not necessarily so. The sensitivity of the cycle efficiency to variation in the parameters determining the cooling flow rates is also examined. While increases in allowable blade metal temperature and film cooling effectiveness are more beneficial than improvements in other parameters, neither is as important as increase in turbomachinery aerodynamic efficiency.