It is well known that, unlike the thermal efficiency of closed gas turbine cycles, the thermal efficiency of open gas turbine cycles varies with the fuel used in the combustion process. Presented in this paper is a thorough investigation of the effects of hydrocarbon fuels and alcohol fuels on the thermal efficiency of open gas turbine cycle. Among the open cycles with different fuels and otherwise identical specifications, the computed thermal efficiencies show a variation of about 2 percent between the extremes, which is appreciable. It was found that the thermal efficiency increases with a parameter of the fuel, c1 + c2, taken from the equation of reaction,  
c(Fuel)+O2c1(CO2)+c2(H2O),
and that the thermal efficiency of open gas turbine cycles is likely to be higher if the original fuel is replaced by a fuel which has a higher fuel parameter, c1 + c2. A universal correlation for both hydrocarbon fuels and alcohol fuels is presented in Fig. 1, plotting the thermal efficiency maximized from the pressure ratio variation, versus the parameter, c1 + c2. Alternatively, this correlation is also generalized by equation (2).
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