Thermodynamic analysis of gas turbine performance using the enthalpy–entropy approach

Abstract

The enthalpy–entropy approach, which is a rigorous and accurate method, was used to model the actual cycle of a gas turbine (GT). The constructed GT C# programming language code was used to study the effects of ambient temperature (Tam), relative humidity (RH), and ambient pressure (Pam) on GT output parameters. The results of the GT modeling program showed that the maximum (minimum) difference in GT output power (PGT) was 1.12% (0.01%) at a Tam of 39.7 °C (23.3 °C) compared with the actual output power of El Atf power station. As Tam increased from 14 °C to 40 °C, the PGT decreased by 19.01% (18.38%) of nominal GT power (250 MW) at 15% (95%) RH while GT thermal efficiency (ηth) decreased by 2.3058% (2.4431%) and the specific fuel consumption (SFC) increased by 7.12% (7.59%). The PGT decreased by 0.1497% and 0.7674% with an RH increase from 15% to 95%, respectively. The PGT decreased by 0.03675 and 0.16835 MW while ηth decreased by 0.0047% and 0.0243% at Tam values of 15 and 40 °C, respectively, when Pam was decreased from 1.013 to 0.990 bar. Using the compressor assumptions of each stage increases the humid air pressure by the same value and the efficiency of each stage is the same and equal to the compressor overall efficiency is more logical and leads to accurate results. The compressor isentropic efficiency was not affected by the bleeding air percent according to the assumptions used.

Keywords

• Gas turbine
• Output power
• Thermal efficiency
• Enthalpy–entropy approach