Design and Part Load Performance Simulation of Natural Gas Combined Cycle with New Operating Regulation for Gas Turbine

The design and part load performance simulation of a natural gas combined cycle power plant (CCPP) is of great importance and is affected by various load regulation strategies during operation. In this work, a new regulation strategy with inlet air cooling (IAC) system integration is proposed for CCPP load regulation and performance assessment. The regulation strategy uses an IAC system and gas turbine inlet temperature (TIT/T4) named as IAC-T4, which is little different from the concept of inlet air heating (IAH) regulation. The analysis is performed using a simulation program and compared with inlet guide vane (IGV-T4) regulation to predict the behaviour of CCPP during part load operation. The result shows that the IAC-T4 regulation strategy reasonably enhance the part load performance. The efficiency increment is in the range of 0.25–1.02% with variation of load from 80 to 100%. The drop-in fuel consumption rate varies 0.53–2.02% for load reduction from 80 to 50%. The variation of topping cycle exergy efficiency for both the regulation strategies is between 7.9 and 8.2% under full load and part load. Whereas for both the control strategy the bottoming cycle efficiency variation was found to be 36.11–37.15% with a steam temperature limit of 564 °C. Moreover, it is observed that the topping cycle exerts a substantial impact in the CCPP performance for the IAC-T4 regulation strategy compared with IGV-T4 regulation strategy. The heat recovery steam generator (HRSG) exergy efficiency variation for both the strategy is relatively small, as the heat exergy of GT exhaust recovered effectively for all load cases. In conclusion, this study attempts a new approach for CCPP load regulation and part load thermal performance enhancement using IAC system integration.