Design/off-design performance simulation and discussion for the gas turbine combined cycle with inlet air heating

Abstract

A novel method for the combined cycle retrofitted with compressor inlet air heating (HEAT) process is proposed in this work for part load performance improvement. The performance of the new cycle is researched with two regulations with HEAT and compared with another two strategies with compressor inlet guide vane (IGV). For the novel method, the compressor inlet air is preheated by part of the exhaust flue gas from the heat recovery steam generator. Moreover, comparation result indicates that the novel strategy with HEAT to maintain design turbine inlet temperature (T3) and then to keep turbine exhaust temperature (T4) at its maximum value (HEAT-T3-T4) is suggested for load arrangement. If being compared with the cycle using IGV control to maintain design T3 then keep extreme T4 (IGV-T3-T4), a maximum combined cycle efficiency increment as 1.7% pt. could be obtained by the cycle with HEAT-T3-T4. Both energy analysis and exergy analysis are given in this paper. The simulation results indicate that higher compressor outlet temperature (T2) decreases the extra exergy destruction during combustion, so that the performance of the cycle with HEAT is improved. Meanwhile the specific work of each cycle has also been presented. Furthermore the pressure loss affection of the compressor inlet air heat exchanger on the combined cycle performance is investigated in range of 0%–5%. Each 1% pressure loss is calculated to decrease 1.4% on the design power output, and 0.25% pt. on the combined cycle efficiency, which will weaken the performance improvement. To summarize, this paper proposes a novel method for the combined cycle power output adjustment to obviously improve its part load efficiency. This innovative solution has never been suggested before and it could be combined with other methods for better result.