Load-regulation characteristics of gas turbine combined cycle power system controlled with compressor inlet air heating

Abstract

Enhancing the peak-regulation performance of gas turbine combined cycle power units is significant in renewable energy accommodation. To improve the peak-regulation efficiency of the power units, the performance of the retrofitted system with compressor inlet air heating under alternative load-regulation strategies was comprehensively investigated. Three strategies were adopted, including inlet guide vane (IGV) control with constant turbine inlet temperature, IGV control with constant turbine exhaust temperature, and fuel flow control (FFC) to perform a comparative analysis of the system performance using a physical model, which was validated using a mathematical model. Operating charts of the retrofitted system were obtained and the effects of the compressor inlet air temperature on the power load rate were further investigated. The analysis indicates that FFC is preferred for gas turbines owing to the lowest exhaust temperature, and IGV control strategies are advantageous to the combined cycle power system owing to the performance improvement of the bottoming cycle. When the compressor inlet air is heated from 15 to 35 °C at the specific gross output of 320 MW, the gas turbine load rate increases by 4.16 and 3.01% under IGV control with constant turbine exhaust temperature and FFC, respectively, and the relative combined cycle power efficiency increases by 0.015 and 0.023, respectively. For a load power of 360 MW at the ambient temperatures of 5, 15 and 25 °C, the optimum outlet air temperature of the recuperator decreases from 32.0, 31.6 to 28.8 °C, respectively for IGV control with constant turbine exhaust temperature.