Off-design performance of gas turbine power units with alternative load-control strategies

Gas turbine power units, as an effective way to cope with the severe challenge of renewable energy accommodation in power grids, arouse the interest of power enterprises in the deep peak-load regulation performance. Two common alternative load-control strategies including constant turbine inlet temperature (TIT) and constant turbine exhaust temperature (TET) regulations were taken into consideration. To comparatively investigate the part-load performance under these strategies, both mathematical and physical models were set up successively to serve as a validation and complementary to each other. For the mathematical model of compressor with inlet guide vane (IGV), combustor and turbine, stage-stacking method based on blade average geometric parameter, energy con-servation and turbine stage model were adopted respectively. For the physical model, design and off-design analysis were carried out based on GT PRO and THERMOFLEX respectively. The simulation result of mathematical model vali-dated the reliability of the physical model. Based on this, the influence of ambient temperature and different load-regulating strategies on the off-design performance of gas turbine power units was studied in THERMOFLEX. The results in the case of a PG 9351FA gas turbine show that the ambient temperature has a great impact on system performance, i.e., every 5°C increase in the ambient temperature pro-duces a reduction of 3.7% in the relative full-load output and 1.1% in the relative efficiency respectively; when the gas turbine operates under constant TIT strategy, TET starts to rise till it reaches the maximum allowable value with the load rate decreasing, and IGV keeps at the minimum angle with both TIT and TET decreasing when the load rate is lower than 65%; when the gas turbine operates under constant TET strategy, TIT drops slightly at load rate of above 60% while both TIT and TET evidently decrease below 60% load rate operating along the constant corrected speed line at the minimum allowable IGV opening; gas turbine efficiency is greatly affected by load rate and the performance degradation is more obvious especially in lower load rate regions; constant TET strategy is superior in the operating efficiency to constant TIT strategy under part-load conditions. © 2021, Tech Science Press. All rights reserved.