Research on energy-saving and pollutants-reduction performance optimization of gas turbines based on combined variable geometry regulation

Current research on gas turbine energy-saving primarily focuses on the individual application of variable geometry technology, such as compressor variable inlet guide vanes (VIGV) or turbine variable area nozzles (VAN). However, the combined adjustment of VIGV and VAN allows for more comprehensive control of gas turbine operating states, offering greater potential for performance improvement. Additionally, the use of variable geometry technology for pollutant-emission reduction remains insufficiently explored. Therefore, this study conducts an in-depth investigation into the effects of combined variable geometry (CVG) regulation (VIGV&VAN) on enhancing thermal efficiency (ηt) and reducing pollutants under part-load conditions. A Non-dominated Sorting multi-objective evolutionary genetic algorithm III (NSGA-III) is used to develop a part-load performance optimization model for the LM2500+ gas turbine. The stagger angles of the power turbine and compressor guide vanes serve as optimization variables, while the ηt and pollutants as dual objectives, the optimization of the LM2500+ is performed. Based on the resulting Pareto-optimal front, the CVG Energy-Saving Strategy (CVG-ESS), CVG Emission-Reduction Strategy (CVG-ERS), and the CVG Balance Strategy (CVG-BS) are proposed. From 100 % to 40 % load, the CVG-ESS improves ηt by 0.03 %–1.77 % relative to the VAN energy-saving strategy. The CVG-ERS attains maximum pollutant-emission reductions of 45.75 % compared with the VIGV emission-reduction strategy and 34.69 % compared with the VAN emission-reduction strategy. The performance of the CVG-BS lies between CVG-ESS and CVG-ERS: relative to the CVG-ESS, pollutants are reduced by 24.01 %–11.33 %, with only a 1.07 %–4.07 % decrease in ηt, whereas compared with the CVG-ERS, ηt increases by 2.25 %–14.48 %, with only a 15.47 %–23.33 % increase in pollutants.