Modeling Of Multi-shaft Gas Turbine Powered By Medium And Low Heating Value Fuels

Due to its low investment, short construction period, high power generation efficiency, prompt start-up and stop, flexible load regulation characteristics, gas turbine has always been the hot spots of the power generation technology research. Natural gas or light diesel is usually used as design fuel for gas turbine. Changing to burn medium and low heating value fuel will face flow matching problem due to the low heating value. Aero derivative gas turbine generally adopts multi-shaft design.The speed of compressor can be adjusted, so it is thought to have a more flexible regulation performance when burning low heating value fuel.For LM2500gas turbine and QD128gas turbine, multi-shaft gas turbine models are built in gPROMS@in this paper. Based on the models, the change of gas turbine thermodynamic performance is calculated when burning several low heating value fuels, and the influence of several flow adjustment methods on the gas turbine performance and flow ability is compared. Based on the gas turbine models, thermodynamic performance of fuel humidified and steam injected combined cycle is studied. The main contents in this paper include:1. The modeling of thermodynamic performance of QD128three-shaft gas turbine fired by different fuelsThermodynamic performance of QD128three-shaft gas turbine when burning low heating value fuel is evaluated. The paper analyses the influence of the reduction of the fuel calorific value on compressor pressure ratio, compressor surge margin, turbine gas inlet mass flow-rate and turbine exhaust temperature, gas turbine power and efficiency. The results show that keeping T3constant, when burning low heating value of5MJ/kg syngas, the turbine gas flow-rate increases by about18%, gas turbine output power increases by about33%, compressor total pressure ratio increases by about18%, high pressure compressor surge margin decreased by about20%, low pressure compressor surge margin decreased by about10%. Focusing on the problem of compressor surge and flow match, the influence of flow matching methods, including increasing turbine flow area, decreasing T3temperature, extracting air from compressor, on the gas turbine power, efficiency and compressor surge margin is analyzed. In the end, an integrated flow matching scheme is proposed.2. The modeling of thermodynamic performance of LM2500two-shaft gas turbine fired by different fuels Based on compressor map model, simplified equation model and turbine constant model, turbine map model, gas turbine model is established. The paper analyzes gas turbine performance changes when burning medium and low heating value fuel and the influence of different flow adjustment on gas turbine thermodynamic performance to meet maximum power limit and compressor surge margin. The results show that keeping T3constant, when burning low heating value of5MJ/kg syngas, the turbine gas flow rate increases about by22%, gas turbine output power increases by about32%, compressor pressure ratio increases by about20%, compressor surge margin decreases by about14.5%. The flow adjustment scheme is proposed to meet the limit of maximum power and compressor surge margin.3. Fuel humidified and steam injected combined cycle based on multi-shaft gas turbine powered by medium or low heating value fuelsBased on QD128three-shaft gas turbine and LM2500two-shaft gas turbine models, the models of single pressure heat recovery boiler, dual pressure heat recovery boiler combined cycle and steam injected, fuel humidified combined cycles are established. Furthermore, the thermodynamic performance of them are calculated and compared. The results show that the efficiencies of fuel humidified combined cycles based on both three-shaft gas turbine and two-shaft gas turbine are higher than those of steam injected combined cycles when the steam content in the fuel is equal.