Research On Performance Simulation And Control Law Optimization Of Micro Recuperated Cycle Gas Turbine

Micro gas turbine has the advantages of high power density,low emission,fast start-up and simple maintenance.It can be widely used in distributed energy,special power and combat vehicle.It's a promising high-tech,integrated heat-power equipment.However,there are also technical bottlenecks of low thermal efficiency and off-design performance degradation in micro gas turbine.Recuperated cycle is an effective way to improve the thermal efficiency under all operating conditions.In this dissertation,two kinds of typical and widely used recuperated cycle gas turbine,namely,single-shaft gas turbine and three-shaft gas turbine with power turbine variable area nozzle(VAN),are taken as the research objects.Firstly,the recuperated gas turbine simulation model is studied to improve the convergence and real-time characteristics.Then,the refined recuperator modeling is carried out to improve recuperator simulation accuracy and dimension.On this basis,the performance simulation of single-shaft and three-shaft recuperated gas turbine is carried out respectively,and the optimized control law and optimized control strategy are obtained.Finally,the recuperated gas turbine overall performance chracteristics are analyzed;the influence of control parameters adjustment speed and recuperator thermal inertia on recuperated gas turbine transient state response is also researched,and the operation strategy is proposed to fastly achieve transient state control.The main contents and conclusions of this dissertation are as follows.(1)The recuperated gas turbine performance simulation programs are established based on MATLAB/m language.The simulation convergence of recuperated gas turbine,especially the three-shaft recuperated gas turbine with VAN is significantly improved as well as the real-time characteristics in transient state performance simulation.(2)Based on the heat transfer micro-element modeling method,a modified simulation model suitable for counter-flow,parallel-flow and cross-flow recuperator is proposed.The modified model indeed improves the simulation accuracy in severe operation condition and the temperature distribution along the flow direction is obtained resulting in higher simulation dimension.The modified model also has the potential of simulating recueprator internal leakage and longitudinal heat transfer effect.(3)The study on the performance of single-shaft recuperated gas turbine is carried out.The performance under constant speed control mode and variable speed control mode is compared,and the optimized variable speed control law is obtained.The results prove maintaining the turbine outlet temperature at the design value is the optimized control strategy to significantly improve the performance under all operating conditions.Further research shows that the recuperator performance degradation results in more serious gas turbine performance deterioration under variable speed control mode.(4)The study on the performance of three-shaft recuperated gas turbine with VAN is carried out.The performance under power turbine speed control mode and VAN angle control mode is compared.The internal mechanism of the coupling effect of VAN angle adjustment and recuperator on improving recuperated gas turbine performance is expounded,and the optimized combined control of shaft speed and VAN angle is obtained.Further research implies the optimized control strategy of single-shaft recuperated gas turbine also works in the three-shaft recuperated gas turbine.Under the optimized combined control,6.37%,15.88%,47.80% increase in output power,and 10.84%,25.59%,64.97% increase in thermal efficiency are gained when relative high-pressure shaft speed is 0.95,0.90 and 0.85,respectively.(5)The study on the overall characteristics of recuperated gas turbine is carried out,and recuperated gas turbine transient state response is analyzed.The results indicate that the recuperated gas turbine transient state response is mainly determined by the control parameters adjustment speed and recuperator thermal inertia.In single-shaft recuperated gas turbine,recuperator thermal inertia causes the hysteresis in the parameter change,which is easy to result in parameter overshoot.In the three-shaft recuperated gas turbine with VAN,the adjustment of fuel mass flow and VAN plays the decisive role in transient state response,while the effect of power turbine shaft speed adjustment is relatively small.Because of recuperator thermal inertia,the transient state response of recuperated gas turbine is divided into two regions: the fast response region and the lagging region.The fast control parameter adjustment is helpful to shorten the stable time,and the combined adjustment of fuel mass flow and VAN is helpful to realize fast transient state response of three-shaft recuperated gas turbine.