Performance Simulation Of Chemically Recuperated Gas Turbine Under Variable Working Conditions

Gas turbines have the advantages of small volume,light weight,good maneuverability,low vibration noise,long life span,stable operation and maintenance friendly.However,the economy efficiency of the gas turbine is not good enough,especially under low working conditions;and gas turbines have highNO_Xemissions.Chemically recuperated gas turbine(CRGT)has the advantages of gas turbine;and additionally,it has high recuperative effectiveness not limited by pressure ratio,little modification of prototype,high economy efficiency and environmental friendliness.Thus,CRGT is suitable for marine propulsion.However,in the area of marine propulsion,it is not sufficient for the study of the scheme confirmation and variable working conditions performance analysis because of the research blank of fuel-steam reforming,modelling of chemical recuperator and high efficiency plus compact structure.In this article,simulation method was used to perform thermodynamic design of CRGT scheme,thermodynamic parameters matching,operation scheme achieving and control manoeuvres formulating.All the works is of engineering and practical meaning for promoting the CRGT being applied in marine propulsion.(1)The energy and material conversion process in gas turbine systems was analyzed,and the method of equivalent heat value was proposed to obtain the energy recovery evaluation criteria of the advanced cycle gas turbine.On this basis,the combustor model and the method for calculation of thermophysical properties of working fluids of advanced–cycle gas turbine were built.(2)To build the prototype engine model,mathematical models of thermodynamic process of compressor and turbine were built.BP neural network(PSO-BP)which based on particle swarm optimization was used to predict characteristics of compressor under overall working conditions;and variable specific heat capacity was used to describe the thermodynamic processes of the compressor.Meanwhile,an improved ISO temperature method was taken up with to calculate the turbine expansion work with cooling air.The results show that it is of high fitting accuracy and precision for PSO-BP to predict the characteristics of compressor,and the improved ISO temperature method is also of high accuracy.On this basis,a prototype engine simulation program was built;and comparing with experimental data,calculation errors are smaller than 1.5%,which is suggested that the prototype engine model is suitable to the CRGT simulation.(3)A chemical regenerator model of compact structure,simple calculation and high reliability was built,with the consideration of the effect of coupling of heat transfer and steam reforming reaction of fuel.Methane-steam reforming experiments were performed;and the lowest Gibbs free energy method was used to calculate the reaction.Experiment results and calculation results have a good agreement.On this basis,thermal design of chemical regenerator was performed to establish the core module of CRGT,in order to ensure appropriate depth of reforming as the goal,after the modeling of the fuel-steam reforming reaction with the lowest Gibbs free energy method.(4)In order to meet the needs of high pressure steam in the CRGT,an efficient and compact steam generating system was designed,based on the principle of energy cascading utilization,with the core module of high-pressure flash.On this basis,the variable condition performance of the system was calculated;and the system running scheme was achieved.Results show that the steam output has a maximum which can meet the needs of high pressure steam in the CRGT and the value can be achieved mainly by adjusting the amount of water feed.In addition,with the dramatic changes of the gas parameters,the steam output and the temperature vary widely to result in system failure,when outgassing can be adopted to ensure smooth running of the system.(5)In order to deal with the long-term and complex study of the CRGT,object-oriented method was used to build the simulation platform of gas turbine system,based on the MFC framework.The module library for components of the CRGT was built,and interface was prepared for joining the future work.The simulation platform is convenient for schematic design and performance simulation of the CRGT.(6)Considering the requirements of the economics of marine power plant,weight and dimension specifications,three configuration programmes of CRGT were proposed.The system economy,environmental friendliness,stability and dynamic response properties of the three configurations were studied;and the appropriate option was selected.Three CRGT configurations are:simple CRGT systems(S-CRGT),back reheated CRGT system(BR-CRGT)and middle regenerative CRGT system(MR-CRGT).Comparative study results show that MR-CRGT has the highest economy.BR-CRGT has the best stability,and others also have good running stability.The CRGT systems have decrease dynamic response,compared with the prototype engine.MR-CRGT is selected as the research programme.(7)To obtain the best economic of the MR-CRGT as the target,major influence of operating parameters on the economics of the system was studied;and the running programmes and corresponding control manoeuvres were achieved.Results show that in the case of changes with oil supply,there are a corresponding best water supply and fuel distribution.According to the research,the best water supply and fuel distribution ratio to fuel supply running curves were drawed.The start and loading,unloading and changes of main performance parameters of the system shutdown process were researched;and the basic control manoeuvres of these processes were developed.