Study On Cycle Parameter Optimization For Intercooled Recuperated Turbofan Engine And Design Method For Intercooler And Recuperator

Lower fuel consumption,reduced emissions and less noise have become the key drivers for technological innovation in the fields of civil aero-engine technology.In addition to the continuous technology improvement to the conventional aero-engine,all sorts of new aero-engine concepts of energy conservation and environmental protection have drawn more and more attentions.The intercooled recuperated turbofan engine(IRT)is a representative of the new aero-engine concepts.Compared with the conventional turbofan engine,matching the thermodynamic cycle parameters for the IRT is much more complex,due to the introduction of the intercooler and recuperator.And to a great extent,the designs of the intercooler and recuperator have a decisive role on the performance improvements of the IRT.Therefore,the method of matching and optimizing the engine parameters and the design method for the intercooler and recuperator are the key issues of the IRT technical research.This dissertation focuses on the two key issues,and the research work is conducted at three levels.The first level is about models and methods.In this level,the IRT thermodynamic cycle calculation and analysis method was studied,so was the design and optimization method of the intercooler and recuperator used for aero-engine.The second level is about tools and instruments.In this level,two computer programs were developed: one was for aero-engine conceptual design,and could be used to calculate and analyze the IRT performance;the second was used to design and optimize a variety of configurations of intercooler and recuperator.The third level is about calculation and analysis.Based on the results of the first two levels,three aspects of investigation were conducted in this level,namely,IRT cycle parameter matching and optimization,choice of performance parameters for the intercooler and recuperator,and IRT characteristic analysis.In the level of models and methods,the following three aspects of research work were conducted.Firstly,it made clear about the essence of the intercooled recuperated cycle technology to improve the engine performance through thermodynamic cycle analysis and exergy analysis for the IRT.The essence is that,the intercooling process and the recuperation process can improve the operation of the engine components,and eventually improve the thermodynamic cycle of the turbofan engine.It can reduce the consumption of compression work in the high pressure compressor,and at the same time,reduce the energy loss caused by engine exhaust waste heat.And then,how to implement the intercooled recuperated cycle on the turbofan engine was analyzed,considering the traits of the aero-engine in the structure,theway of energy utilization and the operation environment.It made clear about the structural features of the IRT,especially the arrangement of the intercooler and recuperator in the engine.Secondly,the related models and methods of the IRT were studied.The models and methods include aerothermodynamics models of engine and its components,NOX emission prediction method,engine dimension prediction method,engine weight prediction method,and aircraft mission model.Besides,the conceptual design process of the IRT was proposed.Thirdly,a new method of design and optimization of the intercooler and recuperator used in the IRT was established.The method was to combine the heat exchanger matrix performance calculation method and the differential evolution algorithm to solve the intercooler and recuperator optimum design problem.In the aspect of heat exchanger matrix performance calculation method,heat transfer and flow losses calculation method of the heat exchanger matrix were studied,as well as the empirical correlations of surface characteristic for different flow patterns.In the aspect of differential evolution algorithm,a modified differential evolution algorithm was developed to solve the mixed integer nonlinear programming problem.In the level of tools and instruments,two sets of numerical simulation program on the C++ platform were developed.The first one was a program used to calculate and analyze the IRT performance.It was developed according to the requirements of IRT conceptual study and preliminary design.The calculation accuracy and the functions of the program could meet the requirements of the engine parametric analysis and conceptual design.And the program has been used in the study of IRT cycle parameters matching.The second one was a program used to design and optimize the intercooler and recuperator for aero-engine applications.Heat transfer and flow losses calculation method of the heat exchanger and the modified differential evolution algorithm were combined in the program.And it could provide technical support for the intercooler and recuperator optimum design.In the level of calculation and analysis,the following research work was carried out based on the methods and programs developed in the former two levels.NASA N+1 AGTF was chosen as the baseline engine.Firstly,investigation of matching and optimizing the design point thermodynamic cycle parameters of the IRT was carried out.By doing parametric study,the rules of matching the IRT design point parameters were obtained.Secondly,the most suitable matrix configuration as well as its arrangement was chosen for the intercooler and the recuperator,respectively.The results were obtained through the analysis of the matrix performance parameters between the different intercooler and recuperator configurations.Based on it,the optimum matching of the intercooler effectiveness and the recuperator effectiveness was analyzed for the aircrafts with different take-off weight and different flight mission.Thirdly,in order to evaluate the IRT off-design performance,the characteristics of the IRT were calculated and analyzed with altitude velocity and throttling.In addition,the effects of the variable area fan nozzle and the variable geometry low pressure turbine on the engine characteristics were investigated.Finally,with N+1 ASAT as the background aircraft,the conceptual design of the IRT and its intercooler and recuperator has been conducted using the above methods.And the engine parameters have been compared between the IRT and the conventional turbofan engine.The parameters include the exergy loss,the specific thrust,the specific fuel consumption,the engine size,the engine weight,the NOX emission,and so on.The results indicate that,the intercooler and recuperator can operate normally and the IRT performance can meet the requirements of the aircraft in the whole flight envelope.Compared with the baseline conventional cycle turbofan engine,the specific fuel consumption of the IRT is reduced significantly.However,the introduction of the intercooler and recuperator will cause the engine weight increasing dramatically.And it will offset the benefits of lower specific fuel consumption to some extent.So,developing the light-weight high-strength intercooler and recuperator is of great significance to the IRT to be engineering practical.