A Study On Integrated Optimization Of Airframe And Engine Parameters In Conceptual Design Of Airliners

In traditional optimization design of aircraft conceptual,only airframe parameters were optimized with the object of aircraft economic performance.However,aircraft cost,noise and emissions depend on not only the airframe parameters but also engine cycle parameters.The traditional method is unable to deal with the economic and environmental considerions in current airliner conceptual design.Therefore,in airliner conceptual design stage,there is a need to optimize airframe and engine cycle parameters simultaneously in order to meet the increasingly stringent economic and environmental requirements.A multidisciplinary analysis and optimization platform including aircraft and engine analysis modules was developed in this thesis.By using the platform,integrated analysis and optimization of airframe and engine cycle parameters of a wide body aircraft were investigated.The main contents of the thesis are summarized as follows:1)An engine analysis model with component features was developed to estimate engine thrust and fuel consumption,which is suitable for use in airliner conceptual design,and noise and emission calculations.An engineering empirical method was used to estimate the weight and size of engine.The engine analysis model was validated with available data of engine in service.2)A semi-empirical noise analysis model was developed to rapidly predict the aircraft noise level.The aircraft noise analysis process and the calculation of noise trajectory of takeoff and landing were presented.The noise calculation model of aircraft airframe,engine fan and jet is established by using latest semi-empirical methods.The effects of atmospheric absorption,ground absorption and reflection on noise level were also considered in the noise propagation model.3)An emission estimation model was established in order to calculate the pollutant emissions of engines.Empirical formula was used to calculate the emission of NO_x in take-off and landing cycle.Base on the Boeing fuel flow method,DLR method and P₃-T₃ method,the process of calculating NO_x,CO and HC emissions of the entire mission route were established.4)The engine,noise and emissions analysis models were integrated into the aircraft integrated analysis and optimization platform,and a new comprehensive platform for analysis and optimization of airframe and engine parameters was developed.The accuracy and efficiency of the engine analysis model,noise prediction model and emissions calculation model were verified by using the new platform.The results show that the errors of the calculated engine thrust characteristic in the ground,takeoff and landing performance,mission performance,noise level and LTO NO_x emissions are within 5%when compared with actual values,which indicates that the analysis models meet the accuracy requirements of aircraft conceptual design.5)The conceptual design of a wide body aircraft was used as an example to conduct comprehensive analysis and optimization of airframe and engine parameters in the new integrated analysis and optimization platform.The effects of engine bypass ratio on the aircraft economic and environmental performance were assessed firstly.The results show that the aircraft with the highest bypass ratio engine achieves the lowest noise and Landing-Takeoff NO_x emission.However,the aircraft with the engine of moderate BPR has the lowest operating cost.The effects of different optimization object on aircraft design and the tradeoff between economic with environmental performance were then studied.The results show that the total noise decreases by 10.4 dB while direct operating cost?DOC?increases by 13.15%from minimum DOC design to minimum noise design.The LTO NO_x emissions decrease by 39.47%while DOC increases by 2.19%from minimum DOC design to minimum LTO NO_x emissions design.With the consideration of the impact of actual airline operations,a multipoint optimization method was proposed.Then single-and multipoint optimizations of baseline wide body aircraft were carried out.The optimization results show that the fuel efficiency of entire route of the multipoint optimal design is higher than that of the single-point optimal design.6)Based on the analysis of the power demand estimation for both conventional system and more electric system of aircraft,the fuel benefit of the more electric system was evaluated using the integrated analysis and optimization platform.The results show that the block fuel of the aircraft with more electric system is 1.52%less than that of the conventional aircraft,and the takeoff weight of more electric aircraft reduces by 0.96%.