Large eddy simulation and proper orthogonal decomposition analysis of turbulent flows in a direct injection spark ignition engine:Cyclic variation and effect of valve lift  

作　　者：QIN WenJin XIE MaoZhao JIA Ming WANG TianYou LIU DaMing 

机构地区：[1]School of Energy and Power Engineering, Dalian University of Technology [2]State Key Laboratory of Engines, Tianjin University

出　　处：《Science China(Technological Sciences)》2014年第3期489-504,共16页中国科学（技术科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.51176020 and 51376029)

摘　　要：Large eddy simulation(LES)is used to calculate the in-cylinder turbulent flow field in a direct injection spark ignition(DISI)engine.The computations are carried out for three different maximum valve lifts(MVL)and throughout 100 consecutive engine cycles.The simulated results as well as corresponding particle image velocimetry(PIV)measurement database are analyzed by the proper orthogonal decomposition(POD)method.Through a new developed POD quadruple decomposition the instantaneous in-cylinder flow fields are decomposed into four parts,named mean field,coherent field,transition field and turbulent field,respectively.Then the in-cylinder turbulent flow characteristics and cycle-to-cycle variations(CCV)are studied separately upon the four part flow fields.Results indicate that each part exhibits its specific characteristics and has close connection with others.The mean part contains more than 50%of the total kinetic energy and the energy cascade phenomenon occurs among the four part fields;the coherent field part possesses the highest CCV level which dominates CCV of the bulk flow.In addition,it is observed that a change in MVL affects significantly the in-cylinder flow behavior including CCV,especially for the coherent part.Furthermore,the POD analysis demonstrates that at least 25 sample cycles for the mean velocity and 50 sample cycles for the RMS velocity are necessary for obtaining converged and correct results in CCV.

关 键 词：in-cylinder flow TURBULENCE proper orthogonal decomposition（POD） large eddy simulation cycle-to-cycle variations（CCV） 

分 类 号：TK402[动力工程及工程热物理—动力机械及工程]