| In order to mitigate the environmental pollution and energy shortage crisis,the researchers are not only committed to reducing the fuel consumption and emissions of the traditional internal combustion engine,but also explore new vehicle power plant of high efficiency,energy saving and low emission.The free-piston engine linear generator(FPELG)has developed under this background.The FPELG is composed of a free-piston engine and a linear generator,which can convert the chemical energy of the fuel into electric energy directly.Compared with the conventional engine(CE),the FPELG has the advantages of simple structure,low energy loss,high efficiency of energy conversion and multi-fuel adaptability because of the elimination of the crank mechanism.Therefore it has become one of the research hotspots in the power machinery field.Based on the prototype of the free-piston gasoline engine linear generator(FPGLG)built by the research group,the in-cylinder combustion and heat transfer characteristics of a spark-ignited FPELG fuelled by gasoline were studied by the method of three-dimensional numerical simulation and prototype tests.On the basis of this,the thermo-mechanical coupling finite element analysis of the FPGLG’s cylinder head was conducted.Firstly,the multidimensional coupling modeling of FPGLG was carried out.The zero-dimensional piston dynamic model built by Matlab/Simulink was used to simulate the FPGLG’s piston motion,and then the obtained piston displace curve was imported into the AVL/FIRE to establish the CFD combustion and scavenging models.The CFD combustion model with reasonable boundary conditions was acquired by adopting coupling iterations between the caculation results and the initial conditions of the three models.The CFD combustion model was validated by the prototype test data.Based on the three-dimensional CFD numerical simulation results,the difference of the combustion characteristics between FPGLG and conventional engine was studied,including the the gas flow characteristics,the performance parameters,the combustion heat release law and the combustion duration characteristics.In terms of the heat transfer,it was studied on the parametric regularity of the heat transfer process in the FPGLG simulated by the Han-Reitz wall heat transfer model.And the time-domain variation and the spatial distribution cahracteristics of the heat transfer parameters of the combustion chamber wall were analyzed.At last,the thermo-mechanical finite element analysis of the FPGLG’s cylinder head was carried out.The finite element modeling method of the thermo-mechanical coupling analysis was emphatically studied.By adopting the finite element analysis,the steady-state temperature distribution of the cylinder head was obtained and the influence of thermal load on the stress-strain level and sealing performance of the FPGLG was discussed. |
