Research On Diesel Engine Piston Heat Transfer Coefficient Analysis And Test Method

In the working process of diesel engines,the thermal load characteristics of pistons in direct contact with high-temperature and high-pressure gas are the key research content in diesel engine predictive design and load characteristics analysis.At present,the finite element simulation analysis technology is the main technical means for the research of piston thermal load.As one of the important boundary conditions in the finite element calculation,the heat transfer coefficient of the piston surface will directly affect the accuracy of the final calculation results.In this paper,for the purpose of "accurately calculating the heat transfer coefficient of each surface of the piston",four parts of research contents are completed,including the analysis and calculation of the heat transfer process of the piston,the design of the test system,the analysis of the temperature field and the heat flux field of the piston,and the calculation and analysis of the heat transfer coefficient of the piston surface.According to the heat transfer formula,the calculation method of piston heat conduction process is deduced,and the piston model is simplified.The calculation method of the heat transfer coefficient at this point is calculated by the finite difference method and Newton’s cooling formula,and the calculation process is used to determine the calculation process.The grid size should be adjusted to 0.4mm.According to the characteristics of the transient temperature field of piston and the requirements of data acquisition in heat transfer calculation,the test scheme and real-time data wireless transmission scheme for the transient temperature measurement of piston surface are designed and developed.The hardware and various sensors of the test system are introduced in detail,and the verification test is carried out for each part of the system,and the prototype test is finally completed.The temperature field on the piston surface is calculated by the finite element analysis of the diesel engine piston,and the finite element model is modified by the measurement results of the transient test.The steady-state temperature field,transient temperature field,heat flux density field and axial temperature distribution of the piston are analyzed.The three-dimensional distribution of transient heat transfer coefficient on the gas side of the piston is solved and analyzed.The heat transfer coefficient of other surfaces is analyzed,and the calculation method of heat transfer coefficient on each surface is determined.Based on the PA6 diesel engine,the woschni formula and seal formula are modified,and the accurate empirical formula based on the model is determined.Through the summary of the research scheme in this paper,because the scheme does not depend on the structural parameters of the piston alone,it is also suitable for the determination of heat transfer coefficient of different types of diesel engine piston and other parts of combustion chamber,which provides an effective solution for the accurate determination of heat transfer coefficient of piston surface.