Study On The Measurement Of Friction Between Piston-cylinder Liner Assembly In Diesel Engine Under Combustion Operation

As the core component of combustion work of internal combustion engine,the friction and lubrication performance of piston-cylinder liner assembly directly affects the operation of the whole engine,and its friction loss accounts for 40%-50% of total mechanical friction loss of internal combustion engine.Therefore,the research on the friction and lubrication of piston-cylinder liner assembly has always been an important direction in the field of internal combustion engine.In order to study the friction and lubrication between piston-cylinder liner assemblies,it is necessary to accurately measure the friction between the components.Up to now,most of the researches on the friction measurement of the compression combustion engine remain in the non-combustion state,without considering the influence of combustion pressure and other factors on the piston-cylinder liner assembly.To this end,a new type of friction measuring machine is designed based on the floating cylinder liner method,and the real-time measurement of friction in combustion state is carried out through a series of bench tests.This paper first describes the basic principle of the floating cylinder liner method,deeply analyzes the difficulties in the realization of the method,and takes the problem of gas seal of the floating cylinder liner as the research focus.For this purpose,the active sealing device is designed,and its main structure and the basic principle of sealing gas are described in detail.Secondly,based on the QCH1125 type single cylinder diesel engine and the selected type of sensor,a new type of floating cylinder liner,seal chamber,cylinder block,external oil circuit and valve distribution mechanism is designed.After the 3D model is established by UG software,a complete friction measuring test machine model is formed by assembling with the original engine parts.The matching degree between the designed parts and the original machine parts and the running condition of the whole friction measuring machine are verified by kinematic simulation.Then,the three-dimensional model of the floating cylinder liner is taken out separately,and the modal analysis under the free state is carried out.The validity of the model is verified by comparing the simulation results with the modal test data.The same method is applied to the combined device composed of floating cylinder liner,friction sensor and cylinder block.By applying constraints,the modal analysis of the floating cylinder liner under the constraint state is carried out,so as to verify the rationality of the friction measuring device.Afterwards,the simulation lubrication model of piston ring-cylinder liner assembly was established through Matlab software,and the lubrication program was written to conduct relevant calculation.The minimum oil film thickness and friction curve of piston ring and cylinder liner components under different working conditions were obtained.The reasons for the formation were studied and analyzed in depth,providing a basis for the comparison of subsequent test results.Finally,the friction measurement test bench is designed and built,and the friction measurement work is carried out under different working conditions.After the test data is compared with the results of simulation,the friction and lubrication performance of the piston-cylinder liner assembly in the combustion operation state is studied and analyzed,so as to verify the effectiveness and rationality of this friction measurement device and method,which provides guidance and basis for the later research work.