Research On The Influence Of Temperature On Ultrasonic Measurement Method Of Diesel Piston Ring Oil Film Thickness

Diesel engine was the most common power device in the existing industry,whose working state was of great significance to economic benefits and environmental protection.The normal operation of diesel engine and the improvement of mechanical efficiency had an important relationship with the friction and wear produced by its mechanical structure.As one of the important friction pairs,whether the lubrication state at the position of cylinder liner and piston assembly is good or not had a great impact on the overall mechanical efficiency and working life of diesel engine.In the study of lubrication state,the thickness of lubricating oil film can be regarded as an indicator to judge the lubrication state.In the actual running state of diesel engine,the huge heat generated by combustion and the heat generated by friction will act on the lubricating oil film,which will affect its properties and lead to the deterioration of lubrication,and the diesel engine can be damaged in serious cases.Therefore,this paper took the measurement of lubricating oil film thickness as the research objective,based on the measurement theory of lubricating oil film thickness of diesel engine piston ring,theoretical analysis and experimental measurement of lubricating oil film thickness under different temperature conditions were carried out in this paper.Firstly,the theory of ultrasonic measurement was studied.According to the characteristics of ultrasonic measurement and its propagation boundary conditions,the research of the relationship between ultrasonic frequency,reflection coefficient and lubricating oil film thickness was conducted.The calculation formulas of resonance model,spring model and phase model were deduced,and the measurement range was analyzed theoretically.The corresponding measurement methods were established for different thickness of lubricating oil film.The factors affecting the measurement accuracy of ultrasonic measurement method of lubricating oil film thickness were discussed,including the influence of temperature and pressure,ultrasonic attenuation,frequency resolution,spatial resolution and focusing of ultrasonic transducer,and ultrasonic coupling performance.The above factors were analyzed in order to improve the test accuracy and reduce the experimental error.Combined with the above analysis and the characteristic that the lubricating oil film thickness varies widely in the actual environment,the ultrasonic experimental measurement system of lubricating oil film thickness with macro and micro composite structure was built independently.According to the system,the thickness of lubricating oil film in the range of1.45-127.76 μm was measured.The experimental results proved the measuring ability and precision of ultrasonic measurement method.According to the original structure of diesel engine,the ultrasonic measurement scheme of lubricating oil film thickness was constructed.Combined with the measurement scheme,the structure of diesel engine housing was partially reformed,and the experimental system of ultrasonic measurement of lubricating oil film thickness of diesel piston ring was further built.The thickness of lubricating oil film at 20℃,50℃ and 80℃ was measured by the measuring system at 10-100r/min.It was verified that temperature changes could affect the measurement results,and the thickness calculation results under the corresponding temperature conditions were obtained according to the modified algorithm.It provided a certain support for subsequent measurement of lubricating oil film thickness in diesel engine combustion state.