Research Of Ultrasonic Method For Oil Film Thickness Measurement On Diesel Engine’s Cylinder

The cylinder oil film thickness can be used to evaluate the lubrication effect of the cylinder and play an important role in the operation of the engine.At present,there are many methods to measure the thickness of cylinder lubricating oil film,such as capacitance method and electromagnetic method of electrical method,optical interference method and laser fluorescence measurement method,etc.However,such methods have some defects,such as temperature,external interference and the impact of the equipment itself.In order to solve these problems,ultrasonic measurement method arises at the historic moment.The ultrasonic measurement method has the advantages of wide applicability,high sensitivity,strong penetration,non invasion,high detection depth,convenient use and good safety.It is the mainstream method of cylinder oil film measurement in the future.In this paper,the ultrasonic measurement is analyzed theoretically and the relationship between the reflection coefficient of ultrasonic wave and the thickness of thin oil film is found out,and the feasibility and accuracy of the ultrasonic measurement method are proved.According to the related knowledge of acoustics and fluid mechanics,the resonance model and the equivalent spring model are established according to the theory of acoustic wave propagation in the medium,and the relationship between the ultrasonic frequency,the reflection coefficient and the thickness of the oil film is analyzed and compared.After the establishment of the model,the measurement accuracy is analyzed and calculated,and the influence of temperature factors on the thickness of oil film measurement is analyzed.Due to experimental demonstration,after understanding the working principle of ultrasonic transducer,two models of resonant model and equivalent spring model are designed and produced respectively,and the software development is carried out,and the MATLAB program is used to deal with the signal data.Through the experiment,the data collection is completed,and the rationality of ultrasonic measurement of thin oil film thickness is further proved,and the error of the measurement results is analyzed,which provides the theoretical basis for further research.