Investigation Into The Lubrication Conditions Of Engine Cylinder Liner-Piston Ring Based On Acoustic Emission Technologies

The lubrication condition between cylinder liner-piston ring directlyassociates with the efficiency and reliability of the engine. But it is difficult tomeasure the lubrication condition online and hence to examine the performanceof lubrication after any improvements made to the engine which include usingdifferent alternative fuels. Acoustic emission technologies have manyadvantages because of its fast, high accuracy, strong orientation, wide range ofuse, early prediction and online diagnosis etc. Acoustic emission technologieshave been used in the investigation of engine fault monitoring and diagnosis. Inorder to evaluate the lubrication conditions between the cylinder liner-pistonring for different applications this study focuses investigation of AEmechanisms between cylinder liner-piston ring indirectly and AE measurementand analysis techniques.Considering the variation characteristics of the lubricating oil viscosity,density and temperature, this thesis establishes a mathematic model of thecylinder liner-piston ring lubrication and acoustic emission process based on theReynolds equation. And solve the lubrication model by the finite differencemethod and successive over relaxation iteration method. Subsequently, the AEcharacteristics are predicted based on friction behavior in an engine cycle. Then,a series of experimental studies were carried out based on QCH1110II typesingle cylinder diesel engine. Detecting the acoustic emission signals of frictionand lubrication conditions under different operation condition and lubricating oilbrand. It uses the technology of combining wavelets with envelope to analysis the acoustic emission signals. And establish the relationship between theacoustic emission signals and lubrication conditions.The analysis results show that the friction between cylinder and piston ringis higher on top and bottom dead centers, especially the compression on TDC,where minimum thickness of lube film is minimal and the lubrication conditionis the worst. Rising lubricating oil viscosity has a promoting effect on theimprovement the lubrication condition on top and bottom dead center. But thefriction of other location will increase along with the increase of viscosity. Soengine should choose lubricating oils with appropriate viscosity. The friction oftop and bottom dead center will decrease with the engine speed increasing. Butthe friction of other location will increase. So choose the appropriate speed inorder to reduce the wear of cylinder liner-piston ring. In the same time, acousticemission signals not only can detect the event that intake valve closed, exhaustvalve closed and burning, but also can detect the acoustic emission phenomenawere from the friction between cylinder liner-piston rings. And the acousticemission signals are consistent with the conclusion of the cylinder line-pistonring lubrication model. It proves that acoustic emission technique can wellrealize the non-intrusive diagnosing and monitoring about engine internalcylinder friction lubrication condition.