Research On Magneto-resistive Monitoring Method For Piston Ring Wear Of Marine Low Speed Diesel Engine

As one of the key parts of the combustion chamber of marine diesel engine,piston ring plays the role of sealing,heat-conducting,oil scraping and oil distributing between piston and cylinder.Due to the poor working conditions of the piston ring,the excessive friction and the wear of the piston ring are likely to occur,which will reduce the sealing between the piston ring and the cylinder liner and will lead to the leakage of the high-temperature and the high-pressure gas to the crank box.Oil mist concentration is too high to cause the crankcase explosion and other serious fault.The leakage of the cylinder gas will also reduce the output power of the diesel engine and increase the specific fuel consumption.Therefore,it is of the great significance and the practical value to study the magneto-resistor on-line monitoring method of the piston ring wear for the marine low-speed diesel engine.The magneto-resistor on-line monitoring method of the piston ring wear in the paper is studied by combining the theoretical calculation and the experimental research.The main research contents and conclusions are shown as follows:1.Based on the theory of a constant magnetic field,the magneto-resistor on-line monitoring principle of the piston ring wear is described,and the influence of the axial movement of the piston ring and the wear of the piston ring on magnetic induction intensity at the monitoring point is analyzed.2.A three-dimensional finite element model for the magnetic field calculation of "Cylinder-Piston-Piston ring-Magneto-resistor sensor" for the marine low-speed diesel engine is established.The magnetic induction intensity of the axial movement and wear of the piston ring is calculated and analyzed.The results have shown that there is a correspondence between the piston ring wear amount and the characteristic value of the magnetic induction intensity.The feasibility of monitoring the piston ring wear based on magnetic resistance sensing technology for the marine low-speed diesel is verified.3.Due to the difficulties of the simulating test of the piston ring wear for a real marine diesel engine on boat,a test bench is developed to simulate the piston ring wear for the marine low-speed diesel engine,which provide the test condition for piston ring wear test.Based on the mechanism of the magneto-resistive sensing technology of monitoring the piston ring wear,the internal structure and signal conditioning circuit of the magneto-resistive sensor are optimized.4.The simulating test of the piston ring wear for the marine low-speed diesel engine is carried out,and the signal characteristics of the different piston speeds,the different assemble gaps between the sensor and the piston ring and the different piston ring wear conditions are analyzed.The results have shown that there is a corresponding relationship between the wear of the piston ring and the characteristic value of the magneto-resistive sensor signals,and the amplitude of the magneto-resistive sensor signal increases with the increase of the piston ring wear.The correctness of the magnetic field calculation model is verified by the piston ring wear test.5.The effectiveness of the on-line monitoring piston ring wear condition method based on magneto-resistance sensing technology for the marine low-speed diesel engine is verified by calculating and experimenting.