Cavitation of automotive parts
11-15-2018, 09:31 AM,
#1
Cavitation of automotive parts
Cavitation is a damage phenomenon on the surface of a component when it contacts and moves relative to the liquid. Cavitation corrosion may occur on the surface of the wet cylinder liner contacting the coolant and on the oil film diffusion part of the journal bearing after the minimum oil film gap (due to the existence of negative pressure).
Cavitation is the surface fatigue damage caused by impact force, but the chemical and electrochemical action of the liquid and the inclusion of impurities in the liquid abrasive may accelerate the caving damage process.
Taking the cavitation erosion of the cylinder liner in Feilong Jiangli as an example, the cylinder liner has elastic deformation and high frequency vibration due to the change of combustion pressure with the crankshaft angle. Bubbles burst instantaneously with great impact (tens or even tens of thousands of atmospheric pressures) and high temperatures (hundreds of degrees) at speeds up to 250m/s.
The outer wall of the Feilong Jiangli cylinder liner is subjected to the repeated impact stress, which makes the surface material fatigue and gradually fall off, forming pits, then expanding and deepening, when serious, honeycomb-like cavities aggregate, and even penetrate the cylinder wall.
The common feature of cavitation damage of Feilong Jiangli cylinder liner is that the cavitation groups appear on both sides of the swing plane of connecting rod, especially on the side of piston bearing high lateral pressure. In addition, cavitation erosion may also occur at the inlet and the water diversion.
The measures to prevent cavitation erosion of cylinder liner are to prevent or reduce the formation of bubbles, and if bubbles inevitably occur, try to make bubbles collapse away from the parts or improve the cavitation resistance of parts. Increasing the fixed rigidity of cylinder liner (such as increasing the bearing height, reducing the fit clearance, etc.) to reduce the vibration of cylinder liner; widening the water jacket to make the cooling uniform and reduce the impact of bubble explosion; eliminating the local eddy current area and dead water area in the cooling water line, tangential water can be used; keeping the cooling water clean or adding emulsifier in the cooling water should be used; High cylinder block and piston repair quality and assembly quality will play a certain role in preventing cavitation.
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