the engine cooling water pump has been paid more and more attention by design, manufacture and users for its applicability and reliability. Especially with the continuous improvement of engine quality, the working space of the water pump is further restricted, the running speed is constantly breaking through, and the problems such as component failure and cavitation damage seriously restrict the development of the engine cooling water pump.
1. Reliability
As the "heart" of the cooling system, the engine cooling water pump has a harsh working environment and extremely limited space. In order to avoid disassembly and maintenance during the overhaul period, the working life of the water pump should be equal to or multiples of the engine overhaul period. Therefore, the reliability of the engine cooling water pump and its components, such as water seals, bearings, pump shafts and impellers, is extremely high, and it is necessary to achieve the same life of the engine and pump.
However, the highly compact assembly structure makes the shaft-connected bearing widely used in the engine cooling water pump to replace the common shaft and bearing combination in the centrifugal pump, which can easily cause the pump shaft to break due to insufficient strength.
The constant change of the rotational speed makes the axial force generated by the cooling fan and the water pump impeller change accordingly. The existence of the clearance between the pump shaft and the support will increase the noise and vibration, which will be detrimental to the operation performance of the pump and the water seal work. influence. In particular, the engine cooling water pump works in a high temperature environment, and the working conditions of the shaft seal are very poor, and the seal failure is very likely to occur.
At the same time, in order to ensure sufficient circulating water volume, a certain head and an appropriate rotation speed, to realize the circulation of the coolant under any working conditions and to take away the heat of the engine, the multi-parameter and high-demand matching puts forward more requirements for the reliable operation of the engine cooling water pump. More challenges. Therefore, the reliability problem has become a key factor restricting the quality and life cycle cost of the engine cooling system.
2. Cavitation damage
Compared with ordinary centrifugal pumps, engine cooling water pumps are more prone to cavitation due to changes in temperature, working conditions and rotational speed. When cavitation occurs, vibration and noise are accompanied. The performance of the pump, such as head and efficiency, drops rapidly. If the impeller is operated under corrosive conditions, the impeller will be eroded by the strong impact of the collapse of the bubble, or even damaged by perforation.
The honeycomb pits on the surface of the engine cooling water pump blades and the pits near the volute separation tongue are common cavitation damage.
In addition, the cavitation of the engine cooling water pump will also corrode and destroy the overcurrent components, and accelerate the failure of the components. The cavitation damage of the engine cooling water pump has become an important factor to shorten the service life of the pump and generate vibration and noise, which seriously affects the normal operation of the automobile cooling system. Therefore, improving its anti-cavitation performance is the first issue to be considered to ensure the reliable operation of the cooling system.
The harsh working environment of the engine cooling water pump makes the reliability and cavitation damage of the pump particularly prominent, which seriously affects the safe, stable and reliable operation of the cooling system. It is of great significance to the development of engine cooling system to discuss how to improve the reliability of engine cooling water pump and study the mechanism of cavitation.