The performance curve is used to express the conversion characteristics of the water flow energy of the pump under different working conditions, and is an external manifestation of the internal flow pattern of the pump. Like ordinary centrifugal pumps, the constant speed characteristic curve of the engine cooling water pump is the relationship between flow and head, flow and efficiency, and flow and power at a certain speed. It can visually describe the operating performance of the engine cooling water pump at constant speed. However, since the speed of the engine cooling water pump is constantly changing when it is working, the speed change characteristic curve of the water pump must also be given. The variable speed characteristic curve of the engine cooling water pump mainly maps the flow, head and power curves corresponding to different rotational speeds, reflecting the energy conversion characteristics at different rotational speeds. In order to more intuitively reflect the comprehensive performance of the engine cooling water pump, sometimes it is necessary to draw two performance curves on the same graph to represent their performance parameters.

Since the engine cooling water pump has special characteristics such as high working water temperature (75~85℃), large rotation speed range (2000~5000r/min), and overall structural size restrictions, compared with ordinary water pumps, it has a complex design of the inlet and outlet water channels of the water pump. The flow direction and cross-sectional shape of the inlet and outlet liquid flow change drastically, which increases the hydraulic loss and reduces the efficiency. At the same time, cavitation is more likely to occur in the engine cooling water pump under high temperature, high speed and large flow conditions. At the same time, the cross-flow in the top gap of the semi-open impeller causes the squeezing of the mainstream and the increase of the flow velocity in the impeller channel, which makes the impeller steam The corrosion characteristics will worsen, seriously affecting the normal operation of the cooling system and greatly shortening the service life of the cooling water pump. The special working environment and matching conditions determine that the design of the engine cooling water pump is different from that of ordinary centrifugal pumps.