2. General characteristics of centrifugal pumps(1) The flow direction of water along the centrifugal pump is sucked in along the axial direction of the impeller, and flows out perpendicular to the axial direction, that is, the direction of water flow in and out is 90° to each other.(2) Since the centrifugal pump relies on the inlet of the impeller to form a vacuum to absorb water, it is necessary to pour water into the pump and the suction pipe before starting, or use a vacuum pump to exhaust the air to form a vacuum, and the pump casing and the suction pipe must be strictly sealed. There must be no air leakage, otherwise a vacuum will not be formed and water will not be absorbed.(3) Since the impeller inlet cannot form an absolute vacuum, the suction height of the centrifugal pump cannot exceed 10 meters. In addition to the loss along the process caused by the water flowing through the suction pipeline, the actual allowable installation height (the height of the pump axis to the suction water surface) is much less than 10 m. If the installation is too high, it will not absorb water; in addition, because the atmospheric pressure in mountainous areas is lower than that in plains, when the same water pump is installed in mountainous areas, especially in high mountainous areas, its installation height should be lowered, otherwise it will not be able to absorb water.axial flow pumpWorking principle and characteristics of axial flow pump1. Working principle of axial flow pumpThe working principle of the axial flow pump is different from that of the centrifugal pump. It mainly uses the thrust generated by the high-speed rotation of the impeller to lift water. When the blades of the axial flow pump rotate, the lift generated by the water can push the water from below to above.The blades of axial flow pumps are generally submerged in the pool of water being sucked. Due to the high-speed rotation of the impeller, under the action of the lift generated by the blades, the water is continuously pushed upwards, so that the water flows out along the outlet pipe. The impeller rotates continuously, and the water is continuously pressed to a high place.