Why does the speed decrease when the water pump runs in reverse?

When the water pump runs in reverse, the reason for the reduced speed may be as follows: 1. Increased resistance: When operating normally, the water pump generates power by pushing the liquid to move. When the water pump runs in reverse, the direction of fluid flow is opposite to that during normal operation, which causes greater resistance in the pipes. As a result, more thrust is required from the pump, and its speed naturally decreases. 2. Impeller angle issue: The impeller of a water pump is usually designed at a certain angle to achieve optimal performance. When the water pump runs in reverse, the angle of the impeller is opposite to the normal direction, which may prevent the liquid from being pushed effectively and result in a decrease in rotational speed. 3. Internal wear or failure: When the water pump operates in reverse, it may place additional stress and pressure on the internal components of the pump, which can lead to increased wear of these components or their failure, thereby resulting in a decrease in speed. In short, the reason for the reduced speed of the water pump may be due to increased resistance, issues with the pump impeller angle, or internal wear or faults. .

This post was last edited by In silence on 2023-6-21 at 11:02. 1. Generally, a reversal occurs when the check valve fails, but it remains a check valve even when it has failed; as a result, the flow rate is lower than the normal flow rate, except in cases of siphoning. 2. Reversing the drive motor causes it to rotate in the opposite direction, which enables power generation; this constitutes a load that consumes part of the work done during reversal. 3. Therefore, the reverse operation of a pump can be understood in terms of turbines; in hydraulic drive applications, axial flow impellers are always chosen, as there is little difference in efficiency between forward and reverse operation for axial flow impellers (which exert thrust on the water). For centrifugal impellers (where the centrifugal force generated by rotation does the work), there is a significant difference in efficiency between forward and reverse operation. Centrifugal pumps rely on this ‘throwing’ effect; the higher the head, the lower the specific speed ； An axial flow pump operates by ‘pushing’; the higher its specific speed, the greater its reversing efficiency, and this can be understood by referring to shot putting – with balls of the same weight, a shot put is thrown outward due to centrifugal force, so it travels farther than a weight thrown by pushing A ball thrown back along its shot put trajectory would cause severe injuries, whereas a hammer throw returns along its original path, swinging while the string retracts, causing little harm other than some fatigue. You can also note that a windmill is an axial-flow impeller; for a centrifugal impeller, the hydraulic force acting on it is equivalent to that of wind blowing at a very steep angle onto the windmill – it can still move, but not very effectively. Ordinary centrifugal pumps with low specific speed have high head but low flow rate; conversely, they can hardly rotate at all. Centrifugal impellers with high specific speed are designed for high flow rates—for example, in circulating water pumps. In such cases, the stress conditions more closely resemble those in turbines, allowing for higher reverse-flow hydraulic efficiency. I’ve experienced reversals caused by siphoning; those were absolutely thrilling – I just couldn’t stop. The resistance mentioned above is actually the same in both directions; the greatest resistance lies in the check valve. The resistance of the inlet filter actually decreased after backwashing.