Basic knowledge about vortex pumps

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A pump that transports liquid by the rotation of an anchor impeller between cover plates with discontinuous channels is called a vortex pump. Its working principle is as follows: as the star wheel rotates, centrifugal force is generated. Under this centrifugal force, the liquid flows in through the holes on the side of the pump casing to the base of the blades and is then thrown outward to the channels in the side plates. This portion of liquid originally moved in a circular motion with the blade, possessing kinetic energy; in the channel of the cover plate, this kinetic energy is converted into pressure energy. It was then seized by the leaves. As the liquid particles move from the inlet to the outlet, this process repeats multiple times, with the energy increasing step by step, just as the liquid is affected by multiple stages of impellers in a centrifugal pump. The liquid moves within the channel along with the star-shaped impeller; when it reaches the cutoff point, the channel suddenly gets blocked, and the liquid then flows out through the outlet hole. The outlet hole is located on the outlet cover, while an inlet hole is provided on the inlet cover; it is situated at the point where the channel suddenly appears after the shut-off zone, and a negative pressure exists there in order to draw in the liquid. Vortex pumps have excellent self-priming capabilities. The pressure and flow rate of the vortex pump are given by: H=φu²/2g and Q=cF, where u is the circumferential velocity of the impeller ； φ — coefficient, ranging from 3.5 to 4.5; F — cross-sectional area of the channel ； C — the flow velocity within the channel; it can be approximated as c = u/2 or (0.55–0.65)u. An impeller usually has 24 to 60 blades. The characteristic curve of a vortex pump is somewhat similar to that of a centrifugal pump, but it is steeper; it has a low flow rate and a high head, yet its efficiency is not high. The side clearance of the vortex pump (i.e., the gap between the impeller and the cover) cannot be too large, otherwise efficiency will be significantly reduced; therefore, this type of pump can only handle relatively pure liquids. The clearances that should be measured during the maintenance of vortex pumps are: 1. The axial clearance between the impeller and the cover plates on both sides. Generally, 2a ranges from 0.17 to 0.20 millimeters, and it is measured using the lead wire compression method. 2. Radial clearance between the impeller and the pump casing. Generally, c is set to 0.15–0.20 millimeters in the radial direction, as measured with a feeler gauge. 3. Bearing clearance: generally, b is set at around 0.10 millimeters, and it is measured using a feeler gauge or a vernier caliper. 4. Coupling assembly clearance. Generally, i = 1 millimeter and d = 4 ± 0.5 millimeters, measured using a vernier caliper and a depth gauge. 5. Both the fit between the impeller and the key and the fit between the impeller and the shaft are sliding fits. The clearance at the top of the key should be no less than 0.20 millimeters, while the clearances on both sides should be between 0.01 and 0.04 millimeters.