Modifications To Impeller And Casing

Diameter Reduction To reduce cost, pump casings usually are designed to accommodate several different impellers. Also, a variety of operating requirements can be met by changing the outside diameter of a given radial impeller. Eq. 6 shows that the head should be proportional to (nD)2 provided that the exit velocity triangles (Figure 2b) remain similar before and after cutting, with w2 always parallel to itself as u2 is reduced. This can be achieved if the impeller meridional exit area Am2 is the same before and after cutting—and if the flow angle / (Figure 15, Section 2.1) also stays the same. would stay the same if the blade angle b2 (= Sb,2) does, the difference being due to slip velocity Vs that should also scale down with D.] For radial discharge impellers, area Am2 equals pDb2 (minus blade and boundary layer blockage) and requires that b2 increase as D decreases. This is typical of many impellers—as is constancy of b2 over the cutting range—and, together with Eqs. 27-33 of Section 2.1, leads to the so-called "affinity laws" for predicting performance:

Qi

n1D1

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Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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