(21.6) 21.0% error"

(315.5) 8.00% error"


(18.2) 6.22% error"

"Error in predicting best efficiency point.

"Error in predicting best efficiency point.


(B ) Hf S H QF > Q FIGURE 18 Discharge velocity triangles for underfiled blades (neglecting slip)

inlet blade tips If the inlet blade tips are blunt, as shown at D in Figure 17, the cavitation characteristics may be improved by sharpening them, as shown at E. In this case overfiling increases the effective flow area, which reduces cm1 for a given flow rate. If more area is needed, it may be advantageous to cut back part of the blade and sharpen the leading edge. Overfiling tends to increase b1, which is incompatible with a decrease in cm1 (Figure 19). The increase in b1 increases the angle of attack of the liquid approaching the blade. In Figures 2 and 19, w1is tangent to the centerline of the blade at entrance and w0

TABLE 7 Changes in performance when impeller blades are underfiled

Specific speed a n.

No. of stages

Impeller diameter D2, in (cm)

Change in blade spacing dF/d

Changes at best efficiency point after filing, %

862 945 1000 1080 1525 1950 3300« 3450« 4300

(0.3154) (0.3458) (0.3659) (0.3952) (0.5580) (0.7135) (1.2075) (1.2623) (1.5734)

Renewable Energy Eco Friendly

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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