OK Slurry blade diameter inlet side In the impeller inlet side to take the center, as the flow channel of the inscribed circle , inscribed circle centroid is twice the distance of the axis of the entrance side of the blade diameter D1, shown in Figure 5-5 .
Diameter D1 of the entrance side of the blade can be generally identified specific speed ns : In general , increasing the number of blades can improve fluid flow , an appropriate increase in the pump head , but increase the number of leaf blade friction loss would increase , reducing the flow through the flow area .
Therefore, the increase in number of leaves too much , not only to reduce efficiency and make the impeller cavitation performance deterioration , but also cause the pump performance curves hump ( see Chapter V ) . The blade angle under the same package , reducing the number of blades , each blade of the load increases, the role of the lower fluid diversion , but also decrease the pump head . Somewhat lower than the number of revolutions of the pump , to take place in the form of the length of the blade spacing , shown in Figure 5-10 .
This will ensure the adequate number of leaves , but also to prevent the impeller inlet blockage. 8 Make sure the blade inlet angle β1 placed Angle of the blade inlet is placed at the entrance of the blade , the blade face of the tangent ( strictly speaking, the surface should be in the flow line of the blade tangent bone ) angle between the circumferential tangent , as shown in Figure 5-6 . Assumed that the liquid is irrotational flow impeller , slurry pump manufacturer by the velocity triangle shows: In determining the vane inlet angle β1 place when the angle of △ β select a reason:
( 1 ) before the liquid enters the impeller , already subject to the suction chamber , the influence of the impeller shaft or a rotating motion (ie pre- spin ) , increasing the angle of attack is to consider the influence of the pre-swirl to reduce the impact of the loss of liquid .
( 2 ) takes a positive angle of attack , the blade entrance crowding coefficient . , Reduced, namely increasing the inlet area of the blade , improving the flow of liquid , can slightly improve pump cavitation performance .
On the conical tube pump suction chamber , the liquid enters the impeller before prerotation smaller, but in half spiral suction chamber is . Prerotator relatively large, so the angle of attack must be considered when selecting the suction chamber structure in the form of affected. Angle of the pump cavitation resistance to some extent.
Tests showed that the positive angle of attack range, attack angle change on the pump cavitation resistance has little effect , increase the angle of attack can delay the pump flow conditions in a large anti-cavitation performance when working the abrupt deterioration . However, if the positive angle of day more than 200 , will cause reduced efficiency . If you take the negative angle of attack , the pump ‘s cavitation resistance is significantly deteriorated .
Post time: Jul-13-2021