为了解决叶轮出口宽度b_2狭小给叶轮铸造带来的困难,一方面设计者从设计手段上采取增大比转数的方法,使得b_2适当增大。但b_2的增大是有限的。另一方面从制造工艺上寻求新的路子,如采用铸造加铆合的办法,制造叶轮以增大b_2,但工艺较复杂。又如采用精密铸造叶轮,但工效低。 In order to solve the problem that impeller exit width b_2 is narrow, it is difficult for the impeller casting. On the one hand, the designer adopts the method of increasing the specific rotational speed from the design method so as to make b_2 increase appropriately. However, the increase of b_2 is limited. On the other hand, the manufacturing process to find new ways, such as the use of casting plus riveting approach, the manufacture of impeller to increase b_2, but the process is more complicated. Another example is the use of precision casting impeller, but low efficiency.