Question

High specific speed of a pump implies it is:
A. Centrifugal pump
B. Mixed flow pump
C. Axial flow pump
D. Any one of the above

Answer 1

Hint:Recall the basics of the concepts specific speed of a pump. Check the values of specific speed of the various types of pumps given in the options. Compare the values of the specific speeds of all the pumps given in the options and then determine which type of pump has the highest specific speed and choose the correct option.

Complete answer:
The specific speed of a centrifugal pump is of the range from 500 to 10000.The specific speed of the mixed flow pump is of the range from 2000 to 8000.The specific speed of an axial flow pump is of the range from 10000 to 20000.From all the values of the specific speed of centrifugal pump, mixed flow pump and axial flow pump, the specific speed of the axial flow pump is the highest.Thus, the high specific speed of a pump implies that the pump is an axial flow pump.

Hence, the correct option is C.

Additional information:
The specific speed of a pump is the measure of the capacity of the pump to work and it also defines the shape of the pump impeller.The specific speed $$N_s$$ of a pump is given by
$$N_s={\displaystyle \frac{n\sqrt{Q}}{{\left(gH\right)}^{3/4}}}$$
Here, $$n$$ is the rotational speed of the pump, $$Q$$ is the flow rate at the best efficiency, $$g$$ is acceleration due to gravity and $$H$$ is the total head per stage at the best value of efficiency.
The specific speed of a pump is a dimensionless quantity.

Note:The students may think that the specific speeds of all the types of pumps given in the options are high. The only difference is that if we compare the specific speeds of all types of the pumps then the axial flow pump has the highest range of specific speed. But the students should keep in mind that we have asked to compare the specific speeds of all the types of motor and choose one with high specific speed from them.