# Mechanical Engineering - Hydraulic Machines - Discussion

Discussion Forum : Hydraulic Machines - Section 1 (Q.No. 6)
6.
Discharge of a centrifugal pump is
directly proportional to diameter of its impeller
inversely proportional to diameter of its impeller
directly proportional to (diameter)2 of its impeller
inversely proportional to (diameter)2 of its impeller
Explanation:

Discharge of a centrifugal pump is directly proportional to (Diameter)^2 of its impeller.

Head of a centrifugal pump is directly proportional to (Diameter)^2 of its impeller.

Power Developed of a centrifugal pump is directly proportional to (Diameter)^4 of its impeller.

Discussion:
49 comments Page 1 of 5.

Discharge of centrifugal pump is given by Q = (pi)(D2)(B2)(Vf2).

As per above equation option (A) is correct.

Discharge of centrifugal pump is Q = area* velocity of flow.

Q = (pi)(D1)(B1)(VF1) = (PI)(D2)(B2)(VF2).

Where B1 and B2 are width of impeller at inlet and outlet and B1 and B2 are diameter of impeller at inlet and outlet and VF1 and VF2 are velocity of flow at inlet and outlet.

Afrasiyab said:   9 years ago
Directly proportional to square of diameter.

Directly proportional to diameter of its impeller. A is the correct answer.

Harry said:   8 years ago
As per Affinity Laws:

Speed is constant,

Q1/Q2 = (D1/D2)^3.

So, the answer is Discharge is inversely proportional to the cube of the diameter.

Anurag Adhikary said:   8 years ago
Correct the answers, it should be option A.

Kartheek said:   8 years ago
Discharge in centrifugal pump (Q) = pi * D * b * v.

where D = dia of the impeller at the inlet,
b = width of the impeller at the inlet
v = velocity of flow at the inlet.

So, according to the formula, discharge is directly proportional to Diameter of the impeller.

Faisal mumtaz said:   8 years ago
Directly proportional to diameter so, option A is correct.

Honey said:   8 years ago
I think, All the options are not satisfied. The correct answer will be directly proportional to the cube of the diameter of vanes.

Smith said:   8 years ago
The discharge flow rate of a centrifugal pump is directly proportional to diameter. Discharge head is directly proportional to the square of the diameter. And power is directly proportional to the cube of the diameter. You can understand all this with the help of affinity laws.