Question

The characteristic curves of a centrifugal pump has the following relationship:
A. Discharge versus Efficiency
B. Head versus BHP
C. BHP versus Discharge
D. Discharge versus Head
E. Efficiency versus Head
Choose the correct answer from the options given below:

• A. A, C and D only
• B. B, D and E only
• C. A, C and E only
• D. C, D and E only

Hint:

The "big three" characteristic curves for a centrifugal pump all plot a key variable against the discharge (Q): 1. Head vs. Q (H-Q) 2. Power vs. Q (P-Q) 3. Efficiency vs. Q (\(\eta\)-Q) Discharge is almost always the independent variable (x-axis).

Answer 1

The Correct Option is A

Step 1: Define centrifugal pump characteristic curves.
These are graphical representations of a pump's performance, showing the interrelationships between head, discharge (flow rate), brake horsepower (BHP), and efficiency at a specific rotational speed.
Step 2: Identify the standard characteristic curves.
The independent variable, plotted on the x-axis, is typically the discharge (Q). The key performance parameters are then plotted against discharge:
- D. Discharge versus Head (H-Q curve): This is the primary performance curve, showing that the head a pump can generate decreases as the flow rate increases. This relationship is fundamental.
- C. BHP versus Discharge (P-Q curve): This shows the power required by the pump. Typically, BHP increases from a minimum at zero discharge to a peak as discharge increases.
- A. Discharge versus Efficiency (\(\eta\)-Q curve): This shows that efficiency is zero at zero discharge, rises to a single peak value (the Best Efficiency Point or BEP), and then declines as discharge increases further.
Relationships like "Head versus BHP" (B) and "Efficiency versus Head" (E) are not standard primary characteristic curves; they can be derived from the main three, but are not the direct relationships plotted.
Step 3: Conclude the correct combination.
The standard relationships plotted for a centrifugal pump are A (Discharge vs Efficiency), C (BHP vs Discharge), and D (Discharge vs Head).