Turbine Selection by Specific Speed — 1500 kW at 300 rpm under 150 m Head A turbine must develop 1500 kW while running at 300 rpm under a net head of 150 m. Which turbine is most appropriate?

Introduction:
Selecting a turbine type depends primarily on head and specific speed. High heads with relatively low specific speed favor impulse (Pelton) machines, while medium heads suit Francis and low heads suit Kaplan/propeller types.

Given Data / Assumptions:

• Power P = 1500 kW (≈ 1.5 MW).
• Speed N = 300 rpm.
• Head H = 150 m.
• Standard metric specific speed definition.

Concept / Approach:
Compute specific speed Ns ≈ N * sqrt(P) / H^(5/4). For the given data, Ns falls within the Pelton range (typically ~8–35). To achieve the required power at this speed, multi-jet arrangements are commonly used to increase discharge without oversizing the wheel, hence a Pelton with two or more nozzles is preferred.

Step-by-Step Solution:
Estimate Ns qualitatively: high head (150 m) drives the choice toward Pelton.Given the moderate speed (300 rpm) and MW-scale power, multiple jets are used to deliver higher flow at the same runner diameter and speed.Therefore choose a Pelton wheel with two or more nozzles.

Verification / Alternative check:
Manufacturer charts show Francis/Kaplan specific speeds far larger than the computed Ns for this duty, reinforcing the Pelton choice; multi-jet designs extend Pelton capacity at a given speed.

Why Other Options Are Wrong:

• Single-nozzle Pelton may be insufficient to deliver the needed flow at 300 rpm.
• Kaplan: suited to low head, high flow.
• Francis: suited to medium head and higher Ns than indicated.

Common Pitfalls:
Ignoring speed constraints and assuming head alone determines type; both head and specific speed matter.

Final Answer:
Pelton wheel with two or more nozzles