Pelton wheel nozzle selection by specific speed Evaluate the statement: “A Pelton wheel with one nozzle is preferred for specific speed between 35 and 60 (metric r.p.m. scale).”

Introduction:Pelton turbine selection often uses specific speed to decide the number of jets. Lower specific speeds usually require single-jet Peltons, while higher specific speeds push designers to use multiple jets for practical runner diameters and speeds.Given Data / Assumptions:

• Specific speed in the metric system (commonly N_s in r.p.m. with P in kW and H in m).
• Standard selection charts for Pelton jets.

Concept / Approach:Typical guidelines: single-jet Peltons are favored at lower specific speeds (roughly up to the 30–35 range). As specific speed increases (e.g., 35–60), multiple-jet Peltons (two or more jets) are preferred to achieve feasible rotational speeds and runner sizes without exceeding jet velocity or nozzle limits.Step-by-Step Solution:

Verification / Alternative check:Design handbooks frequently show: N_s low → 1 jet; moderate (35–60) → 2 jets; higher still → 3–6 jets. While exact cutoffs vary slightly by source, the trend is consistent.

Why Other Options Are Wrong:

• True variants: contradict standard jet-number selection charts.
• Insufficient information: specific speed by itself is, in practice, adequate to suggest jet count ranges.

Common Pitfalls:Assuming a single-jet Pelton suits all heads; ignoring the effect of specific speed on feasible runner diameter and speed limits.

Final Answer: