Pelton Terminology — Definition of Jet Ratio In Pelton wheel design, the jet ratio is defined as the ratio of which two diameters?

Introduction:
Jet ratio is a key geometric parameter in Pelton design influencing bucket sizing, bucket count, and efficiency. It links the runner diameter to the jet diameter provided by the nozzle(s).

Given Data / Assumptions:

• Pelton wheel with one or more jets.
• Runner pitch-circle diameter = D, jet diameter = d.

Concept / Approach:
By definition, jet ratio JR is the diameter ratio JR = D / d. Practical ranges (often around 10–16) balance jet coherence, bucket acceptance, and mechanical size.

Step-by-Step Solution:
Identify diameters: D = runner diameter; d = jet diameter.Form the ratio: JR = D / d.Conclude: jet ratio is diameter of Pelton wheel to diameter of jet.

Verification / Alternative check:
This definition appears alongside empirical relations like bucket number z ≈ 15 + D/(2 d) and sizing rules for bucket width and depth.

Why Other Options Are Wrong:

• Jet-to-wheel diameter reverses the definition.
• Velocity ratios are unrelated to the geometric jet ratio.

Common Pitfalls:
Confusing pitch-circle diameter with overall outside diameter; design commonly uses the pitch-circle for D in ratio definitions.

Final Answer:
diameter of Pelton wheel to the diameter of jet