Turbine stage efficiencies – definition check Is the following statement correct? “The ratio of energy supplied to the blades per kg of steam to the total energy supplied per stage per kg of steam is called mechanical efficiency.”

Introduction / Context:
Turbine performance uses several efficiency definitions: nozzle efficiency, diagram (blading) efficiency, stage efficiency, and mechanical efficiency. Confusion among these terms leads to incorrect diagnostics.

Given Data / Assumptions:

• Energy supplied to blades per kg = work transferred to the rotor (per kg steam).
• Total energy supplied per stage per kg = isentropic (or actual) stage heat drop basis, depending on convention.
• Mechanical efficiency accounts for rotor windage, bearing, and transmission losses.

Concept / Approach:
Mechanical efficiency is the ratio of brake (shaft) power to rotor power (power developed in the blades). The quoted ratio compares rotor work to stage energy input, which corresponds to diagram (blading) efficiency or stage efficiency, not mechanical efficiency.

Step-by-Step Solution:
Identify the numerator: energy to blades → rotor work.Identify the denominator: total stage energy supplied.This ratio reflects how effectively the stage converts available enthalpy drop into rotor work → diagram/stage efficiency.Mechanical efficiency = shaft (deliverable) power / rotor power, accounting for mechanical losses.

Verification / Alternative check:
Standard definitions list: η_mech = P_shaft / P_rotor; η_nozzle relates kinetic energy to isentropic drop; η_stage = W_rotor / Δh_stage, aligning with the statement's ratio.

Why Other Options Are Wrong:

• (a) Mislabels the metric.
• (c) Stage type (impulse vs reaction) does not convert this into mechanical efficiency.
• (d) and (e) reference different efficiency types.

Common Pitfalls:
Using “mechanical efficiency” to describe fluid-dynamic conversion quality; that is a separate (diagram/stage) efficiency.

Final Answer:
No; that ratio defines blading/diagram or stage efficiency, not mechanical efficiency