Difficulty: Easy
Correct Answer: Steam turbines generally achieve higher efficiencies than reciprocating steam engines
Explanation:
Introduction / Context:
Steam turbines replaced reciprocating steam engines in power generation due to superior efficiency, compactness, and smoother rotation. This question probes basic qualitative understanding of turbine behavior versus engines and the role of blades in momentum exchange.
Given Data / Assumptions:
Concept / Approach:
Turbines achieve higher isentropic and overall efficiencies than piston engines because they admit continuous flow with lower mechanical friction, better expansion matching, and multistaging. Turbines also deliver nearly steady torque (so large flywheels are unnecessary), and their blades are explicitly shaped to change the steam’s direction, producing a momentum change and hence work. In reaction turbines, pressure drops in both stator and rotor; it does not increase.
Step-by-Step Solution:
Evaluate A: correct — turbines are typically more efficient than reciprocating engines for power generation.Evaluate B: incorrect — turbines have smooth torque; large flywheels are generally not required.Evaluate C: incorrect — blades turn and redirect flow to extract work.Evaluate D: incorrect — in reaction stages, pressure decreases in both fixed and moving blades.
Verification / Alternative check:
Utility-scale steam plants universally use turbines; piston engines are obsolete for large-scale continuous power due to lower efficiency and maintenance demands.
Why Other Options Are Wrong:
They conflict with fundamental turbine mechanics and standard stage descriptions.
Common Pitfalls:
Assuming all rotating machines need flywheels; misinterpreting “reaction” as pressure rise rather than pressure drop in the rotor.
Final Answer:
Steam turbines generally achieve higher efficiencies than reciprocating steam engines
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