Engine performance terms — power developed inside the cylinder What do we call the power actually generated by the working fluid on the piston within the engine cylinder (as obtained from the indicator diagram)?
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Aindicated power
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Bbrake power
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Cfrictional power
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Dnone of these
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Erated power
Answer
Correct Answer: indicated power
Explanation
Introduction / Context:Different power measures are used for engines: indicated, brake, and frictional power. Knowing their meanings is necessary for testing, design, and performance evaluation.Given Data / Assumptions:
- Mechanically measured indicator diagram (pressure–volume) or its modern equivalent.
- Steady-state operation at the test point.
Concept / Approach:Indicated power (IP): power developed by the gas on the piston, computed from the indicated mean effective pressure (IMEP), cylinder dimensions, and speed.Brake power (BP): power available at the crankshaft as measured by a dynamometer.Frictional power (FP): the difference, FP = IP − BP, representing mechanical losses.Thus, the power asked for—the power actually generated in the cylinder—is the indicated power.
Step-by-Step Solution:
Obtain IMEP from the indicator diagram.Compute IP = (IMEP * L * A * N * k) / time (using consistent units).Recognize that IP precedes mechanical losses; BP is after losses.Verification / Alternative check:In tests, BP is always less than IP; their difference trends with lubrication, speed, and load, confirming the definitions.
Why Other Options Are Wrong:
- Brake power: shaft output after losses.
- Frictional power: a loss term, not generated power.
- None/rated power: do not match the precise definition.
Common Pitfalls:Using brake-specific fuel consumption (bsfc) with IP by mistake; mixing IMEP with BMEP.
Final Answer:
indicated power