Understanding Otto Cycle: Calculating Cycles, Heat Input, and Efficiency

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SUMMARY

The discussion focuses on calculating cycles, heat input, and efficiency in the context of the Otto cycle for a four-stroke engine delivering 150 horsepower at 3600 RPM. The calculations confirm that the engine completes 1800 cycles per minute. To determine the heat input per minute, the thermal efficiency of 20% is applied, leading to the conclusion that the work done can be calculated using the conversion of horsepower to kilowatts, specifically using the formula E=W/Q.

PREREQUISITES
  • Understanding of the Otto cycle and its principles
  • Knowledge of thermal efficiency calculations
  • Familiarity with horsepower to kilowatt conversion (1 hp = 0.7457 kW)
  • Basic grasp of thermodynamic equations, particularly E=W/Q
NEXT STEPS
  • Learn detailed calculations for thermal efficiency in internal combustion engines
  • Explore the relationship between horsepower and work done in mechanical systems
  • Study the implications of heat loss in thermodynamic cycles
  • Investigate advanced concepts in engine performance metrics
USEFUL FOR

Students in mechanical engineering, automotive engineers, and anyone studying thermodynamics or internal combustion engine performance.

kris24tf
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Otto Cycle?? Please help ASAP!

I have a question that my entire class is confused over. I need help on it for a test, but I have no idea where to go with it. It doesn't seem to fit any of the equations or situations I have been using.

The question is: A four-stroke engine runs on the otto cycle. It delivers 150 hp at 3600 rpm. a) how many cycles are there in one minute?
I know that this is just 3600/2 = 1800 cycles

b) If the thermal efficiency of the engine is 20% what is the heat input per minute?

I don't know how to get this one. I know the equation I want is E=W/Q, but I don't know how to find the work done. do I use the 150 hp, 3600 rpm, or combine them somehow?

c)How much heat is wasted to the environment / minute.

I need the answer to part b I think for this right?

Any help at all would be great. Thanks for looking.
 
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For (b), the 150 horse power is the clue.

1 hp = 0.7457 kW

What is the energy delivered in 1 minute.
 

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