Gas power cycles worksheet with answers

Free printable Gas power cycles worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
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In an ideal Otto cycle with a compression ratio of 10, air enters the compression stroke at 25 °C. Use the cold-air-standard assumptions: air is an ideal gas with constant specific heats, k = 1.4, cp = 1.005 kJ/(kg·K) and cv = 0.718 kJ/(kg·K). Find the temperature T2 at the end of compression, in K.

r = 10T1 = 25 °Ck = 1.4
T2 = K
2.Easy
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An ideal Otto cycle has a compression ratio of 6. Use the cold-air-standard assumptions: air is an ideal gas with constant specific heats, k = 1.4, cp = 1.005 kJ/(kg·K) and cv = 0.718 kJ/(kg·K). Find its thermal efficiency η in percent.

r = 6k = 1.4
η = %
3.Medium
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An ideal Diesel cycle has a compression ratio r = 18 and a cutoff ratio rc = v₃/v₂ = 1.8. Use the cold-air-standard assumptions: air is an ideal gas with constant specific heats, k = 1.4, cp = 1.005 kJ/(kg·K) and cv = 0.718 kJ/(kg·K). Find its thermal efficiency η in percent.

r = 18rc = 1.8k = 1.4
η = %
4.Medium
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An ideal Diesel cycle has a compression ratio r = 19 and a cutoff ratio rc = v₃/v₂ = 3. Use the cold-air-standard assumptions: air is an ideal gas with constant specific heats, k = 1.4, cp = 1.005 kJ/(kg·K) and cv = 0.718 kJ/(kg·K). Find its thermal efficiency η in percent.

r = 19rc = 3k = 1.4
η = %
5.Hard
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An ideal Brayton cycle operates with a compressor pressure ratio of 12. Use the cold-air-standard assumptions: air is an ideal gas with constant specific heats, k = 1.4, cp = 1.005 kJ/(kg·K) and cv = 0.718 kJ/(kg·K). Find its thermal efficiency η in percent.

rp = 12k = 1.4
η = %
6.Hard
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An ideal Brayton cycle operates with a compressor pressure ratio of 10. Use the cold-air-standard assumptions: air is an ideal gas with constant specific heats, k = 1.4, cp = 1.005 kJ/(kg·K) and cv = 0.718 kJ/(kg·K). Find its thermal efficiency η in percent.

rp = 10k = 1.4
η = %

Answer key

  1. 1. T2 = 748.9 K
  2. 2. η = 51.16 %
  3. 3. η = 64.12 %
  4. 4. η = 59.79 %
  5. 5. η = 50.83 %
  6. 6. η = 48.21 %

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