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.

New worksheetPractise online with hints

For teachers: free to print, copy and use in class. Every new worksheet has new values and its own answer key. A link to ExamProblems on your course page is appreciated.

Name: ____________________   Date: ____________

1.Easy
vP1234qin​qout​

In an ideal Otto cycle with a compression ratio of 10.5, 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 = 10.5T1 = 25 °Ck = 1.4
T2 = K
2.Easy
vP1234qin​qout​

An ideal Otto cycle has a compression ratio of 9.5. At the start of compression the air is at 295 K, and the highest temperature in the cycle is 2200 K. 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 net work output w per kilogram of air, in kJ/kg.

r = 9.5T1 = 295 KT3 = 2200 Kk = 1.4cv = 0.718 kJ/(kg·K)
w = kJ/kg
3.Medium
vP1234qin​qout​

An ideal Diesel cycle has a compression ratio r = 20 and a cutoff ratio rc = v₃/v₂ = 2.2. 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 = 20rc = 2.2k = 1.4
η = %
4.Medium
vP1234qin​qout​

An ideal Diesel cycle has a compression ratio r = 19 and a cutoff ratio rc = v₃/v₂ = 1.5. At the start of compression the air is at 320 K. 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 T3 at the end of heat addition, in K.

r = 19rc = 1.5T1 = 320 Kk = 1.4
T3 = K
5.Hard
vP1234qin​qout​

A gas-turbine plant runs on a Brayton cycle with a compressor pressure ratio of 18. Air enters the compressor at 295 K and the turbine at 1300 K. The compressor has an isentropic efficiency of 85% and the turbine 85%. 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 net work output wnet per kilogram of air, in kJ/kg.

rp = 18T1 = 295 KT3 = 1300 Kηc = 85%ηt = 85%k = 1.4cp = 1.005 kJ/(kg·K)
wnet = kJ/kg
6.Hard
vP1234qin​qout​

A gas-turbine plant runs on a Brayton cycle with a compressor pressure ratio of 20. Air enters the compressor at 310 K and the turbine at 1300 K. Both machines are isentropic. 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 net work output wnet per kilogram of air, in kJ/kg.

rp = 20T1 = 310 KT3 = 1300 Kk = 1.4cp = 1.005 kJ/(kg·K)
wnet = kJ/kg

Answer key

  1. 1. T2 = 763.7 K
  2. 2. w = 628.3 kJ/kg
  3. 3. η = 63.8 %
  4. 4. T3 = 1559 K
  5. 5. wnet = 176.5 kJ/kg
  6. 6. wnet = 329.7 kJ/kg

Full step-by-step solutions: practise this topic on examproblems.com.