26. The compression ratio of a compression-ignition engine is 14 to 1. The diameter of the cylinder is 500 mm and the stroke to bore ratio is 1.2 to 1. At the beginning of compression the pressure and temperature of the air in the cylinder is 105 kPa and 51 °C, and compression follows the law PV" = C, where n = 1.35. Calculate the work done on the air during compression. Answer: A A. -57.69 kJ B. -67.59 kJ C. -76.59 kJ D. -95.67 kJ

Elements Of Electromagnetics
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Pls answer items 26-30
26. The compression ratio of a compression-ignition engine is 14 to 1. The diameter of the cylinder is
500 mm and the stroke to bore ratio is 1.2 to 1. At the beginning of compression the pressure and
temperature of the air in the cylinder is 105 kPa and 51 °C, and compression follows the law PV" =
C, where n = 1.35. Calculate the work done on the air during compression. Answer: A
A. -57.69 kJ
B. -67.59 kJ
C. -76.59 kJ
D. -95.67 kJ
27. Gas initially at a pressure of 101.325 kPa and temperature of 60 °C undergoes the following cycle.
1-2 Adiabatic compression through compression ratio of 4.5:1.
2-3 Heating at constant volume through a pressure ratio of 1.35:1.
3-4 Constant pressure expansion to initial pressure.
4-1 Constant pressure cooling to initial volume.
If Cp = 1 kJ/kg-K and Cv = 0.678 kJ/kg-K for the gas, determine the thermal efficiency of the
cycle. Answer: A
A. 41.41%
B. 39.39%
C. 43.43%
D. 45.45%
28. One kilogram of air at a pressure and temperature of 101.325 kPa and 15 °C initially, undergoes the
following process in a cycle:
1-2 Isothermal compression to 202.65 kPa
2-3 Polytropic compression from 202.65 kPa to 405.30 kPa
3-1 Isentropic expansion from 405.30 kPa to initial condition
Calculate the heat transfer for process 1 to 2. Use R = 0.287 kJ/kg-K and k = 1.4 for air. Answer:
A
A. -57.29 kJ
B. -30.21 kJ
C. 70.30 kJ
D. 100.50 kJ
29. The compression ratio of an engine working on the dual combustion cycle is 10.7. The pressure and
temperature of the air at the beginning of compression is 101.325 kPa and 32 °C. The maximum
pressure and temperature during the cycle is 4.154 Mpa and 1593 °C. Assuming adiabatic
compression and expansion, calculate the temperature at the end of compression. Answer: B
A. 414.14 °C
B. 514.14 °C
C. 314.14 °C℃
D. 614.14 °C
30. In an Otto engine if the compression ratio is 5.5, what is the percent clearance? Answer: A
A. 22.22%
B. 31.11%
C. 19.64%
D. 25.34%
Transcribed Image Text:26. The compression ratio of a compression-ignition engine is 14 to 1. The diameter of the cylinder is 500 mm and the stroke to bore ratio is 1.2 to 1. At the beginning of compression the pressure and temperature of the air in the cylinder is 105 kPa and 51 °C, and compression follows the law PV" = C, where n = 1.35. Calculate the work done on the air during compression. Answer: A A. -57.69 kJ B. -67.59 kJ C. -76.59 kJ D. -95.67 kJ 27. Gas initially at a pressure of 101.325 kPa and temperature of 60 °C undergoes the following cycle. 1-2 Adiabatic compression through compression ratio of 4.5:1. 2-3 Heating at constant volume through a pressure ratio of 1.35:1. 3-4 Constant pressure expansion to initial pressure. 4-1 Constant pressure cooling to initial volume. If Cp = 1 kJ/kg-K and Cv = 0.678 kJ/kg-K for the gas, determine the thermal efficiency of the cycle. Answer: A A. 41.41% B. 39.39% C. 43.43% D. 45.45% 28. One kilogram of air at a pressure and temperature of 101.325 kPa and 15 °C initially, undergoes the following process in a cycle: 1-2 Isothermal compression to 202.65 kPa 2-3 Polytropic compression from 202.65 kPa to 405.30 kPa 3-1 Isentropic expansion from 405.30 kPa to initial condition Calculate the heat transfer for process 1 to 2. Use R = 0.287 kJ/kg-K and k = 1.4 for air. Answer: A A. -57.29 kJ B. -30.21 kJ C. 70.30 kJ D. 100.50 kJ 29. The compression ratio of an engine working on the dual combustion cycle is 10.7. The pressure and temperature of the air at the beginning of compression is 101.325 kPa and 32 °C. The maximum pressure and temperature during the cycle is 4.154 Mpa and 1593 °C. Assuming adiabatic compression and expansion, calculate the temperature at the end of compression. Answer: B A. 414.14 °C B. 514.14 °C C. 314.14 °C℃ D. 614.14 °C 30. In an Otto engine if the compression ratio is 5.5, what is the percent clearance? Answer: A A. 22.22% B. 31.11% C. 19.64% D. 25.34%
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