Homework Assignment

#1.  Air at 300^oK and 101 kPa is compressed in an engine modeled using the cold air-standard Diesel cycle. The engine has a compression ratio of 10 and a cutoff ratio of 1.4.   Determine:

1. the temperature and pressure at each state (2,3&4) in the cycle
2. the net work in kJ/kg
3. the heat addition in kJ/kg
4. the thermal efficiency
5. the mean effective pressure in kPa

#2.  Repeat problem 1 on an air-standard basis and compare the results to those obtained in problem 1.

#3 Derive an expression for the efficiency of a cold air-standard dual cycle as a function of the the specific heat ratio (k), compression ratio (r), the pressure ratio (r_p), and the cutoff ratio (r_c) only.

#4 An engine is modeled as a cold air-standard dual cycle (k=1.4).  At the beginning of compression process the temperature is 300 K and the pressure is 100 kPa.  The compression ratio is 10, the pressure ratio for constant volume heat addition is 1.2, and the cutoff ratio is 1.3.  Sketch a P-v diagram for the cycle, complete the table below, and determine the thermal efficiency.  Note: R=0.287 kJ/kg-K.

Additional Material

Worked out examples (tutorials).

See if you can find the mistake in my movie. :) The efficiency of the cold air-standard Otto cycle is

• Otto Cycle
  • Cold Air Standard Analysis
  • Air Standard Analysis
  • Comparison of methods

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