In a diesel cycle, heat is added at constant pressure and rejected at constant volume as shown in Figure 6.16. During heat addition, to maintain the constant pressure piston starts to move towards BDC. At point 3, injection is stopped which is known as cut-off point.
Figure 6.16 Indicator Diagrams for Diesel Cycle
Putting the value of T2, T3 and T4 in the equation of efficiency, we get
Example 6.4: In an air standard diesel cycle, the compression ratio is 18. The pressure and temperature at the beginning of compression are 0.1 MPa and 300 K, respectively. Heat is added at constant pressure until the temperature is increased to 1,700 K. Calculate (i) cut-off ratio, (ii) heat supplied per kg of air, (iii) cycle efficiency, and (iii) mean effective pressure Cp = 1.005 kJ/kg, γair = 1.4.
Solution:
Heat addition at constant pressure,
Example 6.5: An ideal diesel cycle operates on 1kg of standard air with an initial pressure of 0.98 bar and a temperature of 350°C. The pressure at the end of compression is 33bar and cut-off is 6% of the stroke. Determine: (i) compression ratio, (ii) percentage clearance, and (iii) heat supplied.
Solution:
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