Concept explainers
a)
The net power output of the cycle.
a)
Answer to Problem 164RP
The net power output of the cycle is
Explanation of Solution
Draw the
Write the expression for compression ratio to calculate the clearance volume or one cylinder.
Here, clearance volume is
Write the expression to calculate the volume at state 1.
Write the expression to calculate the mass of the air.
Write temperature and specific volume relation for the isentropic compression process 1-2.
Write the pressure, temperature, and specific volume relation for isentropic compression process 1-2.
Here, the temperature at state 1 is
Write the expression for heat addition process 2-3
Here, temperature at state 3 is
Write the temperature, pressure, and specific volume relation for the constant volume heat addition process 2-3.
For process 2-3,
Conclusion:
From Table A-1, “Ideal-gas specific heats of various common gases”, obtain the value of gas constant
Substitute
Substitute
Substitute
Substitute
Substitute
Substitute
Substitute
b)
The net work per cycle per cylinder and the thermal efficiency of the cycle.
b)
Answer to Problem 164RP
The net work per cycle per cylinder is
The thermal efficiency of the cycle is
Explanation of Solution
Write the temperature and specific volume relation for isentropic expansion process 3-4
Here, temperature at state 4 is
Write the expression for heat rejection process 4-1,
Write the expression to calculate the net power output
Write the expression to calculate the thermal efficiency of the cycle
Conclusion:
Substitute
Substitute
Substitute
Thus, the net work per cycle per cylinder is
Substitute
Thus, the thermal efficiency of the cycle is
c)
The mean effective pressure of the cycle.
c)
Answer to Problem 164RP
The mean effective pressure of the cycle is
Explanation of Solution
Write the expression to calculate the mean effective pressure for an ideal otto cycle
Here, the compression ratio is
Conclusion:
Substitute,
Thus, the mean effective pressure of the cycle is
d)
The power output for an engine speed of 3000 rpm.
d)
Answer to Problem 164RP
The power output for an engine speed of 3000 rpm is
Explanation of Solution
Write the expression to calculate the power produced by the engine
Here, speed of the engine is
Here, the compression ratio is
Conclusion:
In one cycle there are two revolutions in four stroke engines.
Substitute
Thus, the power output for an engine speed of 3000 rpm is
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Chapter 9 Solutions
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