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
Want to see more full solutions like this?
Chapter 9 Solutions
THERMODYNAMICS: AN ENGINEERING APPROACH
- 1.An ideal Otto cycle has a compression ratio of 8. At the beginning of the compression process, air is at 105 kPa and 28 °C, and 850 kJ/kg of heat is transferred to air during the constant-volume heat-addition process. Taking into account the variation of specific heats with temperature, determine (i) the pressure and temperature at the end of the heat addition process, (ii) the net work output, (iii) the thermal efficiency, and (iv) the mean effective pressure for the cycle.arrow_forwardQ11) An ideal Diesel cycle with air as the working fluid has a compression ratio of 18 and cutoff ratio of 2. At the beginning of the compression process, the working fluid is at 100 kPa and 300 K, and 0.002 m3. Utilizing the cold-air standard assumptions, and assume the specific heats are constants, determine: a- The temperature and pressure of the air at the end of each process. b- The net output and the thermal efficiency, and c- The mean effective pressure.arrow_forwardAn Otto cycle with a compression ratio of 8 begins its compression at 94 kPa and 10°C. The maximum cycle temperature is 900°C. Utilizing air-standard assumptions, determine the thermal efficiency of this cycle using variable specific heatsarrow_forward
- An Otto cycle with a compression ratio of 8 begins its compression at 94 kPa and 10°C. The maximum cycle temperature is 900°C. Utilizing air-standard assumptions, determine the thermal efficiency of this cycle using constant specific heats at room temperature.arrow_forwardA Diesel cycle has a compression ratio of 22 and begins its compression at 85 kPa and 15°C. The maximum cycle temperature is 1200°C. Utilizing air-standard assumptions, determine the thermal efficiency of this cycle using variable specific heats.arrow_forwardOtto cycle operating under air standard condition has a compression ratio of 8.0. If the heat added on the cycle amounts to 3500kJ/kg of working substance, determine the peak temperature of the cycle.a. 899.62390C b. 899.62370C c. 899.62870C d. 899.65370Carrow_forward
- Consider a regenerative Brayton cycle operating with a pressure ratio of 8, where the air enters the compressor at 300 K and 100 kPa, while it enters the turbine at 1060 K. Assume that both the compressor and turbine are isentropic, that specific heats vary with temperature, and that the regenerator has an effectiveness of 74%. Round all intermediate calculations to three decimal places. 1. How much net work is produced in kJ/kg? Round your answer to two decimal places. 2. What is the thermal efficiency as a percentage (0% - 100%)? Round your answer to one decimal place. 3. What is the thermal efficiency as a percentage (0% - 100%) if there was no regenerator? Round your answer to one decimal place.arrow_forwardAn Otto cycle operating in an air standard conditions has a peak temperature of 800C. If the heat added in each cycle is equal to 350kJ/kg, determine the compression ratio of the cycle.a. 5.4004 b. 5.4005 c. 5.4006 d. 5.4007arrow_forwardThe max temperature of an Otto cycle working under air standard conditions is 8000 degrees Celsius. Determine the compression ratio of the cycle if the heat injected in each cycle is 350kJ/kg.arrow_forward
- An ideal diesel engine has a compression ratio of 20 and uses air as the working fluid. The state of air at the beginning of the compression process is 95 kPa and 20°C. If the maximum temperature in the cycle is not to exceed 2200 K, determine the thermal efficiency.arrow_forwardAn air standard diesel cycle has a compression ratio of 13 and a peak combustion temperature of 1681.55C. If the heat rejected by the engine amounts to 3kW, determine the theoretical output power that can be produced by the engine.a. 3.8552kW b. 3.8553kW c. 3.8551kW d. 3.8550kWarrow_forwardHow does the thermal efficiency of an ideal Otto cycle change with the compression ratio of the engine and the specific heat ratio of the working fluid?arrow_forward
- Elements Of ElectromagneticsMechanical EngineeringISBN:9780190698614Author:Sadiku, Matthew N. O.Publisher:Oxford University PressMechanics of Materials (10th Edition)Mechanical EngineeringISBN:9780134319650Author:Russell C. HibbelerPublisher:PEARSONThermodynamics: An Engineering ApproachMechanical EngineeringISBN:9781259822674Author:Yunus A. Cengel Dr., Michael A. BolesPublisher:McGraw-Hill Education
- Control Systems EngineeringMechanical EngineeringISBN:9781118170519Author:Norman S. NisePublisher:WILEYMechanics of Materials (MindTap Course List)Mechanical EngineeringISBN:9781337093347Author:Barry J. Goodno, James M. GerePublisher:Cengage LearningEngineering Mechanics: StaticsMechanical EngineeringISBN:9781118807330Author:James L. Meriam, L. G. Kraige, J. N. BoltonPublisher:WILEY