Thermodynamics: An Engineering Approach
8th Edition
ISBN: 9780073398174
Author: Yunus A. Cengel Dr., Michael A. Boles
Publisher: McGraw-Hill Education
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Textbook Question
Chapter 9.12, Problem 28P
Why are high compression ratios not used in spark-ignition engines?
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Cylinder conditions at the start of compression in a spark ignition engine operating atwide open throttle on an air-standard Otto cycle are 60oC and 98kPa.The engine has a compression ratio of 9.5:1 and uses petroleum with an air-fuel ratio(AF) of 15.5.Combustion efficiency is 96%, and it can be assumed that there is no exhaust residual.If the petroleum has a heating value (QHV) of 43kJ/kg,Calculate the following:
1) Temperature in oC and Pressure in kPa at all states in the cycle 2) Specific work done during the power stroke in kJ/kg 3) Heat added during combustion in kJ/kg 4) Net specific work done in kJ/kg5) Indicated thermal efficiency
Differentiate a diesel-fired engine and a gasoline fired engine.
In an isochoric and isobaric combustion cycle, the indicated mean pressure is 10 bars and the maximum pressure is 60 bars. The pressure and temperature at the start of the cycle are 1 bar and 17 oC. The volumetric compression ratio is 16/1. The mass constant of gas, R = 287 J / kg K The specific heat at constant volume, cv = 718 J / kg K. Calculate the maximum temperature of the combustion cycle for a thermal efficiency of 60%.
Chapter 9 Solutions
Thermodynamics: An Engineering Approach
Ch. 9.12 - What are the air-standard assumptions?Ch. 9.12 - What is the difference between air-standard...Ch. 9.12 - How does the thermal efficiency of an ideal cycle,...Ch. 9.12 - What does the area enclosed by the cycle represent...Ch. 9.12 - Prob. 5PCh. 9.12 - Prob. 6PCh. 9.12 - Can the mean effective pressure of an automobile...Ch. 9.12 - Prob. 8PCh. 9.12 - What is the difference between spark-ignition and...Ch. 9.12 - Prob. 10P
Ch. 9.12 - Prob. 11PCh. 9.12 - Prob. 12PCh. 9.12 - Prob. 13PCh. 9.12 - Prob. 15PCh. 9.12 - Prob. 16PCh. 9.12 - Prob. 17PCh. 9.12 - Prob. 18PCh. 9.12 - Repeat Prob. 919 using helium as the working...Ch. 9.12 - Consider a Carnot cycle executed in a closed...Ch. 9.12 - Prob. 21PCh. 9.12 - Prob. 22PCh. 9.12 - What four processes make up the ideal Otto cycle?Ch. 9.12 - Are the processes that make up the Otto cycle...Ch. 9.12 - How do the efficiencies of the ideal Otto cycle...Ch. 9.12 - How does the thermal efficiency of an ideal Otto...Ch. 9.12 - Prob. 27PCh. 9.12 - Why are high compression ratios not used in...Ch. 9.12 - An ideal Otto cycle with a specified compression...Ch. 9.12 - Prob. 30PCh. 9.12 - Prob. 31PCh. 9.12 - Prob. 32PCh. 9.12 - An ideal Otto cycle has a compression ratio of 8....Ch. 9.12 - Prob. 35PCh. 9.12 - Prob. 36PCh. 9.12 - Prob. 37PCh. 9.12 - An ideal Otto cycle with air as the working fluid...Ch. 9.12 - Repeat Prob. 940E using argon as the working...Ch. 9.12 - Prob. 40PCh. 9.12 - Prob. 41PCh. 9.12 - Prob. 42PCh. 9.12 - Prob. 43PCh. 9.12 - Prob. 44PCh. 9.12 - Prob. 45PCh. 9.12 - Prob. 46PCh. 9.12 - Prob. 47PCh. 9.12 - Prob. 48PCh. 9.12 - Prob. 49PCh. 9.12 - Prob. 50PCh. 9.12 - Prob. 51PCh. 9.12 - Prob. 52PCh. 9.12 - Prob. 53PCh. 9.12 - Prob. 54PCh. 9.12 - Repeat Prob. 957, but replace the isentropic...Ch. 9.12 - Prob. 57PCh. 9.12 - Prob. 58PCh. 9.12 - Prob. 59PCh. 9.12 - The compression ratio of an ideal dual cycle is...Ch. 9.12 - Repeat Prob. 962 using constant specific heats at...Ch. 9.12 - Prob. 63PCh. 9.12 - An air-standard cycle, called the dual cycle, with...Ch. 9.12 - Prob. 65PCh. 9.12 - Prob. 66PCh. 9.12 - Consider the ideal Otto, Stirling, and Carnot...Ch. 9.12 - Consider the ideal Diesel, Ericsson, and Carnot...Ch. 9.12 - An ideal Ericsson engine using helium as the...Ch. 9.12 - An ideal Stirling engine using helium as the...Ch. 9.12 - Prob. 71PCh. 9.12 - Prob. 72PCh. 9.12 - Prob. 73PCh. 9.12 - Prob. 74PCh. 9.12 - Prob. 75PCh. 9.12 - For fixed maximum and minimum temperatures, what...Ch. 9.12 - What is the back work ratio? What are typical back...Ch. 9.12 - Why are the back work ratios relatively high in...Ch. 9.12 - How do the inefficiencies of the turbine and the...Ch. 9.12 - A simple ideal Brayton cycle with air as the...Ch. 9.12 - A gas-turbine power plant operates on the simple...Ch. 9.12 - Prob. 82PCh. 9.12 - Prob. 83PCh. 9.12 - Prob. 85PCh. 9.12 - 9–86 Consider a simple Brayton cycle using air as...Ch. 9.12 - 9–87 Air is used as the working fluid in a simple...Ch. 9.12 - Air is used as the working fluid in a simple ideal...Ch. 9.12 - An aircraft engine operates on a simple ideal...Ch. 9.12 - 9–91E A gas-turbine power plant operates on a...Ch. 9.12 - Prob. 92PCh. 9.12 - 9–93 A gas-turbine power plant operates on the...Ch. 9.12 - A gas-turbine power plant operates on a modified...Ch. 9.12 - Prob. 95PCh. 9.12 - Prob. 96PCh. 9.12 - Prob. 97PCh. 9.12 - Prob. 98PCh. 9.12 - 9–99 A gas turbine for an automobile is designed...Ch. 9.12 - Prob. 100PCh. 9.12 - A gas-turbine engine operates on the ideal Brayton...Ch. 9.12 - An ideal regenerator (T3 = T5) is added to a...Ch. 9.12 - Prob. 103PCh. 9.12 - Prob. 104PCh. 9.12 - Prob. 106PCh. 9.12 - A Brayton cycle with regeneration using air as the...Ch. 9.12 - Prob. 108PCh. 9.12 - Prob. 109PCh. 9.12 - Prob. 110PCh. 9.12 - Prob. 111PCh. 9.12 - Prob. 112PCh. 9.12 - Prob. 113PCh. 9.12 - Prob. 114PCh. 9.12 - Prob. 115PCh. 9.12 - A simple ideal Brayton cycle without regeneration...Ch. 9.12 - A simple ideal Brayton cycle is modified to...Ch. 9.12 - Prob. 118PCh. 9.12 - Consider a regenerative gas-turbine power plant...Ch. 9.12 - Repeat Prob. 9123 using argon as the working...Ch. 9.12 - Consider an ideal gas-turbine cycle with two...Ch. 9.12 - Repeat Prob. 9125, assuming an efficiency of 86...Ch. 9.12 - Prob. 123PCh. 9.12 - Prob. 124PCh. 9.12 - Prob. 126PCh. 9.12 - Prob. 127PCh. 9.12 - Prob. 128PCh. 9.12 - Prob. 129PCh. 9.12 - A turbojet is flying with a velocity of 900 ft/s...Ch. 9.12 - Prob. 131PCh. 9.12 - A pure jet engine propels an aircraft at 240 m/s...Ch. 9.12 - A turbojet aircraft is flying with a velocity of...Ch. 9.12 - Prob. 134PCh. 9.12 - Consider an aircraft powered by a turbojet engine...Ch. 9.12 - 9–137 Air at 7°C enters a turbojet engine at a...Ch. 9.12 - Prob. 138PCh. 9.12 - Prob. 139PCh. 9.12 - 9–140E Determine the exergy destruction associated...Ch. 9.12 - Prob. 141PCh. 9.12 - Prob. 142PCh. 9.12 - Prob. 143PCh. 9.12 - Prob. 144PCh. 9.12 - Prob. 146PCh. 9.12 - A gas-turbine power plant operates on the...Ch. 9.12 - Prob. 149PCh. 9.12 - Prob. 150RPCh. 9.12 - Prob. 151RPCh. 9.12 - Prob. 152RPCh. 9.12 - Prob. 153RPCh. 9.12 - Prob. 154RPCh. 9.12 - Prob. 155RPCh. 9.12 - Prob. 156RPCh. 9.12 - Prob. 157RPCh. 9.12 - Prob. 159RPCh. 9.12 - Prob. 161RPCh. 9.12 - Prob. 162RPCh. 9.12 - Prob. 163RPCh. 9.12 - Consider a simple ideal Brayton cycle with air as...Ch. 9.12 - Prob. 165RPCh. 9.12 - Helium is used as the working fluid in a Brayton...Ch. 9.12 - Consider an ideal gas-turbine cycle with one stage...Ch. 9.12 - Prob. 169RPCh. 9.12 - Prob. 170RPCh. 9.12 - Prob. 173RPCh. 9.12 - Prob. 174RPCh. 9.12 - Prob. 184FEPCh. 9.12 - For specified limits for the maximum and minimum...Ch. 9.12 - Prob. 186FEPCh. 9.12 - Prob. 187FEPCh. 9.12 - Helium gas in an ideal Otto cycle is compressed...Ch. 9.12 - Prob. 189FEPCh. 9.12 - Prob. 190FEPCh. 9.12 - Consider an ideal Brayton cycle executed between...Ch. 9.12 - An ideal Brayton cycle has a net work output of...Ch. 9.12 - In an ideal Brayton cycle, air is compressed from...Ch. 9.12 - In an ideal Brayton cycle with regeneration, argon...Ch. 9.12 - In an ideal Brayton cycle with regeneration, air...Ch. 9.12 - Consider a gas turbine that has a pressure ratio...Ch. 9.12 - An ideal gas turbine cycle with many stages of...Ch. 9.12 - Prob. 198FEP
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- Which factors prevent the combustion reactions from going to 100% completion in a four-stroke, gasoline-burning internal combustion engine?arrow_forwardplease provide full solutionarrow_forwardIn an isochoric and isobaric combustion cycle, the indicated average pressure is 10 bars and the maximum pressure is 60 bars. The pressure and temperature at the start of the cycle are 1 bar and 17 oC. The volumetric compression ratio is 16/1. The mass constant of gas, R = 287 J / kg K The specific heat at constant volume, cv = 718 J / kg K. Calculate the maximum temperature of the combustion cycle for a thermal efficiency of 60%.arrow_forward
- Problem 1 1. Describe with the aid of diagrams the operational sequence of four stroke spark ignition engines 2. Explain how do you calculate the efficiency for an ideal otto cycle. 3. What is the difference between four and two stroke spark ignition engines?. 4. Why are high compression ratios not used in spark ignition engines?.arrow_forwardThe compression ratio of an air standard diesel cycle is 13 and the peak combustion temperature is 1681.55 oC. Determine the potential output power that the engine can generate if the heat rejected by the engine is 3kW. a. 3.8552kWb. 3.8553 kWc. 8.8551 kWd. 3.8850 kWarrow_forwardA spark ignition engine that operates on Otto cycle has a compression ratio of 10. At the beginning of the compression process, air is at 100 kPa and 25 C. 750 kJ/kg of heat is transferred to air duringthe constant-volume heat-addition process. Consider the variation of specific heats with temperature. 1)Describe with the aid of diagrams the operational sequence of four stroke spark ignition engines 2)Explain the mechanical efficiency for ideal otto cycle of two and four stroke enginesarrow_forward
- Discuss the importance of the valve system in an internal combustion engines.arrow_forwardWhat would be the expected increase in efficiency of an Otto-cycle gasoline engine if the compression ratio were increased from 6.5 to 8.0?arrow_forward(a) A spark ignition engine operates on the air-standard Otto cycle. Air is induced at 1 bar and 30 oC and attains a temperature of 1600 oC after heat addition. If the compression ratio is 9 to 1. Sketch the p-v and T-s diagrams for the Otto cycle and calculate the cycle thermal efficiency. (b) How does the thermal efficiency of a real Spark Ignition engine compares to that for the air standard Otto cycle and what are the reasons for the difference. (c) Describe the operation of a vertical, four-stroke normally aspirated spark-ignition (SI) automobile engine.arrow_forward
- In an ideal dual combustion cycle, what is the pressure at the beginning of constant pressure combustion if the pressure ratio is 1.4 and the pressure at the beginning of the constant volume portion of combustion is 2500 kPa.arrow_forward1. In an engine operating on the ideal dual combustion cycle the compression ratio is 13.5:1 the maximum cycle pressure and temperature are 4.4 bar and 1350 deg. Celcus respectively. If the initial pressure and temperature are 1 bar and 27 deg. C. Calculate the thermal efficiency of the cycle and the mean effective pressure of the cycle. kJ Cp = 1.005. kg-K ,Cy = 0.718–J kg-Karrow_forwardA vehicle powered by a spark ignition engine follows air standard Otto cycle 1.4 . The engine generates 70kW while consuming 10.3kg/hr of fuel. The calorific value of fuel is 44,000kJ/kg. The compression ratio is ___arrow_forward
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