9th Edition

ISBN: 9781259822674

Author: Yunus A. Cengel Dr., Michael A. Boles

Publisher: McGraw-Hill Education

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Textbook Question

Chapter 9.12, Problem 42P

Someone has suggested that the air-standard Otto cycle is more accurate if the two isentropic processes are replaced with polytropic processes with a polytropic exponent n = 1.3. Consider such a cycle when the compression ratio is 8, P1 = 95 kPa, T1 = 15°C, and the maximum cycle temperature is 1200°C. Determine the heat transferred to and rejected from this cycle, as well as the cycle’s thermal efficiency. Use constant specific heats at room temperature.

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Chapter 9.12, Problem 41P

Chapter 9.12, Problem 43P

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! Required information Problem 09.034 - Ideal Otto Cycle with Variable Specific Heats - DEPENDENT MULTI-PART PROBLEM - ASSIGN ALL PARTS An ideal Otto cycle has a compression ratio of 8. At the beginning of the compression process, air is at 95 kPa and 27°C, and 760 kJ/kg of heat is transferred to air during the constant-volume heat-addition process. Take into account the variation of specific heats with temperature. The gas constant of air is R = 0.287 kJ/kg-K. Problem 09.034.a - State After Heat Addition in Variable Heat Capacity Ideal Otto Cycle Determine the pressure and temperature at the end of the heat-addition process. (You must provide an answer before moving on to the next part.) The pressure at the end of the heat-addition process is 3915.8 kPa. The temperature at the end of the heat-addition process is 1647.7 K.

Let’s examine the engine of a Honda CB1000RR. But first, some idealizations:we will evaluate the engine using an ideal Otto cycle with variable specific heats.At the start of each cycle, air is at 100 kPa and 298 K, and has a gas constant of around 0.287kJ/kg-K. The maximum temperature at the end of heat addition is assumed to be 2200 K.The Honda CB1000RR has a four-stroke I4 spark-ignition (SI) engine: four cylinders, each with 25 cc (or cm3) of maximum volume. Its compression ratio is 10.8. At our preferred condition, the engine runsat 9,000 revolutions per minute, with two cylinders undergoing a power stroke every revolution.a. Sketch the Pressure (kPa) - volume (cc) and Temperature (K) - entropy (s) diagram of the cycle.For entropy, you may leave it as s1, s2, etc. b. Calculate the specific net work (kJ/kg) and the efficiency (%). c. Calculate the mean effective pressure (kPa) and the power produced by the engine (in kW).

Consider an air-standard Otto cycle. Prior to the isentropic compression process, the air is at 100 kPa, 290 K, and 600 cm^3. The temperature at the end of the isentropic compression process is 613.59 K. Assume the specific heat is constant with Cv = 0.718 kJ/kgK and k = 1.4. %3D In the question that follows, select the answer that is closest to the true value. What is the compression ratio?

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 - Prob. 3P Ch. 9.12 - How does the thermal efficiency of an ideal cycle,...Ch. 9.12 - How are the combustion and exhaust processes...Ch. 9.12 - What does the area enclosed by the cycle represent...Ch. 9.12 - Prob. 7P Ch. 9.12 - Can the mean effective pressure of an automobile...Ch. 9.12 - What is the difference between spark-ignition and...Ch. 9.12 - Prob. 10P

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Solution Summary: The author explains how the two isentropic processes of the Otto cycle are replaced with polytropic

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