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RESEARCH PAPERS

Optimum Criteria on the Important Parameters of an Irreversible Otto Heat Engine With the Temperature-Dependent Heat Capacities of the Working Fluid

[+] Author and Article Information
Yingru Zhao

Department of Physics,  Xiamen University, Xiamen 361005, P.R.C.

Bihong Lin

Department of Physics,  Xiamen University, Xiamen 361005, P.R.C.; Department of Physics,  Quanzhou Normal University, Quanzhou 362000, P.R.C.

Jincan Chen1

Department of Physics,  Xiamen University, Xiamen 361005, P.R.C.jcchen@xmu.edu.cn

1

Corresponding author.

J. Energy Resour. Technol 129(4), 348-354 (Apr 26, 2007) (7 pages) doi:10.1115/1.2794770 History: Received September 10, 2006; Revised April 26, 2007

An irreversible cycle model of the Otto heat engine is established, in which the temperature-dependent heat capacities of the working fluid, the irreversibilities resulting from the nonisentropic compression and expansion processes, and heat leak losses through the cylinder wall are taken into account. The adiabatic equation of ideal gases with the temperature-dependent heat capacity is strictly deduced without using the additional approximation condition in the relevant literature and used to analyze the performance of the Otto heat engine. Expressions for the work output and efficiency of the cycle are derived by introducing the compression ratio of two isochoric processes. The performance characteristic curves of the Otto heat engine are presented for a set of given parameters. The optimum criteria of some important parameters such as the work output, efficiency, compression ratio, and temperatures of the working fluid are given. Moreover, the influence of the compression and expansion efficiencies, the variable heat capacities, the heat leak, and other parameters on the performance of the cycle is discussed in detail. The results obtained are novel and general, from which some relevant conclusions in literature may be directly derived. This work may provide a significant guidance for the performance improvement and optimal design of the Otto heat engine.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

Grahic Jump Location
Figure 1

The schematic diagram of an irreversible Otto heat engine

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Figure 2

The W *∼rV curves of an irreversible Otto heat engine for the parameters n=1.57×10−2mol, T1=350K, k1=6.035×10−5J∕K2, and k=1.400. rVW is the compression ratio of two isochoric processes at the maximum dimensionless work output Wmax *. Curves I, II, and III correspond to the cases of T3=2000K, 2100K, and 2200K, respectively. The solid, dashed, and dash-dot curves correspond to the cases of ηc=ηe=0.8, 0.9, and 1, respectively.

Grahic Jump Location
Figure 3

The η∼rV curves of an irreversible Otto heat engine for the parameters β∕b=0.1 and T0=T1. rVη is the compression ratio of two isochoric processes at the maximum efficiency ηmax. The values of other relevant parameters are the same as those used in Fig. 2.

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Figure 4

The W *∼η curves of an irreversible Otto heat engine. The values of the relevant parameters are the same as those used in Fig. 3.

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Figure 5

The influence of k1 on the W *∼rV curves of an irreversible Otto heat engine for the parameters T3=2000K and ηc=ηe=0.8. The dashed curve corresponds to the case of k1=0. The values of other relevant parameters are the same as those used in Fig. 2.

Grahic Jump Location
Figure 6

The influence of k1 on the η∼rV curves of an irreversible Otto heat engine for the parameters T3=2000K and ηc=ηe=0.8. The dashed curve corresponds to the case of k1=0. The values of other relevant parameters are the same as those used in Fig. 3.

Grahic Jump Location
Figure 7

The influence of k on the W∼rV curves of an irreversible Otto heat engine for the parameters n=1.57×10−2mol, T1=350K, T3=2000K, k1=6.035×10−5J∕K2, and ηc=ηe=0.8. The solid, dashed, and dash-dot curves correspond to the cases of k=1.400, 1.667, and 1.333, respectively.

Grahic Jump Location
Figure 8

The influence of k on the η∼rV curves of an irreversible Otto heat engine for the parameters β=0.03263J∕K and T0=T1. The values of other relevant parameters are the same as those used in Fig. 7.

Grahic Jump Location
Figure 9

The influence of the heat leak on the η∼rV curves of an irreversible Otto heat engine. Curves I and II correspond to the cases of β∕b=0.1 and 0, respectively. The solid, dashed, and dash-dot curves correspond to the cases of ηc=ηe=0.8, 0.9, and 1, respectively. The values of other relevant parameters are the same as those used in Fig. 3.

Grahic Jump Location
Figure 10

The influence of the heat leak on the W *∼η curves of an irreversible Otto heat engine. The values of the relevant parameters are the same as those used in Fig. 9.

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