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Research Papers: Internal Combustion Engines

Effect of Piston Friction on the Performance of SI Engine: A New Thermodynamic Approach

[+] Author and Article Information
E. Abu-Nada, I. Al-Hinti, A. Al-Sarkhi, B. Akash

Department of Mechanical Engineering, Hashemite University, Zarqa 13115, Jordan

J. Eng. Gas Turbines Power 130(2), 022802 (Jan 22, 2008) (8 pages) doi:10.1115/1.2795777 History: Received July 19, 2006; Revised August 27, 2007; Published January 22, 2008

This paper presents thermodynamic analysis of piston friction in spark-ignition internal combustion engines. The general effect of piston friction on engine performance was examined during cold starting and normal working conditions. Considerations were made using temperature-dependent specific heat model in order to make the analysis more realistic. A parametric study was performed covering wide range of dependent variables such as engine speed, taking into consideration piston friction combined with the variation of the specific heat with temperature, and heat loss from the cylinder. The results are presented for skirt friction only, and then for total piston friction (skirt and rings). The effect of oil viscosity is investigated over a wide range of engine speeds and oil temperatures. In general, it is found that oils with higher viscosities result in lower efficiency values. Using high viscosity oil can reduce the efficiency by more than 50% at cold oil temperatures. The efficiency maps for SAE 10, SAE 30, and SAE 50 are reported. The results of this model can be practically utilized to obtain optimized efficiency results either by selecting the optimum operating speed for a given oil type (viscosity) and temperature or by selecting the optimum oil type for a given operating speed and temperature. The effect of different piston ring configurations on the efficiency is also presented. Finally, the oil film thickness on the engine performance is studied in this paper.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Different distribution models for the ring oil film thickness

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Figure 2

Efficiency versus engine speed for skirt and total friction contribution, SAE 30, A=1, B=6, number of rings=2 (each 1.5mm thick), C=23μm

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Figure 3

(a) Efficiency versus engine speed for various oil types at 80°C, (b) Efficiency versus oil temperature for various oil types at 3000rpm. (Both (a) and (b) have A=1, B=6, number of rings=2 (each 1.5mm thick), C=23μm.)

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Figure 5

Efficiency contours A=1, B=6, number of rings=2 (each 1.5mm thick), C=23μm: (a) SAE 10, (b) SAE 30, (c) SAE 50, and (d), no friction case

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Figure 6

(a) Efficiency versus engine speed for different ring configuration, SAE 30, T=80°C, A=1, B=6, C=23μm. (b) Efficiency versus oil temperature for different ring configuration for SAE 30, N=3000°C, A=1, B=6, C=23μm.

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Figure 4

(a) fmep versus engine speed for various oil types at 80°C, (b) fmep versus oil temperature for various oil types and 3000rpm. (Both (a) and (b) have A=1, B=6, number of rings=2 (each 1.5mm thick), C=23μm.)

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Figure 7

(a) Efficiency versus engine speed for various oil film thickness, SAE 30, T=80°C, number of rings=2 (each 1.5mm thick), C=23μm. (b) Efficiency versus oil temperature for various oil film thickness, SAE 30, N=3000, A=1, B=6, number of rings=2 (each 1.5mm thick), C=23μm.

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