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Research Papers

A Model From First Principles of the Radial Heat Flux in a Cylinder Bore of a Modern Diesel Engine

[+] Author and Article Information
C. A. Finol, D. A. Parker, K. Robinson

Department of Mechanical Engineering, University of Bath, Bath BA2 7AY, UK

J. Thermal Sci. Eng. Appl 1(3), 031003 (Dec 17, 2009) (11 pages) doi:10.1115/1.4000583 History: Received July 03, 2009; Revised October 31, 2009; Published December 17, 2009; Online December 17, 2009

A simple model from first principles has been developed to estimate the heat transferred from the piston rings and skirt to the cylinder wall. The model considers the various forms in which heat is transferred from the combustion gases to the containing walls, namely, convection and radiation between the gases and wall surface, and conduction from piston rings and skirt through the oil film. The model also includes frictional heat generation by the rings and skirt as a result of the piston movement. Results presented in this paper show that the heat flux predicted by the model on the thrust side of the bore, at an engine speed of 4000 rpm and engine load of 100% of the limiting torque, was generally of the same order of magnitude as the heat flux estimated from experimental measurements. They also demonstrated that in the process of heat transfer from combustion gases to the cylinder wall, convection and radiation of heat have their greatest influence on the total heat flux in the top section of the cylinder bore and provide a contribution of approximately 25% over the rest of the stroke. However, the distribution of heat flux in the middle and bottom parts of the stroke shows that the main mechanism of heat transfer is conduction from the piston assembly.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Predicted heat fluxes at 4000 rpm for several load conditions

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Figure 2

Heat flux from the cylinder gases estimated in the cylinder wall at 4000 rpm and 100% LTC

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Figure 3

Simplified piston-cylinder diagram

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Figure 4

Piston velocity at 4000 rpm

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Figure 5

Piston acceleration at 4000 rpm

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Figure 6

Piston gas pressure force at 4000 rpm and 100% LTC

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Figure 7

Piston inertia force at 4000 rpm

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Figure 8

Measured cylinder gas pressure and the predicted inter-ring gas pressure at 4000 rpm and 100% LTC

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Figure 9

Predicted friction coefficient for the piston rings during the engine cycle (expansion stroke starts at 360 deg) at 4000 rpm and 100% LTC

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Figure 10

Predicted friction force on piston rings at 4000 rpm and 100% LTC

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Figure 11

Predicted side thrust at 4000 rpm and 100% LTC

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Figure 12

Predicted skirt friction force at 4000 rpm and 100% LTC

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Figure 13

Predicted oil film thickness between the piston rings and the cylinder wall during the engine cycle (expansion stroke starts at 360 deg) at 4000 rpm and 100% LTC

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Figure 14

Predicted oil film thickness between the piston skirt and the cylinder wall at 4000 rpm and 100% LTC

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Figure 15

Predicted conductive heat flux between the piston rings and the cylinder wall on the thrust side of the bore at 4000 rpm and 100% LTC

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Figure 16

Predicted conductive heat flux between the piston skirt and the cylinder wall on the thrust side of the bore at 4000 rpm and 100% LTC

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Figure 17

Predicted heat flux due to friction between the piston rings and the cylinder wall at 4000 rpm and 100% LTC

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Figure 18

Predicted heat flux due to friction between the piston skirt and the thrust side of the cylinder wall at 4000 rpm and 100% LTC

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Figure 19

Comparison between the total heat flux predicted by the model (conduction and friction) plus the heat flux from combustion gases and the experimentally derived heat flux for the thrust side of the bore at 4000 rpm and 100% LTC

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Figure 20

Comparison between the total heat flux predicted by the model plus the heat flux from combustion gases and the experimental heat flux for the thrust side of the bore at 4000 rpm and 100% LTC

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