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TECHNICAL BRIEFS

Clarification of a Semi-Empirical Approach in Piston Ring-Cylinder Bore Conformability Prediction

[+] Author and Article Information
V. Dunaevsky

 Ingersoll-Rand, Minneapolis, MN

J. Rudzitis

 Riga Technical University, Riga, Latvia

J. Tribol 129(2), 430-435 (Oct 31, 2006) (6 pages) doi:10.1115/1.2647800 History: Received May 07, 2006; Revised October 31, 2006

This technical brief clarifies origins of the piston ring conformability bounds presented by Dunaevsky (1990, Tribol. Trans.33(1), pp. 33–40) and provides their correct expression. The subject has strong practical significance in the field of piston engines and compressors, and it is currently getting additional prominence due to stringent emission regulations. The bounds stem from an earlier version, developed by the authors using a semi-empirical approach, and published in the 1970s in Russian technical journals. A semi-empirical background of the bounds was inadvertently missed in the aforementioned Tribology Transactions’ publication. This fact, and the virtual inaccessibility of Russian sources to the English reader, interfere with the proper use of the bounds and cloud their authorship. In this technical brief, the correct expression of these conformability bounds, the development process, and uses are highlighted.

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Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

Grahic Jump Location
Figure 1

Experimental study, per (3), of the conformability of a piston ring enclosed in the deformed cylinder. The diagram is based on Fig. 3.12 from (11) and presents the naked-eye observations of a ring-bore separation (α0) at the measured bore distortions resulting from increased load P(P3>P2>P1). The observations are given in the form of the approximate (not to scale) patterns of a ring-bore separation at the various ovality e values: (a) piston rings exhibit full (light tight) contact in the round bore of a nondeformed sleeve, e=0; (b,c,d) piston ring exhibits a partial contact with a bore when the sleeve is compressed by diametral forces, e≠0; (b)e=0.28mm (critical ovality); (c)e=0.36mm; and (d)e=0.5mm, respectively. For convenience of illustration, deformations of the bore/sleeve are not shown.

Grahic Jump Location
Figure 2

Dependence of conformability, measured as an angular loss of ring/bore contact α0 (separation), depending on the relative deformations Δ∕S or e∕S of the cylinder (where S=end gap of the ring in a free state, m; Δ0=deviation of a bore diameter from the nominal, m; e=bore ovality, m) and ring’s end gap location relative to the major axes of the oval (based on Fig. 25 from (12)): (a) piston ring in the oval bore with end gap aligned with a major axis of the oval; (b) piston ring in the oval bore with end gap located 45deg off the major axis of the oval; (c) piston ring in the round bore of a reduced diameter; (d) piston ring in the round bore of an increased diameter; and (e) piston ring in the oval bore with end gap aligned with the smaller axis of the bore

Grahic Jump Location
Figure 3

Comparison of the critical bore distortions Aω per several analytical and semi-empirical formulas (Table 1) using the results of Table 3 for the piston rings with parameters shown in Table 2

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