Piston ring pack design effects on production spark ignition engine oil consumption : a simulation analysis

Abstract

One of the most significant contributors to an engine's total oil consumption is the piston ring-pack. As a result, optimization of the ring pack is becoming more important for engine manufacturers and lubricant suppliers. This leads to current efforts to control the oil transport and flow through the ring pack. Decreasing the amount of oil needed for proper lubrication while minimizing, frictional losses are the goals of such research. The hope is to fully understand the mechanisms that govern oil's flow, and then control it. Analytical tools and computer simulation models have been created to assist in predicting the performance of a given ring pack. This study intended to be an experimental look at the effects of piston-ring-pack design changes on the steady-state and transient oil consumption of a spark ignition engine. Namely, the effects of a V.-Cut on the 2nd land, a chamfer on the 3rd land, OCR groove drain holes, and the OCR design were to be examined. However, after some minor measurements, the engine experienced a major malfunction that caused it to cease operation. The focus of the study shifted to a more theoretical, computer simulated concentration of the aforementioned design changes. Different speeds -and loads were analyzed along with the notation of some general observations. In the end, the effects of the design modifications on ring dynamics and gas flow were qualified. The presence of a V-Cut on the 2nd land of the piston had beneficial and adverse effects on the general performance of the ring pack. The added volume decreased the 2nd land pressure enough to avoid 2nd ring radial collapse, but it also caused reverse flutter to occur at lower loads. Using a chamfer on the upper portion of the 3rd land also had mixed results. Stability of the 2nd ring was greatly improved with less radial collapse and an increase in average blowby flow.

(cont.) The performance of the OCR design was primarily dependent on the gap area of the ring and the variation of groove clearances. The OCR groove drain holes were also deemed a necessity. This research, though theoretical in nature, brings together many ideas that offer solutions to common problems. Radial collapse, reverse flutter, OCR cost, and the use of drainage holes all are part of the attempts to improve the piston-ring-pack performance while driving down cost of production. Future experiments will put the theoretical conclusions to the test with the continuation of the pistons not installed in the engine due to the events previously explained.