Effect of Cylinder Distortions and Piston Ring Design on Oil Consumption and Friction Losses in Automobile Engines.

摘要

Much analysis has been done on piston ring design in circular cylinder bores; however, engine bores are never perfectly circular. Mechanical loads, from machining operations and assembling the engine, and thermal loads cause distortion of the engine bores. Engine bore distortions are important in predicting the effectiveness of piston rings to control oil consumption, yet minimize friction in spark ignited engines. Only recently has the effect of these bore distortions been investigated. The RING program has been developed to analyze ring conformability in distorted cylinder bores. In particular, oil transport and friction are predicted for the engine cycle. The finite element technique was used in a non-linear contact solution for the piston ring pack in a distorted bore. The inter-ring gas pressure loads and piston and ring dynamic loads are computed for the ring pack. The Reynolds' equation is solved for lubricant film thickness. Hydrodynamic or boundary friction power losses are calculated based on the lubricant film thickness between the ring and bore. During development of the program, correlation of results were made with experimental measurements. Oil consumption and friction measurements of operating production engines with measured bore distortions were compared with results from the RING program. Predicted gaps between the piston ring and distorted bore were verified with measurements of gaps for a ring in a ring gage. Results from the RING program and the correlation analysis confirm the importance of distortions in predicting engine performance. Bore distortions should also be considered in predicting emission and wear in reciprocating engine designs to improve engine performance and life. 106 refs., 70 figs., 7 tabs. (ERA citation 14:015077)