Engine Speed and Load on the Sealing Capacity of a Piston Ring-Pack

Arian Bisha,Erjon Selmani

doi:10.24018/ejers.2020.5.3.1775

Abstract

The combustion chamber is ought to be perfectly sealed, however, part of the air and fuel mixture can escape from it. Among the several losses there is the gas flow from the inter-ring crevices, which is always present. This leakage is known as blow-by, and affects efficiency, correct lubrication and emissions. The amount of leakage is dependent on many factors, and among the most important are the engine speed and load, which are able to affect the system through the forces applied on it. The aim of this paper was to understand in a more detailed way how the engine speed and load could affect the sealing efficiency of a ring-pack. For this purpose, a complete range of speeds and loads were used in the simulations. The equations of the ring motions and gas dynamics has been implemented and solved in ©Ricardo RINGPAK solver. The results showed that inertia and inter-ring gas pressures drives the sealing behavior of the rings. The blow-by trend showed to decrease with the speed and increase with the load, exception made for the idle condition where the values were different to the other cases, especially at higher speeds. Among the two parameters, the engine speed resulted to affect more significantly the blow-by trend.

Highlights

The piston rings main duty is to seal off the combustion chamber, their tightness is not perfect and part of the intake gas mixture is lost toward the crankcase
- The results proved that the system is highly dependent on the engine speed and load
- The inter-ring gas pressures and the inertia force are the main forces in an inter-ring pack and affect the amount of blow-by

Summary

Introduction

The piston rings main duty is to seal off the combustion chamber, their tightness is not perfect and part of the intake gas mixture is lost toward the crankcase This phenomenon is commonly known as blow-by gas and was recognized to brink negative effects on performances, lubrication and emissions [1,2,3,4,5], in particular Kim et al in [19] found the blow-by gasses to be responsible for 10 to 30 % of the UHC emissions of a SI engine. Zottin et al in [21] saw that the blow-by tended to increase with the engine load, but its peak value was obtained at the medium load, explaining it with the ring instability. Arnault in [5] referring to a diesel engine, saw that the blow-by increased with speed and load, and the maximum value was seen at full load and medium speed condition. In any of the references wasn't indicated how the blow-by varies within the entire engine map, or which of the two parameters may be more important to the blow-by rates

Objectives

Results

Conclusion