Abstract
One of the several losses of a combustion chamber is the gas leakage toward the crankcase due to imperfect sealing of the rings. It is commonly known as blow by and it affects efficiency and emissions. The paper initially describes a bibliographic review of the phenomenon, together with the equations of the system. A typical piston ring pack for internal combustion engine is proposed to be analysed and solved using ©Ricardo RINGPAK Solver. A specific issue such as Bore distortion orders were used to investigate the sealing capacity of the ring-pack in terms of ring dynamics, inter-ring pressures and mass flows. Bore distortion orders and their magnitude showed to affect the ring pack behavior. Order zero distortion resulted to be the most important order due to the highest amount of gas lost in the crankcase, while orders three and four resulted to generate high blow-by values, even if their magnitude of distortion is lower in comparison to other orders.
Highlights
The combustion chamber of an internal combustion engine is desired to be gas tightness, piston rings are the mechanical elements interposed between the piston and the liner to guarantee this requirement
In the case of non-distorted bore, top ring remained stable during the entire cycle while second and second ring experienced a motion inside their grooves
- Bore distortion is a very important factor because it affects the sealing capability of the ring pack in different manner for each order. - Ring axial or radial dynamics are affected from the distortion orders, this motion not always explains the amount of gas flowed in the regions. - The highest values of blow by were recorded in the cases where there was no radial collapse of the rings
Summary
The combustion chamber of an internal combustion engine is desired to be gas tightness, piston rings are the mechanical elements interposed between the piston and the liner to guarantee this requirement. Their tightness is not perfect and part of the intake gas mixture is lost toward the crankcase, known as blow-by. Piston rings are designed to seal off the chamber by making continuous contact with the cylinder liner. On the cylinder side, the contact is influenced by the lateral force exerted by the ring and by the distortion of the liner. The main forces acting in the axial direction of the ring cross section are given in Figure 1, while equation (1) describes the mechanical equilibrium of forces in this direction [1]
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