An integrated model for the performance of piston ring pack in internal combustion engines

Abstract

Piston rings are important components in internal combustion engines. Their primary function is to seal dynamically the gap between moving piston and cylinder liner surface in order to prevent the combustion gases from penetrating into the crankcase. The rings also control the oil leakage from the crankcase to the combustion chamber. The performance of the piston ring pack impacts the engine efficiency, durability and emissions. The recognition of the impact of the ringpack performance on the engine design resulted in a sustained effort of research and development aimed at understanding the operation of the piston ring pack. Most of the published models developed in this field are two-dimensional assuming that the ring and liner are perfect circles for the purpose of modelling the axial and radial dynamics. Although this approach has proved to be useful, there exist a number of asymmetrical characteristics of the power cylinder system that can be crucial to the ring-pack performance and therefore it is considered to be appropriate. In this work, an integrated methodology that handles the complex ring-pack mechanism is presented. The physics of the ring-pack mechanism covers the three-dimensional piston ring dynamics of asymmetric engine cylinder due to bore distortion, the mixed lubrication at ring running face as well as the ring flanks and the interring gas dynamics. The modelling method is verified in two steps. In the first step, the dynamic behaviour of the three-dimensional ring model is verified against a commercial finite element software by comparing the eigenmodes up to a frequency of about 1 kHz. In the second step, the ring-pack modelling approach using three-dimensional ring models is also verified against a commercial ring dynamics program, which is based on the two-dimensional modelling. It is shown that the three-dimensional ring dynamics modelling method has advantages over the two-dimensional modelling approach as it facilitates studying the influence of the non-uniform twist along its circumference (ring winding), the effect of bore distortion on blow-by, ring friction, friction power losses and wear.

Lubrication analysis of the piston ring for the two-stroke marine diesel engine based on modified radial tension

“…As we can see, the MOFT decreases with the increase of piston ring elastic modulus, while the friction forces and friction loss increase. This is due to the increase of piston ring radial tension with the increase of elastic modulus, causing an increase in the combined external force on the piston ring according to equation (7), which is of similar conclusion with Ma et al 39 To obtain more specific information, Figure 17 shows the variation of the maximum load-carrying capacity of oil film p oil (180, x, 0) and the asperity contact pressure p asp (180, x, 0) at TDC. As we can see, the load-carrying capacity of oil film decreases while the asperity contact pressure increases with the increase of the piston ring elastic modulus at the TDC.…”

“…Moreover, the distribution of piston ring tension plays a vital role in the tribological performance of piston ring/cylinder liner friction pairs. [5][6][7] Therefore, it is of great significance to study the distribution of piston ring tension and its influence on the lubrication performance of piston ring/cylinder liner tribo-pair.…”

Analysis of circumferential oil film thickness for piston ring in twin-rotor piston engine under differential velocity motion of combined annular cylinder

“…Guo, et al 17 developed a mixed lubrication model for minimum oil film thickness estimation of a rotary lip seal using flow factors. Mahmoud, et al 18 used the mixed lubrication model study the performance of piston ring pack. The oil film thickness and pressure were determined by Reynolds equation with consideration for the piston dynamics, piston ring dynamics.…”

“…Mahmoud, et al. 18 used the mixed lubrication model study the performance of piston ring pack. The oil film thickness and pressure were determined by Reynolds equation with consideration for the piston dynamics, piston ring dynamics.…”

Assessment and Optimization of Friction Losses and Mechanical Efficiency in Internal Combustion Engines

“…This lubrication condition lead to include different models to take into account the different boundary condition in each crankangle. Different authors have developed complete ring-pack models in order to study the friction losses on it [31,[74][75][76][77].…”