An Integrated Model of Ring Pack Performance

Abstract

This paper describes an integrated model developed for the detailed characterization and simulation of piston ring pack behavior in internal combustion engines and the prediction of ring pack performance. The model includes comprehensive and coupled treatments of (1) ring-liner hydrodynamic and boundary lubrication and friction; (2) ring axial, radial, and (toroidal) twist dynamics; (3) inter-ring gas dynamics and blowby. The physics of each of these highly inter-related phenomena are represented by submodels, which are intimately coupled to form a design-oriented predictive tool aimed at the calculation of ring film thicknesses, ring motions, land pressures, engine friction, and blowby. The paper also describes the results of a series of analytical studies investigating effects of engine speed and load and ring pack design parameters, on ring motions, film thicknesses, and inter-ring pressures, as well as ring friction and blowby.

Mathematical Model of Piston Ring Sealing in Combustion Engine

“…number of stages and a way of their connection by means of throttling gaps depend on a odeled engine and a degree of model advancement. In the simplest models in which gas is assumed to flow only through ring locks, labyrinth has a series structure and number of throttling channels is equal to that of sealing rings [2, 4,27,17,18,9,16]. There are also models of this kind in which sealing action of piston oil rings is taken into account [15,25,1,22].…”

“…In the obtained model the behind-ring and inter-ring spaces were considered separately by applying a series -parallel scheme of the labyrinth. Such labyrinth scheme is commonly used in the integrated models [13,9,26,10,28,30].…”

“…In prevailing majority of the models , usually referring to Furuhama , it was assumed that gas flow is isothermal and gas temperature within stage is equal to that of piston [18,17,20], or quasi-isothermal , i.e. that gas temperature changes but is determined on the basis of temperature of walls surrounding a given inter-ring space [9,26,22]. Such assumption significantly simplifies calculations because in order to determine parameters of medium within stage it is sufficient to use the equation of mass balance and gas state.…”

“…Furuhama and Tada [3] calibrated empirically the so determined mass flux by means of a flow coefficient of constant value. This manner of the modeling of gas flow through ring lock was used in the models [27,18,9,16, 1] where however various values of the coefficient were assumed. In the model [26] a flow coefficient of value depending on the ratio of pressure before and behind the orifice, was used.…”

“…In the integrated models of gas flow and ring dynamics it is commonly assumed that cross-sections of channels between ring and groove result from an instantaneous position of ring against groove [18,13,9,26,10,28,11].…”