Heat transfer between gas and the surrounding walls in the model of gas flow from the combustion chamber to the crankcase

Grzegorz Koszałka

doi:10.19206/ce-117175

Abstract

The paper discusses different approaches to the modeling of the heat transfer between gas and surrounding walls used in the models of gas flow from the combustion chamber to the crankcase. Most models described in the literature assume that the flow is isothermal or quasi-isothermal. Such an assumption remarkably simplifies the calculations, however, the real gas flow has an mixed character (between adiabatic and isothermal). Taking the above into account, the submodel of heat transfer, which allows assuming the conditions of heat transfer from isothermal to adiabatic was worked out and included into the model of the gas flow and ring dynamics. The research of the effect of the assumed heat transfer intensity on the calculated inter-ring gas pressures, rings axial positions in the grooves and blow-by has been presented in this paper.

Highlights

In modeling of the gas flow through the piston–rings– cylinder seal it is commonly assumed, that the gas flows through a series of stages connected with throttling passages
Regardless of the structural complexity of the labyrinth through which the gas flows from the combustion chamber to the crankcase, there are different approaches to modeling of the heat transfer between the gas and the surrounding walls
A numerical investigation of the effect of an assumed intensity of heat transfer between the gas flowing through a ring pack and the surrounding walls on the calculated values of temperature and pressure of the gas in the inter-ring spaces, axial displacements of rings in their grooves and blow by was carried out

Summary

Introduction

In modeling of the gas flow through the piston–rings– cylinder seal it is commonly assumed, that the gas flows through a series of stages connected with throttling passages (labyrinth seal). Particular models differ from each other with the number of considered factors influencing the gas flow intensity. In the simplest models it is assumed that gas flows through only one stage of constant volume, corresponding to the top inter-ring space, and through two throttling passages of constant intersections, corresponding to the top and the end-gaps of the second compression ring [7]. More factors influencing the volumes of the stages and cross-sections of the passages are taken into account, e.g. ring axial and angular positions, cylinder, piston and rings thermal deformations [1, 4, 6, 8].

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