# An extended Elrod-Adams model to account for backpressure and blow-by inception

## TL;DR

This paper extends the Elrod-Adams model for piston-ring-liner systems to include backpressure effects and blow-by prediction, improving the accuracy of hydrodynamic and friction force assessments in engines.

## Contribution

It introduces a novel model that incorporates combustion chamber backpressure and a criterion for blow-by inception into the Elrod-Adams framework.

## Key findings

- Backpressure significantly affects predicted friction and MFT.
- The extended model accurately predicts blow-by inception.
- Inclusion of pressure difference improves hydrodynamic assessments.

## Abstract

The Piston-Ring-Liner system is the main tribological component of internal combustion engines. The Elrod-Adams model is customarily used to numerically assess the hydrodynamics of different ring designs and liner surface treatments. However, that model does not incorporate the backpressure boundary condition, which in this case corresponds to the combustion chamber pressure and is quite significant. In this contribution a model is proposed that imposes the combustion-chamber pressure in a mass-conserving way, together with an effective algorithm for its numerical approximation. The new model incorporates the pressure difference across the ring, which is shown to have a substantial effect on the predicted friction force and MFT. The model is further elaborated so as to provide a criterion for predicting blow-by inception.