Transient temperature calculation method for complex fluid-solid heat transfer problems with scattering boundary conditions

TL;DR

This paper introduces a novel transient temperature calculation method for complex fluid-solid heat transfer in engines, accounting for scattering boundary conditions and dynamic behaviors during race conditions, validated with experimental data.

Contribution

The method uniquely models transient engine behavior during a race lap, including frequency range and various thermal effects, with model reduction techniques for efficient computation.

Findings

Successfully simulates different thermal behaviors at various positions

Predicts cylinder temperature effects from ignition sequence and residual gases

Achieves energy balance of water jacket within a few percent

Abstract

A calculation method for engine temperatures is presented. Special focus is placed on the transient and scattering boundary conditions within the combustion chamber, including fired and coasting conditions, as well as the dynamic heat transfer of the water jacket. Model reduction is achieved with dimensional analysis and the application of probability density functions, which allows for a timescale separation. Stationary in-cylinder pressure measurements are used as input values and, according to the transient behavior, modified with an own part-load model. A turbocharged SI race engine is equipped with 70 thermocouples at various positions in proximity to the combustion chamber. Differentiating from already published works, the method deals with the transient engine behavior during a race lap, which undergoes a frequency range of 0.1-1 Hz. This includes engine speed build-ups under gear changes, torque variations, or the transition from fired to coasting conditions. Different thermal behaviors of various measuring positions can be simulated successfully. Additionally, cylinder individual temperature effects resulting from an unsymmetrical ignition sequence and different volumetric efficiencies with unequal residual gas can be predicted. Up to a few percent, the energy balance of the water jacket is fulfilled and variations of water inlet temperatures can be simulated accurately enough.