Heat transfer in engines

Background

The focus of the research on hydrogen as an alternative fuel at Ghent University has shifted from experimental to numerical research with the development of a thermodynamic model of the engine cycle, the GUEST-code (Ghent University Engine Simulation Tool). GUEST enables a cheap and fast optimization of engine settings for operation on hydrogen. Several sub models are necessary to solve the conservation equations of energy and mass including a combustion, a turbulence and a heat transfer model.

GUEST will be expanded with emission calculations of oxides of nitrogen. These emissions can occur in hydrogen internal combustion engines at high loads and they are an important constraint for power and efficiency optimization. The heat transfer sub-model is important to accurately simulate the emissions of oxides of nitrogen because they are influenced by the maximum gas temperature.

Scope of research

Several heat transfer models for internal combustion engines (ICE) exist in the literature. Most of these models have been developed for fossil-fuelled engines. However, the heat transfer process of hydrogen differs a lot compared to that of a fossil fuel so the models have to be evaluated for hydrogen and adjustments will be made if necessary.

Measurements of heat transfer and wall temperatures are necessary to evaluate the heat transfer models. Measuring heat transfer in a combustion engine is complex because it is a fast transient process where high temperatures are involved, and there is strong cycle to cycle variation. The first part of the research is therefore focused on the development and comparison of different measurement methods. Three types of local heat flux sensors are being compared: a coaxial type, an eroding ribbon type and a film type. The engine used for the heat transfer measurements is a four-stroke single-cylinder spark ignited gas engine based on a CFR (Cooperative Fuel Research) engine operated at a constant speed of 600 rpm. It is equipped with port fuel injection (PFI) and has a variable compression ratio.

This research is performed in cooperation with the Research Group Transport Technology.