In this paper various methods of studying in-cylinder heat transfer in small displacement two-stroke engines are presented and compared.
First of all, the mistakes that can be caused by the application of steady heat transfer models to the study of such a complex phenomenon are considered.
After the demonstration that an ordinary convective heat transfer model determines mistakes in the evaluation of the thermal load, three-dimensional analysis and improved heat transfer models are considered.
The multidimensional code Fluent is used for the 3-D fluid mechanics simulation. Numerical analysis evidences the importance of the non-uniformity of the gas temperature inside the cylinder.
The improved models considers the fact that heat transfer during compression and expansion is out of phase with bulk gas-wall temperature difference and that the great part of the heat transfer is linked to the combustion.
The calculated amount of heat transferred to the walls of the combustion chamber during the closed portion of the engine cycle by the various methods is compared with the values obtained with experimental analysis.
The experimental analysis refers to three engines of different performances, each having a displacement of 125 cm3.