Numerical Analysis of Cooling Effects of a Cylinders in Aircraft SI Engine

This paper focuses on the issues concerning gyroplane powertrain cooling. The Rotax 912S engine was selected as a propulsion system following a detailed analysis. A one-dimensional model, simulated with the AVL Boost software, was applied to determine the heat balance of the engine and the heat flux penetrating through each of engine's surfaces. The geometrical quantities defined in the model were obtained by measuring a three-dimensional geometry provided by an authorized Rotax engine supplier company. Calculation results were then verified by comparing the obtained values with data available from the Rotax 912S engine and with the values of individual parameters given in the literature. The CFD simulation studies, performed with Ansys Fluent, enabled to determine the required airflow capable of absorbing up to 6 kW of heat, the properties for sufficient cooling of the cylinders in the gyroplane powertrain system and the manner of directing the air flow in order to achieve the smallest possible temperature gradient. The modelling tasks were to develop four different design solutions of the cylinder cooling system. As specified in the in-built instruction, the inlet channel was mounted with a constant cross-section of not less than 0.01 m². The air flow velocity prevented from exceeding the cylinder maximum temperature which should not excess 200°C, as specified by the manufacturer. The proposed solution meets the requirements of the engine installation instructions. The results contain meeting the maximum cylinder temperature requirements with a margin of 18°C and the correct temperature gradients.