Analysis of cooling of the exhaust system in a small airplane by applying the ejector effect

摘要

This paper presents a thermal analysis of elements of the exhaust system of the redesigned airplane I-23. In order to improve the thermal performance of the exhaust system and decrease thermal loads inside the engine bay, modifications of the initial geometry of the cover pipe were proposed. This pipe shields the nacelle interior from thermal interaction and direct contact with the hot exhaust pipe. Several openings were created in its wall to increase the mass flow rate of the cold air sucked in from the nacelle interior to the gap between the exhaust pipe and its cover due to the ejector effect. Then numerical models were developed and simulations for flight conditions were carried out for the original and modified exhaust systems. The results obtained for both geometries were compared, showing that openings in the cover duct resulted in a high mass flow rate flowing through the gap between exhaust pipe and its cover and a lower exhaust pipe temperature. Even though the number, locations and cross-section area of the openings were selected arbitrarily, better thermal performance was obtained for the modified exhaust system.