Bench Tests for Exhaust Gas Temperature Distribution in an Aircraft Piston Engine with and without a Turbocharger

In ultralight aviation, a very important engine parameter is the power-to-weight ratio. On the one hand, there is a tendency to minimize the size and weight of engines, and on the other hand, there is a demand to achieve the highest possible power by using supercharging systems. Increasing power brings many benefits, but it also increases temperature in the exhaust system, posing a threat to delicate parts of the ultralight aircraft fuselage. Therefore, it is necessary to control temperature values in the engine exhaust system. This article presents the temperature distribution in the exhaust system of an aircraft engine by the example of a four-cylinder Rotax 912 engine with an electronic fuel injection system. The research was conducted in two stages: measurements were made first for the engine without a turbocharger with an original exhaust system and later for its modified version with an added turbocharger system. The paper presents a comparative analysis of exhaust gas temperatures measured at three points: 30, 180 and 1000 mm from the cylinder head. The tests were conducted for the same preset engine operating conditions at constant speed and manifold air pressure. It has been shown that the exhaust temperature in the exhaust manifold decreases with the distance from the cylinder head. The highest gradient, over three times higher than the gas temperature from 589.9 °C to 192.3 °C, occurred in the manifold with a turbocharger for 2603 RPM and 31 kPa of manifold air pressure. The introduction of turbocharging causes an increase in exhaust gas temperatures before the turbocharger by an average of 12%, with this increase being greater for operating points of higher inlet manifold pressure. Turbocharging also causes a significant decrease in exhaust gas temperatures behind the turbocharger and the silencer because the temperature drops there by an average of 25%.