Parametric study on the performance of a gasoline turbocharged aircraft engine at high altitudes using a one-dimensional model

One-dimensional modeling of aircraft piston engines is one of the methods for studying their behavior and performance in different environmental conditions. In this research, the Rotax 914, an aerial Spark Ignition (SI) turbocharged engine, was modeled one-dimensionally to predict its behavior at different altitudes. To address this issue, the one-dimensional model of all engine components including air filter, carburetor, air manifold, inlet and outlet valves, cylinder and piston along with crankshaft, exhaust manifold and turbocharger were created in GT-Power software.Then by validating the model with the data provided by the manufacturer and ensuring the accuracy, the significant performance parameters of engine and turbocharger performance curves were evaluated for different flight conditions up to 30,000 feet. According to the results, the turbocharger prevented a dramatic decline in engine performance parameters up to 18,000 feet. However above that altitude, due to the compressor reaching the choking region, it is not possible to charge the required air and avoid severe engine performance loss. It was also observed, by studying the effect of ambient temperature changes on engine performance, an increase of 40 °C in the ambient temperature caused a 10% reduction in the braking horse power, and consequently, performance loss during climb period. The effect of changes in ambient temperature and altitude on engine performance varies so that, until the engine reaches the compressor's choking region, the impact of the ambient temperature variations is more perceptible, after that, the height factor will have a greater influence on the engine performance.