An investigation into the performance and regulation rules of electric supercharged two-stroke engine for various altitudes operation

Aviation piston two-stroke engines suffer from severe power loss at high altitudes, and electric superchargers can enhance their power output. This paper presents the engine power enhancement solution based on its required power at various altitudes. By calculating the compressor's flow rate and pressure ratio, the electric supercharger is designed, and an exhaust backpressure control valve is added to enhance scavenging efficiency. A one-dimensional numerical simulation model of the electrically supercharged engine is developed to match the engine and supercharger performances at altitudes from 0 to 7000 m, ensuring the supercharger operates in a high-efficiency zone with adequate surge and choke margins. Accordingly, the speed regulation rules for the electric supercharger are proposed. Additionally, the influence of the exhaust backpressure valve opening on the engine scavenging process at different altitudes is analyzed, and regulation rules were further proposed. Simulation and experimental results demonstrate that the proposed regulation rules enable the electrically supercharged engine to recover 70.4 % of its sea-level power at 7000 m altitude. Meanwhile, as altitude increases, the engine's BSFC (brake specific fuel consumption) rises accordingly, accompanied by increased BSHC (brake specific hydrocarbon) and BSCO 2 emissions. Notably, BSNO x (brake specific nitrogen oxides) peaks at 6000m altitude.