Research on the determination method of stable combustion boundaries for aviation two-stroke engines based on inter-cylinder differences

To meet the demand for high power-to-weight ratio in small aviation power systems, multi-cylinder two-stroke engines have emerged as an ideal choice. However, their inter-cylinder differences are exacerbated under high-altitude, low-temperature, and low-pressure environments, threatening the combustion stability of the engine and even leading to misfire in severe cases. Therefore, quantifying the stable combustion boundaries is crucial for reducing inter-cylinder differences. This study proposes a method for determining the stable combustion boundaries of aviation two-stroke engines based on inter-cylinder differences. Through optimally selected in-cylinder combustion state parameters, out-of-cylinder performance parameters, and emission parameters, the combustion boundaries of individual cylinders are determined by utilizing the curvature mutations caused by parameter fluctuations. Subsequently, the intersection of the stable combustion regions of each cylinder is sought to obtain the final boundaries of multi-cylinder common stable combustion. The experimental results demonstrate that this method can accurately identify the common stable combustion boundaries and common stable combustion region of the two cylinders. Under the condition of mixture temperatures ranging from 280 °C to 320 °C, the area ratio of the stable combustion regions enclosed by the respective stable combustion boundaries of the two cylinders is determined to be 13.1:9.1. The research findings can provide data support and a theoretical basis for achieving precise control of multi-cylinder aviation two-stroke engines in complex high-altitude environments.