Controlling environmental adaptability in marine engines: The coupling effects of injector position, injection timing, and intake temperature under low-load, high-ammonia conditions

To enhance the comprehensive performance and environmental adaptability of marine two-stroke ammonia/diesel high-pressure direct dual-fuel injection engines under low-load, high-ammonia energy ratio, a three-dimensional simulation study was conducted to investigate the coupled effects of relative injector position (α), injection timing, and intake temperature. The research reveals that the indicated thermal efficiency and various emission indicators, along with their sensitivities to intake temperature and injection timing, vary significantly with different relative injector positions. When the ammonia and diesel injectors are positioned farther apart (α = 0°), the overall performance is the poorest and exhibits the highest sensitivity; even optimizing intake temperature and injection timing fails to achieve efficient and clean combustion. When the ammonia and diesel injectors are positioned closer together, compared to the upstream configuration (α = 45°), the configuration where the ammonia injector is located downstream of its adjacent diesel injector (α = −60°) demonstrates superior performance and lower sensitivity, particularly at lower intake temperatures. Although higher intake temperatures can mitigate performance differences among various configurations, it is challenging and costly to achieve a substantial increase in intake temperature under low-load conditions. Therefore, it is recommended that researchers prioritize optimizing the relative position between the ammonia and diesel injectors. This study provides crucial theoretical and design insights for optimizing the injection system to achieve high-efficiency and clean combustion in ammonia engines under a wide range of ambient temperature conditions.