Dual-fuel diesel engine features powered by ammonia under various pilot-fuel injection timing: Comprehensive analysis and response surface methodology-based optimization

Abstract

Ammonia is cogitated as a future fuel due to the carbon-free emission during its combustion. However, for obtaining high efficiency and low emissions while using ammonia as fuel, optimizing the operational parameters of the engine is necessary. Therefore, the present study focuses on evaluating the performance, emission, and combustion characteristics of a diesel engine fueled with ammonia with diesel fuel under dual-fuel mode. The novelty of the present work lies in the fact that optimizing the operating parameters was conducted through the experimental results based on the variation of pilot-fuel injection timing (PFIT) and engine load, as well as the implementation of response surface methodology (RSM) for determining the optimized conditions. In the first stage, the experimental analysis was conducted on a 3.5-kW diesel engine with a PFIT variation (23°, 26°, 29°, and 32°bTDC) and engine load (20%, 40%, 60%, 80%, and 100%) by inducting ammonia directly into the inlet manifold with the help of a solenoid valve through port injection. The findings indicated the ideal PFIT for an ammonia-powered diesel engine of 29°bTDC. In the second stage, engine performance and emission parameters were optimized using desirability optimization in RSM. Resultantly, an engine load of 74.5% and PFIT of 31°bTDC could produce optimal brake thermal efficiency of 17.3%, liquid fuel ratio of 62.99%, and peak cylinder pressure of 48.43 bar. Moreover, emission parameters like 11.74 ppm CO, 0.49 vol.% CO₂, 12.46 ppm HC, and 127.82 ppm NO_x were also achieved. Interestingly, the as-used model could offer high efficiency and accuracy (<5% error) compared to experimental results. It could be generally concluded that ammonia-powered diesel engines should be operated at high engine loads and advanced PFIT to obtain better performance and emission characteristics.