Effect of Injection Pressure and Equivalent Ratio on Combustion and Emissions of The Ammonia/Diesel Dual Fuel Engine

In the context of low-carbon and zero-carbon development strategies, the transformation and upgrading of the energy structure is an inevitable trend. As a renewable fuel, ammonia has a high energy density. When ammonia is burned alone, the combustion speed is slow. The emissions of nitrogen oxides and unburned ammonia is high. Therefore, a suitable high-reactivity combustion aid fuel is required to improve the combustion characteristics of ammonia. Based on this background, this study converted a six-cylinder engine into a single-cylinder ammonia/diesel dual-fuel system, with diesel fuel as the base and a certain percentage of ammonia blended in. The impact of varying the injection pressure and equivalence ratio on engine combustion and emissions was examined. The results demonstrate that an appropriate increase in injection pressure can promote fuel-gas mixing and increase the indicated thermal efficiency (ITE). With regard to emissions, an increase in injection pressure has been observed to reduce unburned ammonia emissions and the equivalent greenhouse gases. An increase in the equivalence ratio results in the suppression of combustion within the engine cylinder, accompanied by a reduction in the peak of pressure curve and a delay in the phase corresponding to the peak. An increase in the equivalence ratio results in a longer ignition delay time and combustion duration. Indicated thermal efficiency and ammonia combustion efficiency show a tendency to increase first and then decrease. With regard to emissions, the combustion process is adversely affected by an increase in the equivalence ratio. It leads to an increase in total hydrocarbon and CO emissions. Unburned ammonia decreases. NOx emissions increase first and then decreases influenced by cylinder temperature.