Detailed analysis of a pure hydrogen-fueled dual-fuel engine in terms of performance and greenhouse gas emissions

Abstract

The current study seeks to greenhouse gas emissions reduction in an existing engine under dual-fuel combustion fueled with diesel fuel and natural gas due to great concerns about global warming. This simulation study focuses on the identification of areas prone to the formation of greenhouse gas emissions in engine cylinders. The simulation results of dual-fuel combustion confirmed that the possibility of incomplete combustion and the formation of greenhouse gas emissions in high levels are not far from expected. Therefore, an efficient combustion strategy along with replacing natural gas with hydrogen was considered. Only changing the combustion mode to reactivity-controlled compression ignition has led to the improvement of the natural gas burning rate and guarantees a 32 % reduction in unburned methane and 50 % carbon monoxide. To further reduce engine emissions, while changing the combustion mode, a part of natural gas replacement with hydrogen to the complete elimination of it was evaluated. Increasing the share of hydrogen energy in the intake air-natural gas mixture up to 54 % without exhaust gas recirculation does not lead to diesel knock. Moreover, improvement of engine load and efficiency can be achieved by up to 18 % and 6 %, respectively. Natural gas consumption can be reduced by up to 67 %. Meanwhile, the unburned methane and carbon dioxide mass, known as greenhouse gas emissions, can be reduced to less than 1 % and up to 50 %, respectively. Continued replacement of natural gas with hydrogen until its complete elimination guarantees a reduction of 92,000 cubic meters of natural gas per year in one engine cylinder. Although, the engine efficiency and load face a decrease of 0.8 % and 5.0 %, respectively; the amount of carbon dioxide can be decreased by about 4.5 times. Unburned methane, carbon monoxide and nitrogen oxides can be reduced to below the relevant EURO VI range while the amount of unburned hydrogen compared to the hydrogen entering the engine is about 0.5 %.