Abstract
The combustion emissions of the hydrogen-fueled engines are very clean, but the problems of abnormal combustion and high NOx emissions limit their applications. Nowadays hydrogen engines use exhaust gas recirculation (EGR) technology to control the intensity of premixed combustion and reduce the NOx emissions. This study aims at improving the abnormal combustion and decreasing the NOx emissions of the hydrogen engine by applying a three-dimensional (3D) computational fluid dynamics (CFD) model of a single-cylinder hydrogen-fueled engine equipped with an EGR system. The results indicated that peak in-cylinder pressure continuously increased with the increase of the ignition advance angle and was closer to the top dead center (TDC). In addition, the mixture was burned violently near the theoretical air–fuel ratio, and the combustion duration was shortened. Moreover, the NOx emissions, the average pressure, and the in-cylinder temperature decreased as the EGR ratio increased. Furthermore, increasing the EGR ratio led to an increase in the combustion duration and a decrease in the peak heat release rate. EGR system could delay the spontaneous combustion reaction of the end-gas and reduce the probability of knocking. The pressure rise rate was controlled and the in-cylinder hot spots were reduced by the EGR system, which could suppress the occurrence of the pre-ignition in the hydrogen engine.
Highlights
In recent years, the number and application scale of internal combustion engines has increased dramatically, and the consequent shortage of petroleum resources has become an important issue facing the world [1,2]
The results showed that ignition timing and backfire were the two important factors contributing to generate combustion knock at high engine speed in a port fuel injection (PFI) engine
This study aims at improving the abnormal combustion and decreasing the NOx emissions of the hydrogen engine by applying a three-dimensional (3D)
Summary
The number and application scale of internal combustion engines has increased dramatically, and the consequent shortage of petroleum resources has become an important issue facing the world [1,2]. Hydrogen energy can meet the requirements of the environment, the resources, and sustainable development based on its advantages of strong renewability, high environmental protection, clean and efficient combustion, and abundance in resources [5,6]. This is unmatched by other new energy sources. Hydrogen is considered as the cleanest fuel for internal combustion engines [7]. This is because hydrogen combustion produces only water and a small amount of nitrogen oxides without carbon deposits and particles, greatly reducing engine wear and lubricant contamination [8,9].
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