Hydrogen port fuel injection: Review of fuel injection control strategies to mitigate backfire in internal combustion engine fuelled with hydrogen

Hydrogen is an ideal alternative fuel due to its carbon -free content, wide flammability limit, high specific energy, and unique physical and thermo-chemical behavior. Hydrogen -powered internal combustion engine (H 2 -ICE) has been experimentally proven to achieve greater brake thermal efficiency compared to traditional fossil fuel ICE. However, in addition to its advantages, a few challenges are also encountered in the use of hydrogen in port fuel injection internal combustion engine (PFI-ICE) application, such as decreased of volumetric efficiency, high nitrogen oxides (NO x ) emissions, and abnormal combustion issues including backfire, preignition, and knocking. Backfire, one of the biggest problems in hydrogen -fuelled PFI ICE (PFI-H 2 ICE), is an abnormal combustion in the intake manifold that lead to decreased engine performance, power loss, and potentially damaging the internal components inside the combustion chamber. This paper provides an overview of the factors leading to the occurrence of backfire in PFI-H 2 ICE; such as hot spots in the combustion chamber, high residual exhaust gas temperature, abnormal electric discharge, inappropriate spark timing, inappropriate injection timing and so forth. Importantly, this study is a literature review focusses on backfire control strategies specifically through the optimization of hydrogen fuel injection system and analyzing their effectiveness in mitigating backfire while achieving optimal performance in PFI-H 2 ICE. The effect of optimized injection control strategies including the pressure of hydrogen during injection, injection timing and duration of hydrogen injection on the combustion behaviors, performance and also emissions in PFI-H 2 ICE should be emphasized in the direction of future research so that ICE technology employing PFI can be upheld through minor adjustments.