Experimental investigation of the working boundary limited by abnormal combustion and the combustion characteristics of a turbocharged direct injection hydrogen engine

In the process of hydrogen energy conversion and utilization, the direct-injection hydrogen internal combustion engine has been proven to produce zero carbon emissions with high thermal efficiency. However, the risk of abnormal combustion and high requirements of turbocharging limits the improvement of engine performance. This paper focuses on exploring the performance boundary of a 2.0 L turbocharged direct injection hydrogen engine with bench test under all working conditions. Applied variable geometry turbocharger can provide high intake pressure of 270 kPa with proper exhaust back pressure under all engine speed working conditions by changing the turbo opening angle. Delayed injection timing can enhance the performance, while improper injection timing may cause severe pre-ignition and afterburning. The burn duration ranges from 11 °CA to 29 °CA is significantly impacted by the engine speed and the excess air fuel ratio, whereas the load exerts less influence. Furthermore, the boundary of the minimum excess air fuel ratio limited by knock with different intake pressure, compression ratio and ignition timing are investigated and optimized. The minimum excess air fuel ratio limited by knock reaches 1.80 with a maximum torque of 325 Nm at the engine speed of 2500 rpm due to the limitation of the pre-ignition and super -knock. A high brake thermal efficiency of 43.02 % and a maximum power of 125 kW are achieved with the minimum excess air fuel ratio limited by knock of 2.05 and 1.4 respectively.