Experimental observation of pre-chamber ignited mixing-controlled hydrogen jet flame with high-pressure injection

In this work, a new concept of pre-chamber (PC) turbulent jet ignition (TJI) induced mixing-controlled hydrogen jet flame with high-pressure injection is proposed to solve the combustion issues of hydrogen engines. The different ignition and combustion modes in a constant-volume combustion chamber under various ignition locations and mixture reactivity in the pre-chamber (PC) are obtained with both Schlieren and hydroxyl (OH*) chemiluminescence images for the first time. The TJI can successfully achieve the ignition of hydrogen (H2) jets, and the flame propagation can be separated into a partially premixed flame and a mixing-controlled jet flame. By increasing the injection delay, four ignition and combustion modes, including direct ignition by PC jet flame, head-to-head ignition, thermo-induced ignition, and ignition failure, are observed. In addition, the ignition ability affected by the mixture reactivity in PC is carefully discussed in terms of different hot jet intensities and locations of the hydrogen jet impinging on the PC hot jet. The ignition ability decreases with the increase in injection delay as the delay for ignition increases. A rich mixture with an equivalence ratio of 3 in the pre-chamber can increase the ignition ability and extend the range for successful ignition, and the ignition delay increases from 0.025 to 0.4 ms when the injection delay increases from −2 to 0 ms with φpc = 3.0.