Effect of pre-combustion chamber hydrogen injection strategy on emissions and fuel economy of jet ignition engines under ultra lean-burn conditions

To reduce the consumption of gasoline, improve thermal efficiency and promote the cyclic development of internal combustion engine technology, this paper utilizes the jet ignition technology and uses hydrogen as fuel in the active pre-combustion chamber to achieve ultra lean-burn of gasoline under lambda of 2.1. On this basis, influence of various pre-combustion chamber hydrogen injection timing (HIT), pre-combustion chamber hydrogen injection pressures (HIP) and their corresponding ignition timings (IT) on the engine emission profile are investigated. The findings indicate that the selection of a rational pre-combustion chamber hydrogen injection strategy can effectively reduce the emission of engine pollutants and improve the combustion economy. For HC and CO, IT of 15 degrees CA BTDC is optimal. By adjusting the injection strategy on this basis, both HC and CO emissions are minimized at HIP of 3 MPa with HIT of 140 degrees CA BTDC, decreasing by 49.26% and 54.75%, respectively. A favorable combustion atmosphere will inevitably lead to higher NOx emissions, and a smaller IT is required to achieve lower NOx emissions. The injection strategy and IT mainly affect particle number concentration with diameter less than 30 nm, so the effect on NPN emissions is very significant, while the effect on APN is insignificant. Meanwhile, the particulate emissions in general decrease with the advancement of IT. A relatively low HIP and a relatively late HIT can result in the best BSFC and brake thermal efficiency. "HIP of 3 MPa,HIT of 160 degrees CA BTDC and IT of 14 degrees CA BTDC" is considered to be the best control strategy.