An experimental study on the NO_x emission characteristics of PFI hydrogen internal combustion engine

A test is conducted to study the effects of the equivalent fuel air ratio (FAR), ignition advance angle, exhaust gas recirculation (EGR) and engine speed on the NO_x emission from a 4 cylinder port fuel injection (PFI) hydrogen internal combustion engine. The results show that the equivalent FAR is the key factor to the formation of NO_x. When the equivalent FAR is larger than 0.5, the NO_x emission increases quickly with equivalent FAR and reaches its peak (10, 000×10^-6) at an equivalent FAR of around 0.9, and with the fall in engine speed the peak NO_x emission lowers and corresponding equivalent FAR reduces; When the equivalent FAR is in the range of 0.5~0.7, the retard in ignition angle leads to the great reduction in NO_x emission, and the lower the engine speed, the more the reduction in NO_x emission; The adoption of hot EGR also results in obvious fall in NO_x emission and the lower the engine speed, the more decrease the NO_x emission.