Simulation of Inner-Engine NOx Emission Control on Pure Hydrogen Engines

Abstract:

Hydrogen is an ideal engine fuel. Pure hydrogen engines do not produce CO and HC emissions but face the high NOx emission problem. Inner-engine control and outer-engine control are two ways to decrease the NO_x emission. Outer-engine control mainly reduce NO_x emission through selective catalytic reduction （SCR）， which has been well studied. However， there are few studies on NO_x emission control of pure hydrogen engines through inner-engine control. In this paper， the closed homogeneous reactor （CHR） in Chemkin Pro was used to simulate the main inner-engine NO_x emission control in pure hydrogen engines. The results show that single exhaust gas recirculation （EGR） decreases NO_x emission by 45.3% at an EGR ratio of 20%， indicating that the NO_x emission is not significantly reduced. However， EGR plus lean-burn decreases NO_x emission by 96.31% at a λ of 1.4 and an EGR ratio of 20%， achieving ultra-low NO_x emission of pure hydrogen engines. Compared with single EGR and EGR plus lean-burn， SNCR are better for NO_x emission control. A NH₃ ratio of only 10% can decrease NO_x emission by 96.32% on pure hydrogen engines， while a NH₃ ratio of 15% can achieve zero NO_x emission on pure hydrogen engines without a large λ value and EGR ratio. However， it is necessary to accurately control the NH₃ ratio in the cylinder， otherwise it is easy to produce residual NH₃ which can pollute the environment.