Exhaust Aftertreatment Characteristics of NH3-SCR System in Lean-Burn Direct injection Hydrogen Engine
The hydrogen internal combustion engine has the characteristics of zero carbon emission and is an important method to achieve low cost carbon neutrality.However,the high temperature environment of incylinder combustion will generate a large amount of nitrogen oxide(NOx )emissions.The use of selective catalytic reductio(SCR)reducing NOx technology is a necessary method to expand its large scale application and continue improving power and economy performance.The experiment verified that the NH3-SCR aftertreatment system of Cu-based molecular sieve was an efficient NOx purification scheme for di-rect injection hydrogen engine.A simplified reaction mechanism was used to model and simulate the NH3-SCR reaction process,and the effects of reaction temperature,space velocity and NH3-nitrogen ratio on NOx reduction by NH3-SCR were studied under the boundary of hydrogen internal combustion engine.The results show that the low-temperature activity of am-monia SCR is still good under the boundary of lean burn hydrogen combustion engine with direct injection.The ignition temper-ature(T50)of aftertreatment system is 110℃,and the activity window(T90)ranges from 150℃ to 425℃.When the airspeed is greater than 25000 h-1 ,the Nox conversion efficiency remains greater than 95％.When the ammonia nitrogen ratio is 0.5 and the reaction temperature maintains at 350-400 ℃,the highest Nox conversion efficiency can be guaranteed and the near-ze-ro Nox emission of direct injection hydrogen combustion engine can be achieved.
hydrogen internal combustion enginenitrogen oxideslean burnselective catalytic reductionincylinder direct injection
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