Power characteristics with different types of turbochargers for lean boosted hydrogen direct injection engine in NOx-free operation.

Lean boosting is a low-temperature combustion technology that can contribute to the expansion of the operation range by reducing the pressure increase rate and the combustion temperature owing to the increase in the intake air amount, even though the amount of heat supplied is the same. By optimizing the boosting device of the direct-injection-type hydrogen engine, it was expected that the operating range could be expanded through the torque increase owing to the increase in the amount of heat supplied according to the increase in the intake air mass, and nitrogen oxides emission was expected to be suppressed owing to lean low-temperature combustion. In the present study, to examine the possible output limit of a hydrogen engine under high-lean boosting conditions by applying a boosting device with a different control method, the performance according to the engine speed was observed under the condition of minimizing nitrogen oxide emission. Owing to the boosting performance by the variable turbocharging device, the output power was improved by 165% compared to that of the naturally aspirated-type combustion at a rotation speed of 5000 rpm.