A number of studies on hydrogen engines have targeted small-sized engines for passenger vehicles. By contrast, the present study focuses on a large-sized engine for a stationary power generator. The objective of this study is to simultaneously achieve low NOx emission without aftertreatment, and high thermal efficiency and torque. Experimental analysis has been conducted on a single-cylinder test engine equipped with a gas injector for direct hydrogen injection. The injection strategy adopted in this study aims generating inhomogeneity of hydrogen mixtures within the engine cylinder by setting the injection pressure at a relatively low level while injecting hydrogen through small orifices. High levels of EGR and increased intake boost pressures are also adopted to reduce NOx emission and enhance torque. The results showed that extreme levels of EGR and air-fuel inhomogeneity can suppress NOx emission and the occurrence of abnormal combustion with little negative impact on the efficiency of hydrogen combustion. The maximum IMEP achieved under these conditions is 1.46 MPa (135 [email protected] rpm) with engine-out NOx emission of less than 150 ppm (ISNOx < 0.55 g/kW) for an intake boost pressure of 175 kPa and EGR rate of around 50%. To achieve further improvement of the IMEP and thermal efficiency, the Atkinson/Miller cycle was attempted by increasing the expansion ratio and retarding the intake valve closing time of the engine. The test engine used in this study finally achieved an IMEP of 1.64 MPa (150 [email protected] rpm) with less than 100 ppm of NOx emission (ISNOx < 0.36 g/kWh) and more than 50% of ITE.

关于氢发动机的许多研究已经针对乘用车的小型发动机。相比之下，本研究着重于用于固定式发电机的大型发动机。这项研究的目的是在不进行后处理的情况下同时实现低NOx排放以及高热效率和扭矩。已经在配备有用于直接氢注入的气体注入器的单缸测试发动机上进行了实验分析。本研究采用的喷射策略旨在通过将喷射压力设置在较低的水平，同时通过小孔喷射氢，从而在发动机气缸内产生氢气混合物的不均匀性。还采用高水平的EGR和增加的进气增压压力，以减少NOx排放并提高扭矩。结果表明，极端水平的EGR和空气-燃料不均匀性可以抑制NOx排放和异常燃烧的发生，而对氢燃烧效率的负面影响很小。在这些条件下达到的最大IMEP为1.46 MPa（135 [电子邮件保护] rpm），对于175 kPa的进气增压压力和EGR率约为190，发动机排出的NOx排放小于150 ppm（ISNOx <0.55 g / kW）。 50％。为了进一步改善IMEP和热效率，尝试通过增加膨胀比并延迟发动机的进气门关闭时间来尝试执行阿特金森/米勒循环。这项研究中使用的测试引擎最终实现了1.64 MPa（150 [电子邮件保护] rpm）的IMEP，其NOx排放量少于100 ppm（ISNOx <0.36 g / kWh），而ITE含量却超过50％。