There are few investigations on the knock characteristics of direct-injection (DI) hydrogen engines, so to reveal the influencing mechanism of synergistic effects of the deep Miller cycle and oxygen-enriched atmosphere on the DI hydrogen engine’s knock characteristics, an experimental study was carried out at 1600 rpm and wide-open throttle conditions. Overall, the Miller effect provides good suppression of combustion knock even at high oxygen concentration (), while the oxygen-enriched atmosphere can mitigate the negative effects of the deep Miller cycle on the combustion process. The results demonstrated that the Miller cycle mitigates the excitation effect of elevated and reduced λ on combustion knock. For example, even if was raised to 27.1 %, the knock intensity (KI) is only close to 1.0 bar at 1.6 λ. It was found that the deep Miller cycle achieved by regulating the intake valve timing to the engine could further suppress the combustion knock, which may be related to the reduced effective compression ratio and volumetric efficiency. Specifically, under the deep Miller effect, KI did not exceed 0.8 bar even when was elevated to 32.0 %, indicating that knock was effectively suppressed, although about 190 cycles corresponding to knock durations exceeding 10°CA.

中文翻译：

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直喷式氢发动机爆震实验研究：深度米勒循环与富氧气氛的协同效应

针对直喷式氢发动机爆震特性的研究较少，为揭示深米勒循环与富氧气氛协同作用对直喷式氢发动机爆震特性的影响机制，进行了实验研究。在 1600 rpm 和节气门全开条件下输出。总体而言，即使在高氧浓度下，米勒效应也能很好地抑制燃烧爆震，而富氧气氛可以减轻深度米勒循环对燃烧过程的负面影响。结果表明，米勒循环减轻了增大和减小 λ 对燃烧爆震的激励效应。例如，即使提高到 27.1%，爆震强度 (KI) 在 1.6 λ 处也仅接近 1.0 bar。研究发现，通过调节发动机进气门正时实现的深米勒循环可以进一步抑制燃烧爆震，这可能与有效压缩比和容积效率降低有关。具体来说，在深米勒效应下，即使KI升高到32.0%，也没有超过0.8 bar，表明爆震得到了有效抑制，尽管大约190个循环对应的爆震持续时间超过10°CA。