【作者】

Tianhao Yang

【摘要】

该论文已在赫尔辛基举行的第28届CIMAC世界大会上发表，论文的版权归CIMAC所有。 In this work novel various internal purification methods were numerically analyzed on a large-bore medium speed diesel engine, under different valve close timings, geometric compression ratios, injection timings and EGR rates, to evaluate their potentialities of emissions abatement. In addition, two types of novel combustion chambers, defined as Chamber One and Chamber Two, were designed and experimentally tested for NOx reduction abilities. Numerical results show that, as the intake valve close timing is advanced up to 50°CA before BDC, NOx is reduced by as much as 27%, while the peak of premixed combustion heat release rate is increased, which can weaken Miller cycle’s ability to reduce NOx emissions. Moreover, the peak of premixed combustion heat release rate can be reduced by increasing the geometric compression ratio up to 15.4, and combining with a 6°CA delay of injection timing, NOx emissions can be reduced by 55.3% from the baseline. Furthermore, over 80% NOx and 20% soot reduction can be achieved, when the above schemes are cooperated with 15% EGR with a constant air fuel rate by raising boost pressure, which can avoid NOx increase from low oxygen concentration. Thus, the trade-off relationship between NOx and soot can be compromised. Afterwards, two novel combustion chambers were tested separately under E3 cycle to evaluate their emissions reduction abilities. Chamber One allows mixture to spread wider resulting in 6%-14% NOx and 5.7% fuel consumption reduction at medium and high load. Chamber two improves combustion process by providing injection spray with open space in the direction of spray development and reducing wall-wetting, and reduces 1.8-2.5% fuel consumption with an original level of NOx emissions at medium and high load. In conclusion, NOx and soot can be reduced simultaneously by using moderate Miller cycles combining with moderate EGR, and novel combustion chambers show great potential in NOx abatement.

【会议名称】

第28届CIMAC会议

【会议地点】

芬兰 赫尔辛基

【下载次数】

3

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