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首页> 外文会议>ASME Internal Combustion Engine Division technical conference >COMPUTATIONAL STUDY TO IDENTIFY FEASIBLE OPERATING SPACE FOR A MIXED MODE COMBUSTION STRATEGY - A PATHWAY FOR PCI HIGH LOAD OPERATION
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COMPUTATIONAL STUDY TO IDENTIFY FEASIBLE OPERATING SPACE FOR A MIXED MODE COMBUSTION STRATEGY - A PATHWAY FOR PCI HIGH LOAD OPERATION

机译：确定混合模式燃烧策略可行操作空间的计算研究-PCI高负荷运行的途径。

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Mixed mode combustion strategies have shown great potential to achieve high load operation but soot emissions were found to be problematic. A recent study investigating soot emissions in such strategies showed that delaying the load extension injection sufficiently late after the primary heat release makes the soot production dependent solely on the temperature field inside the combustion chamber and eliminates any dependence on mixing time and oxygen availability. The current study focuses on furthering this research to identify a feasible operating space to operate in and enable high load operation with this mixed mode combustion strategy. A PCI combustion event was achieved using a premixed charge of gasoline (early cycle injection) and a load extension injection of gasoline was added near top dead center. CFD modeling considering polycyclic aromatic hydrocarbon (PAH) chemistry up to pyrene was used to perform a full factorial design of experiments (DOE) to study the effects of premixed fuel fraction (fraction of total fuel that is premixed), load extension injection timing and exhaust gas recirculation (EGR). The early injection timings for EGR rates less than 40% showed a soot-NOx tradeoff which constrained operating with SOI timings before TDC. The late injection timings showed reductions in soot and NOx at the expense of gross indicated efficiency (GIE). GIE increased with increasing premixed fuel until the premixed fuel quantity reached 80% of the total fuel mass. Premixed fuel quantities higher than 80% resulted in an efficiency penalty due to increased wall heat transfer losses resulting from early combustion phasing. However, at premixed fuel quantities close to 80%, the peak pressure rise rate became the dominating constraint. This confined the feasible operating space to a premix fuel mass range of 70% to 80%. For this premix fuel mass range, the feasible operating space had two regions; one in the early SOI regime before TDC at EGR rates higher than 38% and the other in the late SOI regime (SOI > 15° ATDC) across the entire EGR space. The study was repeated by splitting the premixed fuel into an early cycle injection and a stratified injection with SOI timing of -70° ATDC. The ratio of fuel in the two injections was varied in the DOE. The results showed that adding a stratified injection increases the ignition delay due to in-cylinder equivalence ratio stratification and relaxes the pressure rise rate effect on the operating space. This allows operation at high premix fuel quantities of 70% and higher with EGR rates less than 40% which yields significant increase in GIE. It was also identified that by targeting the fuel from the stratified injection into the squish region, there is improved oxygen availability in the bowl for the load extension injection, which results in the reduction of soot emissions. This allows the load extension injection to be brought closer to TDC while meeting the soot constraint, which further improves the GIE. Finally, the results from the study were used to demonstrate high load operation at 20 bar and 1300 rpm.
机译：混合模式燃烧策略显示出达到高负荷操作的巨大潜力，但发现烟灰排放是有问题的。最近调查这种策略中的烟灰排放的研究表明，初级热释放后足够晚期延迟负载延伸喷射，使得烟灰产生仅仅依赖于燃烧室内的温度场，并消除对混合时间和氧气可用性的任何依赖性。目前的研究侧重于进一步研究该研究，以确定可行的操作空间，以通过这种混合模式燃烧策略实现高负载运行。使用预混合电荷（早期循环喷射）和汽油的载荷延伸注射达到PCI燃烧事件，并在顶部死亡中心附近加入汽油。考虑到多环芳烃（PAH）化学的CFD模型用于对芘进行实验（DOE）的完整因子设计，研究预混燃料分数（预混合的总燃料的分数），负载延伸注射正时和排气气体再循环（EGR）。 EGR率小于40％的早期注射时间显示出烟灰 - NOx权衡，该权衡受到TDC之前在SOI定时进行的限制。晚期注射时间显示烟灰和NOx的减少，以牺牲总指出的效率（GIE）为代价。 GIE随着预混燃料的增加而增加，直到预热的燃料量达到总燃料质量的80％。由于早期燃烧相位产生的壁传热损失增加，预混燃料量高于80％导致效率损失。然而，在预混燃料量接近80％，峰值压力升高率成为主导约束。这将可行的操作空间局限于70％至80％的预混燃料质量范围。对于这种预混燃料质量范围，可行的操作空间有两个区域;在TDC之前的早期SOI制度中，在整个EGR空间上的后期SOI制度（SOI> 15°ATDC）高于38％的EGR率。通过将预混合的燃料分成早期循环注射和具有-70°ATDC的SOI定时来重复该研究。在DOE中，两种注射中的燃料比例变化。结果表明，增加分层注射增加由于缸内等效比分层引起的点火延迟，并松弛对操作空间的压力升高速率效应。这允许以70％和更高的高预混燃料量的操作，EGR率小于40％，从而产生显着增加。还认为通过将燃料从分层喷射到鳞片区域靶向，在碗中有改善的氧可用性，用于负载延伸喷射，这导致烟灰排放的减少。这允许负载延伸喷射在满足烟灰约束的同时将较近TDC带到TDC，这进一步改善了GIE。最后，该研究的结果用于在20巴和1300rpm下展示高负荷操作。

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