...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Fuel >An experimental and numerical study on diesel injection split of a natural gas/diesel dual-fuel engine at a low engine load
【24h】

An experimental and numerical study on diesel injection split of a natural gas/diesel dual-fuel engine at a low engine load

机译：低负荷时天然气/柴油双燃料发动机柴油机喷油分离的实验和数值研究

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Natural gas/diesel dual-fuel combustion is currently one of the most promising LTC strategies for the next generation of heavy-duty engines. While this concept is not new and it has been deliberated lengthily in the past two decades, several uncertainties still exist. A major shortcoming of this concept is associated with its low thermal efficiency and high level of unburned methane and CO emissions under low engine load conditions. The present paper reports an experimental and numerical study on the effect of different injection strategies (single and two pulses injection of pilot diesel fuel) on the combustion performance and emissions of a heavy duty natural gas/diesel dual-fuel engine at 25% engine load. The results of single diesel injection mode showed that advancing diesel injection timing from 10 to 30 degrees BTDC reduced unburned methane and CO emissions by 62% and 61% and increased thermal efficiency by 6%; however, NOx emissions increased by 74%. In order to achieve NOx - CH4 and NOx - CO trade-off and increased thermal efficiency at low load conditions, the effect of split injection strategy was experimentally and numerically examined. The results of split injection mode revealed that split injection strategy considerably increases the in-cylinder peak pressure compared to that of single injection (10 degrees BTDC). The results showed also that the heat release produced by the first injection of diesel fuel considerably increased the in-cylinder charge temperature before the start of the second injection. The flame zone of the split injection mode is markedly higher than that of the single injection due to larger heat release produced during the first injection which promotes the combustion of the second one. When the first injection timing is close to the second injection timing, the MPRR of split injection mode is higher than that of single injection (10 degrees BTDC). However, further advancing of the first injection timing continuously decreased the MPRR. OH radical analysis showed that for advanced first injection timings (38-50 degrees BTDC), the overall growth rate of OH radical becomes slower and its distribution is narrower as indicated by the wider non-reactive blue zones compared with those observed at a late first injection timing in the initial stages of combustion. However, OH radicals gradually grow during last stages of combustion in the expansion stroke, indicating that a more pre-mixed combustion takes place in these cases. For very advanced first injection timing of 55 degrees BTDC, the OH distribution is similar to that of the single injection mode with lower OH intensity at initial stages of combustion and they barely grow during the late expansion stroke. At this condition, the ignition of premixed mixture is mainly controlled by the second diesel fuel injection. The trade-off between NOx - CH4 and NOx - CO is achieved when applying split injection. Compared to single injection (10 degrees BTDC), the first injection timing of 50 degrees BTDC decreased unburned methane and CO emissions by 60% and 63%, respectively, and increased the thermal efficiency by 8.9%. However, NOx emissions were maintained at the same level as single injection mode (10 degrees BTDC).
机译：天然气/柴油双燃料燃烧目前是下一代重型发动机最有前途的LTC策略之一。尽管这个概念并不新鲜，并且在过去的二十年中经过了长时间的审议，但仍然存在一些不确定性。该概念的主要缺点在于在低发动机负载条件下其热效率低以及未燃烧的甲烷和一氧化碳排放量高​​。本文报道了在25％发动机负载下不同喷射策略（单次和两次脉冲喷射引燃柴油燃料）对重型天然气/柴油双燃料发动机的燃烧性能和排放的影响的实验和数值研究。单次柴油喷射模式的结果表明，将柴油喷射时间从BTDC提前到10度到30度，可将未燃烧的甲烷和一氧化碳排放量分别减少62％和61％，并将热效率提高6％。但是，NOx排放量增加了74％。为了在低负荷条件下实现NOx-CH4和NOx-CO的折衷并提高热效率，通过实验和数值研究了分流喷射策略的效果。分流喷射模式的结果表明，与单点喷射（10度BTDC）相比，分流喷射策略显着提高了缸内峰值压力。结果还表明，第一次喷射柴油产生的放热大大增加了第二次喷射开始之前的缸内充气温度。分开喷射模式的火焰区明显高于单次喷射的火焰区，这是因为在第一次喷射过程中产生了较大的热量释放，从而促进了第二次燃烧。当第一喷射时刻接近第二喷射时刻时，分开喷射模式的MPRR高于单次喷射的MPRR（10度BTDC）。然而，第一喷射正时的进一步前进连续降低了MPRR。 OH自由基分析显示，对于较早的首次注射时间（BTDC 38-50度），OH自由基的总体生长速度变慢，并且其分布较窄，与未反应的较晚蓝色区域相比，该区域较窄。燃烧初期的喷射正时。但是，OH自由基在膨胀冲程中燃烧的最后阶段逐渐增长，这表明在这些情况下发生了更加预混合的燃烧。对于非常先进的BTDC 55度的首次喷射正时，OH分布与单喷射模式相似，在燃烧的初始阶段具有较低的OH强度，并且在后期的膨胀冲程中几乎没有增长。在这种情况下，预混混合物的点火主要由第二次柴油喷射控制。使用分流喷射时，可以在NOx-CH4和NOx-CO之间进行权衡。与单次喷射（10度BTDC）相比，首次喷射正时为50度BTDC时，未燃烧的甲烷和一氧化碳排放量分别降低了60％和63％，热效率提高了8.9％。但是，NOx排放保持与单次喷射模式（BTDC 10度）相同的水平。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号