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首页> 外文期刊>Energy & fuels >Effects of Hydrogen Addition on the Performance of a Pilot-Ignition Direct-Injection Natural Gas Engine: A Numerical Study
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Effects of Hydrogen Addition on the Performance of a Pilot-Ignition Direct-Injection Natural Gas Engine: A Numerical Study

机译：加氢对引燃直喷天然气发动机性能的影响：数值研究

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摘要

Adding hydrogen to natural gas is a promising way to improve the ignition stability and reduce the greenhouse gas emissions of pilot-ignition direct-injection natural gas engines. Most of the previous studies concerning hydrogen-enriched natural gas engines are focused on spark-ignition engines. The limited investigations on the addition of hydrogen in direct-injection natural gas engines are conducted by experimental method. Therefore, some detailed information on the in-cylinder combustion and emission formation process are left unknown. In this work, numerical simulations have been performed for the combustion process of a pilot-ignition direct-injection natural gas engine based on an integrated mechanism which is capable of describing the chemical kinetics involving diesel, natural gas, and hydrogen. Three-dimensional (3D) computational fluid dynamics simulations were conducted at different hydrogen blend ratios to explore the effects of hydrogen addition on the whole combustion process and the mole fraction traces of small radicals as well as CO, NOx, and soot emissions. Hydrogen addition was achieved by both volume-equivalent principle and energy-equivalent principle to guide the choice of hydrogen-addition method. Zero-dimensional simulations were conducted to elaborate the explanations of the phenomena in 3D simulations and disclose the interactions among the sensitivity of the key reactions, the formation of the active radicals, and the heat release process. The results show that the ignition delay is shortened and the ignition of natural gas is enhanced with the increase of hydrogen addition, which is primarily caused by the enhanced reactions related to active small radicals induced by increased hydrogen concentration. When hydrogen is added based on the volume-equivalent principle, all emission values will reduce with little sacrifice on thermal efficiency at hydrogen blend ratios smaller than 20%. However, CO emissions experience an increasing trend when hydrogen blend ratio is further increased to higher than 20% while NOx and soot emissions retain the decreasing trend. When hydrogen is added based on the energy-equivalent principle, CO emissions and soot emissions will decrease with the increase of hydrogen blend ratio while NOx emissions will witness an opposite trend with considerable improvements in thermal efficiency.
机译：在天然气中添加氢气是提高点火稳定性并减少引燃直喷天然气发动机温室气体排放的一种有前途的方式。先前有关富氢天然气发动机的大多数研究都集中在火花点火发动机上。通过实验方法对在直喷式天然气发动机中添加氢气进行了有限的研究。因此，有关缸内燃烧和排放物形成过程的一些详细信息仍然未知。在这项工作中，基于能够描述涉及柴油，天然气和氢气的化学动力学的集成机制，对引燃直喷式天然气发动机的燃烧过程进行了数值模拟。在不同的氢混合比下进行了三维（3D）计算流体动力学模拟，以探索氢的添加对整个燃烧过程的影响以及小自由基的摩尔分数迹以及CO，NOx和烟尘排放的影响。通过体积当量原理和能量当量原理实现加氢，指导加氢方法的选择。进行了零维模拟，以详细解释3D模拟中的现象，并揭示了关键反应的敏感性，活性基团的形成和放热过程之间的相互作用。结果表明，随着氢气添加量的增加，点火延迟缩短，天然气的点火增强，这主要是由于氢气浓度升高引起活性小自由基的反应增强所致。当基于体积当量原理添加氢时，在氢混合比小于20％时，所有排放值都会降低，而热效率几乎没有损失。但是，当氢气混合比进一步提高到20％以上时，CO排放量呈上升趋势，而NOx和烟尘排放量保持下降趋势。当基于能量当量原理添加氢时，CO排放量和烟尘排放量将随着氢混合比的增加而降低，而NOx排放量则将呈现相反的趋势，热效率会大大提高。

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  • 来源
    《Energy & fuels》 |2017年第4期|4407-4423|共17页
  • 作者

    Li Menghan; Zhang Qiang; Li Guoxiang; Li Peixin;

  • 作者单位

    Shandong Univ, Sch Energy & Power Engn, Jinan 250061, Peoples R China;

    Shandong Univ, Sch Energy & Power Engn, Jinan 250061, Peoples R China;

    Shandong Univ, Sch Energy & Power Engn, Jinan 250061, Peoples R China;

    Weichai Holding Grp Co Ltd, 197A Fushou East St, Weifang 261001, Shandong, Peoples R China;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
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