摘要
利用定容燃烧弹开展了天然气掺混0％～40％氢气混合燃料直喷燃烧循环变动研究，高压气体燃料（8．0MPa）喷入定容燃烧弹模拟直喷发动机燃烧条件。在整体当量比为0．6和0．8下，试验采集了火焰发展图片和燃烧过程容弹内压力，从火焰发展图片和燃烧特征参数两个方面分析了掺氢和混合气分层分布对天然气直喷燃烧循环变动的影响。结果表明：燃烧循环变动起始于火焰发展初期阶段。随着掺氢比增加，火焰形态更规则且更集中于点火电极。同时，由于直喷燃烧方式混合气分层分布，能够实现低循环变动的稳定稀燃。循环变动随着掺氢比的增加而减小，这种趋势在稀燃工况（Ф=0．6）下更加明显。在直喷燃烧方式下，由于混合气分层分布减弱了火焰发展初期阶段对后续燃烧过程的影响，因此燃烧特征参数间呈现相互独立的关系。
Cycle-by-cycle variations of direct-injection combustion fueled with natural gas/hydrogen blends were experimentally studied using a constant volume bomb. Flame propagating photographs and pressure history were recorded at various hydrogen volumetric fractions （ from 0% to 40% ） under the overall equivalence ratios of 0.6 and 0.8, respectively. The effect of fuel-air mixture stratification and hydrogen addition on the cycle-by-cycle variations was analyzed via flame development photographs and pressure-derived combustion parameters. The results showed that the cycle-by-cycle variations were initiated at the early stage of flame development. The flame kernel is more concentrated to the spark electrode and flame pattern has less irregularity with hydrogen addition. Direct-injection natural gas combustion can achieve the stable lean combustion along with low cycle-by-cycle variations due to the mixture stratification. Cycle-by-cycle variations decreased withthe increase of hydrogen addition and this trend is more obvious at ultra-lean burn condition. Hydrogen addition weakens the effect from the turbulent flow on flame propagating process. There exists interdependency between the early combustion stage and the subsequent combustion process for direct-injection combustion.
出处
《内燃机学报》
EI
CAS
CSCD
北大核心
2008年第5期410-419,共10页
Transactions of Csice
基金
国家自然科学基金(50422261
50636040
50521604)
国家重点基础研究计划项目(2007CB210006)
关键词
天然气
氢气
循环变动
直喷燃烧
Natural gas
Hydrogen
Cycle-by-cycle variations
Direct-injection combustion
