天然气工业2017，Vol.37Issue(10)：79-86,8.DOI:10.3787/j.issn.1000-0976.2017.10.011
点燃式重型天然气发动机燃烧技术的发展及其应用
The development and application of combustion technologies for spark ignition heavy-duty natural gas engines
摘要
Abstract
Lean burn and stoichiometric are two main combustion modes in spark ignition heavy-duty natural gas engines.And due to its efficient and clean combustion,the lean-burn technology has been playing a dominant role for a long time.As EU-Ⅴ legislation is implemented gradually,however,a lean-burn engine cannot satisfy the nitrogen oxides (NOx) emission requirements unless it is equipped with a selective catalytic reduction (SCR) unit.On the contrary,stoichiometric combustion has been given more and more attention,for ultra-low emission and obvious low post-treatment cost can be realized when it is combined with a three-way catalyst.In this paper,the advantages and problems of both combustion modes were illustrated and optimization measures were proposed correspondingly.Based on the analysis,the following conclusions were reached.First,a lean-burn engine can satisfy the EU-Ⅴ emission legislation if its combustion limit is extended with no installment of any NOx post-treatment unit,and a higher thermal efficiency can be realized.In order to satisfy EU-Ⅵ legislation,however,it has to be equipped with SCR.Second,compared with the optimization of combustion chambers and intake ports,both regional stratification and pre-combustion chambers are more favorable for lean-burn limit extension and stable combustion.And in the same level of NOx emission,they can increase the thermal efficiency significantly,but much more unburned hydrocarbon will be emitted if the mixed gas zone is too thin.Third,if lean burn is combined with SCR to satisfy EU-Ⅵ emission legislation,the original NOx emission can be inhibited further by recirculation and dilution of a little burned gas,so that the combustion phase will get better.And fourth,if stoichiometric combustion is combined with the recirculation of a little burned gas,the thermal efficiency can be increased effectively by means of Miller cycle.If the air valve is not closed on time,however,the combustion rate will still drop even though the effective compression ratio is kept constant or increased slightly.If the closing time of the air valve is seldom before or after the schedule,the effective compression ratio will be increased,and consequently heat transfer loss and high-load knock tend to increase obviously.关键词
点燃式天然气发动机/稀燃/当量燃烧/热效率/排放法规/SCR/三效催化器/优化措施Key words
Spark ignition natural gas engine/Lean burn/Stoichiometric combustion/Thermal efficiency/Emission legislation/SCR/Three-way catalyst/Optimization measures引用本文复制引用
尧命发,闫博文,郑尊清,覃玉峰..点燃式重型天然气发动机燃烧技术的发展及其应用[J].天然气工业,2017,37(10):79-86,8.基金项目
国家自然科学基金项目“基于混合气分层与燃料化学活性控制的内燃机燃烧理论研究”(编号:51320105008). （编号:51320105008）
