【作者】 姚春玲；

【导师】 储江伟；

【作者基本信息】 东北林业大学 ， 载运工具运用工程， 2011， 博士

【摘要】 随着汽车保有量的不断增加和排放法规的日益严格,传统能源利用技术的创新已成为备受瞩目的焦点问题。其中,发动机混合进气富氧化以其优越的节能与环保效应引起了广泛的关注。进气混合助燃气体与非助燃气体对发动机性能存在不同影响,即进气混合助燃气体(如02),将提高动力性与燃料经济性,降低HC和CO排放,但是NOx排放显著升高；进气混合非助燃气体(如CO2),将使动力性与燃料经济性恶化,HC和CO排放升高,但是NOx排放显著降低。因此,本文从改善燃烧降低排放的目标出发,以数值模拟和台架试验为主要研究手段,针对汽油机富氧进气混合气性质、化学反应动力学燃烧机理与排放特性,混合02对汽油机低温冷起动燃烧与排放的改善作用,O2/CO2混合最佳进气配比等问题,主要进行了以下研究工作：第一,以理论分析为基础,分析了增加O2体积分数对异辛烷氧化过程燃烧产物与中间产物的影响,以及富氧进气汽油机的燃烧机理和排放特性,总结了富氧进气汽油机燃烧过程的本质特性和规律。提高O2体积分数使汽油机化学反应速度加快,OH和CH20等重要燃烧中间产物的生成量和生成宽度增加,从而促使燃料燃烧更加彻底,燃烧温度与燃烧压力增加,不完全燃烧产生的CO和未燃HC排放降低。但是,提高O2体积分数在改善缸内燃烧状况的同时,带来了NOx排放显著升高的问题。所以,本文采用进气中混合CO2的方法,以降低富氧进气产生的较高NOx排放。第二,根据汽油机进气成分中O2/CO2的进气配比,确定相应的研究内容及研究方法,并使用相应的试验系统与测试仪器,构建混合进气汽油机性能试验台架及低温冷起动试验台架,开展相关试验研究。第三,基于循环控制的方法,对不同O2体积分数汽油机低温冷起动最初60s内的CO、CO和NOx排放及缸内燃烧状况的影响进行分析；根据汽油机应用富氧进气后的发动机运行状态,选择最佳富氧比例范围。研究结果表明：从控制汽油机冷起动阶段排放的角度出发,23%-25%富氧进气更适合本试验汽油机在低温环境冷起动。第四,针对不同稳态工况和不同混合进气组分条件,设计试验方案,测试发动机的动力性能、经济性能、燃烧特性和排放特性。研究汽油机进气单独混合02、同时混合O2/CO2后的性能,重点研究进气组分与发动机工况的匹配,在保证发动机功率和油耗率的基础上,尽可能地减少CO、CO和NOx等有害气体排放。富氧进气汽油机的负荷特性与速度特性试验结果显示,23%-25%O2体积分数为最佳富氧进气方式。进一步增加O2体积分数将使NOx排放成倍增长,但其他有益指标的变化幅度明显减弱。向25%02体积分数富氧进气汽油机添加体积分数为2%的CO2,可以在提高动力性和燃料经济性的同时,降低HC、CO和NOx排放,提高燃烧温度。第五,利用CHEMKIN软件,导入异辛烷化学反应动力学机理,模拟不同混合进气组分时的燃烧过程,并结合试验检测结果对模型的精度进行了验证,分析了进气成分对中间反应基团及异辛烷氧化机理的影响,补充试验研究的不足,对改变压缩比和过量空气系数后富氧进气汽油机燃烧过程的变化也进行了分析。更多还原

【Abstract】 As the vehical number increases and the emission regulations are stringent, innovation on traditional energy technology has become a focused issue. And the engine with oxygen enriched intake air, of superior energy-saving and environmental protection effects, has been broadly concerned. As combustion-supporting gas or non-combustion-supporting gas can be respectively mixed into the intake air, different impact on engine performance is caused; that is, if combustion-supporting gas is mixed into intake air (such as O2), the motive performance and fuel economy will be raised, but NOx emissions will be much higher; if non-combustion-supporting gas is mixed into intake air (such as CO2), the motive performance and fuel economy will worsen, but NOx emissions will be much lower. Therefore, in this paper, with the objective to improve combustion and reduce emissions, according to the main means of numerical simulation and bench test, and based on the property of oxygen enriched intake air in gasoline engine, combustion mechanism and emission performance of chemical reaction kinetics, improvement impact of mixed O2 on combustion and emission of gasoline engine low temperature cold start, and optimum proportioning of O2/CO2 in intake air, etc., the following researches are conducted:First, based on theoretical analysis, from the perspective of chemical reaction kinetics, the impact of O2 rate increase on combustion products and intermediate products in isooctane oxidation process is analyzed; and based on combustion mechanism and emission performance of oxygen enriched intake air gasoline engine, innate characteristics and principle of combustion process of oxygen enriched intake air gasoline engine is summarized. By increasing O2 rate chemical reaction speed in gasoline engine is raised, generation volume and range of major intermediate products such as OH and CH2O, etc. in combustion increase, thus .the fuel is burnt more completely, the combustion temperature and combustion pressure increase, and CO2 caused by incomplete combustion and unburned HC emissions are reduced. However, at the same time the increased O2 rate improves combustion in the cylinder, the significantly increased NOx emissions problem is also caused. Therefore, in this paper, with the method to reduce CO2 mixed in intake air, the high NOx emissions produced by the oxygen enriched intake air are prevented.Second, according to proportioning of O2/CO2 in intake air of gasoline engine, the relevant research contents and research method are determined, and the relevant test system and test instrument are applied to build test-bed of mixed intake air gasoline engine performance and test-bed of low temperature cold start for experimental research.Third, HC, CO and NOx emission under different O2 rates within 60s after the low temperature cold start, as well as impact on combustion status in the cylinder is analyzed; and according to the running status of gasoline engine after oxygen enriched intake air applied, the optimum oxygen enrichment proportional range is chosen. From the research, from the perspective of control emission within 60s after the low temperature cold start,23%-25% oxygen enriched intake air is more appropriate for low temperature cold start of gasoline engine in this experiment.Fourth, based on the different steady working conditions and the different mixed intake air constituent conditions, the testing program is designed, and the power performance, economy performance, combustion characteristic and emission performance are tested. Gasoline engine performance with intake air of O2 and O7/CO2 is respectively researched; the emphasis is on research of matching between intake air constituents and engine working conditions, and with the premise that engine power and fuel consumption reach required value, HC, CO and NOA emission should be reduced as much as possible. From the test result of load& speed characteristics in oxygen enriched intake air gasoline engine, the 23%-25%O2 rate is the optimum oxygen enriched intake air proportion. As O? rate is further raised, NOx emission can be doubled, while other beneficial indicators range ability obviously weakens. Addition of 2% of CO2 into the 25% O2 will not only boost the motive performance and fuel economy, but also reduce HC, CO and NOx emission, and increase the combustion temperature.Fifth, with CHEMKIN, the mechanism of isooctane Chemical Reaction Kinetics is imported, and combustion process with different intake air constituents is simulated, the model accuracy is verified based on test, impact of intake air constituents on intermediate reaction groups and isooctane oxidization mechanism is analyzed, thus insufficiency of experimental study is supplemented, and change of combustion process of oxygen enriched gasoline engine after compression ratio and excess air ratio altered is also analyzed.更多还原