【作者】 黄钰；

【导师】 姚春德；

【作者基本信息】 天津大学 ， 动力机械及工程， 2008， 博士

【摘要】 柴油机因为其良好的经济性以及可靠性,得到越来越广泛的应用。但是,微粒和氮氧化物(NOx)排放达标问题仍是制约其发展的关键。随着我国经济的快速发展,对石油的需求量日益增加,所以寻找石油替代燃料也已是当务之急。针对甲醇燃料的特点,提出柴油-甲醇组合燃烧方式。组合燃烧系统在发动机起动、暖车以及怠速工况下使用纯柴油工作模式,当发动机机体温度上升,进入正常运行工况后,进入柴油-甲醇组合燃烧模式。根据组合燃烧发动机的特点,将发动机运行工况分为6类,针对每类工况提出不同的控制策略。采用C语言和汇编语言的混合编程方法编写完成组合燃烧控制软件。控制软件的编写运用模块化设计思路,自顶向下、逐步细化的结构化软件设计方法。软件以MC9S12DP256芯片作为运行平台,通过对发动机传感器的信号识别,能够准确判断柴油-甲醇组合燃烧发动机的运行工况,在发动机电子控制单元的内部数据存储区间存储了发动机运行二维控制MAP图,该软件通过MAP插值计算方法将二维控制MAP图中离散、有限的控制量转变成连续的控制量,根据发动机负荷的变化自动定时定量的控制甲醇燃料喷射电磁阀。提出了以甲醇对柴油的替代率和替换比为控制目标,以排放作为约束条件的组合燃烧标定方法,在发动机台架上进行了标定工作,采用神经网络算法对MAP数据进行了优化,得到了更为紧密和平滑的控制MAP数据。结果表明运用神经网络优化的方法不仅能够减少标定工作量,而且完全能够达到组合燃烧系统的要求。在490QDI发动机台架上对组合燃烧发动机进行了不同控制方式、不同替代比率以及加装了DOC(氧化催化转化器)之后的对比试验。试验结果表明组合燃烧系统在小负荷时,甲醇对柴油的替代率不宜过高,在中等负荷采用30%～40%的替代率,在大负荷时采用40%～50%替代率能够取得较好的燃油经济性和排放性能。通过加装DOC后处理器后能够大幅度的降低HC和CO的排放量。采用甲醇的顺序喷射控制方式,发动机燃油经济性、HC、CO排放均略优于甲醇连续喷射控制方式,但是,NOx排放略高于后者。组合燃烧汽车道路试验结果表明,甲醇对柴油的平均替代率达到了36%,仅需要1.66单位质量的甲醇替换1单位质量的柴油,燃烧效率提高8.78%。组合燃烧系统能够有效消除柴油机在起步加速过程中“冒黑烟”的现象。在WD615增压中冷柴油机上进行了排放试验,结果表明,采用组合燃烧系统后国Ⅱ排放品质的发动机完全能够达到国Ⅲ排放限值。更多还原

【Abstract】 Diesel engines have gotten more and more widely used in trucks, buses and even in passenger cars, because of its excellent fuel economy as well as performance and reliability. However, PM and NOx emissions from diesel engine restrict it for further development. With the economy development of china, oil demand increases rapidly. Therefore, to develop the alternative fuel for oil is an urgent task for us. China is abundant in coal resource, but less storage in oil. Methanol can be produced from various kinds of materials such as coal, natural gas and biomass, which is one of the best alternative fuels for oil in future.As cetane number of methanol is quite low, it is difficult to be applied to compression ignition engine. So diesel-methanol compound combustion (DMCC) was brought forward based on methanol’s property. DMCC engine uses diesel fuel only in start, warming-up and idle operating condition. After water temp and engine speed rise up, diesel fuel model swiches to DMCC model.Six operation conditions were put forward according to DMCC engine characteristics. Each operation condition has its own control strategy. ECU controller software was compiled with language C and assembling language mixed programmed method. Controller software uses MC9S12DP256 chip as platform. Recognizing signals from sensors, software can judge operation condition of engine exactly.Calibration of MAP data has been undertaken on the engine bench. Using neural network optimize MAP data. This method makes the MAP data smoother. These data after optimization were tested on the bench test. The result showed that neural network can reduce the workload.Comparison of different control method, different proportion of methanol to diesel, with DOC and without DOC was conducted on the engine bench. The results showed that the proportion of methanol to diesel should be less at low load; the ratio 30%～40% at the medium load. Although the ratio could be higher at high load, it should not be more than 40%～50%. Additionally, the oxide catalyst had important impact to exhaust emissions,Economical performance gets better, HC and CO emission decrease using multi-point sequential injection. NOx emission almost remains the same.DMCC vehicle load test showed that the proportion of methanol to diesel was 36%, 1.66 kilogram methanol can replace 1.0 kilogram diesel, combustion efficiency increase 8.78%. DMCC vehicle reduce smoke emission in large extent during standing start.The exhaust experiments on the WD615 turbocharged, intercooled diesel engine showed that the emission quality of engine can be remarkably improved from basic ChinaⅡupgrade to ChinaⅢalthough the engine equipped with conventional in-line injection pump,line and injectors.更多还原