【作者】 强添纲；

【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， 2012， 博士

【摘要】 乙醇汽油作为主要的可再生清洁替代能源之一,现已被多个国家广泛使用,我国自2001年起已在9个省份开始车用乙醇汽油的推广试点工作。但是,黑龙江省从2004年11月1日起才开始全封闭推广使用乙醇汽油且工作开展以来,其一直备受争议。特别是在冬季低温季节,部分使用者反映使用乙醇汽油后的汽车的动力性能差、油耗高,排气管排出水量剧增,导致城市道路结冰,以致在坡路、交叉口路段造成严重的交通拥堵,有时会使整条城市r干道或局部城区交通陷于瘫痪,甚至导致交通事故频发。因此,在寒区冬季的低温条件下,燃用乙醇汽油的汽车的动力性与燃料经济性、汽车的排放性及汽车排气凝结滴水与城市道路路面结冰的关系、以及其对城市交通拥堵的影响等,成为近年亟需进行深入而系统的探讨、分析及论证的问题。本文围绕着低温条件下,对乙醇汽油的燃烧、使用性能、排气凝结滴水、排气凝结滴水与道路结冰的关系及其对城市道路交通的影响和交通控制策略进行了全面系统的研究,其主要内容概述如下：(1)乙醇汽油燃烧模型的建立。在分别探讨汽油和乙醇的燃烧机理的基础上,建立了乙醇汽油的混合燃烧模型。同时,对混合模型进行了简化处理,以达到减少计算运行时间的效果,从而为较客观地分析乙醇汽油的燃烧过程奠定了理论基础。(2)乙醇汽油的燃烧过程分析。借助CHEMKIN软件模拟分析了不同温度条件下,较低进气温度对乙醇汽油燃烧过程的影响,并对比分析了不同乙醇含量的乙醇汽油对进气温度的敏感程度。模拟仿真结果表明,在低温条件下点火滞燃期随着进气温度降低而延长,且气缸内所能达到的最大压力和温度也随之降低。(3)低温条件下乙醇汽油汽车使用性能评价。选择典型的低温条件,分别进行了燃用乙醇汽油和汽油的汽车低温起动试验、加速性能试验、等速燃油消耗量试验及排放试验。试验结果表明,汽车燃用乙醇汽油和汽油的使用性能存在差异。使用两种燃料的动力性和燃料经济性的优劣表现呈区间性,存在“拐点车速”,且随着温度的降低“拐点车速”也随之下降。低温起动性能在-15℃以上无明显差别,低于-15℃时乙醇汽油汽车低温起动较困难,当温度降至-25℃时,乙醇汽油汽车低温起动非常困难。(4)乙醇汽油汽车排气凝结滴水的机理分析。以汽车排气凝结滴水机理为基础,采用CFD方法建立汽车排气凝结数值模拟模型,分别分析了排气温度、大气风速、大气环境温度及排气管壁导热对排气冷凝滴水的影响。模拟分析结果表明,随着排气温度的提高,冷凝水的体积百分含量呈现降低趋势；风速变化对汽车排气冷凝水产生较大影响,较高的大气流速使冷凝水含量有升高趋势；较低的环境温度使排气管冷却强度增强,使排气管内尾气中水蒸气易于发生相变,冷凝水具有较高的体积含量；降低排气管材料的导热系数,可以减少汽车排气在管内生成冷凝水。(5)乙醇汽油汽车排气凝结滴水的控制策略研究及试验验证。设计了使用乙醇汽油的汽车排气凝结滴水检测方案,并与燃用汽油的汽车进行了比较。同时,提出了使用乙醇汽油的汽车排气凝结滴水控制方法,分析了汽车排气凝结滴水控制方法的可行性并进行了试验验证。基于低温条件下发动机怠速工况时燃烧等量燃油的排气滴水试验结果表明,E10乙醇汽油排气管滴水量低于93号汽油排气管滴水量。另外,随环境温度升高,燃烧时间呈现多项式趋势线的上升趋势,而排气管滴水量随着环境温度的上升呈现先降低后升高趋势。(6)寒地城市冬季路面结冰现象分析。从理论上评价了燃用乙醇汽油汽车在道路上行驶排气凝结滴水对路面结冰的影响程度,重点对交叉口、坡道及弯道等易于出现路面结冰现象的典型路段进行了分析,对降雪与路面结冰的关系进行了理论论证。另外,以哈尔滨市的城市主干道为例,探究了路面结冰对城市交通的影响,并针对此提出了相应的应对策略。基于汽车在低温条件下排气凝结滴水与路面结冰关系的理论分析及其对城市交通的影响的调查结果可知,城市汽车保有量增长所导致的汽车排气凝结滴水总量的增加,是冬季寒地城市道路交叉口、坡道及弯道路段易于出现路面结冰现象的主要因素之一,且降雪进一步加剧了此类现象的产生。更多还原

【Abstract】 Gasohol is one of renewable clean alternative energies, which is widely used around the world. Gasohol had been raised to use Gasohol in9provinces of China since2001. However, it was merely promoted the closed use in Heilongjiang Province since November1,2004. Moreover, this issue aroused the extensive discussion and controversy. Especially in the cold winter, some users reflect that the power performance becomes worse, fuel needs increase and exhaust condensation dripping from exhaust pipe is sharp increased of gasohol vehicles. And as a result, city roads appear the freezing phenomenon, sloping roads and sections of the intersection suffer form the serious traffic congestion, and sometimes the whole city roads or local areas emerge the traffic standstill, even appear frequent traffic accidents. Therefore, in the low-temperature conditions of winter for cold regions, the car’s power, economy, emissions performances with gasohol, the relationship between exhaust condensation dripping and icy road in the city and its effects on the traffic congestion and the list goes on. These issues need to be discussed, analyzed and illustrated systematically.Around the special conditions of low temperature, this paper presents a series of issues on gasohol, i.e., the combustion of gasohol, its using performance, its condensation dripping, and how the dripping impact on traffic and traffic control strategies. The main contents are presented as follows:(1) Establishment of the combustion model for gasohol. Based on the discussion of the combustion mechanism of gasoline and ethanol, a hybrid combustion model is established. In addition, it is simplified to reduce the computation runing time. These works lay the foundation for a more objective analysis of gasohol combustion process.(2) Analysis of combustion process of the gasohol. Based on the CHEMKIN software, the impact of lower intake air temperature on the combustion process of gasohol with different low temperatures is simulated. In addition, the comparative analysis of the degree of sensitivity of different ethanol content gasohol on the intake air temperature is analyzed. The simulation results show that ignition delay extends as the lower intake air temperature decreases at low temperatures. What’s more, the achieved maximal pressure and temperature in the cylinder decrease.(3) Evaluation of the gasohol vehicle performance at low-temperature experimental conditions:In typical low-temperature conditions, the cold-start test, the accelerate performance test, the fuel consumption test at constant speed and emission test for gasoline and gasohol are implemented, respectively. Through their comparative analysis, the comprehensive operating performance of gasohol is evaluated. The results show that there are differences in car’using performance between gasoline and gasohol. The pros and cons of their power and fuel economy show range features and "inflection point speed",what’ more, the "inflection point speed" decreases as temperature decreases. Cold starting performance has no significant difference above-15℃, vehicle’s cold starting with gasohol is more difficult under-15℃, This phenomenon is even more serious under-25℃.(4) Analysis of the mechanism of exhaust condensation dripping of gasohol. Based on the mechanism of vehicle exhaust condensation dripping, the numerical simulation model for vehicle condensation dripping is established via the CFD method. In addition, the influence of exhaust gas temperature, atmospheric wind speed, atmospheric ambient temperature and the thermal conductivity of exhaust pipe on condensation dripping is analyzed. The simulation results show that the volume fraction of the condensation dripping shows the decreasing trend as the exhaust temperature increases. In addition, the variation of wind speed has a significant impact on automobile exhaust condensation dripping. The higher atmospheric flow rate causes the increase of condensation dripping. Finnaly, the lower ambient temperature increases the exhaust pipe cooling intensity, thus exhaust water vapor within the exhaust pipe tends to produce phase transition, and as a relut, the condensating dripping has a higher volume. What’ more, the reduction of thermal conductivity of exhaust pipe materials can reduce the generation of automobile exhaust condensation dripping in the tube.(5) Control strategy analysis and experimental validation of exhaust condensation dripping. First, this work designs a program to detect the exhaust condensation dripping of gasohol, and then compare with the general gasoline. In addition, the control method to reduce exhaust condensation dripping is designed and its experimental verification and feasibility are analyzed. According to exhaust dripping test results of burning the same amount of fuel at low temperature and in the idling condition of engine, the follwing conclusion is obtained. The exhaust pipe dripping of the gasohol is less than that of the gasoline. What’s more, burning time shows an upward trend of the polynomial trend line, while the amount of exhaust pipe dripping shows the trend of "first reduction and then decreasion"as the temperature increases.(6) Analysis of phenomenon of icy road for cold regions in winter:Theoretically, this work evaluates the impact of the vehicles’exhaust condensation dripping on the icy road, especially some typical road sections, i.e., the intersection, ramps and corners. In addition, taking the main road of Harbin City as an example, combined with the impact mechanism of icy road on urban traffic, its appropriate coping strategies are proposed. Based on the theoretical analysis of relationship between exhaust condensation dripping and the icy road and its impact on urban traffic at low temperatue, the following conclusion is obtained. The increased condensation dripping of automobile exhaust caused by the growth of urban car ownership is one of the main factors of icy road at the intersection, the ramp and corners in cold winter. What’s more, the snowfall further exacerbates this phenomenon.更多还原