| 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. |
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