Research On Vehicle Dynamic Emission Model On Urban Road

With the increasing of automobile consumption, automobile retain capacities are increasing. As a result, city environment becomes worse and worse. In China, the ratio of transportation gas pollution becomes bigger and bigger in some big cities, some of which even exceeds half of the total pollution. Reducing transportation gas pollution and controlling vehicle emission have become urgent affairs. However, at present the level of vehicle emission is low and the single vehicle emission factor is high in China. What's more, some means of transportation are relatively behindhand, the measure of traffic control and management are disadvantageous, and traffic demand contradiction makes vehicle operation conditions worse, which are the factors that greatly aggravate emission. To change the present situation, optimize traffic control and management to improve vehicle emission, this measure has strong point without changing means of transportation on road. This method mainly provides logical measure of traffic control and management, and seeks the high efficiency of transportation and environment protection through studying vehicle emission characteristic, micro emission model and the factors that effect vehicle emission performance in traffic flow. The key technology is the research on micro emission model in traffic flow. Therefore, research on the effect factors of vehicle emission performance and micro emission modeling are significant.Now the study on vehicle emission models have developed for many years, especially macro models which predict emission in macro region have developed to a mature degree. But in road net, intersection and some detailed regions, the emission predict has no effective measure. So in recent years, the overseas investigators commit themselves to micro emission model, and they have acquired some positive results. On lacking in enough valid data, when studying on vehicle emission effect factors and emission models, investigators in China usually rectify models that have exited in oversea only. But because traffic condition, road establishment, vehicle condition and fuel quality in domestic areas are great different from them in overseas, simply copying and rectifying them are invalid. So it is necessary to make models suitable for China.We know whether the signal timing of an intersection has been optimized not only takes effect on traffic control directly but affects vehicles'running status at intersection even to the entire city's traffic functioning. The former studied optimized signal timing using the pure traffic indexes such as delay and queue length mainly, but seldom considered some indexes like environment, economy and other assistant factors, and therefore it is imperative under the situation to improve traffic control from the point of view of traffic roads network's emission estimation. That is to say choosing the representative vehicles'running status and emission characteristic to improve traffic control problem at a special intersection combined with reappearance of the traffic flow's emission characteristic using the method of microcosmic simulation in order to optimize the signal timing finally.This dissertation is composed of the following parts1. A platform of real time on board mobile emission test system was set up. On the basis of OEM-2100 test system, a platform of real time on board mobile emission test system was set up. The emission measure instrument is OEM-2100, which is manufactured by Clean Air Technologies Inc. of USA. The total system includes four parts: emission testing module, exhaust collecting module, engine sensors module, and vehicle run condition inspecting module. The on-board emission testing system collects emission data, engine rotate speed, intake pressure, intake temperature, and vehicle operation condition parameter ect. The data collected from experiments provide evidence for analysis on emission affecting factors and modeling of micro emission.2. Relatively important affecting factors on emission rate of light duty cars are chosen and analyzed.The emission rate change of operation conditions of 3 types car ,Jetta, Jinbei, and Hongqi Century Star was analyzed, the result shows: Emission rate of acceleration operation condition is much higher than that of other operation conditions, cruise operation condition is the second, deceleration is the third, and idle is the least. The characteristic of vehicle operation condition distribution on urban road is the proportion of idle, acceleration, and deceleration. The emission contribute rate of operation condition is that cruise is higher than acceleration, acceleration than deceleration, deceleration than idle. Through comprising emission of the same vehicle on the same road under the conditions of high and low traffic, peak and natural traffic flow, it can draw a conclusion that vehicle operation period of time affect emission greatly. In detail, emission under high peak is the highest, traffic congestion is grave, the frequency of acceleration and deceleration is the highest; emission under low peak is the least, vehicle speed is relatively high; emission under natural traffic flow is medial. Experiments show in the first 5 seconds on acceleration, CO add rapidly, NOX hold the line basically, from 5 seconds to 10 seconds, NOX and HC also add rapidly. From deceleration to idle, about 10 seconds CO and NOX become stable, but HC keep high emission all along. Through the analysis of emission rate of vehicle affecting on speed and acceleration shows that: acceleration is one of the most important factors that affect emission rate, its high emission results from big acceleration, and NOX and CO emission rate are also affected greatly by the speed because burning temperature and degree of burning sufficiency are main factors that produce them.3. Dynamic emission model of motor vehicles on real road was established.Based on analysis the effect on the rate of emission resulting from vehicle speed, acceleration and vehicle operation condition, I build up Speed Regression Model, Cruise emission rate model, idle emission rate model, Acceleration emission rate model, Deceleration emission rate model, Speed-acceleration two dimension high-hypo emission rate model and BP neural network emission rate model by using regression and neural network method. Models errors are all within 30%. So it is effective to predict instantaneous emission on real road. Speed Regression Model, Idle emission rate model, Acceleration emission rate model together with traffic simulation model can predict micro emission of urban road nets, provide some traffic control and management strategies. Two dimension model and neural network model are applicable in many areas. They fit for predicting light-duty vehicle micro emission on urban road. Since all models are based on Jetta emission data, they are limited. If predicting other light-duty vehicle emission, you can use coefficient method temporarily, i.e. multiply models by vehicle coefficient.4. Simulation data are gained through the investigation of the status in selected intersection of traffic and on the basis of dynamic model integrating TSIS, the signal timing of Gongnong Square in Changchun city are studied using TSIS software as a Simulation tool .TSIS simulation software as a starting point to the Changchun City signal distribution, analysis simulation results and the status of the junction with traffic TSIS simulation software to verify the validity and accuracy of the investigation; 5. The author uses the unitary method to confirm the optimization model of the emissions of CO, HC and NOx and then gets the optimization results of the signal timing for Gongnong Square by the compound method .The simulant result of the optimization plan is that the emission quantity of NOx, HC and CO has been reduced 2.11%,1.94%and 1.18% separately. In order to get a better plan, the author takes the vehicle delay as an assistant index to analyze the situation and the results indicate that the optimization plan has a distinct advantage in vehicle delay. The three kinds of delays have been reduced 3.55%, 2.77% and 3.94%, and the total delay has been reduced 3.44%. Therefore, when the road condition of the selected intersection is not changed, the intersection optimal signal timing plan based on emission is one of the most satisfying method.