多尺度机动车辆尾气排放仿真软件的主要技术展示

In the face of such a situation that there is rampant traffic exhaust gas pollution in urban areas, the monitoring cannot distinguish the proportions, occupied by exhaust pollutants, and also current motor vehicle pollutant diffusion models and corresponding products have limitations for both the use conditions and applicable scopes, but people have to continue to rely on hydrocarbon fuel for along-term, the author’s main aim is to develop a practical tool for users to alculating quantitatively air pollutant levels and its details with the urban scale, caused by motor vehicle exhaust gas emissions, and also to visualize the scene and its variation of odorless, invisible, silent emission plumes. Followings demonstrate five main techniques, self-containedby GUI of this software:
   1. Map-Road Positioning

The simulation platform software provides for the user following technique, by which clicking mouse on digital map can locate the links and then input corresponding traffic parameters. This function has not the limits about the number of roads and the number of links for each road, but the total node number for link input should not exceed 2500. The user can input known roads’ data once or in several times (multiple inputs can form different calculation schemes).  Above two Figures express the road location figures for both 1997 links of highways and arterial streets in SaoPaulo City, Brazil, (input in seven times) and 125 links at some local region of the same city (once input).

2. Z0-File Generation

The simulation platform software provides for the user a special maker to generate surface roughness factor Z0 (for representative of land use types) file. For the urban areas, where Z0 frequently varies, the innovation algorithm of this software needs to read in the file, in order to calculate Z0 arithmetic mean at the local area within the blowing process range under the direction of the wind for each link, and into the concentration calculation. By setting up a grid on the digital map with a resolution less than 25000, operating the maker can input Z0 values, store Z0 files, and display, revise and update the generated Z0 files for later on. Following two figures demonstrate the surface roughness factor Z0 distributions in some local region of Sao Paulo City, Brazil, and the Forth Ring Road of Beijing City, China, respectively.

3.2-D Concentration Distribution Graphics and Analyzer

The simulation platform software can draw the calculated pollutant concentration fields on a plane with some height above the ground or datum, and also provide analysis function. Within these drawn graphics, the 2-dimensional figures include the homochromatic and color concentration contours as well as color filled image, which values can be determined by automatic or manual mode,with and without digital map background. For the cases with multiple wind azimuths, the color concentration contours and color filled images can be plotted by fixed or not fixed the maximum values of color bar. The so-called fixed mode is to take the maximum concentration value among different wind azimuths for one calculation as the maximum of the color bars, i.e., the maximum of all color bars is the same for all wind directions.  For no fixed mode, the color bar maximum is only the maximum concentration value of current wind azimuth. Above four figures are the color contours and color filled images of CO concentration fields for some calculated case, with 30 degree and 80 degree wind azimuths on the plane with 1.8 meter breath height, at some local region of Sao Paulo City, Brazil.

By moving mouse, the coordinates (X, Y) and concentration value can be displayed in the three edit boxes, situated at the upper left corner of the generated 2-dimensional concentration distribution figure. In addition, users can drag any local rectangle on the concentration distribution figure with digital map background, to calculate and display the various characteristic concentrations of local rectangular, including the maximum, minimum and mean concentrations both for the determined wind azimuth and the ‘mean’ of all wind azimuths in the current calculation, and also to provide detailed table analysis. Above three figures represent the area analysis at a dragged local rectangle in Sao Paulo City, Brazil, with 30 degree wind azimuth, including the dialog box for characteristic concentrations and two detailed tables.

4.3-D Concentration Distribution Graphics

3-dimensional graphics of concentration field include six types’ views of concentration distribution on XOY plane, which can rotate around Z axis (vertical axis), with and without digital map background, i.e., monochrome and color balls, wires, and color surface and color surface-wires, respectively.  The user can make full use of the abundant drawing functions, provided by the simulation platform software; choose the right visual angle to plot the 3-D pollutant concentration field distribution graphics for the solved problem. In the three boxes, located at the upper left corner, the software also provides the mouse coordinates (X,Y) and concentration value.  Above four figures are the color balls, color wires and color surface as well as color surface-wires of the CO concentration field for some calculated case of Sao Paulo City, Brazil, with 300 degree windazimuth on the plane with 1.8 meter breath height.

5.360 Degree Test

The simulation platform software allows users to do a test with up to 36 wind azimuths in one calculation, for example, users can do an omnibearing computing, i.e., to set the wind azimuths equal to 0, 10, 20, …, up to 360 degree, respectively, in order to deduct the scene and its change of pollutant diffusion and transport in the city (region), under different wind directions. In addition, changing the height value to the datum and keeping other parameters unchanged, users can calculate the pollutant concentration field on the plane with different height. Following six figures are the 3-dimensional color surface graphics of CO concentration fields for some calculated case of Sao Paulo City, Brazil, with 30, 60, 90, 120, 150 and 180 degree wind azimuths on the plane with 1.8 meter breath height to ground. These figures clearly display the pollutant diffusion and transport scene, changing 180 degree alone with wind direction alterations, where the red part within these graphics expresses the traffic pollution harder-hitareas. The user also can make the views of 2- and 3-dimensional concentration fields with different wind directions as cartoons by oneself, and then to showhis/her readers.