| The increasing number of epidemiological studies has shown that there is a significant positive correlation between morbidity and mortality in the crowd with the concentration of inhalable particulate matter in the atmosphere, and some biological mechanism has been confirmed by the toxicology studies. Automobile exhaust emissions are the major air pollution particles in urban, and 50% of particulate matter in the central areas of some major cities comes from the automobile exhaust, while that of the highway mainly comes from motor vehicles. Mass concentration of the ambient in urban road about PM2.5, PM10 is significantly higher than other regional cities. It has relation to traffic flow, car type, ambient temperature and humidity, wind velocity and so on. Urban air pollution caused by automobile exhaust emissions has been concerned by all sectors in society, but the hazards on interior staff's in the cabin caused by the particulate matter in the road environment have not yet attracted enough attention to and the research results are also very limited, China has not yet enacted the quality standards about inhalable particulate matter in vehicle.The level of inhalable particulate matter in vehicle occupant is a comprehensive reflection of air pollution in the road environment, performance of the air filter and working conditions of the air conditioning system. Taking effective technical methods to control inhalable particulate matter in the cabin, it needs to obtain the distribution status of particulate matter in the road environment, research automotive air filter's technical performance in inhalable particulate matter, acquire interior motion regulation of inhalable particulate matter under air-conditioning, take the advisable method to evaluate distribution status of particulate matter inside the vehicle and optimize air filter and airflow organized design so as to limite effective concentration of particulate matter.In this paper, according to WHO air quality guidelines for particulate matter and the distribution status of particulate matter in the road environment, it sets up the inhalable particulate matter quality standards in cabin. A domestic passenger car in Classas A0 is chose as benchmark to research automotive filter's performance about inhalable particulate matte by means of experimental method. The paper analyzes the relation among filtration efficiency with face velocity and particle diameter in initial and final status. According to the experiment results, preliminarily analyze the inhalable particulate matter distribution in the vehicle. Then, get the first boundary condition for simulation research and the parameters of key points in cabin included the wind speed, temperature, concentration of particulate matter and other parameters so as to verify the simulation model.In this paper, it adopts CFD simulation method to calculate air velocity field, temperature field, concentration field of inhalable particulate matter in the cabin, and analyze the influence character of inhalable particulate matter on the thermal motion caused by the air velocity field and temperature field as well as the distribution regulation under many kinds of complicated conditions.As the inhalable particulate matter in cabin was non-uniform distribution,the particulate matter of the passenger's nose height can be breathed in,The author first proposes the effective particle concentration and the distribution coefficient of that as the evaluation parameters to assess the distribution status of inhalable particles inside the cabin.Through experimental analysis, we can see that as a result of the vehicle exhaust emissions and one-time reflection by vehicle and pedestrian, the concentration of particulate matter in the road environment is more than that of other regional in urban. It infers that the particulate matter number of automobile exhaust emissions is mainly distributed in 1.0-5.0um diameter range, and PM2.5/PM10 ratio is lower in the area, that is to say, the mass concentration of PM2.5-PM10 in the road environment is higher than that of the general regions in urban.The number of various particles in the road environment is measured in winter is greater than the measurement results in summer.The relationship between PM2.5 and staff's health in the cabin is closer, so research working shouldn't neglect PM2.5 .According to the experimental results, we can also see that larger diameter particles shows higher filtration efficiency and filtration efficiency of the inhalable particulate matter increases with the increasing face velocity of the filter. The filtration efficiency of PM10 is better than that of PM2.5. Increasing air rate can reduce the mass concentration of inhalable particulate matter in supply air.At present, the air filter used in the car is not effective in keeping out PM2.5 and PM10 from air. The inhalable particulate matter in the fresh air still remains high concentration, mass concentration of PM10 exceeds the standard value inside the cabin which is proposed by the author, mass concentration of PM2.5 is close to the standard value, which will have adverse effects on staff's health on the long-term or short-term exposure in the cabin. As dust capacity of the filter is low, the dust on the filter's material has a greater impact on the resistance. The resistance increased significantly at a low filter velocity. For face velocity at 0.26 m / s, the final resistance is double times compared to that of the beginning; for face velocity at 0.09 m / s, the final resistance is 5.23 times compared to that of the beginning. The increased resistance reduces the air rate. It has a great potential to improve the automobile air filter, so it's necessary to improve the producing technology of filtration materials, improve filtration efficiency, reduce filter resistance and ncrease service life.Through analyzing the inhalable particulate matter characteristics of numerical simulation in cabin, it shows that the key problem of numerical simulation is phase distribution status, the descriptive methods, the determination of physical parameters and choice of numerical methods. Under conditions of heating and cooling, the results of simulation compare with the experimental results, which prove that random orbit model of the Eulerian-Lagrange method can almost simulate thermal motion of inhalable particulate matter in vehicle, and the mathematical and physical model, numerical calculation method, boundary conditions, heat conditions and the rationality and effectiveness about the thermal resource assumed in simulation was verified.The motion of the carried particles is gas-solid multiphase flow,the motion trajectories of the particles is acted by physical properties of the inhalable particles and flow field,temperature field. As movement mechanism of turbulence and gas-solid multiphase flow is very complicated. It is faced with many difficulties to use the traditional theoretical analysis and experimental methods to solve such problems. In this paper, under different conditions included air velocity field, temperature field, choose CFD method to calculate thermal motion of inhalable particulate matter, and study the distribution of conditions change included air-conditioning working conditions, air flow organization, airflow rate, separation efficiency.The results in simulation show that the air flow is restricted jet in cabin ,most of the space is covered by vortex region. The velocity field is consolidated by the forced and natural convection, and temperature gradient in horizontal and vertical directions is very large. With the variety of external forces working together, most of particles follow the airflow out of the air opening, part of particles in the region with eddy currents do disorderly movements, part of particle move to the surface of the object, take the elastic collision or are captured to end the trajectory. The movement of particles in the cabin is a comprehensive reflection of its own property,flow field and temperature field, and shows the characteristic of non-uniform distribution.The results in simulation also show that the concentration of inhalable particulate matter is higher in winter, and in most cases effective concentrations is below the average concentration in cabin, taking the upper return air system can reduce effective concentration of the interior zone. But, changing air-conditioning working conditions and airflow organization cannot make effective concentrations achieve the environmental quality standards by the author proposed. changing air rate is very complex to impact the concentration of PM2.5,and that is negative correlation with the effective concentration of PM10.Because of the separation capacity of filter is limited, at common air rate, the effective concentration still can not achieve the standard requirements proposed.the effective concentration of interior zone and separation efficiency of the filter have negative correlation, increasing filtration efficiency can effectively reduce effective concentration.If the filtration efficiency is improved at 30 percent, under the calculated condition, the effective concentrations of inhalable particulate matter inside the vehicle may achieve the environmental quality standards proposed.Therefore, relying solely on increasing airflow rate and changing air flow organization can not make the environment inside cabin meet the quality standards proposed in this paper, the most effective way to control inhalable particulate matter in cabin is improving separation efficiency of automotive air-conditioning filter.
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