Development of aerosol wind tunnel and its application for evaluating the performance of ambient PM10 inlets

Size selective particulate matter (PM) sampling inlets play an important role in ambient PM measurement. Improper design of the sampling inlets results in collecting of PM with undesired size, which leads to significant errors in the measurement of ambient PM concentrations. Therefore, the performance of PM inlets should be carefully evaluated in a proper environment prior to their field of applications. In this study, a new aerosol wind tunnel system was designed to evaluate the performance of ambient PM10 inlets and evaluated for the uniformity of wind speed distribution and aerosol concentration. In addition, a custom–made PM10 inlet was tested in the aerosol wind tunnel to determine its 50% cutoff diameter. Results of the wind speed distributions show that the percentage deviations from the mean wind speeds at any measurement point are less than 10% with turbulence intensity of less than 5% for three different wind speed levels (0.57m/s, 2.22m/s, and 6.67m/s). Results from the aerosol concentration measurements show that the percentage deviations from the mean aerosol concentrations at any measurement point are less than 10% for three different wind speed levels, which meets the aerosol wind tunnel performance specifications specified by the U.S. Environmental Protection Agency (EPA). Results from PM10 inlet performance tests show that the 50% cutoff diameters of the PM10 inlet are 10.0 μm, 10.3 μm, and 10.0 μm at wind speeds of 0.57m/s, 2.22m/s, and 6.67m/s, respectively. The PM10 inlet is characterized to meet the performance specifications for PM10 inlets, 10.0±0.5 µm, specified by the U.S. EPA. The results indicate that the newly developed aerosol wind tunnel meets the performance requirements for evaluating the performance of PM10 size selective inlets.