Theoretical and Experimental Evaluation of a Compact Aerosol Wind-tunnel and its Application for Performance Investigation of Particulate Matter Instruments

ABSTRACT  A compact low-speed wind-tunnel is designed and developed. In this work, first the most critical section of a wind-tunnel, i.e., contraction section is studied computationally using different designed models of contraction wall shapes for flow quality. The contraction design is selected on the basis of minimal boundary layer separation at simulated flow velocities of 2 and 8 km h-1. Subsequently, overall performance of the developed wind-tunnel is experimentally validated for different parameters as per USEPA guidelines (40 CFR 53.62). Air velocity and turbulence profiles are uniform and within 10% of variation in the test section. A custom-made rotating type dust feeder is also developed for precise dosing of particles. Measurements are made at air velocities of 2 and 8 km h-1 for mass concentration and size distribution of polydisperse dust particles. The percentage deviation from mean across the test section is achieved to be within 10% from the centre of the test section for particle mass and size distribution. Application of developed wind-tunnel is demonstrated for D50 cutoff of PM2.5 impactor and cyclone. The penetration efficiency of a PM2.5 WINS impactor and VSCC cyclone is tested in developed wind-tunnel at an air velocity of 8 km h-1. The D50 cutoff sizes of 2.44 ± 0.05 µm (WINS) and 2.54 ± 0.05 µm (VSCC) are determined which agree to USEPA stated measurements. In other application, performance of a low-cost PM sensor is also investigated for PM2.5 concentration measurements against a reference instrument which agrees well to the multiple studies conducted previously.