Date of Award
Master of Science (MS)
Mechanical & Aerospace Engineering
Inertial cascade impactors are devices commonly used for industrial hygiene and pharmaceutical studies. Their main purpose is to separate particulate matter suspended in aerosols according to their sizes, which can vary from over 10 µm to 0.5 µm. Their versatility and ease of operation make them suitable for on-site sampling; however, designing them requires a careful consideration of the different geometric parameters that characterize them.
In this thesis, a 5-stage inertial cascade impactor was designed, modelled, constructed, and tested. The main design parameter was the volumetric flow rate, 40 l/min, which was provided by a vacuum pump. By continuous iterations, it was possible to determine the number of nozzles, and their diameters at each stage, so that the calculated Reynolds number was as close to 3,000 as possible. It was also critical to keep the ratios S/W=1 and 1≤T/W≤5; where S represents the distance between the end of the nozzle (also known as jet) to the collection plate in each stage, T represents the nozzle throat length, and W represents the diameter of the circular nozzle.
These stages (1 through 5) were designed so that their cutoff diameters were 10, 5, 2, 1, and 0.5 µm, respectively. Due to the complexity of the air flow within the inertial cascade impactor, the flow field of the designed cascade impactor was numerically simulated by a turbulent kinetic epsilon 2D-flow model in a stationary study, using the commercial finite element package COMSOL. The numerical results provided an insight on the behavior of the aerosol as it flows through it. After the cascade impactor was constructed, it was tested taking a 24-hour and a 60-hour air samples. Its performance was further characterized by analyzing the mass and size of the collected samples on each stage of the impactor. The numerical and experimental results show satisfactory agreement with the predicted behavior of this cascade impactor.
Gortaire, Hector J..
"Design and Manufacture of an Inertial Cascade Impactor for Industrial Hygiene Purposes"
(2019). Master of Science (MS), thesis, Mechanical & Aerospace Engineering, Old Dominion University, DOI: 10.25777/ec3r-et56