The development of a jet augmented local exhaust system

Typescript (photocopy).The feasibility of a plane turbulent jet working in conjunction with a local exhaust system to provide effective air contaminant control was investigated in theory and experimentally. The combination of these air moving methods formed a unique ventilation arrangement which based its principle of operation on the dynamic properties of a relatively thin plane of air at the hood face interacting with the pressure forces of a local exhaust system to contain air-borne materials inside a hood. This system utilizes the advantages of its components to produce an effective contaminant control method which efficiently uses air and energy. Theoretically, an analysis of the jet flow behavior indicated that (1) the jet would follow a circular arc from its outlet in the direction of the exhaust and (2) the jet division at the wall would be controlled by the angle of impingement or the relative position of the "dividing streamline" within the main jet flow. Parameters which effected jet behavior were investigated experimentally by using a 1:8 scale model hood. Air flow similitude was obtained by Reynold's number equivalence. The research premise was that understanding how to control the system's fluid behavior would lead to the design of an effective contaminant control method. Results of regression modeling and graphical analysis indicated the jet trajectory position was determined by four parameters; (1) the average jet outlet velocity, (2) the average exhaust velocity, (3) the jet outlet angle and (4) the hood depth/width aspect ratio