Wind tunnel investigation of jet fan aerodynamics

This study has investigated the perfomance aerodynamics of jet fans in order to identify and understand the fundamental parameters in their use in mine and tunnel ventilation.;This study used a wind tunnel to study jet fan ventilation. The fan was simulated by aluminum pipes of different diameters connected to a centrifugal blower. The aluminum pipes were inserted at the entrance section of the wind tunnel and jet outlet velocities ranging between 20 and 40 m/s were used to produce the flow field. In order to study passage wall effects on the flow the jet fan was traversed from a near-wall position to the wind tunnel axis in equal successive steps. The axial pressure development for all positions were determined together with a detailed velocity distribution and the overall entrainment characteristics. Both the magnitudes of the pressure drop and rise depended on the jet fan position from the walls. Near-wall jet fan positions tended to have initially larger pressure drops and lower pressure rises than positions farther from the wall which had lower pressure drops and higher pressure rises. The consequence of this pressure variation was that generally at near wall positions the jet fan entrained more air into the tunnel than at positions farther from the wall. The smaller diameter jet fan produced higher friction losses (as much as 15% at the wall position) than the larger diameter fan with lower outlet velocity which had about 8%. The flow field was found to develop rapidly with axial distance. The jet axis velocity developed faster than that of a free jet of the same initial velocity and revealed that jet fans can move air over distances greater than 70 jet fan discharge diameters and still maintain a minimum air velocity of at least 0.5 m/s. For fan positioning at F;Theoretical equations based on momentum and energy considerations were formulated. These derivations identified a range of flow ratios (n = 0.1 to 0.9) which can be used to design an effective jet fan ventilation system. For each flow ratio (n) there is an optimum area ratio (...