Numerical investigation of air suction through the louvers of a funnel due to high velocity air jet

摘要

The present investigation predicts the suction flow rate from the atmosphere through the louvers of a funnel (used in naval and merchant ships) when the high velocity exhaust comes out from a nozzle or a set of nozzles placed inside the funnel. Conservation equations of mass and momentum have been solved for the funnel with a surrounding computational domain so that the suction can take place at the louvers entry. The resulting equations have been solved numerically using finite volume technique in an unstructured grid employing eddy viscosity based two equation k-ε turbulence model. It has been found from the computation that the air suction rate into the funnel increases with the increase in louvers opening area, nozzle flow rate and height of the funnel. There exists optimum protrusion of the nozzle into the funnel for which maximum suction of air can be achieved with a prescribed nozzle flow rate and all other parameters of the funnel remaining fixed. Similarly there also exists optimum funnel diameter where the suction rate of air becomes the highest with all other parameters remaining fixed. There also exists optimum louver opening area on the funnel where the suction rate becomes the maximum as a function of the funnel diameter. The inclination of the funnel with respect to the vertical has no effect on mass ingress of air into it. An optimum nozzle diameter could be decided for a particular funnel diameter by considering the funnel suction rate and the back pressure developed by the nozzle per meter length of the pipe containing the nozzle (intersection of the two curves gives the optimum point of operation).