Abstract: A fan inlet flow distributor comprises a skewed elliptical cone or equivalent body installed between an inlet opening of a centrifugal blower and an adjacent wall that faces the inlet. When all of the incoming airflow approaches the blower from the same general direction parallel to the wall and then makes a right turn to enter the blower's inlet, the unique shape of the flow distributor promotes a circumferentially uniform flow pattern as the air enters the fan's inlet. In some embodiments, the flow distributor comprises a skewed elliptical hyperboloid near its base and a skewed elliptical paraboloid near its vertex. The flow distributor is preferably attached to the wall and spaced apart from the fan's housing to ensure an unobstructed flow path between the distributor and the fan housing.

Abstract: A centrifugal blower with forward curved fan blades includes an inlet shroud whose shape is specifically designed for creating a smooth incoming airflow pattern that leads into the inner leading edges of the fan blades. The inlet shroud has first and second curved surfaces, wherein the centers of curvature of the two surfaces lie in the same plane, and the center of curvature as well as the radius of curvature of one curved surface is greater than that of the other. At least one center of curvature lies beyond the outer diameter of the impeller, and at least one center of curvature lies beyond the impeller's inner diameter, wherein the impeller's inner diameter is defined by the inner leading edges of the fan blades. Performance benefits are achieved when a forward curved blower with such an inlet shroud operates with a flow coefficient of between 9 and 52.

Abstract: An efficiency matching device and method. The efficiency matching device is utilized in combination with a centrifugal fan adapted to deliver an air mass flow through an air delivery system. The fan has a housing that defines an inlet port and an exit port. The fan additionally has an impeller disposed within the housing. The impeller draws air into the inlet port, accelerates the air, and discharges the air through the exit port. The efficiency matching device is shiftably carried within the exit port for selectively varying the area of the exit port such that the efficiency of the centrifugal fan can be varied to match the output efficiency of the fan to the desired air mass flow through the air delivery system.