1. Field of the Invention
This invention relates to a fan suction chamber having a front wall defining a suction inlet and a back wall having upper and lower sections. The upper section of the back wall is parallel to the front wall, and the lower section of the back wall slants downward and forward, toward the front wall of the suction chamber.
2. Description of the Prior Art
In fans it is sometimes necessary, owing to shortage of space, cost of making conduits, etc., to connect an air or gas conduit to the suction inlet of a fan in a direction which is perpendicular to the axis of the fan. If the conduit is connected to the suction inlet by means of a pipe bend, the bulk of the air will flow along the outer wall of the bend, whereby the impeller is loaded asymmetrically. In this case the fan will not achieve the pressure and the volume flow according to the calibration values, and its efficiency is also crucially lowered. In certain cases the measured increase in power consumption has been up to 60%.
Attempts have been made to eliminate this disadvantage by developing suction chambers for fans. It is virtually necessary to use a suction chamber in two-inlet fans, in which air flows via two suction chambers and two suction cones to two impellers, which suck in air from opposite directions, and further into one mutual casing. Such fans are used mainly when the volume flow is so great that two single-inlet fans would be needed.
There are power losses even in a suction chamber, and attempts have been made to eliminate them by making the chamber conical. Furthermore, attempts have been made to reduce power losses by placing a baffle plate or guide vanes in the chamber.
Even in these relatively complicated suction chamber structures, which are difficult to manufacture, the power loss is 4-10% of the total power consumption of the fan within the conventional operating range, depending on the manufacturer, the fan type, and the location of the operating point on the performance curve. Since suction chambers are used most in large fans, the power losses in question are considerable.