This is because of the vector sums of the two velocities. Air leaves impeller at velocity less than tip speed. Question Fan direction advice: Cases & Cooling: 9: Dec 9, 2020: Similar threads; The speed of the truck is the wheel velocity and thrown ball is the velocity of the the air leaving the tip of the blade. CURVED BLADE ELECTRIC FANS Selecting Pusher Or Puller Style Operation Determine if the fan will be installed as a pusher or puller style. Fig. Why is it that when you look at the spinning propeller of a plane or fan, at a certain speed, the blades seem to move backwards? Backward Inclined Fans. Deep blades allow efficient expansion within blade passages. For DWDI or Arrangement 3 SWSI fans, it is the side of the fan housing at which the belt drive sheave is mounted. Fan rotation is determined by looking at the fan from the drive end. 1. 3: Example of a uni-directional fan, with straight blades. The pitcher turns around and throws in a direction opposite the direction of the truck otherwise same as before. Fig 3 shows the velocity diagram for the air flowing into the fan (inlet) and out of it (outlet). R. RavenSEAL Diamond Member. The shape of your blades and the direction they travel will define the performance characteristics of your fan. Backward curved fan: - Efficiency only slightly less than airfoil fans. A pusher style fan mounts in front of the radiator and pushes air ... Verify direction of fan blade matches the corresponding image below, it may be necessary to flip the fan blade … Fig. Backward curved fans have blades with leading edge curved or inclined away from the direction of rotation. Available in Models PB, SPB, PBS, RBE and some HP-Series II blowers. The principle used for determining the direction of rotation is “backwardly curved blades… The drive end is is the side of the fan housing through which the fan or motor shaft protrudes. Type 1, Shrouded Radial Blade blower wheels are designed to deliver higher pressures for pressurizing, blow-off systems and long duct or pipe runs. A forward curved centrifugal fan is characterised by its cylindrical shape and lots of small blades on the circumference of the impeller. 4: The “backwardly curved blades” principle is used in determining the direction of rotation for angled or curved blades. Share on Twitter. - Efficiency slightly lower than airfoil fan. In the example shown below, the fan rotates in a clockwise direction. They produce relatively medium to high airflow at static pressures. For centrifugal fans, discharge is the direction the fan outlet points. The profile and axial designs of a volute tongue have great influences on the internal flow conditions and aerodynamic performance of a forward-curved blade centrifugal fan. 10 to 16 single-thickness blades curved or inclined away from direction of rotation. Type 2, Open Radial Blade with Back Plate blower wheels are designed for conveying powdery or granular material and long stringy paper trimmings or fibers. The blades are generally heavier and larger than forward curved and move away from the direction of wheel rotation. The backward inclined centrifugal fans offer three standard blade types – flat single thickness, curved single thickness and curved airfoil. June 15, 1998; Share on Facebook. Air will flow from the convex side to the concave side. This corresponds to a forward curved blade fan. Case 2. The fan blades are curved, convex (outward curved) on one side, concave (inward curved) on the other.