Air blowers generally use centrifugal force to propel air forward. Inside a centrifugal air blower is a wheel with small blades on the circumference and a casing to direct the flow of air into the center of the wheel and out toward the edge. The design of the blades will affect how the air is propelled and how efficient the air blower is. Blade designs in air blowers are classified as forward-curved, backward-inclined, backward-curved, radial and airfoil.
Forward-Curved Air Blowers
Forward-curved blowers are impulse devices with blades that are curved in the direction of rotation. The blower accelerates air to a high velocity while rotating at a low speed. Forward-curved blower wheels spin at relatively low speeds and produce high volumes of air at low static pressures. This type of blower is incapable of operating at the speeds necessary to create high static pressures because of its lightweight construction. Still, forward-curved blowers are the most common type of air blower because they propel the most air volume in relation to blower size and speed.
Backward-Inclined and Backward-Curved Air Blowers
A backward-inclined blower, operating at roughly twice the speed of a forward-curved air blower, has flat blades that slant away from the direction of travel. This type of blower is highly efficient (low horsepower requirement) and has a rugged construction suitable for high static pressure applications. This type of air blower is best used in locations where the air is either clean or mildly contaminated. Similar to this style is a backward-curved air blower. The blades of a backward-curved blower are a single thickness throughout and curve away from the direction of travel. These blades are sturdier than backward-inclined blades and can be used in corrosive and erosive environments.
Radial Air Blowers
Radial blowers are designed for industrial use in small exhaust systems. These air blowers are capable of handling air that contains bits of dirt, grit, lint and other foreign particles while still maintaining a high-pressure supply of air for conveying and cooling. Their use in particle-laden air means that this type of blower is generally designed to be self-cleaning. Radial air blowers have the lowest efficiency levels because the blades have no curve or lean and are perpendicular to the wheel’s rotation. Think of a paddleboat racing a boat with an outboard motor. No matter how fast the paddle spins, it will not catch up to the boat with the outboard motor.
Airfoil Air Blowers
Airfoil blowers have the most efficient design of all air blowers. Their blades have an airfoil shape that is wide at the center and curves down to narrow edges. Airfoil blowers are extremely efficient because they require lower horsepower levels to operate. This type of blower is used in clean air situations.