Fans and blowers are defined based on their discharge pressure and suction pressure ratio.  Compressors are also defined in the same way.  According to ASME, a fan is a device with a pressure ratio of up to 1.11 (system pressure rise 1136).  A blower has a pressure ratio between 1.11 to 1.2 (system pressure rise 1136 to 2066).  On the other hand, the pressure ratio in a compressor is more than 1.2 (system pressure rise more than 2066).  Any kind of ventilation device when operational will bring in air and throw out some air which may also comprise dirt, dust, contaminants, and so on.  Industrial blower fans may also be subjected to various oils, chemicals, fumes, high temperatures, and so on depending on the industry type. Here is a quick comparison of fans and blowers.

• Induced draft fans generally suck air through a system and discharge it to the atmosphere.
• Forced draft or pressure blowers generally suck atmospheric air and push or blow that air through a system.

Fans and blowers are electrical equipment that provide air for ventilation and industrial process requirements.  They generate pressure that moves the air or gases through a resistance from ducts and dampers present in the fan system.  An electrical motor powers the rotor supporting the fan, which then transfers the energy to the air.

• See Articles  -  List of Tags, List of Categories, List of Articles, List of Glossaries, Nomenclature and Symbols, (See Fan and Blower Glossary)

Fan and Blower Design Classification

Fan

• Axial Fan  -  There is no change in direction of air flow.  They produce lower pressure than the Centrifugal fans.  Propeller-type fans are capable of high flow rates at low pressures.  Tube-axial fans have low/medium pressure and high flow capability.  Vane-axial fans have an inlet or outlet guide vanes, exhibit high pressure and medium flow rate capabilities.
• Centrifugal Fan  -  The airflow changes direction.  They can be inclined, radial, forward curved, backward curved, etc.  This kind of fan is suitable for high temperatures and low and medium blade tip speeds at high pressures.  These can be effectively used for highly contaminated airstreams.

Blower

• Positive Displacement Blower  -  PD Blower can move either gas or air for various applications using rotary lobes or reciprocating pistons.  A positive displacement blower is a constant flow air mover that will always maintain constant air velocity in the pipe against various discharge pressures, which helps prevent blockages.  A feature of a PD Blower is that they can be used for both positive pressure and negative pressure (vacuum) pneumatic conveying applications.
  
  • Rotary Lobe Blower  -  Inside the blower, there are two rotors in synchronized motion, spinning in opposite directions.  This synchronized rotation creates a suction force, drawing air into the blower.  As the air enters, specialized lobes on the rotors guide it through a controlled path within the blower.  This process compresses the air, increasing its pressure.  Once the air is compressed, the blower expels it with significant force.  This high-pressure airflow is utilized for various industrial applications, such as aeration and material handling.  What distinguishes rotary lobe blowers is their ability to achieve a high airflow rate at relatively low pressure levels.
  • Reciprocating Piston Blower  -  A reciprocating piston uses the motion of a piston in a cylinder to move the gas or air and allow for only inwards and outwards movement of the pumping media.  The cylinder has an inlet and outlet valve.  Reciprocating piston blowers move media within a very tight tolerance cylinder.  The process of compressing air decreases its volume while increasing its density.   Due to this mechanical design, these blowers produce high discharge pressures.
  • Positive Displacemen Screw Blower  -  The rotors turn in opposite directions and maintain precise alignment by means of timing.  When the rotors mesh, they form a series of working chambers between the rotors and the casing wall.  The gas is sucked from the intake side and trapped between the rotors and the casing.  It then moves to the compression side (discharge) where the working chamber shrinks, and the air or gas is compressed.  The internal compression leads to a supply of steady, non-pulsating air flow. 
• Centrifugal Blower  -  These blowers are a solution for vacuum applications or as a more efficient and cost effective alternative to air compressor systems.  Centrifugal blowers provide dry, clean, oil-free air and require low energy consumption.  Unlike compressed air systems, centrifugal blowers run at low pressure and enable much faster production speeds without the safety risk of high pressure systems.  Air enters the center of a centrifugal blower’s spinning impeller and is divided between the impeller’s vanes.  As the impeller turns, it accelerates the air outwards using centrifugal force.  This high-velocity air is then diffused and slowed down in the surrounding blower housing to create pressure.
  
  • Multistage Centrifugal Blower  -  With multistage centrifugal blowers, air is pulled into the first stage through an inlet volute.  The different stages are linked through return channels, where a discharge volute collects the air from the exit.  In the different stages of a multistage centrifugal blower, each stage acts like a single-stage centrifugal blower that compresses the flow.  As the flow moves from stage to stage, its pressure increases while the flow rate remains the same.  Using multiple impellers to distribute the pressure load, multistage blowers can generate more power and higher pressure using a smaller motor and less energy.  As the number of stages increases, the discharge pressure increases, which makes multistage centrifugal blowers capable of producing very high-pressure.

Fan and Blower Impeller Design

• Backward-curved Blade  -  Backward-curved blades are the most common type of blade used in efficient fans.  These blades are curved in such a way that they impart a backward rotation to the airflow.  This backward rotation helps to reduce turbulence and improve fan efficiency.         This backward inclined centrifugal blower design can move air and gasses with small amounts of corrosive material and high temperatures. For extra protection, curved single thickness centrifugal blowers have liners and hard surfaces.
• Airfoil Blade  -  Airfoil blades are another type of blade that can be used to improve fan efficiency.  Airfoil blades are shaped like the wings of an airplane and are designed to reduce drag and improve airflow.            The curved airfoil design of backward inclined centrifugal blowers is used in high-volume air flow applications with low pressure. They are mainly used to clean air or move gasses with small amounts of erosive material.
• Radial Blade  -  Radial blades are blades that are attached to a central hub and extend outward in a radial pattern.  They are commonly used in fans, turbines, and compressors.  Radial blades are designed to maximize the amount of air or gas that can be moved through a given space.  They are also efficient at converting pressure into velocity.           Radial centrifugal blowers have straight radial blades without any curvature. The blades are perpendicular to the direction of the wheel rotation. The radial design of the blades prevents dirt or dust from sticking to them. This feature makes them ideal for harsh conditions and material handling applications. Such environments require that the blades be heavier and deeper, with a simple, straightforward design.
• Backward-inclined Blade  -  Backward-inclined blades in a centrifugal blower are designed with blades angled away from the direction of rotation.  They are known for energy efficiency, reduced noise, versatility, and resistance to dust, making them a popular choice in various applications.       This backward inclined centrifugal blower is very strong and efficient and is a cost-effective alternative to backward curved designs. The flat single thickness design has a slightly lower efficiency, which is compensated for by easily installed liners.

Impeller design is a major factor in determining the efficiency of an industrial fan or blower.  An efficiently designed impeller can provide a number of benefits, including reduced energy consumption, increased fan performance, reduced noise levels, and extended fan life.

The efficiency of a dust collector fan depends significantly on the design of its impeller.  Optimizing the impeller design allows these fans to effectively capture and transport dust particles, contributing to cleaner and safer work environments.