What is Blower?
It is used for move process gases with moderate pressure. It also increases the velocity of process gases. Blower or fan are used for low pressure application for plants or industries whereas compressors are used for high pressure application as compared to blower. When the resistance to flow is at the downstream of the machine, it is known as fan or blower. Whereas the resistance to flow is upstream of the machine, they are known as exhausters.
Every Blower required sone external power by other machines like motor, or motor and gearbox for pressurized the services fluid. All these machines are connected by the help of couplings. There are many types of coupling available in the market
Application of Fan and blowers
Blower discharge pressure is between .5 to 1.5 psi. But fans pressure is less than.5 psi. The axial fan has higher capacity but lower discharge pressures as compared to the centrifugal (fan).
The uses capacity is mentioned below.
- Circulating air in rooms or any other close confines area.
- For cooling and heating purposes
- Cooling motors, materials and products.
- For exhausting toxic, hazardous gases or exhausting dust
- For conveying very light materials
- Heat removal purposes by forced draft or by induced draft
Types of blower
Blower is also used for transfer gases or air like fans and compressors, but blower is used for transfer non-pressurize air or gases.
- Positive displacement
- Helical screw
- High speed
|TYPE OF BLOWER|
Centrifugal type uses for transfer constant volume of air or other gases. The operating speed of centrifugal blowers is around 15000 RPM. Centrifugal type blower use in single or multistage impellers arrangement. The single stage centrifugal types are used for uniform airflow but whereas the multi stage centrifugal type uses for varying air flow at fixed volume required. In centrifugal blower uses high speed impeller to impact velocity to air or gases. In the impeller three types of blade are used like backward curved, forward curved and straight. Centrifugal blower is driven by an electrical motor, and that can be closed couple or coupled by a spacer and coupling to electrical motors. Affinity law (Fan) is used for modification or any changes (speed, pressure, power) in centrifugal blowers. Centrifugal blowers are also used for transfer combustion air, for cooling or drying systems. Sometimes also used for fluid bed aerators with air conveyor system for dust control. In this type of blower air enter axially and exit radially. Relatively high efficiency almost 70 to 90 %. Forward curved blade impeller use for high volume and clean services. And efficiency range is almost 72 to 76%. Backward curved vane impeller has lowest efficiency and the range almost 77 to 91%. Radial vane impellers have efficiency almost 70% but it has stable operation.
Positive displacement Type
Positive displacement blower is used to push the relatively constant volume of gases to outlet. It is used for 30 to 65000 m3/h, and services like air, natural gases but it is oil free.
The axial flow blower is used for transfer or move air or gases in parallel direction to the shaft. Whereas centrifugal types are used for transfer air at 90 degrees as compared to centrifugal types it has more capacity to transfer air. Based on the design axial fan are divided in three categories.
- Propeller fan the application are wall or ceiling mounted exhausts fan, cooling tower and air-cooled heat exchanger.
- Van axial fan- in this type of fan vans installed on the stator housing before or after the rote to direct and streamline the gaze for better fan action.
- Tube axial fans in this type of fan use a guide vane, but it is less efficient than other type of fans.
Fan laws the fan lows are basic proportional relationship between power, speed, diameter, and flow.
- The flow change in fan is directly proportional to speed.
Q2 / Q1 α N2 / N1
- The pressure change in fan is directly square proportional to speed.
H2 / H1 α (N2 / N1 )2
- The power change of fan is directly cube proportional to speed.
- P2 / P1 α (N2 / N1 )3