Application of CFD in Turbomachinery Industry

 

Turbomachinery is a rotating device which includes a fan, blower, compressors and turbines. It can be classified into two category on the basis of energy conversion turbomachinery:

 

• Power consuming (e.g. Fan, blower, compressor & pump)

• Power generating (e.g. Hydraulic, steam & gas turbines)

​

Industrial fan

 

Industrial fan is a mechanical device whose primary function is to move air or other gasses to ventilate various parts of a building or other structures. Industrial fans include combustion, ventilation, aeration, particulate transport, exhaust, cooling, air-cleaning and drying in various industries which is accomplished by rotating a number of blades, connected to a hub and shaft, and driven by a motor or turbine.  Types of Industrial Fan

 

1. Centrifugal Fan

2. Axial Fan

3. Jet fan

​

Centrifugal fan

 

A centrifugal fan is one in which air is extracted at right angles to the inlet of the fan, and swirl the air outwards to the outlet by deflected blade and centrifugal force. Centrifugal fan is highly recommended industrial fan due to its easy manufacturing, low cost, durability, stability with multiple airflows & pressure combination, easy maintenance and reliable efficiency.

 

Main parts of centrifugal fan are:

• Fan housing

• Impellers

• Inlet and outlet duct

• Drive shaft

• Drive mechanism

​

Axial fan

 

Axial fan causes air or gasses to flow through it in parallel to the shaft about which the blades rotate. The flow is axial at entry and exit. An axial fan is suitable for a larger flow rate with a relatively small pressure rise and a centrifugal fan for a comparatively smaller flow rate and a large pressure rise. Performance of the fan depends on the number and shape of the blades. Typically installed in Cooling Towers, Air-Cooled Condensers and Air Cooled Heat Exchangers.

 

Types of Axial fan 

• High-temperature axial fans

• Tube axial fans

• Vane-axial fans

• Variable pitch axial fans

• Variable pitch on-the-fly axial fans

• Cooling fans ("cooling tower fans")

• Mixed-flow fans

 

Jet fan

 

Jet fan is an impulse or induction fan, installed in a low speed air region, to support the natural flow between the supply air and extract air zones. Jet fans are only installed at specific locations therefore they take up less than 0.5% of the ceiling area which leaves room for other technical installations. Although it saves money and time by reducing the storey heights a precise planning and a perfectly-controlled interaction of all the components is required to reach the system to its full potential in an emergency case.

​

Industrial Blower

 

Unlike industrial fans, the blower has an impeller for rotation and consumes more power. Blower offers better airflow than fans. According to the American Society of Mechanical Engineers (ASME) fans, blowers and  compressors are classified based on their ratio of discharge to suction pressure

​

• Fan - pressure ratio up to 1.11

• Blower- pressure ratio between 1.11 to 1.2

• Compressor - pressure ratio greater than 1.2

 

Types of Industrial Blower: There are mainly five types of industrial blower

• Centrifugal blowers

• Helical Screw Blowers

• Positive Displacement

• High Speed Blowers

• Regenerative Blowers

 

Centrifugal blower

 

Centrifugal blower increases speed and volume of air stream in a rotating impeller. It is commonly used for ventilation, gas transportation & controlling air pollution. It maintains a continual gas transfer and also changes the airflow direction.

​

Helical Screw Blowers

 

Helical screw blower has two rotors in which the main rotor fits into the flute of a second rotor.  Special attention has been given to avoid collision between two rotors which rotates in a helical pattern. It is more quiter and produces high pressure compared to rotary blowers. It is used to move both air and gas with limited leakage.

​

Positive Displacement blower

 

A positive displacement blower is an effective blower for low pressure applications. It has two sections, one is expanding and other is discharging. Air enters through expanding and exists through the  discharging section. Regardless of changes in pressure it maintains constant flow speed. It is used to move both air and glasses. Closing the discharge valve while using it will burst the line. Therefore, a safety valve is vital for this blower.

 

High Speed Blowers

 

This type of blower is preferred for high pressure and high speed flow. For double suction impellers placed either side of a shaft. Low maintenance, high efficiency, easy to install, low noise level etc. are the features of high speed blowers.

​

Regenerative Blowers

 

Regenerative blower used where high rates of air flow required at low pressure or for vacuum creation. It removes dust or smoke from the air, extract vapor from soil or for sewage aeration, Regenerative blowers are self lubricated with no oil which is important in sensitive areas like food manufacturing, labs & hospitals.

​

Compressor

 

Compressor is a device used to convert low pressure air into high pressure air. It is used in a pneumatic system, air tools and tire industry etc.  Followings are the type of compressors:

​

• Centrifugal compressor

• Axial flow compressor

• Rotary compressor

• Reciprocating compressor  

 

Centrifugal compressor

 

A rotor or impeller centrifugal compressor converts kinetic energy into mechanical energy (pressure) and maintains continuous fluid flow. Compared to an axial compressor, the radius of a centrifugal compressor changes significantly from inlet to outlet to produce a much greater pressure rise in a single stage. Applications: Chemical plants, refineries, food processing unit, refrigeration unit etc.

​

Axial flow compressors

 

It is a rotating compressor in which air or gas flow parallel to the rotating shaft. Axial flow compressor is used for large mass flow rate and high efficiency in relation to their size and cross-section, however it requires multiple stages to achieve a large pressure rise. It is expensive compared to a centrifugal compressor because of multi-stages to achieve a large pressure rise for similar stages. Application: Jet engines, high speed ship engines, and small scale power stations.

​

Rotary compressor

 

Rotary compressor is a positive displacement machine. Unlike reciprocating compressors rotary compressors are lighter in weight, experience less vibration, and do not require heavy foundations. This compressor is used where a larger  volume of compressed gas is needed. Applications: Large refrigeration system, jackhammer system.

​

Reciprocating compressor

 

Reciprocating compressor is also a positive displacement machine that uses piston cylinder arrangement to increase pressure. It is sensitive to dirt. Applications: Oil refineries, gas pipelines, chemical plants, gas turbines, air conditioning, and refrigeration plants.

​

​