Middle East Technical University Department of Chemical Enginnering

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Middle East Technical UniversityDepartment of
Chemical Enginnering
Fans, Blowers and Compressors

• By Group E
• Mert ÖZKAN
• Günseli KÜÇÜK
• Mehmet Sinan SEN
• Selin ÖZDEMIR

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OUTLINE

• INTRODUCTION
• FANS AND BLOWERS
• COMPRESSORS
• DYNAMIC TYPE COMPRESSORS
• POSITIVE DISPLACEMENT COMPRESSORS
• CONCLUSIONS

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INTRODUCTION

• The main use of the fans, compressors and blowers
  is the transportation of gases
• The main item of most processes is the compresor
  selection
• There are wide variety of compressors so it is
  crucial to define the operating conditions before
  selection

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Major Factors During Selection

• Head or Pressure Rise
• Flow Rate
• Temperature Limitations
• Consumption of Power
• Cost

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• The pressure rise which is the main difference
  between fans, compressors and blowers can be
  stated as follows
• ?P(psig)
• Fans 2
• Blowers 2-10
• Compressors gt10

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FANS BLOWERS
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FANS

• They are the air displacement systems moving air
  continuously to moderate pressures
• Due to little change in pressure of air in fans,
  air is considered to be incompressible
• They can have pressure rise up to 2 psig.

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The characteristics of fans can be classified as

• The volumetric flowrate of the gas displaced by
  the fan is directly proportional with the fan
  speed
• The static pressure varies with the square of the
  fan speed
• The power consumed varies with the cube of the
  fan speed

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FANS
Axial
Centrifugal
Radial Blade
Forward Curved
Backward Curved
Air Foil
Tube
Vane
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AXIAL FANS

• Gas moves parallel to the axis of rotation
• There are two types of axial fans
• Tube axial fans
• Vane axial fans

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• Tube axial fans are used for wide range of
  volumes at medium pressure
• In vane axial fans there is air guide vane on
  the discharge side and the air flow pattern is a
  straight line hence improvement in efficiency and
  reducement in turbulance is observed

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CENTRIFUGAL FANS

• Gas stream moves perpendicular to the axis of
  rotation
• They are classified as radial blade, forward
  curved, backward curved and air foil

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RADIAL BLADE CENTRIFUGAL FANS

• They are used for pneumatic transportation and
  exhausting process gas in high resistance systems
• With relatively low capacity, they can achive
  high static pressure
• They can develop high pressures with high speeds
• Blades clean themselves
• They are not used for ventilating purposes

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FORWARD CURVED CENTRIFUGAL FANS

• They discharge higher volume of air at slower fan
  speeds
• They operate with a moderate amount of noise
• They require little space
• They are used for clean gases

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BACKWARD CURVED CENTRIFUGAL FANS

• They develop much of their energy directly as
  pressure
• They develop less velocity heads by operating at
  medium speeds
• Small variations in system volume result in small
  variations in air pressure

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AIR FOIL CENTRIFUGAL FANS

• They are backward curved centrifugal fans with an
  air foil cross section
• They can operate more silently since air forms no
  turbulance while flowing through the wheels

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BLOWERS

• Blowers are used for supplying low pressure air
  up to between 2-10 psig.
• They consist of two parallel shaft rotors
• They may have 2 4 lobes
• The rotating shaft in the constitution of the
  blower traps some gas
• The compression of the gas in the blower is
  negligible

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• They are used for
• Pneumatic transportation of particulate material
• Water and waste treatment
• Providing moderate vacuum

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COMPRESSORS
COMPRESSOR
Dynamic
Positive Displacement
Centrifugal Type
Axial Type
Reciprocating
Rotary
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CENTRIFUGAL DYNAMIC TYPE COMPRESSORS

• There is flow of air in radial direction
• They are the most popular type of compressors
  since they are simple and have maintainance free
  designs
• They are used for wide variety of services which
  are cooling and drying, compressing gas or
  steam, supplying combustion air to furnaces,
  agitation and aeration

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• The advantages of centrifugal compressors can
  be classified as
• They are more efficient than reciprocating ones
• They provide high flowrates
• They are compact, less site area
• They need lower maintainance requirements
• They are tolerant to liquid carry

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• The disadvantages of centrifugal compressors
  can be classified as
• They have lower capacity
• They have lower efficiency at low flow rates

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AXIAL COMPRESSORS

• They have blades having air foil structure pushes
  air in axial direction
• They have high speed and they are large volume
  compressors
• They have low head

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• Blades of axial compressors have airfoil
  structure and decrease in diameter
• There is a stationary phase between each row,
  redirecting the flow and accompolishing a level
  of conversion of velocity to pressure
• There is a pressure increase in each row

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• The advantages of axial compressors
• They have higher efficiency
• They have higher capacity (flow rate)
• They are in smaller size

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• The disadvantages of axial compressors
• They limited operating range
• They are more subjected to corrosion
• They are subjected to deposits
• They have higher capital costs
• They have lower heads

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Combined Axial and Radial Compressor Applications
They have flow rates ranging from 50,000 to
690,000m3/hr
They have pressure ratio ranging from 5.8 to 12.5
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Multistage Integrally Geared Compressor
Applications

• Flow rate ranging from 1,000 to 500,000m3/hr
• Having pressure upto 100 bar

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Single Stage Centrifugal Compressor Application

• Flow rate is 500,000m3/hr and having
  compression ratio 3 with discharge pressure 80bar

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Pipeline Compressor Applications

• This is the natural gas compressor for
  pipeline transportation having pressure ratio
  ranging from 1.05 to 1.5, shaft speed ranging
  from 3,000 to 13,500 rpm anddischarge pressure
  ranging from 80 to 125 bar

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Axial Flow Compressor Applications

• This is used in catalyst regeneration plant
  having flow rate ranging from 50,000 to
  1,400,000m3/hr having pressure ratio ranging from
  1.9 to 6.5

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POSITIVE DISPLACEMENT COMPRESSORS
Positive Displacement Compressors
Reciprocating Compressors
Rotary Compressors
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RECIPROCATING COMPRESSORS

• They are the oldest type of compressors
• They have higher maintainance costs and lower
  capacity than dynamic compressors
• They are widely used in industry
• They have cylinders which are equipped with
  suction and delivery valves
• Compression cycle is composed of 3 cycles which
  are intake, compression and discharge

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• They intake gas by the help of cylinders
• The pistons motion is reversed and the gas which
  taken in is compressed
• The gas is expelled during the delivery stroke

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• In multistage reciprocating compressors
• The gas is compressed to an intermediate pressure
• The other cylinders raise the pressure to the end
  pressure
• There also exist intercoolers

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• The two rotating components confine a volume of
  gas
• The volume of the pocket decreases in rotation so
  pressure increases

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• The rotary compressors have high range of
  capacity and compression ratio
• The rotary compressors are classified as Lobed,
  Helical Screw, Sliding Vane

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HELICAL SCREW COMPRESSORS

• There are mainly two screws which are called male
  and female
• The gas is compressed between the lobes of the
  screw and move along the axis to an outlet port

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• These units can be oil flooded and dry
• The contamination of oil is prevented by dry
  compressors
• Oil flooded units are used in refrigeration
  systems and plant air service

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SLIDING VANE COMPRESSORS

• The gas trapped between the vanes and it is
  compressed as the compartment moves around the
  casing

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CONCLUSIONS

• The fans have wide range of flowrate
• The material selection is important during
  manufacturing fans
• The blowers have low power and pressure
  applications
• The blower is less efficient method of compression

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CONCLUSIONS

• When centrifugals are run at lower flow rates the
  efficiencies decrease
• The centrifugals are tolerant to liquid carry
• The liquid with the gas can cause erosion and
  severe damage in centrifugals
• In axial equipment, high compression efficiency
  is observed
• The axial equipment is applied for high flow
  andlow discharge pressures

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CONCLUSIONS

• The reciprocating systems are applicable for low
  flow rate of high pressure ratio
• The oil contamination is important in
  reciprocating systems
• The reciprocating systems have higher
  maintainance cost
• The reciprocating systems are not suited to dirty
  gasses
• The process gases that are taken in should be
  clean and dry in axial equipments
• The reciprocating systems are not tolerate liquid
  droplets in the suction flow

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CONCLUSIONS

• The screw compressor have higher initial cost
  than reciprocating compressors for the same duty
• The sliding vane compressors have low pressure
  applications
• The sliding vane compressors operate at low
  speeds
• The noise level of the sliding vane compressors
  is low