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Middle East Technical University Department of Chemical Enginnering

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The main item of most processes is the compresor selection ... Blades of axial compressors have airfoil structure and decrease in diameter ... – PowerPoint PPT presentation

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Title: Middle East Technical University Department of Chemical Enginnering


1
Middle East Technical UniversityDepartment of
Chemical Enginnering
Fans, Blowers and Compressors
  • By Group E
  • Mert ÖZKAN
  • Günseli KÜÇÜK
  • Mehmet Sinan SEN
  • Selin ÖZDEMIR

2
OUTLINE
  • INTRODUCTION
  • FANS AND BLOWERS
  • COMPRESSORS
  • DYNAMIC TYPE COMPRESSORS
  • POSITIVE DISPLACEMENT COMPRESSORS
  • CONCLUSIONS

3
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

4
Major Factors During Selection
  • Head or Pressure Rise
  • Flow Rate
  • Temperature Limitations
  • Consumption of Power
  • Cost

5
  • 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

6
FANS BLOWERS
7
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.

8
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

9
FANS
Axial
Centrifugal
Radial Blade
Forward Curved
Backward Curved
Air Foil
Tube
Vane
10
AXIAL FANS
  • Gas moves parallel to the axis of rotation
  • There are two types of axial fans
  • Tube axial fans
  • Vane axial fans

11
  • 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

12
CENTRIFUGAL FANS
  • Gas stream moves perpendicular to the axis of
    rotation
  • They are classified as radial blade, forward
    curved, backward curved and air foil

13
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

14
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

15
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

16
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

17
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

18
  • They are used for
  • Pneumatic transportation of particulate material
  • Water and waste treatment
  • Providing moderate vacuum

19
COMPRESSORS
COMPRESSOR
Dynamic
Positive Displacement
Centrifugal Type
Axial Type
Reciprocating
Rotary
20
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

21
  • 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

22
  • The disadvantages of centrifugal compressors
    can be classified as
  • They have lower capacity
  • They have lower efficiency at low flow rates

23
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

24
  • 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

25
  • The advantages of axial compressors
  • They have higher efficiency
  • They have higher capacity (flow rate)
  • They are in smaller size

26
  • 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

27
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
28
Multistage Integrally Geared Compressor
Applications
  • Flow rate ranging from 1,000 to 500,000m3/hr
  • Having pressure upto 100 bar

29
Single Stage Centrifugal Compressor Application
  • Flow rate is 500,000m3/hr and having
    compression ratio 3 with discharge pressure 80bar

30
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

31
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

32
POSITIVE DISPLACEMENT COMPRESSORS
Positive Displacement Compressors
Reciprocating Compressors
Rotary Compressors
33
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

34
  • 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

35
  • 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

36
  • The two rotating components confine a volume of
    gas
  • The volume of the pocket decreases in rotation so
    pressure increases

37
  • The rotary compressors have high range of
    capacity and compression ratio
  • The rotary compressors are classified as Lobed,
    Helical Screw, Sliding Vane

38
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

39
  • 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

40
SLIDING VANE COMPRESSORS
  • The gas trapped between the vanes and it is
    compressed as the compartment moves around the
    casing

41
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

42
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

43
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

44
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
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