1. C.Hariharan and M.Govardhan
Chennai – 36
Indian Institute of Technology
Madras
Loss in Input Power due to Increase in
Clearance between Inlet Duct and Impeller in an
Industrial Centrifugal Blower
Thermal Turbomachines Laboratory
Department of Mechanical Engineering
Indian Institute of Technology Madras
1
2. Introduction
• Lee [3]
• C Hariharan et al [5]
Chennai – 36
Indian Institute of Technology
Madras
• Aayder et al. [1]
2
3. • In most of the time while design we omit the
clearance gap in between suction duct and
impeller.
Chennai – 36
Indian Institute of Technology
Madras
Problem definition
• The area of clearance is only 0.5 to 2% of
inlet area.
3
4. Design
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Indian Institute of Technology
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Specification:
specific work
Design mass flow rate
operating range
Speed
- 24000 m2/s2
- 28.5 kg/s
- 20 kg/s to 31.5 kg/s
- 3000rpm
4
5. Dimension
Blades
Inlet Diameter
Inlet Blade angle
Exit Blade angle
- 15
- 0.7 m
- 32o
- 48o
Clearance gap
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Indian Institute of Technology
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Impeller:
- 1mm, 3mm and
5mm
- 0.6 %, 1.8% and
3%
clearance area
5
6. - constant angular momentum
- tongue clearance 5% of impeller
exit diameter
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Indian Institute of Technology
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Volute :
- Ratio between volute width and
impeller exit width 5.
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7. Chennai – 36
Indian Institute of Technology
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Fan Assembly with Ratio 5 volute
7
11. -Suction duct 0.8 million
-Impeller 4.5 million
-Volute 5.5 million
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Indian Institute of Technology
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Meshing
Y+ < 50
volume expansion factor < 25
Number of nodes in interfaces maintained almost
same
11
28. Chennai – 36
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Flow angle at inlet to impeller for
design mass flow rate
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29. Chennai – 36
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Flow angle at inlet to impeller for
lowest mass flow rate
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30. Chennai – 36
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Static pressure at impeller exit for
design mass flow rate
30
31. Chennai – 36
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Static pressure at impeller exit for
lowest mass flow rate
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32. Chennai – 36
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Total pressure at impeller exit for
design mass flow rate
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33. Chennai – 36
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Total pressure at impeller exit for
lowest mass flow rate
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34. Chennai – 36
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Flow angle at Exit of impeller for
design mass flow rate
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35. Chennai – 36
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Flow angle at Exit of impeller for
lowest mass flow rate
35
36. Chennai – 36
Indian Institute of Technology
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Stream lines in impeller for
clearance of (a) 0mm
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37. Chennai – 36
Indian Institute of Technology
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Stream lines in impeller for
clearance of (a) 1mm
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38. Chennai – 36
Indian Institute of Technology
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Stream lines in impeller for
clearance of (a) 3mm
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39. Chennai – 36
Indian Institute of Technology
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Stream lines in impeller for
clearance of (a) 5mm
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40. Chennai – 36
Indian Institute of Technology
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Volute Pressure recovery coefficient
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41. Chennai – 36
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Change in volute Pressure recovery
coefficient
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42. Chennai – 36
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Volute loss coefficient
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43. Chennai – 36
Indian Institute of Technology
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Volute loss coefficient
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44. Chennai – 36
Indian Institute of Technology
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Change in Total pressure at volute
exit
44
45. Chennai – 36
Indian Institute of Technology
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Change in static pressure at volute
exit
45
46. -The overall stage performance at design
and off design conditions, especially at
higher mass flow rate is not favorable
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Indian Institute of Technology
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conclusion
-Stage efficiency drops considerably as the
mass flow is increased and also there is an
increase in input power up to 32 kW
-There is a noticeable drop in total and
static pressure at exit of impeller
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47. As the clearance increases, the flow is
found to be more uniform at the exit of the
impeller and also the possibility of flow
separation gets reduced at lower mass
flow rates especially near the trailing edge
of impeller.
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Indian Institute of Technology
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conclusion
The increased pressure recovery and
reduced loss at higher clearance has
positive effect on volute at all mass flow
rates.
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