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The low pressure axial flow fans with an outer ring, used for cooling automobile radiators, have a significantly large tip clearance between the ring tip and the fan shroud. It has been found that the turbulent reverse flow, or leakage flow, which occurs at the tip clearance, greatly affects the fan performance and noise level. Therefore, in order to improve the fan performance and noise level it is important to decrease the effect of leakage at the tip clearance. The authors investigated the performance of the straight-through type of labyrinth seal which operates in an extremely low static pressure difference with a large clearance. It was hoped that by sealing this clearance with the labyrinth seal the performance would be improved. It was verified that the labyrinth seal satisfied almost the same performance as that predicted by the previous theory. This theory was established by experimental studies in the condition of quite high static pressure difference when the labyrinth is stationary. However, it was later discovered that the leakage rate decreased significantly even though there was far lower ring speed in comparison to past research results where the ring rotated. This phenomenon is conspicuous in a lower differential pressure. However, the cause of this phenomenon has not been determined.
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Abbreviations
- D:
-
Diameter of the rings (mm) [constant: 362]
- F:
-
Opening area of the throttling (m2)
- G:
-
Leakage rate (kg/s)
- L:
-
Axial length of the rings (mm) [constant: 49.7]
- ℓ:
-
Pitch of fins (mm)
- n:
-
Number of fins
- P:
-
Absolute pressure (Pa)
- Ps:
-
Static pressure difference (Pa)
- S:
-
Inner distance between fins (mm)
- U:
-
Peripheral velocity of fin tip (m/s)
- α:
-
Flow coefficient of contraction at the throttling
- Γ:
-
Specific leakage rate Γ=GEr/GEs
- δ1:
-
Thickness of first and end fins (mm) [constant: 2.5]
- δ2:
-
Thickness of fins (mm) [constant: 1.5]
- ε:
-
Clearance (mm) [constant: 3.0]
- θ:
-
Jet expansion angle (deg)
- λ:
-
Pressure ratio λ=PD/PU
- ν:
-
Specific volume of gas (m3/kg)
- υ:
-
Carry-over factor υ=GE/GI
- Φ:
-
Labyrinth function
- ϕ:
-
Ideal labyrinth function
- a:
-
Approximate
- D:
-
Outlet of labyrinth (Downstream)
- E:
-
Experimental
- I:
-
Ideal
- R:
-
Rotational
- S:
-
Stationary
- U:
-
Inlet of labyrinth (Upstream)
References
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Kota Shimada: He obtained his B.S. degree in mechanical engineering from Tokai University in 1992. He has worked for Toyo Radiator Co., Ltd. as an engineer and has been engaged in the development of cooling fan systems for radiators since 1992. All japanese motorbike companies and some japanese automobiles companies currently use his fan design. His professional interests are focused on the design and analysis of axial flow fans which operate under unusual conditions.
Kazuhide Kimura: He received his B.S. degree in mechanical engineering from Ritsumeikan University in 1999. Since 1999, he has been working for Toyo Radiator Co., Ltd. He has been engaged in a design and analysis of cooling fans and radiators.
Hiroaki Ohta: He received his B. Sc. (Eng.) and M. Sc. (Eng.) degree in mechanical engineering in 1970 and 1972 from Tokai University, and his Ph. Dr. in mechanical engineering in 2000 from the same University. After obtaining his M. Sc., he worked as a research assistant and a lecturer at Tokai University, before taking up his current position as an associate professor of Tokai University. His current research interests cover performance and flow inside impeller of centrifugal pump for high-viscosity liquids, performance of axial flow fans and flow around a half column.
Katsumi Aoki: He received his M.Sc.(Eng.) degree in mechanical engineering in 1967 from Tokai University, and his Ph.D. in mechanical engineering in 1986 from the same University. After obtaining his M.Sc., he worked as a research assistant, a lecturer, and an associate professor at Tokai University before taking up his current position as a professor of Tokai University. His current research interests cover flow around a rotating circular cylinder with and without grooves, flow around a rotating sphere, possibility of drag reduction using triangle-type cavity, and flow visualization by spark tracing method of complicated flow field as in centrifugal blower.
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Shimada, K., Kimura, K., Ohta, H. et al. Phenomenon of labyrinth weal with Low static pressure difference and large clearance. J Vis 6, 395–405 (2003). https://doi.org/10.1007/BF03181746
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DOI: https://doi.org/10.1007/BF03181746