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- Li, Jinxia, et al.
(författare)
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µPIV measurement of grease velocity profiles in channels with two different types of flow restrictions
- 2012
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 54, s. 94-99
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Tidskriftsartikel (refereegranskat)abstract
- Grease is commonly used to lubricate various machine components such as rolling bearings and seals. In this paper the flow of lubricating grease passing restrictions is described. Such flow occurs in rolling bearings during relubrication events where the grease is flowing in the transverse (axial) direction through the bearing and is hindered by guide rings, flanges et cetera, as well as in seals where transverse flow occurs, for example during so-called breathing caused by temperature fluctuations in the bearing. This study uses a 2D flow model geometry consisting of a wide channel with rectangular cross-section and two different types of restrictions to measure the grease velocity vector field, using the method of Micro Particle Image Velocimetry. In the case of a single restriction, the horizontal distance required for the velocity profile to fully develop is approximately the same as the height of the channel. In the corner before and after the restriction, the velocities are very low and part of the grease is stationary. For the channel with two flow restrictions, this effect is even more pronounced in the “pocket” between the restrictions. Clearly, a large part of the grease is not moving. This condition particularly applies to the cases with a low-pressure drop and where high consistency grease is used. In practice this means that grease is not replaced in such “corners” and that some aged/contaminated grease will remain in seal pockets.
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- Westerberg, Lars-Göran, et al.
(författare)
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Understanding grease flow through optical visualizations
- 2012
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Konferensbidrag (refereegranskat)abstract
- The flow dynamics of a lubrication mechanism is very complex, much due to the complex rheology and composition of the grease. In order to obtain an optimal lubrication, both the initial amount of grease and the position of the grease is highly important as too much grease will contribute to an increased friction, and grease in the wrong place will negatively affect the replenishment through oil bleeding. To understand the flow dynamics of grease hence is highly important for the understanding of the lubrication mechanism. Using micro Particle Image Velocimetry (μPIV) we have in a series of studies investigated the dynamics of grease flow in 2D straight channels with- and without restrictions, and in a full 3D configuration comprising a double restriction seal geometry. Velocity profiles for greases of different thickness have been measured, showing the influence of the grease rheology on the grease flow behaviour. KEYWORDS: Lubricants:Greases, Lubricant Physical Analysis:Non-Newtonian Behavior, Lubricant Physical Analysis:Rheology.
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