Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.449339
Title: Some flow characteristics of spool valve orifices
Author: Beck, A.
ISNI:       0000 0001 3452 9736
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 1973
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Abstract:
An experimental study is made of oil jets issuing from effectively two-dimensional spool valve orifices. (Aspect ratio 2.5-45). Reynolds number is varied from 200 to 3000 and cavitation number from 0.15 to 0.8.Valve geometry effects are examined by (a) varying the orifice opening and clearance and (b) by providing each valve with an additional movable boundary wall. Both flow into and flow out of the valve are studied. The work confirms the existence of two now patterns, reattached and detached, noted by other workers and extends their investigations by considering a wide range of Reynolds number and cavitation number. Hysteresis zones, in which the flow may assume either mode, occur. These are affected by Reynolds number; at low Reynolds numbers (200-900), the width of the hysteresis zones becomes zero; at large Reynolds numbers (3000) it settles to a constant value. Increasing severity of cavitation reduces the width of the zone and increases the value of Reynolds number at which the width is zero. Valve clearance is also shown to increase the width of the hysteresis zone. For reattached flow the reattachment bubble is shown to decrease in length as Reynolds number increases from 575. Moving the downstream wall nearer to the orifice has the same effect as an increase in Reynolds number except at the highest values of Reynolds number (2480) at which the bubble lengthens. Cavitation first occurs in the inner shear layer of the bubble. It acts as a turbulence generator again effectively increasing the Reynolds number and reducing the bubble length. When cavitation is fully develop in the bubble it causes it to lengthen. When the Reynolds number exceeds 1000 cavitation occurs more readily in reattached flow than in detached flow. At a given pressure drop more flow is shown to pass with reattached now, over a tested Reynolds number range of 400 to 1200.
Supervisor: McCloy, D. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.449339  DOI: Not available
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