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US 4,644,808 AGranted
Apparatus for measuring the concentration of cavitation nuclei in a liquid
AssigneeAlsthom
InventorYves Lecoffre
Life of this patent
Estimating the term…
Abstract
In hydrodynamic testing, in particular in laboratory testing of propellers, it is necessary to measure the concentration of cavitation nulcei in a liquid. The measurement is performed by counting bubbles of vapor formed by the cavitation nuclei in a zone (C) having minimum cross-section and pressure (Pt) in a forced flow along a duct. A deflector core (18) is disposed on the axis of a diverging downstream portion (C) of said duct in order to avoid the liquid streamlines from becoming detached and to facilitate bubble counting.
Claims7
Apparatus for measuring the concentration of cavitation nuclei in a flowing liquid, said apparatus comprising:
- a pressure-reducing duct for confining flow of said liquid during passage of liquid in a given flow direction through said duct, said duct having a length and an axis along the flow direction and comprising a venturi passage including an upstream portion having a flow cross-section of the liquid which decreases up to minimum flow cross-section so as to progressively decrease the pressure, a minimum pressure portion having a predetermined length, and a downstream portion having a flow cross-section which increases progressively so as to increase the pressure;
- circulation means for causing said liquid to flow through said duct venturi passage at a sufficient rate to ensure that the pressure in said minimum pressure portion is sufficiently low to ensure that the cavitation nuclei whose concentration in the liquid is to be measured, give rise to bubbles of vapor of sufficient individual bubble volume to be detected individually;
- means for detecting the bubbles created in this way;
- means for counting the bubbles to measure the number of bubbles in a given period of time;
- and
- means for obtaining the flowrate of the liquid flow through the duct venturi passage in such a manner as to enable the nuclei concentration to be deduced from said number of bubbles and said flow rate:
- the improvement wherein said duct is made of an outer tube and of an inner coaxial core and the said venturi passage flow cross-section of the liquid is constituted over the length of said core by an annular passage between said core and said tube so that a spherical bubble can occupy only a small fraction of the liquid cross-section, each right cross-section through the duct and said annular passage showing the passage to have a radial widths extending in directions going away from the axis of the duct, and an average circumferential length which is the length of the line which connects the middles of its widths.
4 more elements
Dependencies are inferred from the claim text.