Measuring and testing – Volume or rate of flow – Of selected fluid mixture component
Patent
1985-04-18
1986-09-02
Woodiel, Donald O.
Measuring and testing
Volume or rate of flow
Of selected fluid mixture component
7386183, G01F 174, G01F 1115
Patent
active
046088717
DESCRIPTION:
BRIEF SUMMARY
The present invention refers to a device for measuring the liquid portion of a two-phase flow of gas and liquid, particularly in conveying a liquid by means of a gas, in which two-phase flow the ratio of mixture between gas and liquid is widely varying, said device comprising a tubular housing and a turbine wheel with axial throw-flow rotatably mounted therein, said turbine wheel being provided with at least one magnetic element at a radially outward portion thereof, said element having limited extent axially and peripherally of said turbine wheel, said device furthermore comprising magnetic pick-up means adapted to emit output signals responsive to the rotary speed of the turbine wheel, said wheel being mounted for axial movement in the direction of flow from an initial portion against a biassing force.
Volume flow meters of the aforementioned kind are previously known, see e.g. SE C No. 226 177 (corr. to U.S. Pat. No. 3,370,465), FR A No. 1 603 943, U.S. Pat. Nos. 3,169,397, 3,589,188, 3,636,767. As examples of prior art concerned with the problem of measuring mass and mass-flow it might be referred to e.g. U.S. Pat. Nos. 3,251,227 and 3,292,433. All these prior art examples refer to solutions for eliminating problems met with in connexion with the ends of the measuring range, i.e. either the very small flows or flow velocities or great ones. It is common to all prior art thus mentioned that the flow to be measured is homogeneous, i.e. either gas or liquid.
In many different connexions it is of interest, however, to measure a liquid flow in which there also is present an admixed gas. As example of a field in which such a measuring is desirable it can be mentioned measuring of milk in connexion with milking machines For carrying out such measuring operations the meter according to the aforementioned Swedish patent specification cannot serve as well as no other previously known type of flow meter. In fact, it is since long a very definite understanding within this technical field that no measuring of two-phase flows, i.e. flows constituted by a mixture of liquid and gas, by no means can be carried out otherwise than with meters which can give a measuring error of the magnitude of up to 50%.
The demand for measuring two-phase mixtures recently has increased, however, particularly in connexion with milking machines and particularly due to the increased automatization within the agriculture and use of computer systems for the supervision of the cowsheds. Since air is used as conveying medium for the milk in such milking machines, it is then obtained a two-phase system of gas and liquid which thus has not been measurable with hitherto known equipments, not even with approximately acceptable accuracy.
The main purpose of the present invention therefore is to provide a device for measuring of a varying liquid flow in a two-phase flow of liquid with admixed gas, which device is simple and inexpensive and provides a reliable measuring result. According to the invention, this is achieved by means of a device which is substantially distinguished in that a plurality of pick-up means are arranged axially spaced along the housing for allowing a measuring of rotary speed of the turbine wheel at various positions of movement within the housing responsive to density as well as speed changes of the flow and hence a determination of the liquid portion thereof by means of a converting device connected to all of the pick-up means, the tubular housing preferably being mounted vertically with the turbine wheel in its initial position being located lowermost.
With this device it has been made possible for the first time to meter two-phase flows, i.e. flows containing both gas and liquid, with very good accuracy, the deviations amounting to only a few percent. The main reason for this seems to be the axial movability of the turbine wheel which provides for the turbine wheel to respond to frequent and sudden changes of the density or the mass of the flow, contrary to all prior art meters.
By way of example, the invention will be f
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