Measuring and testing – Volume or rate of flow – Using turbine
Patent
1981-03-25
1983-10-11
Ruehl, Charles A.
Measuring and testing
Volume or rate of flow
Using turbine
7386102, 7386189, G01F 110
Patent
active
044084986
DESCRIPTION:
BRIEF SUMMARY
This invention relates to turbine flow meters.
A turbine flow meter comprises a multi-bladed rotor which runs between bearings and is situated in a flow conduit. The transducer which is located in a wall of the flow conduit senses passage of the blades on the rotor. The rotor has a speed of rotation which is to some extent proportional to the flow rate of fluid passing through the conduit.
A problem with known turbine flow meters is that they tend to become inaccurate when used to measure flow of 2 phase fluids, e.g. mixtures of steam/water, gas/oil and air/water. A similar problem arises with oil/oil mixtures of different densities owing to, for example, different temperatures of constituents. An object of the present invention is to mitigate the above problem by providing a turbine flow meter which tends to measure flow of mixed fluids more accurately than hitherto.
According to the present invention, a turbine flow meter comprises a rotatably mounted multi-bladed rotor arrangement in a housing insertable in a flow conduit, said rotor arrangement comprising a boss and a number of blades attached to the boss, the boss diameter and blade outside diameter having a ratio of not less than 7 to 10, the rotor blades being disposed in respect of the rotational axis at an angle proportional to blade radius. The ratio is provided in order to enhance the immunity of the turbine flow meter to nonuniform flow. The blades are angled in order that the speed of points on the blade can be matched to flow rate. Preferably, the rotor blade angle is not greater than fifteen degrees at the tip.
Preferably, the housing is arranged such that the cross-sectional area of fluid flowing through the flow meter is substantially the same as the cross-sectional area of the conduit. In this way, distortions to the fluid flow profile by the flow meter are retained at a minimum. Advantageously, clearance between the tips of the rotor blades and the housing is less than one half percent of the diameter of the rotor arrangement. It is found that provision of such a clearance increases the immunity of the flow meter to nonuniform flow.
Preferably, the rotor arrangement is manufactured to have a visible clear path therethrough as close as possible to zero. In this way, the rotating rotor arrangement can see all of the flow which passes through it. Advantageously, the rotor arrangement has an odd number of blades. Provision of an odd number of blades is useful because it enables an electronic logic circuit to determine the direction of rotation of the rotor arrangement.
Preferably, a force transducer is arranged within the fluid flow path. Provision of the force transducer enables the turbine flow meter to be used to measure mass flow of fluids within the conduit. Conveniently, the force transducer comprises a drag disc. Advantageously, the drag disc has a number of equi-spaced spokes attached to a center ring. The spokes may be of conical formation. Preferably, the spokes obstruct no more than twenty-five percent of the cross-sectional area of the fluid flow conduit.
According to another aspect of the present invention, a turbine flow meter of the kind in which a bladed rotor is rotated by the flow about an axis lying in the general direction of the flow, is characterized by the combination that the blade length does not exceed 0.3 of the radius to the blade tips, that each blade over its length is twisted (substantially without alteration of profile) in proportion to radius but such that at no point is the angle relative to the rotational axis grater than fifteen degrees, that the dimension of the blades in the direction of the rotational axis is sufficient for the entry and exit edges to be at least coincident so that no visible clear path pertains anywhere through the blades area, and that the blade tips are closely proximate to the interior surface of a housing accommodating the rotor, there being also included in the combination a force transducer which is elastically deflectable by the flow to provide a measure of the momentum enabling
REFERENCES:
patent: 720188 (1903-02-01), Seidener
patent: 3115777 (1963-12-01), Hochreiter
patent: 3811323 (1974-05-01), Swenson
patent: 4164866 (1979-08-01), Mitchell et al.
Ruehl Charles A.
United Kingdom Atomic Energy Authority
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