RU2324146C2 - Turbine flowmeter - Google Patents

Abstract

FIELD: energy.

SUBSTANCE: in the measuring channel of the flow-meter housing, the following devices are mounted in series: training device with a cowling; turbine, mounted with possibility of axial displacement and rotation with a fluid-dynamic device for balancing in the form of ring-shaped streamlining body, concentrically mounted on the turbine from the outlet side; straightening vane with a cowling and turbine rotation converter into an output signal. On the output part of the front cowling there is an internal indentation with diameter greater than the diameter of the front part of the turbine hubs. On the front part of the turbine there is a ring shaped indentation, whose external diameter is greater than the diameter of the front cowling, and the internal diameter less than the diameter of the internal indentation on the front cowling. The fluid-dynamic balancing device can be in the form of ribs on the flanks of the turbine blades, forming projections on the surface of the blades.

EFFECT: increased accuracy and broadening of the measurement range; lower pressure losses.

4 cl, 4 dwg

Description

The invention relates to measuring equipment and can be used, in particular, for measuring the flow of liquids and gases.

Known turbine tachometric flow meters [Bosnyak L.Ya., Byzov L.N. Tachometric flow meters. - L., 1968, pp. 39-40], in which the hydrodynamic balancing of the rotor is based on the artificial creation of an uneven field of static pressure in the rotor zone, affecting the kinetic energy of the flow by narrowing the flow in front of the turbine or communicating rotational motion to the flow.

The disadvantage of such flowmeters is the complicated circuits of balancing force regulators corresponding to changes in other forces applied to the rotor from the flow side.

Known turbine flowmeter [USSR copyright certificate No. 970112, BI No. 40, 1980, class. G01F 1/10], comprising a housing with a calibrated channel and an axial turbine installed in it, with the possibility of rotation and axial movement, input and output flow guiding devices, a device for hydrodynamic balancing of the turbine, made in the form of two rings installed directly in one channel against the other with a gap between the ends, and one of them has a section profile expanding in the direction of flow and fixedly installed, and the second, having a tapering profile, is rigidly closed replicated on the impeller blade.

In such a flow meter, due to the uncertain location of the device for hydrodynamic balancing of the turbine — the rings in the flow part of the channel — sufficient measurement accuracy and operating life are not ensured.

In another flowmeter [USSR copyright certificate No. 1139971, A, 02/15/85, cl. G01F 1/10], the rings for hydrodynamic balancing of the turbine are mounted on the jet straightener and blade blade in the range of 0.9-1.2 rms diameter of the turbine.

In this flowmeter, in spite of a slight increase in the service life and measurement accuracy, reliable hydrodynamic unloading of the turbine in the entire flow range is not ensured.

Known turbine flowmeter [French patent No. 2080762, 1971, class. G01F 1/00], comprising a housing, input and output fairings having special protrusions to reduce the influence of the boundary layer, a turbine, and a converter for rotating the turbine into an output signal.

Such flowmeters do not provide full axial force compensation.

Known turbine flowmeter [US patent No. 3756059, 1973, class. 73-221], containing an axial impeller in the form of a hub with fixed blades fixed on it, mounted for rotation between two fairings, at least one of which has a diameter larger than the diameter of the hub, as well as a signal pick-up unit.

Such a flow meter does not provide accurate measurement over a wide range of flow rates.

The closest analogue of the invention is a turbine flowmeter [USSR copyright certificate No. 611113, 06/15/78, class. G01F 1/12 (prototype)], comprising a housing with a measuring channel; inlet cowl with a device to reduce the influence of viscosity of the medium; output fairing; a turbine, on the blades of which a profiled ring with an outer surface expanding in the flow direction is installed on the blades of the flow, forming annular gaps with the hub of the turbine and with an inlet cowl, and an annular protrusion is made on the wall of the measuring channel opposite the profiled ring.

In such a flow meter, when the medium is flowing through the channel, a force is applied to the turbine directed along the flow. At the same time, a narrowing of the flow occurs between the profiled ring and the protrusion in the channel, which leads to the appearance of a force directed against the flow and compensation of the axial force.

The design of such a flow meter does not provide complete hydrodynamic balancing of the turbine over the entire flow range; It has increased pressure losses due to a decrease in the bore in the region of the annular protrusion and the profiled ring. The operational disadvantage is the small gaps between the profiled ring and the inlet cowl.

The proposed invention is aimed at achieving a technical result, ensuring the reliability of hydrodynamic balancing of the turbine in a wide range of measured flow rates, including at maximum flow rates, expanding the measuring range, increasing the accuracy of measurements, increasing the service life, reducing pressure losses.

The specified technical result is achieved in a turbine flowmeter comprising a housing with a measuring channel, in which a flow guide apparatus with a cowl is sequentially placed; a turbine in the form of a hub with blades fixed on it, mounted with the possibility of axial movement and rotation with a hydrodynamic balancing device in the form of an annular flow body; a flow straightener with a cowl and a converter that rotates the turbine into an output signal due to the fact that the annular body of the flow around the turbine is mounted concentrically on the outlet side, and an internal recess with a diameter larger than the diameter of the front part of the hub of the turbine is made in the output part of the front cowl, and the ring is made in the front of the turbine a recess with an outer diameter greater than the diameter of the front fairing and an inner diameter less than the diameter of the inner recess in the front fairing.

The technical result is also achieved when in the annular body of the flow around at least one of the end sides, recesses (for example, a trapezoidal profile) are made.

The technical result is also achieved when the hydrodynamic balancing device is made in the form of ribs on the sides of the blades of the turbine, forming ledges (at least on one end side) with the surfaces of the blades of the tube.

The technical result is also achieved when the diameter of the front of the hub of the turbine is larger than the diameter of the rear of the hub of the turbine.

The invention is illustrated by graphic materials, which show:

figure 1 is a General view of a turbine flow meter;

figure 2 - sketch of the execution in the annular body of the flow around the recesses of the trapezoidal profile from the end output side;

figure 3 is a sketch of a device for hydrodynamic balancing, made in the form of ribs on the sides of the blades of the turbine, forming ledges with the surfaces of the blades of the turbine from the front end side.

4 is a sketch of the execution of the hub of the turbine with a diameter of the front part greater than the diameter of the rear part of the turbine.

The proposed turbine flow meter (figure 1) contains a housing 1 with a measuring channel 2, in which are sequentially placed: flow guide apparatus 3 with a cowl 4; a turbine 6 in the form of a hub 5 with fixed blades mounted with the possibility of axial movement and rotation with a hydrodynamic balancing device in the form of an annular flow body 7 installed concentrically in the turbine from the outlet side; a jet straightener with a cowl 8 and a converter for rotating the turbine into an output signal 9. In the output part of the front cowl, an inner recess A is made with a diameter larger than the diameter of the front part of the turbine hub, and an annular recess B is made in the front of the turbine with an external diameter greater than the diameter of the front cowl and an inner diameter less than the diameter internal recess in the front cowl.

Turbine flowmeter operates as follows. When the measured medium moves along the channel 2 through the jetting apparatus 3 in the gap A, a reduced static pressure is created between the front fairing 4 and the hub 5 of the turbine 6. Behind the stern of the hub of the turbine, in connection with the large passage section of the channel, an increase in static pressure occurs. The result is a force acting on the turbine against the flow. The turbine begins to move towards the front fairing. This reduces the gap between the front fairing and the annular body of the flow around, which leads to an increase in hydrodynamic resistance and the force acting on the turbine in the flow. The end part of the turbine blades above the annular recess B falls into the zone of a greater dynamic pressure head flowing between the front fairing and the flowmeter body, which also leads to an increase in the force acting on the turbine in the flow. At a certain distance of the turbine from the fairing, the forces acting on the turbine upstream and downstream are balanced. A further increase in flow rate practically does not affect the movement of the turbine, and it remains in a balanced state.

Similarly, balancing of the turbine occurs when: in the annular body of the flow around at least one of the end sides, recesses (for example, a trapezoidal profile) are made (figure 2); the device of hydrodynamic balancing is made in the form of ribs on the sides of the blades of the turbine, forming ledges (at least on one end side) with the surfaces of the blades of the turbine (figure 3); the diameter of the front of the hub of the turbine is larger than the diameter of the rear of the hub of the turbine (figure 4)

The execution in the annular body of the flow around the recesses or the implementation of the ribs on the lateral sides of the turbine blades as described above, leads to a decrease in the hydraulic resistance of the turbine and, as a result, to a decrease in the flow rate at which hydrodynamic balancing of the turbine begins. The presence of an annular flow body or ribs on the lateral sides of the turbine blades reduces the flow of the measured medium along the height of the blades and increases the degree of turbulence, which leads to a shift of the transition point of the laminar boundary layer to the turbulent one in the region of small Reynolds numbers. This achieves the linearization of the static characteristic and reduces the influence of the viscosity of the medium being measured on the accuracy and measurement range. The diameter of the front of the hub of the turbine is larger than the diameter of the rear of the hub of the turbine leads to an increase in the force acting against the flow. The beginning of hydrodynamic balancing of the turbine occurs at lower costs.

Claims (4)

1. A turbine flowmeter comprising a housing with a measuring channel, in which are sequentially placed: flow control apparatus with a cowl; a turbine in the form of a hub with blades fixed on it, mounted with the possibility of axial movement and rotation with a hydrodynamic balancing device in the form of an annular flow body; a flow straightener with a cowl and a converter for rotating the turbine into an output signal, characterized in that the annular body of the flow around the turbine is mounted concentrically on the outlet side, while an inner recess with a diameter larger than the diameter of the front part of the hub of the turbine is made in the output part of the front cowl, and in the front part of the turbine an annular recess with an outer diameter greater than the diameter of the front fairing and an inner diameter less than the diameter of the inner recess in the front fairing 2. The turbine flowmeter according to claim 1, characterized in that in the annular body of the flow around at least one of the end sides, recesses (for example, a trapezoidal profile) are made. 3. The turbine flowmeter according to claim 2, characterized in that the hydrodynamic balancing device is made in the form of ribs on the sides of the turbine blades, forming ledges, at least on one end side with the surfaces of the turbine blades. 4. Turbine flowmeter according to any one of paragraphs. 1-3, characterized in that the diameter of the front of the hub of the turbine is larger than the diameter of the rear of the hub of the turbine.

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