RU2395684C2 - Device for measurement of fluids flow movement speed and temperature - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: device comprises cylindrical tubular body, straightening vane and windows for outlet of fluid flow, heater and heat-sensitive element, electrical circuit for generation of information signal, supply unit and recorder. Additionally device comprises two heat-sensitive resistive elements, having equal values of electrical resistances and different working surfaces of turns washed with flow of oncoming fluid and arranged as mutually perpendicular on bearing frame. Straightening vane is installed in front part of cylindrical tubular body. Heater and heat-sensitive element are installed between straightening vane and windows for outlet of fluid flow. Bearing frame is formed by at least two plates of trapezoidal shape from electric insulation and heat insulation material, and small bases of trapezoids face oncoming flow of fluid. Besides turns of one of resistive heat-sensitive elements are arranged on bearing frame perpendicularly to direction of fluid motion, of the second one - in parallel, and heat sensitive elements are connected serially into one of three branches of measurement circuit arranged as a balances DC bridge. The third heat-sensitive element is installed upstream two above-mentioned heat-sensitive elements in front part of cylindrical tubular body at the end of straightening vane, which is closer to oncoming flow of fluid. Besides heat sensitive elements are connected into bridge circuit, which consists of three parallel branches.

EFFECT: improved accuracy of measurements and information value due to simultaneous measurement of measurement speed and temperature, reduction of heat inertia and heat resistance.

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Description

The invention relates to devices for measuring the velocity of fluid flows and can be used in pipeline transport, as well as during geophysical and gas-dynamic studies of wells in fields and underground gas storages.

A device for measuring the velocity of fluid flows is known as a hot-wire anemometer, the principle of which is based on the removal of heat from heat-sensitive elements (temperature sensors) heated above ambient temperature using special heaters (for example, AGDK-type gas-hydrodynamic logging equipment containing a tubular guard, a heating element and a diode temperature sensor installed inside the guard. [1] (Prospect of OAO Gazpromgeofizika "Complex equipment g zodinamicheskogo logging AGDK-42-8 ").

The disadvantages of the known device are:

- frequent failures of diode temperature sensors due to their overheating during the transition from a liquid medium to a gaseous one;

- low reliability of readings during rapid changes in the fluid velocity due to the large thermal inertia of the heater and the heat-sensitive element (due to their location inside the tubular protective casing, which has a significant thickness and weight), as well as significant thermal resistance between the heater, the heat-sensitive element and the outer wall of the casing sensor;

- the inability to accurately measure the speed of air, gas or liquid flows while changing the temperature (for example, in downhole conditions, where the temperature rises with increasing depth of the well).

A well-known hot-wire anemometer of the fluid velocity used in downhole tools (flow or liquid or gas flow sensor in wells) comprising a sealed tubular casing consisting of two cavities in which heating and heat-sensitive elements are located. [2] (A.S. SU No. 440484, class E21B 47/10, publ. 1974).

The disadvantages of the known hot-wire anemometer are:

- low reliability of readings during rapid changes in the fluid velocity due to the large thermal inertia of the heater and the heat-sensitive element (due to their location inside the tubular protective casing, which has a significant thickness and weight), as well as significant thermal resistance between the heater, the heat-sensitive element and the outer wall of the casing sensor;

- the impossibility of accurately measuring the velocity of fluid flows while changing (during the measurement) their temperature (for example, in the wellbore, the temperature changes as a function of depth by 3-4 ° C for every 100 meters).

Due to the noted drawbacks, obtaining correct measurement results is possible only with:

- slow changes in fluid velocity;

- the introduction of temperature correction of the readings of the hot-wire anemometer (for example, by calibrating it both in speed and temperature), which greatly complicates the processes of calibration and interpretation of research results, and also limits the scope of hot-wire anemometer devices for measuring the speed of fluid flow.

The objective of the present invention is to improve the accuracy of measurements and the information content of the device due to:

- reduction of thermal inertia and thermal resistance;

- simultaneous measurement of both the speed of the fluid flow and its temperature;

- continuous introduction of appropriate temperature corrections (based on temperature sensor readings).

The essence of the present invention lies in the fact that the known device for measuring the speed and temperature of the fluid flow, including a cylindrical tubular body, a jet straightener installed on the open end side in front of the cylindrical tubular body and a window for exiting the fluid flow in its rear part, a heater and a heat-sensitive an element installed between the rectifier and the windows for the output of the fluid flow, an electrical circuit for generating an information signal, a power supply and a register Ator, according to the invention, additionally contains two heat-sensitive resistive elements having equal values of electrical resistances and different working surfaces of the coils, washed by the flow of incoming fluid and located mutually perpendicular to the supporting frame, formed by at least two trapezoidal plates made of electrical insulating and heat-insulating material turned by the small bases of the trapezoid to the oncoming fluid flow, and the turns of one of the resistive heat-sensitive elements The entrances are located on the supporting frame perpendicular to the direction of fluid movement, the second parallel, and the thermosensitive elements are connected in series in one of the three branches of the measuring circuit, made in the form of a balanced DC bridge, in which the second branch is formed by two identical semiconductor zener diodes, which are simultaneously voltage stabilizers bridge and voltage reference sources, a third temperature-sensitive element is installed in front of the above two thermal real elements in the front part of the cylindrical tubular body at the end of the straightener, made of a material with low heat conductivity, which is closest to the incoming fluid flow, and the thermosensitive elements are included in a bridge circuit consisting of three parallel branches connected between two current-carrying clamps, so that the first branch contains two series-connected resistive thermosensitive elements forming two arms of the bridge circuit, the second branch is formed by two identical With semiconductor zener diodes connected in series, the third branch contains one thermosensitive element, connected in series with the adjustment resistor, information on the fluid velocity is taken between the midpoint of the connection of the two thermosensitive resistive elements included in the first branch, and the midpoint of the series of identical zener diodes connected in series the second branch, taking fluid temperature information is carried out between the midpoint about the included temperature-sensitive element and the adjustment resistor in the third branch of the bridge circuit and the midpoint of the connection of two identical semiconductor zener diodes forming the second branch.

Figure 1 shows a schematic design of the device.

Figure 2 presents the supporting insulating frame with windings of heat-sensitive elements.

Figure 3 presents a circuit diagram of the inclusion of elements of the device.

The proposed device comprises a cylindrical tubular body 1, bearing an insulating frame of electrical and heat-insulating material 2, grooves 3 for laying the turns of the winding 4 of the thermally sensitive element Rt ₁ , grooves 5 for laying the turns of the winding 6 of the thermally sensitive element Rt ₂ , the thermosensitive element Rt ₃ 7, the flow rectifier 8, windows 9 for fluid output, electrical terminals 10 for connecting the temperature-sensitive element Rt ₁ to the measuring circuit, electrical terminals 11 for connecting the heat-sensitive element Rt ₂ to the measuring circuit y, electrical leads 12 for connecting the temperature-sensitive element Rt ₃ to the measuring circuit, supporting the insulating frame 2 with windings 4 and 6 of the temperature-sensitive elements Rt ₁ , Rt ₂ , the turns of which are mutually perpendicular to the grooves 3 and 5, respectively, and have a different effective surface, washed the flow of incident fluid, and the heat-sensitive element Rt ₃ 7 is installed on the jet straightener 8, made of heat-insulating material, in front of the heat-sensitive elements Rt ₁ and Rt ₂ .

The thermosensitive elements Rt ₁ , Rt ₂ and Rt ₃ are included in a special bridge electrical circuit consisting of three parallel branches, where

Rt ₁ , Rt ₂ - thermosensitive elements of the first branch;

Rt ₃ - thermosensitive element of the third branch;

R ₁ - adjusting resistor of the third branch;

VT1, VT2 - identical zener diodes of the second branch;

P1, P2 - information signal recording devices;

R2 is a ballast (current limiting) resistor.

In the cylindrical tubular body 1, a supporting insulating frame 2 of electrical and heat-insulating material with grooves 3 for laying the turns of the winding 4 of the heat-sensitive element Rt ₁ and grooves 5 for laying the turns of the winding 6 of the heat-sensitive element Rt _{2 is} installed. The thermosensitive element Rt ₃ 7 is installed at the end of the straightener 8 closest to the fluid flow ahead of the thermosensitive elements Rt ₁ and Rt ₂ . Connecting thermosensitive elements Rt _1, Rt Rt ₂ and ₃ in the electrical bridge circuit is performed via elektrovyvodov 10, 11 and 12, respectively.

Such a constructive solution allows:

- to provide direct contact between the turns of the thermosensitive elements Rt ₁ and Rt ₂ with the fluid flow, i.e. sharply reduce thermal resistance;

- sharply reduce thermal inertia by reducing the mass of thermosensitive elements Rt ₁ and Rt ₂ ;

- improve accuracy (due to the continuous introduction of appropriate temperature corrections based on the readings of the temperature sensor - the thermosensitive element Rt ₃ ) and the information content of the device (by simultaneously measuring both the speed of the fluid flow and its temperature).

The device operates as follows.

When the supply voltage is turned on, a stable electric voltage U is set between the two current-carrying clamps of the bridge circuit (Fig. 3), equal to the sum of the stabilization voltages U _{st of} two identical and series-connected semiconductor zener diodes VT1 and VT 2, i.e. U = 2U _Art .

The electric current J flowing along the first branch, according to the Joule-Lenz law, forms the amount of heat Q ₁ = 0.24J ² R ₁ T during time T in the heat-sensitive element Rt ₁ , and the amount of heat Q ₂ = 0 in the heat-sensitive element Rt ₂ , 24J ² R ₂ T, with Q ₂ = Q ₁ due to the equality of the values of their resistances R ₁ and R ₂ . The increments in the values of the electrical resistances ΔR ₁ and ΔR _{2 of the} heat-sensitive elements Rt ₁ and Rt ₂ (due to their heating by the flowing current J) will also be equal. Therefore, the potential difference between the positive terminal of the power source and the connection point of the thermosensitive elements Rt ₁ and Rt ₂ having equal values of electrical resistances R ₁ and R ₂ and equal temperature coefficient of resistance, will be half the voltage U.

Similarly, the potential difference between the positive output of the power source and the junction point of the zener diodes VT1 and VT2 is equal to the stabilization voltage of the zener diode VT1 and is half the voltage U.

Therefore, the imbalance signal of the bridge circuit, recorded using the device P1 in the first measuring diagonal (between the first and second branches), will be equal to 0 at any temperature of the fluid or the environment, which are in a stationary state (in static). However, the situation will fundamentally change if the fluid flow starts to move from the open end of the housing 1 through the jet 8 to the temperature-sensitive elements Rt ₁ and Rt ₂ and then to the output of the device through the windows 9 in the housing 1), since the turns of the windings 4 and 6 of the heat-sensitive elements Rt ₁ and Rt ₂ , located mutually perpendicular in the grooves 3 and 4 of the supporting frame 2 (Fig. 2) and washed by the flow of incoming fluid, have different effective surfaces (s ₁ and s _2, respectively) and, therefore, different heat transfer coefficients. So, according to [2], the heat transfer coefficient - λ is determined by the expression

Where

q is the power spent on heating the body, W;

s is the surface area of the body, m ² ;

T _n and T _p - temperature of the heated body and flow.

Thus, an unbalance signal of the bridge circuit is generated, which depends on the rate of heat removal from the heat-sensitive elements Rt ₁ and Rt ₂ and carries information about the fluid flow velocity, and the zero value of the speed signal corresponds to the zero value of the unbalance signal of the bridge circuit at any temperature.

The sensitivity of the proposed device for measuring the speed of fluid flows and their temperature, as well as the range of measured speeds can be controlled by the selection of the parameters of the elements of the bridge circuit and the supply voltage. The implementation of the supporting insulating frame of at least two trapezoidal plates connected crosswise and turned by small trapezoid bases to the flow of a moving fluid helps to ensure uniform sensitivity of the device across the cross section of a cylindrical tubular body.

Figure 2 also shows the thermosensitive element Rt ₃ 7 mounted on the end of the jet straightener 8 closest to the incoming fluid flow (in front of the thermosensitive elements Rt ₁ , Rt ₂ ) and forming, together with the control resistor R1 connected in series, the third branch of the bridge circuit for measuring the temperature of the fluid flow . Such a constructive solution makes it possible to almost completely eliminate the influence of intrinsic heat release of the thermosensitive elements Rt ₁ and Rt ₂ on the accuracy of measuring the temperature of the fluid flow. It should also be noted that the temperature-sensitive element Rt ₃ (in contrast to the elements Rt ₁ and Rt ₂ ) must be high resistance to reduce the error in temperature measurement due to the effect of heating due to the current flowing through it.

The proposed device for measuring the temperature and velocity of fluid flows, made of high-temperature materials (for example, mica or ceramics - for the supporting insulating frame 2; nickel or tungsten - for the windings of thermosensitive elements Rt ₁ , Rt ₂ and Rt ₃ , etc. ) can be used in extreme conditions (at high temperatures and pressures, for example, in gas turbine units for pumping gas, aircraft and rocket engines, etc.).

Another advantage of the device is low thermal inertia, due to direct contact of the turns of the thermosensitive elements Rt ₁ and Rt ₂ with the fluid flow, the speed of which is to be measured.

Information sources:

1. Prospectus of JSC Gazpromgeofizika "Integrated gas-dynamic logging equipment AGDK-42-8".

2. A.S. SU No. 440484, class ЕВВ 47/10, 1974 - prototype.

Claims (1)

A device for measuring the speed and temperature of fluid flows, including a cylindrical tubular body, a straightener installed on the open end of the front of the cylindrical tubular body and a window for the exit of fluid flow at its rear, a heater and a heat-sensitive element installed between the straightener and the windows for fluid flow output, an electric circuit for generating an information signal, a power supply and a recorder, characterized in that it further comprises two thermosensitive resistive elements having equal values of electrical resistances and different working surfaces of the coils, washed by the flow of incoming fluid and located mutually perpendicular to the supporting frame, formed by at least two trapezoidal plates made of electrical insulating and heat-insulating material, facing the small bases of the trapezoid to the incoming fluid flow moreover, the turns of one of the resistive heat-sensitive elements are located on the supporting frame perpendicular to to the fluid flow control board, the second one is parallel, and the thermosensitive elements are connected in series in one of the three branches of the measuring circuit, made in the form of a balanced DC bridge, in which the second branch is formed by two identical semiconductor zener diodes, which are simultaneously the voltage stabilizers of the bridge supply and the voltage reference sources, a third heat-sensitive element is installed in front of the above two heat-sensitive elements in the front of the cylindrical a tubular casing at the end of the straightener, proximal to the incoming fluid flow, made of a material with low thermal conductivity, and the thermosensitive elements are included in a bridge circuit consisting of three parallel branches connected between two current-conducting clamps so that the first branch contains two series-connected resistive thermosensitive element, forming two shoulders of the bridge circuit, the second branch is formed by two identical series-connected semiconductor abilitron, the third branch contains one thermosensitive element connected in series with the adjustment resistor, information on the fluid velocity is carried out between the midpoint of the connection of two resistive thermosensitive elements included in the first branch, and the midpoint of the series connected identical zener diodes included in the second branch, fluid temperature information is carried out between the midpoint of a series-connected thermosensitive element and adjustments full-time resistor in the third branch of the bridge circuit and the midpoint of the connection of two identical semiconductor zener diodes forming the second branch.

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