RU200523U1 - FLOW RATE SENSOR - Google Patents

Abstract

The utility model relates to the field of measuring technology, namely to flow velocity sensors, and can be used to measure the flow vector of exhaust gases, including those containing dust, in pipes based on the Doppler effect. The flow velocity sensor contains a holder in the form of a pipe segment and a measuring unit installed at its end in the form of a metal disk with a flat surface, which closes its end. Inside the holes in the disc, four piezoelectric elements are located flush with its surface, evenly along its perimeter. The utility model makes it possible to increase the strength of the speed sensor, significantly expanding the range of its possible application. 2 wp f-ly, 3 dwg

Description

The utility model relates to the field of measuring technology, namely, flow velocity sensors, and can be used to measure the flow vector of exhaust gases, including those containing dust, in pipes based on the Doppler effect.

An ultrasonic wind speed sensor is known from the prior art, comprising a holder and a measuring unit mounted on its end, along the perimeter of which four piezoelements are evenly located (see patent JP5029993, class G01P 13/00, publ. 19.09.2012). The main disadvantage of the known device is its fragility and limited use. In addition, the measurement of the air flow velocity is not accurate and reliable enough due to the occurrence of vortices and turbulence in the flow, which is due to the presence of rods on its path, on which piezoelectric elements are fixed.

A technical problem is the elimination of these shortcomings and the creation of a universal device with a wide range of possible applications, which allows measurements of both low and high flow rates, including supersonic ones, without the risk of damage to the sensitive elements of the sensor, as well as increasing the reliability of the speed measurement and ensuring the possibility measurements of high-speed gas flows after a gas turbine with temperatures up to 950 ° K. The technical result consists in increasing the strength of the flow velocity sensor. The problem is solved, and the technical result is achieved by the fact that in the flow velocity sensor containing a holder and a measuring unit installed at its end, along the perimeter of which four piezoelements are evenly located, said holder is made in the form of a pipe segment, and the measuring unit is in the form of a disk with a flat surface covering its end, and the piezoelectric elements are located inside the holes in the disk flush with its surface. Piezoelectric elements can be made in the form of ceramic discs or ceramic tubes filled with solder. The distance between the centers of the opposite piezoelectric elements is preferably 10 to 500 mm.

Figure 1 shows the proposed sensor in section (arrows x, y indicate the direction of the coordinate axes),

figure 2 is a top view;

figure 3 - its location in the stream.

The measurement of gas velocity is very important for determining the volume of exhaust gases in a production environment, as well as for determining the volume of exhaust gases during vehicle operation.

The proposed flow rate sensor is a holder in the form of a pipe segment 1 and a measuring unit in the form of a metal disk 2 with a flat surface, covering the end of the pipe 1. The surface of the disk 2 has a roughness of at least Ra 6.3 microns. Four holes are made evenly along the perimeter of the disk 2, inside each of which a piezoelectric element 3-6 is located flush with the surface of the disk 2. The distance L between the centers of the opposite piezoelectric elements 3-6 ranges from 10 to 500 mm.

For the manufacture of the proposed sensor, piezoelectric elements 3-6 are used with a Curie point of at least 2 times the working temperature of the gas of the measured flow 7. Piezoelements 3-6 can be made of ceramics grade TsTS-26 in the form of a disk with a diameter of 5 mm and a thickness of 1 mm ( manufactured by JSC "NII ELPA") with a maximum operating temperature of up to 520 K, operating in the mode of the 1st overtone of thickness vibrations for gas flows with a temperature of up to 470 K. It is also allowed to use piezoelectric elements 3-6 made of ceramics of the TNV-1 brand in the form of a tube outer diameter 6.35 mm, inner diameter 4.9 mm and height 6.35 mm (manufactured by JSC NII ELPA), operating in longitudinal vibration mode to measure high-speed gas flows after a gas turbine with temperatures up to 950 K. The tube opening is filled in this case solder PMF-7 or a similar material with a melting point of 710 to 850 ° C.

The device works as follows.

The proposed speed sensor is placed in stream 7 so that the gas moves parallel to the plane of the disk 2. To measure the flow velocity, voltage pulses are sequentially applied to piezoelectric elements 3-6, the time of arrival of the pulse to other piezoelements is measured, and then, analyzing the time obtained, the value of the modulus is determined and the direction of the gas velocity vector.

The projections of the velocity V _x , V _y of the exhaust gas flow are determined by the formulas

V _x = L / (T ₃₅ -T ₅₃ ) / 2,

V _y = L / (T ₄₆ -T ₆₄ ) / 2,

where T ₃₅ is the propagation time of the pressure pulse from the piezoelectric element 3 to the piezoelectric element 5;

T ₅₃ - the propagation time of the pressure pulse from the piezoelectric element 5 to the piezoelectric element 3;

T ₄₆ - the propagation time of the pressure pulse from the piezoelectric element 4 to the piezoelectric element 6;

T ₆₄ is the propagation time of the pressure pulse from the piezoelectric element 6 to the piezoelectric element 4.

Example

If the distance L is 20 mm, T ₃₅ = 60 μs, T ₅₃ = 57 μs, T ₄₆ = 59 μs; T ₆₄ = 59 μs, then the flow velocity is 10 m / s, and the direction coincides with the x axis.

Due to the described design features, the proposed device makes it possible to measure flow rates, including high-temperature flows with a gas velocity of up to 300 m / s. Since the measuring surface of the sensor is smooth and has no protruding elements, it does not create additional resistance to flow, does not generate gas vortices and is not sensitive to abrasive wear. The working gas temperature for which the proposed device is designed during operation can vary from 100 to 200 ° C (from 373 to 473 K). Thus, the utility model makes it possible to increase the strength of the speed sensor, significantly expanding the range of its possible application.

Claims (3)

1. A flow velocity sensor containing a holder and a measuring unit installed at its end, along the perimeter of which four piezoelectric elements are evenly located, characterized in that the holder is made in the form of a pipe segment, and the measuring unit is in the form of a metal disk with a flat surface, covering its end , and the piezoelectric elements are located inside the holes in the disk, flush with its surface. 2. The sensor according to claim 1, characterized in that the piezoelectric elements are made in the form of ceramic discs or ceramic tubes filled with solder. 3. The sensor according to claim 1, characterized in that the distance between the centers of the opposite piezoelectric elements is from 10 mm to 500 mm.

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