RU2847453C1 - Inertial method of medium mass flow rate measuring and device for its implementation - Google Patents

Abstract

FIELD: measuring.

SUBSTANCE: invention relates to measurement of flow rate of medium – liquid or gas, namely mass flow rate of medium. To measure mass flow rate of a medium moving in a pipeline, a certain amount of medium is added to the stream at a certain section of the pipeline or a certain amount of medium is extracted from the stream. Said addition or extraction of the medium is carried out by a flow with a constant direction. Volume flow rate or mass flow rate of the stream with which said addition or extraction is carried out is measured. Pressure difference is measured between two points located one upstream of said section and the other downstream thereof. Then, based on measured pressure drop and measured flow rate of added or withdrawn flow, mass flow rate of medium flow is determined by means of mathematical operations. Device for implementing the method (fig. 1) includes main pipeline 1, additional pipeline 2 with flow meter 3 installed thereon, means 4 providing medium movement along additional pipeline 2, differential pressure sensor 5, connected to the main pipeline at two points, one of which is located upstream of said section and the other downstream thereof.

EFFECT: measurement of mass flow rate of medium flow in pipelines of both small diameter up to 150 mm and large diameter over 150 mm at maintaining or enlarging the range of measurement, at maintaining or reducing measurement error and at reduction of structural complexity of the device.

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Description

Field of technology to which the invention relates

The invention relates to the field of measuring the flow rate of a medium - liquid or gas, namely the mass flow rate of the medium.

State of the art

Currently, there are various methods and devices for measuring the mass flow rate of a medium. To illustrate the current level of technology, we will present several analogues of the claimed invention. Known are mass flow meters based on measuring the Coriolis force in a liquid moving through a pipeline, which performs transverse oscillations together with the pipeline - vibrating Coriolis flow meters. One of such flow meters is described in the patent document: Method and apparatus for mass flow rate measurement. US Patent No. 4,109,524, 1978 [1]. The operating principle and design of flow meters of this type are discussed in detail in the reference book: Kremlevsky P.P. Flow meters and quantity counters, 1989 [2, pp. 348, 354]. The operating principle is that the pipeline through which the measured liquid moves is imparted forced transverse oscillations. In this case, the liquid particles are acted upon by the Coriolis force of inertia, which depends on the velocity of the particles. As a result, a phase shift in the oscillations between the initial and final sections of the oscillating pipeline occurs, proportional to the mass flow rate of the fluid flow. This phase shift is measured using one method or another, and then the mass flow rate of the fluid flow is determined through mathematical calculations. The disadvantages of such devices include the need to ensure sufficient flexibility in the measuring section of the pipeline, which complicates the manufacture of flowmeters for pipeline diameters greater than 150 mm. For example, the description of another similar device, cited in patent document [3] (cited below), states that "currently manufactured mass flowmeters based on the Coriolis effect are not capable of measuring full flows in pipelines with diameters exceeding 150 mm."

An invention is known for overcoming the said drawback: A bypass flow meter. Patent RU No. 2181477 [3]. This device comprises an inlet for separating a portion of the flow in a pipeline and directing it to a flow meter, and an outlet for returning the material passing through the flow meter, both located inside the pipeline. The outlet for the material is connected to the pipeline at a section where an increase in the flow velocity occurs, achieved using a Venturi tube, in the area of its throat. A means for measuring the pressure drop is connected to the inlet and outlet, by which the viscosity of the material is determined. In this invention, the total mass flow in the pipeline is determined by adding the mass flow through the flow meter to the mass flow through the Venturi tube. According to the description of the invention, the flow through the Venturi tube in this invention is determined by multiplying the flow velocity in the Venturi tube by its cross-sectional area in the throat area and by the density of the material. The flow velocity in the throat of the Venturi tube is determined by solving an equation defining the ratio of the flow velocities through the flowmeter and through the Venturi tube, assuming this ratio to be dependent in a known manner on the density, viscosity, and flow velocity of the measured medium. The differential pressure sensor (differential manometer) in this invention is used to calculate the flow viscosity by measuring the pressure drop across the flowmeter. A disadvantage of this invention is that only a small portion of the total flow, diverted to a flowmeter installed on an additional pipeline, is directly measured, while the bulk of the total flow passes through the Venturi tube without actual mass flow measurement. Thus, the mass flow rate through the Venturi tube is determined by calculation based on the flow velocity in the throat, which, in turn, is also determined by calculation. Consequently, the error in determining the mass flow rate in a Venturi tube depends both on the accuracy of the mathematical equations used to determine the velocity and on the correspondence between the mathematical model for which these equations are derived and the actual flow regime of the medium. Consequently, the error in measuring the mass flow rate according to this invention can be high.

A method for determining density and mass flow rate is also known, described in a patent document: Inertial method for determining the density and/or mass flow rate of a liquid (gas). Patent No. 2445602 [4]. According to this method, a liquid or gas moving along a straight section of a pipeline is subjected to cyclic longitudinal alternating action. This action causes a change in the longitudinal velocity of the liquid, the appearance of inertial forces and a pressure difference. Based on this pressure difference, the mass flow rate of the medium flow and its density are determined. The pipeline has a constant cross-section, and the said alternating action is carried out in an additional pipeline through the use of a special piston. In this invention, the full flow moving along the pipeline is measured, therefore, the mass flow rate of the flow can be measured with a small error. The disadvantage of this invention is the technical complexity and high cost of its implementation, due to the following features. The device for implementing the invention includes a piston oscillating in the medium of the measured liquid. There is a need for design measures to minimize wear on the piston's rubbing surfaces and the surrounding pipeline during long-term operation, as well as design measures to seal the piston. Design measures must also be taken to ensure piston actuation and seal the piston drive mechanism, taking into account the potential high pressure of the medium in the pipeline. Finally, according to the description of the invention, two high-precision differential pressure sensors are required to measure mass flow, and, if density measurement is also required, three high-precision differential pressure sensors. These features and associated design measures ultimately lead to increased complexity and cost of the device implementing the method [4].

Disclosure of the essence of the invention

The claimed method is closest in its operating principle to the invention described in the patent document [4], which is the closest analogue. The conducted studies show that for the purposes of measuring mass flow rate it is possible to use not only an alternating-sign effect on the liquid, but also an effect of a constant sign. In the works: Zhilyaev O.V. Application of an approach based on the dynamics of a variable-mass particle to improving the mathematical model of an inertial flowmeter [5], Zhilyaev O.V. Using a model of a variable-mass body in constructing a mathematical model of an inertial flowmeter [6] a mathematical model is presented that describes the occurrence of a pressure drop between points of the medium in a pipeline during the interaction of two flows. To explain the essence of the invention, let us turn to its diagram in the drawing Fig. 1.

The device for implementing the invention includes a main pipeline 1, an additional pipeline 2, a flow meter 3 installed on the additional pipeline 2, a means 4 of one or another operating principle ensuring the movement of a medium along the additional pipeline 2, a differential pressure sensor (differential pressure) 5. The main 1 and additional 2 pipelines are connected at a certain section A. The differential pressure sensor 5 is connected to the main pipeline at points located one before the section A of the connection of the main and additional pipelines 1 and 2, and the other after the said section. Thus, one of the connection points of the differential pressure sensor 5 is connected to the region of movement of the main undisturbed flow, and the other to the region of joint movement of the main and additional flows.

The device operates as follows. The main flow of the medium moves through the main pipeline 1 with a mass flow rate , subject to measurement. To carry out the measurement, the medium must move in the additional pipeline 2 in one direction or another. This movement of the medium is ensured by the action of the means 4. Depending on the direction of flow in the additional pipeline, mixing or separation of the two flows occurs in the area of the junction of pipelines A. For the sake of clarity, let us consider the direction of the additional flow as shown in the drawing in Fig. 1 - that is, corresponding to the mixing of the two flows in section A. Flow meter 3 measures the mass or volumetric Q _{V 2} flow rate of the medium in the additional pipeline 2. Flow meter 3 can be of the volumetric, chamber type, or vortex, ultrasonic, Coriolis, or any other type.

Between the points of the flow, one of which is located above the flow mixing section A and the other below it, a pressure difference Δ p ₁ arises. The differential pressure sensor 5 measures this pressure difference. In accordance with the formulas of the mathematical model given in works [5, 6], the pressure difference Δ p ₁ in the case shown in the drawing in Fig. 1 is determined by the formula:

, (1)

Where - mass flow rate of the medium in the additional pipeline 2, ρ - density of the medium, S - cross-sectional area of the main pipeline 1.

The claimed method is based on the beneficial use of this pressure differential for measuring the mass flow rate of a fluid flow. Expressing the mass flow rate of the main flow from formula (1), we obtain a calculation formula for calculating this value:

. (2)

Next is formula (2) for calculating the mass flow rate of the main flow can be used in different ways, depending on the type of flow meter 3 used in the device according to the diagram in Fig. 1, and its measured value. If a Coriolis mass flow meter is used as flow meter 3, the measured value of which is mass flow flow in pipeline 2, then formula (2) is used directly. If a flow meter of a different type is used as flow meter 3, the measured value of which is the volumetric flow rate of the medium Q _{V 2} , then it is advisable to calculate the mass flow rate as follows. We express the mass flow rate in formula (2) through the volumetric flow rate and density of the medium:

;

. (3)

Formula (3) allows calculating the mass flow rate of the main flow based on the measured pressure drop Δ p ₁ and the measured value of the volumetric flow rate of the additional flow Q _{V 2} .

The average density of the medium, ρ, characteristic of the flowmeter installation location and, in most cases, known with varying degrees of accuracy, can be used as the density of the medium. Alternatively, density can be measured using additional specialized devices not specified in the present invention. In particular, if a Coriolis flowmeter with density measurement capability is used as the flowmeter 3, the density of the medium, ρ, measured using it can be used.

Thus, to measure the mass flow rate of a medium flow, a certain flow of medium is added to the pipeline at a certain section of the pipeline, or a certain flow of medium is withdrawn from the pipeline. The said addition or withdrawal of the medium is carried out due to a flow of a constant direction. The volumetric or mass flow rate of the flow with which the said addition or withdrawal is carried out is measured. The pressure difference between two points, one located upstream and the other downstream of the said section along the flow, is measured. Then, based on the measured pressure difference and the measured flow rate of the added or withdrawn flow, the mass flow rate of the medium flow is determined using mathematical operations. The device for implementing the method (Fig. 1) includes a main pipeline 1, an additional pipeline 2 with a flow meter 3 installed thereon, a means 4 of one or another operating principle ensuring the movement of the medium along the additional pipeline 2, a pressure difference (differential pressure) sensor 5.

Brief description of the drawings

Fig. 1 - diagram of a device for implementing the method.

Fig. 2 - diagram of variant 2 of the device for implementing the method.

Fig. 3 - diagram of variant 3 of the device for implementing the method.

Fig. 4 - diagram of variant 4 of the device for implementing the method.

Implementation of the invention

The implementation of the claimed measurement method, in addition to the device itself described in the drawing of Fig. 1, is possible in the form of various versions of devices that implement the measurement principle described above and include the circuit in the drawing of Fig. 1. Let us consider some circuits of the meter for this method.

The composition of the device according to variant 2 is shown in the drawing Fig. 2.

The device according to option 2 includes a main pipeline 1, an additional pipeline 2, a flow meter 3, a pump 4, a differential pressure sensor 5 or 6.

The main pipeline 1 contains a flow of medium, the mass flow of which is is subject to measurement. Additional pipeline 2 is a pipeline connected to the main pipeline 1 in two sections A and B. Flow meter 3 is designed to measure the volumetric or mass flow rate of the medium in additional pipeline 2. Pump 4 is a means for moving liquid in the additional pipeline in the shown direction. Differential pressure sensor 5 is designed to measure the pressure difference between points, one of which lies before the section of separation of the main and additional flows A , and the other after the specified section. Similarly, differential pressure sensor 6 is designed to measure the pressure difference between points, one of which lies before the section of mixing of the main and additional flows B , and the other after the specified section. For the operation of the device and the measurement of the mass flow rate, one differential pressure sensor 5 or 6 is sufficient; in the diagram, they are both shown simultaneously in order to explain its operation in two versions.

The device according to variant 2 operates as follows. The main pipeline 1 is filled with a medium (liquid) moving in the direction indicated by the arrow with a mass flow rate , subject to measurement. To measure the mass flow rate, pump 4 is turned on, thereby inducing fluid movement in additional pipeline 2 in the direction indicated by the arrow. Fluid enters the additional pipeline from inlet A , passes through flow meter 3, pump 4, and then returns to the main pipeline 1 through outlet B. Using flow meter 3, the mass flow rate of the additional flow is measured. or the volumetric flow rate of the additional flow Q _{V 2} . As indicated above, between points in the flow, one of which is located before the flow separation section A and the other after this section, a pressure difference Δ p ₁ arises. Similarly, a pressure difference Δ p ₂ arises between points in the flow, one of which is located before the flow mixing section B and the other after this section. The pressure difference Δ p ₁ is determined by the formula:

, (4)

Where - mass flow rate of the medium in additional pipeline 2, ρ - density of the medium, S - cross-sectional area of pipeline 1.

Further mathematical transformations are similar to those given above. From formula (4), we express the value of the mass flow rate of the main flow :

. (5)

If a Coriolis mass flowmeter is used as flow meter 3, the measured value of which is the mass flow rate in pipeline 2, then formula (5) is used directly. If a positive displacement chamber flowmeter or another type of flowmeter is used as flow meter 3, the measured value of which is the volumetric flow rate Q _{V 2} , then we perform a transformation similar to that indicated in the derivation of formula (3). We express the mass flow rate in formula (5) through the volumetric flow rate and density of the medium:

;

. (6)

Formula (6) allows calculating the mass flow rate of the main flow based on the measured pressure drop Δ p ₁ and the measured value of the volumetric flow rate of the additional flow Q _{V 2} .

For the case of using differential pressure sensor 6, we will write out calculation formulas for determining the mass flow rate based on the pressure drop Δ p ₂ . The pressure drop Δ p ₂ is determined by the formula:

. (7)

Similar to the previous one, we express the mass flow rate of the main flow from formula (7):

. (8)

Formula (8) can be used directly if a Coriolis flowmeter is used as flow meter 3, the measured value of which is the mass flow rate in pipeline 2. If a positive displacement chamber flow meter or another type of flow meter is used as flow meter 3, the measured value of which is the volumetric flow rate Q _{V 2} , then we perform a transformation similar to that indicated in the derivation of formula (3). We express the mass flow rate in formula (8) through the volumetric flow rate and density of the medium:

;

. (9)

The composition of the device according to variant 3 is shown in the drawing Fig. 3.

The circuit diagram for option 3 is similar in composition and operating principle to the circuit diagram for option 2. The difference lies in the direction of delivery of the pump installed in additional pipeline 2. Let's write out the calculation formulas for the circuit diagram for option 3. The pressure drops on differential sensors 5 and 6 are equal to:

; (10)

. (11)

Expressing the value of the mass flow rate of the main flow from formulas (10, 11), we obtain calculation formulas for calculating the mass flow rate of the main flow:

; (12) ; (12)

. (13)

Formulas (12) and (13) should be used in the case of using a Coriolis mass flow meter as flow meter 3 (Fig. 3), the measured value of which is the mass flow rate of the medium.

Similar to the derivation of formulas (3, 6), we express the mass flow rate in the additional pipeline through the volumetric flow rate:

;

; (14)

. (15)

Formulas (14) and (15) should be used in the case of using a volumetric flow meter of one type or another as the flow meter 3 (Fig. 3), the measured value of which is the volumetric flow rate.

The composition of the device according to variant 4 is shown in the drawing Fig. 4.

The device according to variant 4 includes a main pipeline 1, an additional pipeline 2, a flow meter 3, a restriction device of one type or another, in particular a pipe or a Venturi nozzle 4, a pressure drop sensor (differential pressure) 5. The main pipeline 1 contains a flow of a medium, the mass flow of which is subject to measurement. The additional pipeline 2 is a pipeline connected to the main pipeline 1 in two sections A and B, where section B corresponds to the neck of the Venturi tube. The flow meter 3 is intended to measure the volumetric or mass flow rate of the medium in the additional pipeline 2. The narrowing device, in particular the nozzle or Venturi tube 4, is a means for implementing the movement of liquid in the additional pipeline in the shown direction from the inlet section A to the outlet section B. The differential pressure sensor 5 is intended to measure the difference in pressure between points, one of which lies before the section of separation of the main and additional flows A , and the other after it. The composition of the device according to the diagram of variant 4 (Fig. 4) is close to the composition of the invention described in the patent document [3], but the devices differ in the connection diagram of the differential pressure sensor pos. 5, in its functional purpose as part of the device, and in the operating principle of the entire device.

The device according to variant 4 operates as follows. The main pipeline 1 is filled with a medium (liquid) moving in the direction indicated by the arrow with a mass flow rate . Since the cross-sectional area of the pipeline is different in sections A and B , then according to Bernoulli's law, a pressure difference appears between sections A and B. Further, since the main and additional pipelines 1 and 2 are connected in sections A and B , due to this pressure difference, a flow appears in the additional pipeline. The liquid enters the additional pipeline from inlet A , passes through flow meter 3, and then returns to the main pipeline 1 through outlet B. Using flow meter 3, the mass flow rate of the additional flow is measured. or the volumetric flow rate of the additional flow Q _V2 . As indicated above, between the points of the flow, one of which is located above the flow separation region A, and the other below this region, a pressure difference Δρ ₁ arises. The pressure difference Δρ ₁ is determined by the formula:

, (16)

Where - mass flow rate of the medium in additional pipeline 2, ρ - density of the medium, S - cross-sectional area of pipeline 1.

From formula (16) we can express the value of the mass flow rate of the main flow t ₀ :

(17)

Next is formula (17) for calculating the mass flow rate of the main flow can be used in different ways, depending on the type of flow meter 3 used in the circuit of variant 4, and its measured value. If a Coriolis mass flow meter is used as flow meter 3, the measured value of which is the mass flow rate of the flow in pipeline 2, then formula (17) is used directly. If a flow meter of a different type is used as flow meter 3, the measured value of which is the volumetric flow rate of the medium Q _V2 , then we perform a further transformation. We express the mass flow in formula (17) through the volumetric flow rate and density of the medium:

The technical result of the invention is the measurement of the mass flow rate of a medium in pipelines of both small diameters up to 150 mm and large diameters over 150 mm while maintaining or increasing the measurement range, while maintaining or reducing the measurement error and while reducing the design complexity and cost of the device.

The specified technical result is achieved due to several differences from the given analogues.

Compared to analogs described in documents [1, 2], the claimed method provides a significant expansion of the flow measurement range and an increase in the largest pipeline diameter on which it can be used, by eliminating the need for bending vibrations of the pipeline.

Compared to the analogue described in document [3], the claimed method provides for an expansion of the flow measurement range by eliminating the quadratic nature of the dependence of the measured pressure drop, which affects the determination of the mass flow rate, on the mass flow rate, and by replacing the said dependence with a linear dependence.

Compared to the analog described in document [3], the claimed method reduces the error in measuring the mass flow rate of a medium flow by directly measuring the pressure drop in a section related to the total flow, and by using a simple functional relationship between the influencing quantities and the desired value of the mass flow rate of the medium flow. In the description of the said analog, direct measurement of the pressure drop is performed on a section of the flow to determine the viscosity of the medium, and to determine the mass flow rate of the specified section of the flow, a multi-stage calculation is performed based on a complex relationship, and then the mass flow rate of the total flow is determined as the sum of the flow rates of the specified section of the flow and the measured flow rate through the flow meter.

Compared with the analogue described in the patent document [4], the claimed method ensures a reduction in the design complexity and cost of the flow meter device by eliminating the alternating oscillatory nature of the effect on the liquid in the pipelines, and as a consequence, eliminating the piston, piston drive, piston sealing devices and drive from the design of the device.

List of documents

1. Method and apparatus for mass flow rate measurement. US Patent No. 4109524, 1978.

2. Kremlevskiy P.P. Flow meters and quantity counters: Handbook. - 4th ed., revised and enlarged. - L: Mashinostroenie, 1989, p. 354.

3. Bypass-type flow meter Patent RU No. 2181477, published 20.04.2002, Bulletin No. 11.

4. Patent No. 2445602 C2 Russian Federation, IPC G01N 9/00. Inertial method for determining the density and (or) mass flow rate of a liquid (gas) / V.I. Chudin, (O.V. Zhilyaev, P.V. Ushkov; applicant Scientific and Production Limited Liability Company "New Well Operation Technologies" (OOO NPO NTES). No. 2010121065/28: declared 24.05.2010, published 20.03.2012.

5. Zhilyaev, O. V. Application of an approach based on the dynamics of a particle of variable mass to improving the mathematical model of an inertial flowmeter / O. V. Zhilyaev, V. N. Kovalnogov // Automation of control processes. - 2023. - No. 2 (72). - P. 44-52. - DOI 10.35752/1991-2927-2023_2_72_44. - EDN OTKRBH.

6. Zhilyaev O.V. Using a model of a body with variable mass in constructing a mathematical model of an inertial flowmeter / In the collection of scientific articles following the results of the International Scientific Forum "Science and Innovation - Modern Concepts (Moscow, June 20, 2024). Moscow: Infinity Publishing House, 2024., pp. 129-139.

Claims (2)

1. A method for measuring the mass flow rate of a medium moving through a pipeline, which involves adding a certain amount of medium to the flow or removing a certain amount of medium from the flow at a certain section of the pipeline, measuring the volumetric or mass flow rate of the flow with which said addition or removal of the medium is carried out, measuring the pressure drop between two points, one located upstream of said section and the other downstream of it, and then, based on the measured pressure drop and the measured flow rate of the added or removed flow, using mathematical operations, determining the mass flow rate of the medium, characterized in that said addition or removal of the medium is carried out by a flow of constant direction. 2. A device for measuring the mass flow rate of a medium, including a main pipeline, an additional pipeline, wherein the main and additional pipelines are connected at a certain section, a flow meter installed on the additional pipeline, a means for causing a flow of medium in a constant direction through the additional pipeline, a differential pressure sensor, characterized in that the differential pressure sensor is connected to the main pipeline at two points, one of which is located upstream of the said section, and the other downstream of it.