RU2526898C1 - Coriolis-type meter - Google Patents

Abstract

FIELD: instrumentation.

SUBSTANCE: device incorporates the torsion oscillation exciter arranged between flow rate metering tubes fitted at inlet connector. It is equipped with torsion oscillation receiver arranged between said tubes in outlet connector. It includes the unit designed to calculate torsion oscillation transfer function with torsion oscillation transfer function approximation unit connected to its output. Besides, it incorporates the temperature computation unit. Note here that wideband signal two-channel oscillator generates signal in first channel about resonance frequency of bending vibrations and in second channel - about resonance frequency of torsion oscillations. Note here that second channel output is connected to torsion oscillation exciter. Torsion oscillation receiver is connected with transfer function computation unit input. Inputs of temperature computation unit are connected to appropriate outputs of bending and torsion oscillation approximation unit. Its outputs are connected to appropriate inputs of the unit designed to calculate torsion oscillation transfer function.

EFFECT: higher accuracy and stability of measurements of fluid physical parameters, ie mass flow rate, fluid density, viscosity and temperature.

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Description

The invention relates to the field of measuring equipment and can be used to measure the mass flow rate of liquids flowing through pipelines, for example, during transportation of petroleum products.

Known measuring flowmeters based on the application of the Coriolis force in oscillating tubes through which a fluid flows are used to measure the mass flow of a fluid, its density and some other parameters. The measurement system operates at a specific, usually resonant frequency, of one of the eigenmodes of the oscillations of the measurement oscillation system, consisting of one or more measuring flow tubes of various configurations (US patent No. 4491025, MGZH G01F 1/84, 01/01/1985).

In an ideal device, in the absence of fluid flow through the tube, the oscillations of different points of the measuring (flow) tube occur with the same phase. When a fluid flow appears due to the pressure of moving fluid particles on the walls of the measuring tubes, the vibrations are distorted. The main effect used for measurements is the appearance of a phase difference between the vibrations of different points of the measuring tube. The measured phase difference is proportional to the mass flow of the liquid. The proportionality coefficient is called the calibration flow coefficient.

The disadvantages of this type of measuring devices are associated with the possible appearance of various kinds of slow and fast changes (instabilities) in the parameters of the measuring oscillatory system. Slow instability of the parameters can be associated with a change in the temperature field, the appearance of mechanical stresses in the structure, with a change in the elasticity of the mechanical joints, with a change in the cross section of the measuring tubes, etc. Rapid changes are due to both external vibrations and shocks, and internal sharp changes in the uniformity of the fluid flow (air and gas bubbles, solid and liquid inclusions). With all these factors of influence, the stability and accuracy of measurements carried out in the traditional way, assuming the immutability of the parameters of the oscillatory system, can be violated.

One of the ways to overcome such problems is various quite numerous methods of temperature compensation, mechanical stabilization and balancing, acoustic insulation, made in various forms and combinations.

Measuring instruments can have either a curved tube or a straight flow tube. Those and other types of flow meters need to compensate for changes in the elastic modulus of the flow tube with changes in temperature, external stresses, internal pressure, and for other reasons. Most inventions solve the problem of compensating only part of the adverse factors.

A Coriolis type measuring device is known in which the specially selected shape of the oscillating tube and the fixing points of the tube maximize the acoustic insulation of the oscillating flow tube, increasing the quality factor of the oscillating system. The invention provides good protection against vibrational noise, increases stability, and reduces the power consumption of the measuring device (US patent No. 6477902, IPC G01F 1/84). The disadvantage of this device is the lack of protection from significant sharp changes in the density, pressure and temperature of the flowing fluid.

A Coriolis type measuring device is also known, in which, to stabilize the calibration coefficient, it is proposed to use a special design balancing rod made by casting and having an increased number of fasteners that compensate for changes in the density of the fluid flowing through the flow tube (RF patent No. 2234684, IPC G01F 1/84, January 13, 2003). This invention, like the above, does not provide compensation for a complete set of adverse factors leading to changes in the effective modulus of elasticity of the oscillatory system.

It is known a Coriolis type measuring device in which, in order to solve the problem of minimizing measurement errors arising from the departure of parameters, in particular the bending stiffness of the flow tube, from known initial values, it is proposed to measure the current value of bending stiffness and other parameters and if these values do not coincide, the initial and the current one, signal the presence of an error and adjust the calibration flow coefficient, and the current stiffness is determined by solving the model with one minutes or more degrees of freedom using the direct measurement or rigidity measurement of the transfer function of the frequency response of the oscillating system. Moreover, the method of measuring the mass flow rate of the liquid is based on its proportionality of the phase difference of the oscillations of two different points of a harmonically vibrating flow tube (RF patent No. 2323250, IPC G01F 1/84, 01/14/2006). The disadvantage of this device is a significant measurement error due to the fact that the stiffness measurements are carried out without taking into account the fluid flow through the flow tube, i.e. in conditions of suspension of the mass flow meter.

A Coriolis-type measuring device is known, comprising a housing in the form of a section of a mounted pipeline, an inlet connector connected to the housing, two direct flow tubes providing separation of the flow into two equal flows, an outlet connector through which the flow exits from the flowmeter into the pipeline, an oscillation pathogen located in the center of the flow tubes, the generator, the output of which is connected to the pathogen, two sensor receivers located at equal distances from the pathogen, and two straight flow tubes are mechanically clamped at both ends, forming a mechanical oscillating system, which is located axially symmetrically in the housing, a phase difference meter connected to the outputs of the sensor receivers, the first and second temperature receivers mounted respectively on the housing and on the mechanical oscillating system, a temperature correction unit connected to the input of the phase difference meter to exclude temperature influence on the measurement result (US Patent No. 4768384, IPC G01F 1/84, 09/06/1988).

The disadvantage of this device is that it provides compensation for only a limited number of harmful factors for changes in the elastic modulus of the flow tube. It does not take into account, for example, sufficiently possible simultaneous changes in temperature and pressure in the liquid, variations in the density and viscosity of the medium flowing through the flow tubes, which can also significantly impair the accuracy of the measurement of mass flow.

Closest to the proposed device according to the achieved technical result and technical essence (prototype) is the well-known Coriolis type measuring device, comprising a housing in the form of a section of a mounted pipeline, an inlet connector connected to the housing, two straight flow tubes, which allow the flow to be divided into two equal flows, the outlet a connector through which the flow exits from the flowmeter into the pipeline, a bending vibrator located in the center of the flow tubes, a generator an iroqband signal, the output of which is connected to the pathogen of bending vibrations, two sensor receivers located at equal distances from the pathogen, and two direct flow tubes are mechanically clamped at both ends, forming a mechanical oscillating system, which is located axially symmetrically in the housing, the calculation unit of the transfer function of the bending oscillations, the inputs of which are connected to the outputs of the pathogen and sensor receivers, and the approximation unit of the reference function, connected to the output of the computational unit the transfer function, while the output of the approximation unit by the reference function is connected to the control input of the broadband signal generator (RF patent No. 2457443, IPC G01F 1/84, priority dated January 20, 2011).

The disadvantage of this device is that, due to the absence of a temperature meter, it does not adequately compensate for temperature changes in the phase difference at zero flow and a calibration flow coefficient, as well as the inability to simultaneously measure the viscosity and temperature of the liquid without using temperature sensors .

The technical result of the invention is to increase the accuracy and stability of measurements of the physical parameters of the liquid due to the improved compensation of the temperature drift of the zero phase difference and the calibration flow coefficient, as well as providing the ability to simultaneously measure the flow rate and density of the liquid to measure the viscosity and temperature of the liquid without the use of temperature sensors.

The technical result is achieved due to the fact that the Coriolis type measuring device, comprising a housing in the form of a section of a mounted pipeline, an inlet connector connected to the housing, two direct flow tubes, which allow the flow to be divided into two equal flows, an outlet connector through which the flow exits the flowmeter into a pipeline, a bending vibration pathogen located in the center of the flow tubes, a broadband signal generator, the output of which is connected to the bending vibration pathogen, two seconds sensory receivers located at equal distances from the pathogen, and two straight flow tubes are mechanically clamped at both ends, forming a mechanical oscillating system, which is located axially symmetrically in the housing, the calculation unit of the transfer function of bending vibrations, the inputs of which are connected to the outputs of the pathogen and sensor receivers, and an approximation unit with a reference function connected to the output of the unit for calculating the transfer function of bending vibrations, while the output of the approximation unit of the reference This function is connected to the control input of the broadband signal generator, equipped with a torsional vibration exciter mounted between the flow tubes in the inlet connector, a torsional vibration receiver mounted symmetrically between the flow tubes in the outlet connector, and a torsional vibration transfer function calculation unit with a cool approximation unit connected to its output oscillations, as well as the temperature calculation unit, while the broadband signal generator is made two-channel with the possibility of generating a signal on the first channel in the vicinity of the resonant frequency of bending vibrations, and on the second channel in the vicinity of the resonant frequency of torsional vibrations, the output of the second channel being connected to the torsional vibration exciter, the torsional vibration receiver is connected to the input of the torsional vibration transfer function calculation unit, the inputs of the temperature calculation unit are connected to the corresponding outputs of the approximation units of bending and torsional vibrations, and its outputs are connected to the corresponding inputs odes of blocks for calculating the transfer functions of bending and torsional vibrations.

The invention is illustrated by the drawing, which shows a block diagram of the proposed measuring device of the Coriolis type. The device comprises a housing 1 in the form of a section of a mounted pipeline, an inlet connector 2 connected to the housing 1, flow tubes 3 and 4 through which the flow is divided into two equal flows, an outlet 5 through which the flow exits from the flow meter into the pipeline, two straight flow tubes 3 and 4 are mechanically clamped at both ends, forming a mechanical oscillating system, which is located axially symmetrically in the housing 1, the causative agent of bending vibrations 6, the broadband signal generator 7, made by two-channel providing generation of a signal on the first channel in the vicinity of the resonant frequency of the bending vibrations, and on the second channel, in the vicinity of the resonant frequency of the torsional vibrations, the first output of which is connected to the pathogen of bending vibrations 6, the sensor receivers 8 and 9, located at equal distances from the pathogen 6, in series connected to the calculation unit of the transfer function of the bending vibrations 10 and the approximation unit to the reference function 11, while the outputs of the touch receivers 8 and 9 are connected to the input of the calculation unit before of the exact function 10, and the output of the approximation block by the reference function 11 is connected to the control input of the broadband signal generator 7, as well as a torsional vibration exciter 12 mounted between the flow tubes 3 and 4 in the inlet connector 2, a torsional vibration receiver 13 mounted symmetrically between the flow tubes 3 and 4 in the outlet connector 5, the unit for calculating the transfer function of torsional vibrations 14 with the approximation unit for the channel of torsional vibrations 15 connected to its output, as well as the temperature calculating unit rounds 16, while the output of the second channel of the broadband signal generator 7 is connected to the torsional vibration exciter 12, the torsional vibration receiver 13 is connected to the input of the torsional vibration transfer function calculation unit 14, the inputs of the temperature calculation unit 16 are connected to the corresponding outputs of the bending and torsional vibration approximation blocks 11 and 15, and its outputs are connected to the corresponding inputs of the calculation blocks of the transfer function of the bending and torsional vibrations 10 and 14.

, где A_-(ω), A₊(ω), A(ω)_изг - комплексные Фурье-образы соответствующих сигналов a_-(t), a₊(t), a(t)_изг. Во втором варианте при работе в окрестности второго резонанса предпочтительнее использование функции в виде $$D_2=\frac{A_{-}\left(\omega \right)}{A\left(\omega \right)}$$

. Затем выделяются действительные и мнимые части передаточных функций: ReD_1,2 и ImD_1,2.The device operates as follows. The broadband signal a (t) is _{driven out by a} central frequency approximately equal to one of the resonant frequencies of the first or second mode of bending vibrations of the flow tubes 3 and 4, is fed to the bending oscillator 6 from the first output of the broadband signal generator 7, while in the flow tubes 3 and 4, antiphase bending vibrations are excited, which are a mechanical response to the exciting effect. Sensor receivers 8 and 9 receive bending vibrations, converting them into electrical signals, which are complex functions of the amplitude-frequency response of the oscillatory system, respectively, a ₁ (t) and a ₂ (t). When fluid flow occurs through inlet connector 2, flow tubes 3 and 4 and outlet connector 5, the signals from the receiving sensors 8 and 9 change. The main change caused by the flow is the appearance of the imaginary part in the amplitude-frequency response function, i.e. a signal phase-shifted 90 ° with respect to a signal without flow. These signals and the excitation signal from the pathogen 6 are supplied to the transfer function calculation unit 10. In this block, at the first stage, the sum and difference of the signals taken from the sensor sensors are calculated, A _± (t) = a ₁ ± (t) ± a ₂ (t )). At the second stage, the operation of calculating the transfer function is performed. The functioning of the device is possible in two versions: in the frequency range, including the vicinity of the resonant frequency of the first mode and the second mode. In the first embodiment, in the second stage, the transfer function is calculated, having the form $$D_{\mathrm{one}}=\frac{A_{-}\left(\omega \right)}{A{\left(\omega \right)}_{\mathrm{and}sg}}$$

, where A _- (ω), A ₊ (ω), A (ω) _izg are the complex Fourier transforms of the corresponding signals a _- (t), a ₊ (t), a (t) _izg . In the second embodiment, when working in the vicinity of the second resonance, it is preferable to use a function in the form $$D_2=\frac{A_{-}\left(\omega \right)}{A\left(\omega \right)}$$

. Then, the real and imaginary parts of the transfer functions are distinguished: ReD _1,2 and ImD _1,2 .

In the approximation block 11, on the experimental data presented in the form of ImD _1,2 , the approximation operation is performed using the reference function. The reference function is the result of an analytical solution to the problem of oscillations of a pipe section with a fluid flow inside it (M.A. Mironov, P.A. Pyatakov, A.A. Andreev. Forced vibrations of a pipe with a fluid flow. Akustich. Zh. 2010, v. 56 , No. 5, p.1-9). The reference function used to approximate ImD _1,2 is a function of the circular frequency ω. It has the following form:

, $$\mathrm{Im}{D}_{\mathrm{1,2}}=C+\frac{\left(\mathrm{one}-\frac{{\omega }^2}{{\omega }_{\mathrm{1,2}}}\right)U+B_{\epsilon }}{{\left(\mathrm{one}-\frac{{\omega }^2}{{\omega }_{\mathrm{1,2}}}\right)}^2+{\epsilon }^2}$$

,

where U is a parameter proportional to the mass flow rate, ε is the loss parameter, ω _1,2 are resonant frequencies, B, C are parameters that determine the properties of the oscillatory system. The parameters B, C, U, ω _1,2 , ε, being adjustable, are determined by approximating the obtained data by the reference function using one of the known methods, for example, the least squares method. If, when the mass flow rate changes, the parameters of the oscillatory system change, then this is reflected in the change in the corresponding fitting parameters. During each approximation operation, a complete set of “measured” parameters of the medium and the oscillatory system is formed at the output of the computing unit 11. The calculated value of the resonant frequency is supplied to the broadband signal generation unit 7 for adjusting the center frequency in accordance with the equality F ₀ = ω _1,2 / 2π.

. В блоке 15 выполняется аппроксимация модуля вычисленной передаточной функции |D₃| с помощью эталонной функции, соответствующей простейшей колебательной системе. Подгоночные параметры, соответствующие резонансной частоте ω₂ и параметру потерь ε₃, вычисленные при аппроксимации методом наименьших квадратов, определяют в соответствии с калибровочными зависимостями первое приближение к температуре и вязкость жидкости.Similar transformations are performed in the channel of torsional vibrations. The broadband signal a (t) is _steep with a central frequency approximately equal to the resonant frequency of the first mode of torsional vibrations of the flow tubes 3 and 4, fed to the torsional vibration exciter 12 from the second output of the broadband signal generator 7, while antiphase torsional waves are excited in the flow tubes 3 and 4 oscillations, which are a mechanical response to an exciting effect. The sensor receiver 13 receives torsional vibrations, converting them into an electrical signal a ₃ (t). When a fluid flow occurs, the signal from the receiving sensor 13 changes. Changes in the electrical signal caused by the flow, in contrast to changes in the signal in the channel of bending vibrations, do not depend on the flow velocity, but are only a consequence of changes in temperature, viscosity and density of the liquid. In the calculation function of the transfer function 14, the operations of frequency filtering are performed, the complex Fourier transforms are calculated A (ω) _cool , A ₃ (ω) signals a (t) _cool , a ₃ (t) and the transfer function of the torsional vibration channel $$D_3=\frac{A_3\left(\omega \right)}{A_{\mathrm{to}R\mathrm{at}t}\left(\omega \right)}$$

. In block 15, the approximation of the module of the calculated transfer function | D ₃ | using the reference function corresponding to the simplest oscillatory system. The fitting parameters corresponding to the resonant frequency ω ₂ and the loss parameter ε ₃ calculated by the least squares approximation determine the first approximation to temperature and the viscosity of the liquid in accordance with the calibration dependences.

. Коэффициент пропорциональности находится при калибровке измерительного устройства. Найденное таким образом значение температуры используется для введения компенсаций при температурном дрейфе фазы и температурном изменении расходного коэффициента.The density parameter ρ measured in the channel for processing bending vibrations and the viscosity parameter η in the channel for processing torsional vibrations are used in block 16 to calculate the correction of the second approximation to the temperature value. This correction takes into account possible changes in the density and viscosity of the liquid and is proportional to $$\sqrt{\rho \eta }$$

. The proportionality coefficient is found during calibration of the measuring device. The temperature value found in this way is used to introduce compensations for the temperature phase drift and the temperature change in the flow coefficient.

The invention allows to solve two problems. Firstly, to expand the functionality of the measuring device, taken as a prototype, by adding to the functions of measuring the mass flow and density also measuring the parameters of viscosity and temperature. Secondly, to provide improved temperature compensation of the mass flow value for the Coriolis type measuring device, without using temperature sensors.

Claims (1)

Coriolis type measuring device, comprising a housing in the form of a section of a mounted pipeline, an inlet connector connected to the housing, two direct flow tubes providing separation of the flow into two equal flows, an outlet connector through which the flow exits from the flowmeter into the pipeline, a bending exciter located in the center of the flow tubes, a broadband signal generator, the output of which is connected to the pathogen of bending vibrations, two sensor receivers located at equal distances si from the pathogen, and two straight flow tubes are mechanically clamped at both ends, forming a mechanical oscillating system, which is located axially symmetrically in the housing, a unit for calculating the transfer function of bending vibrations, the inputs of which are connected to the outputs of the pathogen and sensor receivers, and an approximation unit with a reference function, connected to the output of the unit for calculating the transfer function of bending vibrations, while the output of the approximation unit by the reference function is connected to the control input of the generator and a broadband signal, characterized in that it is provided with a torsional vibration exciter mounted between the flow tubes in the inlet connector, a torsional vibration receiver mounted between the flow tubes in the outlet connector, a torsional vibration transfer function calculation unit with an approximation torsional transfer function approximation unit connected to its output oscillations, as well as a temperature calculation unit, while the broadband signal generator is made dual-channel with generating a signal on the first channel in the vicinity of the resonant frequency of the bending vibrations, and on the second channel, in the vicinity of the resonant frequency of the torsional vibrations, the output of the second channel being connected to the torsional vibration exciter, the torsional vibration receiver connected to the input of the calculation unit of the torsional vibration transfer function, the inputs of the calculation unit temperatures are connected to the corresponding outputs of the approximation blocks of bending and torsional vibrations, and its outputs are connected to the corresponding inputs of the calculation blocks the transmission function of bending and torsional vibrations.