SU1093956A1 - Method and device for measuring pulsation of conductivity of liquid turbulent flow - Google Patents

Abstract

1. A method for measuring the pulsations of electrical conductivity of a turbulent fluid flow, which consists in converting the conductivity of the test liquid into an electrical signal with automatic compensation of the constant component of the signal and measuring the variable component, characterized in that, in order to improve the accuracy, sensitivity and range of measurements, additionally Q transforms the turbulent fluid flow in the laminary S, and its conductivities in the turbulent and limiting zones transform into electrically signals and their difference determined value bullets conductivity turbulent flow can be measured directly.

Description

WITH

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2. A device for measuring pulsations of electrical conduction of turbulent fluid flow, comprising a four-shouldered ac bridge with a conductivity sensor in the measuring arm, a power source and a recorder, characterized in that, in order to improve the accuracy, expand the measuring range and simplify the design, the device further comprises a conductivity sensor installed in the balancing arm of the bridge, and a hydrodynamic converter of turbulent flows into a laminar flow, installed between tchikami.

The invention is related to the hydrodynamic & physical measurements and can be used to study processes of heat and mass transfer in turbulent flows, in metrology when creating exemplary means of measuring pulsations, and also in industry in automated systems for monitoring the composition and properties of liquid and gaseous substances. A known method for measuring the conductivity pulsations of the electrical conductivity of the SEEP) turbulent flow uses {CONSTANT conversion of the conductivity of the local volume of the test medium into an electrical signal with subsequent allocation of a variable component proportional to the measured value. The devices implemented by this method are a four-way AC ac bridge with a pulsation sensor in one of the arms. The principle of operation of these devices is based on the measurement of the instantaneous value of the SEC in the local volume of the turbulent flow. When selecting the resistance in the balancing shoulder of the bridge, the conductivity is equivalent to the average fluorescence intensity of the bridge, the signal of the bridge dissipation is approximately proportional to the deviations (pulsations) from the average background fluorescence density, and the magnitude of the pulsations of the fluorescent fluorescence of turbulent flow Cll. The disadvantages of the known technical solutions are low accuracy, sensitivity and narrow measurement range. This is due to the physical non-identical conductivity of the fluid (conductor of the second kind) and the equivalent conductivity of the balancing arm (conductor of the first type), as well as the influence on the measurement results of changes in the background characteristics of turbulent flow / temperature, concentration, velocity) .; There is a known method for measuring the pulsations of electrical conductivity of a turbulent flow, which consists in converting the conductivity of the liquid under investigation into an electrical signal with automatic compensation of a constant component of the signal and measuring the variable component (2. A device is known that implements the well-known f23 high frequency AC bridge; the grueling shoulder of which the contact sensor of the pulsation of the CEC is turned on. A power source and a recorder are connected to the bridge diagonal m. The equilibrium bridge is connected to the recorder's output, and a controlled electrical conductivity output shunting the sensor conductivity t 3}. When the sensor is immersed in the flow, it is affected by a turbulent signal, which is the sum of the CEC and variable (pulsation VEP components. During the measurements, the bridge is automatically balanced by an electronic circuit. The bridge is balanced by changing the conductivity of the element and the switching element in parallel to the sensor. A field-effect transistor is used as a controlled element, to which input a feedback link is obtained from the output of the unbalance recorder. This allows the total electrical conductivity of the measuring arm to be maintained at a fixed level and to judge the magnitude of the pulsations from the recorded unbalance signal of the bridge. The known technical solution stabilizes the coefficient of conversion of pulsations with a change in the background CEC. Thus, the disadvantages of the known technical solution are the low accuracy, sensitivity, limited range of measurements of pulses of CEC and the complexity of the implementation of the device. The aim of the invention is to increase the accuracy, sensitivity and expansion of the measurement range. The goal is achieved by the fact that according to the method of measurement

pulsations of electrical conductivity of a turbulent flow of liquid, which consists in converting the conductivity of the liquid under investigation into an electric signal with automatic compensation of the constant component of the signal and measuring the variable component, will additionally convert the turbulent flow of liquid into laminar, and its conductivity in the turbulent and laminar zones will be converted into electric signals and by their difference the magnitude of the electrical conductivity pulsations of the turbulent flow is determined.

A device for measuring the pulsation of electrical conductivity of a turbulent fluid flow, comprising an AC four-blade bridge with a conductivity sensor in the business arm, a power source and a recorder, further comprises a conductivity sensor installed in the balancing arm of the bridge, and a hydrodynamic transducer; This allows direct hydrodynamic separation, inlet, to be carried out directly in the liquid. signal to static and dynamic, to ensure the physical correspondence of the resistances in the measuring and balancing arms of the bridge, -. to automatically compensate the constant component of the signal by internal feedback of the bridge during the measurement process and to exclude electronic feedback circuits.

The drawing shows a diagram of a device for measuring pulsations of turbulent electrical conductivity. fluid flow.

A device for measuring pulsations of CEC turbulent fluid flow contains a measuring bridge 1, formed by the four arms 2-5. The power source 6 and the imbalance recorder 7 are included in the corresponding diagonals of the bridge 1. The pulsation sensor 2, which is one of the arms of bridge 1, is installed in the flow in the turbulent zone 8. The hydrodynamic converter 9, for example, with small cells or capillaries 10 converts turbulent The flow of flow into the laminar zone in zone 11, in which the additional sensor UEP 3 is installed, is also one of the shoulders of bridge 1, moreover adjacent to arm 2.

The method is carried out as follows.

In the measuring bridge 1, the impedances of the shoulders 2 and 3 of the CEC sensors are continuously compared. These impedances are conductors of the second kind. The two other shoulders of bridge 1 compare

shoulder widths 4 and 5, leading to first-kind conductors, for example, precision resistors. The equilibrium condition of bridge 1 is the equality of the products of resistances of the opposite arms. In the absence of turbulence in the turbulent zone 8, sensors 2 and 3 respond to the mean of the SEC and the balanced (zero) state of bridge 1 does not depend on the flow velocity and the absolute value of the SEC. The impedances of the shoulders 2 and 3, as well as the shoulders 4 and 5 are selected based on the equilibrium of bridge 1, and the impedances of the shoulders 2 and 3 - (conductive constant sensors multiplied by the UEP value) can be equal to each other. In this case, equal impedances of the shoulders 4 and 5 are also required. In the equilibrium state of bridge 1, the imbalance signal on the registrar of imbalance 7 is absent, therefore the zero position of the recorders can be judged on the absence of pulsations of the CEC in the turbulent zone 8. Under the influence of the turbulent flow with CES pulses to sensor 2, the impedance of this cry varies in accordance with the instantaneous value of the AEI in the turbulent zone 8. When a turbulent flow passes through the hydrodynamic transducer 9, in the last 10 capillaries dit change in the nature and the flow is effected transfer turbulent flow in the laminar. Therefore, in zone 11 at the output of converter 9, where sensor 3 is located, there are no turbulences with PEC pulses in the current, and the impedance of arm 3 varies only in accordance with the average value of VEP. As a result, in the shoulder 3 of the bridge only the static signal is affected, and in the shoulder 2 both static and dynamic, i.e. caused by pulsations of UEP. In the measuring diagonal of bridge 1, in which the unbalance recorder 7 is included, fluctuations of the electrical signal appear caused by the influence of a turbulent flow with CEC pulses on the sensor 2. According to the unbalance recorder 7, the value of the CEC pulsations in the corresponding unbalance recorder 7 of the turbulent zone 8. The average, slowly varying value of the CEC acts on both sensors 2 and 3, without affecting the imbalance of the bridge 1. Pulsations of the CEC affect only the sensor 2, therefore the expansion of bridge 1 is caused only by electric ignalom, the value of the proportionality UEP pulsations in a turbulent zone B.

As a hydrodynamic converter 9, cellular rectifiers, smoothing grids, constricting elements, capillaries, tubes with a large hydraulic resistance can be used. The main requirement for the transducer 9 is the formation of a laminar zone 11 at its outlet. Structurally, the hydrodynamic transducer 9 can be made as a separate submersible unit, rigidly connected with sensors 2 and 3, or as a hydrodynamic pipe with sensors 2 and 3, respectively its inlet and outlet. The location of the transducer 9 and sensors 2 and 3 relative to the velocity vector on the run of the stream can be arbitrary, series, parallel, series-parallel. The main requirements for this are minimum distortion of the structure of the field of turbulence in the sensitive area of sensor 2 and the rigidity of the sensors 2 and 3 and converter 9 relative to each other. This is achieved by selecting known hydrodynamic profiles of submersible sensors 2 and 3, installing sensor 2 outside the zone of flow separation from converter case 9 and sensor 3. If the usual rules of hydrodynamic measurements are followed and the distortion introduced is minimized, the magnitude of the error signal at the output of bridge 1 depends only on the intensity of the investigated field pulsations UEP. The proposed method and the device implementing it are applicable for measuring pulsations in gas-plasma and water turbulent flows not only of electrical conductivity, but also of other physical quantities, such as velocity and temperature. In this case, the technical implementation of the device may include an existing set of sensor types and measuring bridges. Compared to the known, the proposed technical solution improves the sensitivity by a factor of 10, for a decade expands the measurement range to the frequency range, improves the measurement accuracy and greatly simplifies the design by eliminating the integrator and the constant-ratio capacitor control device.

Claims (2)

1. A method of measuring the ripple of the electrical conductivity of a turbulent fluid flow, which consists in> converting the conductivity of the test fluid into an electrical signal with automatic compensation of the DC component of the signal and measuring the variable component, which, in order to improve accuracy, sensitivity and expand the measurement range, additionally transform _about , the turbulent fluid flow in the lamina-SS is uniform, and its conductivity in the turbulent and laminar zones is converted into electrical signals and their difference determines the magnitude of the ripple of the electrical conductivity of the turbulent flow. 2. A device for measuring the ripple of the electrical conductivity of a turbulent fluid flow, comprising a four-arm alternating current bridge with a conductivity sensor in the measuring arm, a power supply and .. recorder, characterized in that, in order to increase accuracy, expand the measurement range and simplify the design, the device is additionally contains a conductivity sensor installed in the balancing arm of the bridge, and a hydrodynamic transducer of turbulent flow in laminar, installed between the sensor ami.