JPS60210753A - Method and device for measuring channel average void fraction of gas-liquid two-phase flow - Google Patents

Abstract

PURPOSE:To measure the average void ratio of a flowline with good accuracy by correcting the change in electrostatic capacity by the change in temp., by attaching an electrode having a constant width to the outer surface of a cylindrical insulator connected to a pipeline, through which a gas-liquid two-phase stream is flowed, on the same axis along with a thermocouple and applying high frequency voltage to said electrode to measure the change in electrostatic capacity. CONSTITUTION:A void detector consists of a cylindrical insulator 1, a void detecting electrode 3, a lead wire 4 and a thermocouple 5. The cylindrical insulator 1 having the same dimension as a pipeline 2 through which a gas-liquid two-phase stream is flowed is connected to the pipeline 2 on the same axis and an electrode 3 having a constant width is attached to said insulator 1 so as to extend over the entire outer peripheral surface thereof and sine wave high frequency voltage is applied to the electrode 3 while a resonance circuit is formed of the electrode 3 and an electrostatic capacity detection circuit 6 and the change in the electrostatic capacity of the electrode 3 due to the flow of the gas-liquid two-phase stream is detected as the change in the detected voltage from the lead wire 4 to measure the average void ratio of the flowline. The output of the thermocouple 5 is inputted to a temp. correction signal generation circuit and a temp. correction signal is inputted to a correction operation circuit 8 and an average void ratio, wherein the change in the electrostatic capacity by temp., is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for measuring the flow path average void fraction of a gas-liquid two-phase flow flowing through a pipe from changes in the capacitance of the pipe, and particularly relates to a method and an apparatus for measuring the flow path average void fraction of a gas-liquid two-phase flow flowing through a pipe from changes in capacitance of the pipe. The present invention relates to a method and apparatus for measuring a flow path average void fraction of a gas-liquid two-phase flow in which a change in capacitance is corrected using a signal output based on the temperature of a measured fluid.

Conventional devices for measuring void ratio from changes in capacitance of pipes include probe-type void meters, Zen-shaped void meters, and other types of void meters in which a detector is placed in the flow of fluid. However, this type of void meter has the disadvantage that it can only measure the void fraction in a local area of the flow path, and therefore cannot measure the average void fraction of the flow path, and also has the disadvantage of disturbing the fluid flow because the detector is placed in the flow. there were. Furthermore, with this type of void meter, the capacitance of the conduit fluctuates when the temperature of the fluid being measured changes, making it impossible to accurately measure the average void ratio even when the body temperature changes. It is an object of the present invention to provide a method and device for measuring the average void fraction of a gas-liquid two-phase flow, which can accurately measure the average void fraction of a flow channel by correcting changes in capacitance of a pipeline due to changes in fluid temperature. .

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the flow path average void fraction measuring device for gas-liquid two-phase flow according to the present invention. The void detector of this embodiment consists of a cylindrical insulator 1. Void detection electrode 5. It is composed of a lead wire 4 and a thermocouple 5.

In detail, a cylindrical insulator 1 having the same dimensions as the pipe 2 through which the gas-liquid two-phase flow flows is coaxially connected to the pipe 2 so as not to disturb the flow, and the outer circumference of the cylindrical insulator 1 is A void detection electrode 6 is attached to the surface with a constant width over the entire circumference, a temperature signal extraction lead wire 4 is connected to the void detection electrode 6, and a thermocouple 5 for measuring the temperature of the fluid to be measured is connected to the pipe. 2
It is constructed by penetrating the z.

FIG. 2 is a block diagram of the electric circuit of the flow path average void ratio measuring device for gas-liquid two-phase flow according to the present invention. Void detection electrode 6
A constant frequency, for example, a sinusoidal high frequency voltage of 2ME (Z) is always applied to the voltage. The void detection electrode 3 and the capacitance detection circuit 6 constitute a resonant circuit. When the capacitance of the void detection electrode B changes in accordance with the gas-liquid two-phase flow flowing inside the shaped insulator 1, the impedance of the above-mentioned resonant circuit changes.As a result, the lead wire 4
The detection voltage changes. By knowing this detection voltage, the channel average void ratio of the gas-liquid two-phase flow flowing inside the void detection electrode 3 can be measured.

When the temperature of the fluid to be measured changes, the capacitance within the cylindrical insulator 1 changes and the measurement spoof loses its reproducibility. In this embodiment, in order to correct this, a temperature correction signal generation circuit 7 is provided which generates a temperature correction signal according to the change in capacitance of the cylindrical insulator 1 based on the output of the thermocouple 5. . The temperature correction signal from the temperature correction signal generation circuit 7 and the output signal of the capacitance detection circuit B are subjected to addition, subtraction, and division calculations in the correction calculation circuit 8, thereby creating a flow path in which changes in capacitance due to temperature are corrected. The average void ratio is output from the correction calculation circuit 8.

FIG. 5 is a diagram illustrating actual measurement results of channel average void ratio. The flow path average void fraction measurement device of the present invention, which was actually prototyped, can measure the void fraction of an upward flow of water-air two-phase flow and the void fraction of water-steam two-phase flow when high-temperature water is discharged from a boiler. I did this. The measurement results shown in FIG. 6 show the relationship between the measurement value and the set value of the void fraction of the upward flow of the water-air two-phase flow. As a result, it was confirmed that good measurement results were obtained.

The effects of the present invention are that since the cylindrical insulator 1 for void detection is cylindrical with the same inner diameter as the pipe, the flow channel average void ratio can be measured without disturbing the flow of the two-phase flow, and the temperature of the measured fluid is Temperature correction is performed even if the temperature changes, so measurements can be performed with high reproducibility, and even if a structure such as an electric heater is inserted into the flow path of the void detector, it is independent of the presence of the structure. One of the advantages is that the flow path average void fraction can be measured with high accuracy.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the flow path average void ratio measuring device for gas-liquid two-phase flow of the present invention, FIG. 2 is a block diagram of the electric circuit of the measuring device shown in FIG. 1, and FIG. 6 is a flow path It is a figure which illustrates the actual measurement result of an average void ratio. 1: Cylindrical insulator 2: Pipe line 5: Void detection electrode 4: Lead wire 5: Thermocouple 6: Capacitance detection circuit 7: Temperature correction signal generation circuit 8: Correction calculation circuit (4 people in addition) Concave 2 [! I

Claims (1)

[Claims] +11 A cylindrical insulator having the same dimensions as the conduit is coaxially connected to a conduit through which a gas-liquid two-phase fluid flows, and electrodes are provided at a constant rate around the entire outer surface of the cylindrical insulator. The average void fraction of the gas-liquid two-phase flow is measured by applying a high-frequency voltage of a predetermined frequency to the electrode and measuring the change in capacitance of the pipe. Method for measuring channel average void fraction in gas-liquid two-phase flow. (2. In the method set forth in claim 1, a temperature change in the fluid is detected, a correction signal for temperature-correcting the change in the capacitance accompanying the temperature change is generated, and the temperature is corrected by calculation. A method for measuring the average void fraction of a gas-liquid two-phase flow, characterized in that the average void fraction of the gas-liquid two-phase flow can be measured. A cylindrical insulator coaxially coupled to a conduit, an electrode attached at a constant width around the entire outer surface of the cylindrical insulator to which a predetermined high frequency voltage is applied, and capacitance from the electrode. A lead wire for extracting the signal, a thermocouple for detecting the temperature of the fluid to be measured, a capacitance detection circuit for detecting the change in the capacitance of the electrode, and a capacitance detection circuit for detecting the change in capacitance of the electrode, based on the output of the thermocouple. A correction signal generation circuit that generates a signal to correct changes due to temperature, and an output of the static capacitance detection circuit and an output of the correction signal generation circuit are subjected to addition, subtraction, and division operations. Temperature-corrected capacitance 1. A flow path average void fraction measuring device for gas-liquid two-phase flow, characterized by comprising a correction calculation circuit that outputs a signal.