SU953571A2 - Device for measuring speed of liquid in two-phase flow - Google Patents

Description

The invention relates to a technique for measuring two-phase gas-liquid flow parameters, such as mean fluid velocity and rms pulsation velocity of a fluid. According to the main author. St. A device for measuring fluid velocity is known, consisting of a sensor (cathode-anode), an electrolyte tank, a constant-voltage source, an alternator, a wide-band DC amplifier, a low-pass filter, a key, a driver, and a recording device. The alternating voltage generator is connected between the sensor and the source of direct voltage, the low-pass filter and the switch are connected to the regulating device. The control input of the switch is connected to the output of the wideband amplifier through a series-connected driver and high pass filter 1. The disadvantage of this device is The fact is that when measuring the pulsation characteristics of the fluid velocity (for example, the root-mean-square value of the pulsation velocity of the fluid), the signal dips down to zero at the moment the bubble passes gas will make a large contribution to the output signal, exceeding the contribution from the pulsation velocity of the liquid. This reduces the reliability of the pulsations of the fluid velocity in a two-phase flow. The purpose of the invention is to increase the reliability of measurements of pulsations of the velocity of a fluid in a two-phase flow. This is achieved in that a second key is additionally introduced into the device and an adjustable DC voltage source connected via a second key to a recording device, while the control input of the second key is connected to the driver.

FIG. 1 shows a block diagram of the proposed device; in fig. 2 time diagrams of voltages during device operation in a two-phase flow.

A device for measuring fluid velocity in a two-phase flow includes a sensor (cathode 1, anode 2) placed in an electrolyte solution, an alternating voltage generator 3 connected in series with a constant voltage source k, a broadband DC amplifier 3, the output of which connected in parallel a low pass filter 6 connected to the first key 7 and a high pass filter 8 connected to a shaper 9. whose output controls the first key 7 and the second key 10. The output of the first key 7 is connected to a register with a switching device 11. An adjustable constant voltage source 19 is connected to a second switch 10, the output of which is connected to a recording device 11.

The voltage of source 12 is set equal to the average value of the output voltage of the first switch 7. The indicated voltage is applied to the input of the recording device via the second switch 10. This switch is controlled by the output voltage of the driver 9 and opens at the time corresponding to the gas phase when the first switch 7 locked up Thus, either the output voltage of the low-pass filter 6 (at times corresponding to the liquid) or the voltage from the source 12 is applied to the input of the recording device.

The second key 10 operates in opposite phase with the first key 7 when the last one is locked, the second 10 is open and vice versa. When the sensor is in the fluid, the first key is open; the signal from the amplifier output, corresponding to the velocity of the liquid at the measured point, passes through it to the recording device. At the moments corresponding to the gas phase, the output voltage of the amplifier does not pass through the locked first key, and through the open second key only the voltage from the source of adjustable constant voltage equal to the average value of the output voltage of the amplifier is supplied to the recording device. fluid. As a result, high quality

the waveform of the recording instrument changes. If in the well-known circuit a, corresponding to the gas phase, there is a sharp drop in the signal to zero, then in the new circuit, at the moments corresponding to the gas phase, the signal remains at the level equal to the average value of the signal at the moments corresponding to the liquid. Since any instrument measuring the rms value registers the voltage deviation from the average value, the moments corresponding to the gas phase contribute zero to the rms value of the signal.

FIG. 2 shows voltage diagrams for the operation of the proposed device in a two-phase flow; in fig. 2a is the output signal of the key 7. At the moments corresponding to the gas phase, the signal drops to zero (the key is locked). FIG. 26 is the output signal of the second key 10, O- the average value of the output voltage of the first key set at the source 12. FIG. 2c - a signal arriving at the registering device / when both keys are shared).

 It should be noted that a simple electronic circuit that automatically sets a voltage equal to the average value of the output voltage of the first switch at the output can be used as an adjustable constant voltage source. This simplifies and speeds up the measurement process.

The proposed device can also be used to measure more complex two-phase flow characteristics using standard instrumentation. It can be used, for example, to measure the spectral plane of the pulsations of the velocity of a fluid in a two-phase stream, and also (when using the two-channel version of the proposed device) to measure the correlation coefficients of si-channels at various points in the stream and mutual spectra

The use of the proposed device makes it possible to use simple and cheap devices for measuring the velocity pulsations of a liquid in a two-phase flow, which significantly expands the possibility of using the device.

Claims (1)

1. USSR author's certificate ° №, cl. G 01 P 5/08, 1977. Fig f2