SU1582076A1 - Method of checking concentration of gas in flow of liquid - Google Patents

Abstract

This invention relates to controlling the mass concentration of a gas in a gas-liquid stream, in particular to methods for controlling the concentration of gas in a liquid stream. The purpose of the invention is to increase credibility. For carrying out the method, pressure gauges with electrical output signals P 1 and P 2 are installed on the pipeline, which are used to record the pressure difference ΔP at two points along the flow axis, as well as a density change sensor, from which the electrical signal L is removed. in two stages: in the first, a pure gas is supplied through the pipeline, ΔP is set, and the average absolute value of the gas density increments is determined from the signal L for given values of ΔP

in the second, the average absolute values of density increments in a controlled gas-liquid flow are determined by the signal L of the same sensor, the pressure difference at the same two points along the flow axis is simultaneously recorded, and each of the values of density increments in a controlled gas-liquid flow is compared with the value of density increments gas obtained in the first stage for the same pressure difference, according to the formula ϕ gm = Δϕ g / Δϕ s, where ϕ gm is the true mass concentration of gas in the gas-liquid flow, Δϕ g and Δϕ s are average absolute in The value of density increments in the total cross section, respectively, of the gas flow without liquid and gas-liquid mixture for equal time intervals and with the same pressure difference along the flow axis. 4 il.

Description

The invention relates to the control of process parameters of gas-liquid flows, especially the mass concentration of gas in a stream of a mixture of liquid and gas moving in a closed hydraulic system.

The aim of the invention is to increase the reliability of the control.

FIG. 1 shows the scheme of implementation of the proposed method; in fig. 2 is a diagram of a density change sensor; FIG. 3 - a typical density change curve; in FIG. K - a density change curve in the region of absolute values.

To implement the proposed method, within the closed hydraulic system of the pipeline 1, gauges 2 and 3 with electrical output signals P, are installed on its section of length 1 located along the flow axis x. and Pr, which are connected to the adder A, registering the pressure difference of the AR in the specified area. The location of one of the gauges is fitted with a sensor of 5 density changes, from the output of which electrical CHI is removed. Electric signals JP and e are fed to digital recording devices 6 and 7, which allow processing of signals on computer 8.

To ensure high quality control, the method uses a contactless (mechanically) density change sensor (FIG. 2), which freely covers the control object, i.e. piping 1. This sensor has a cylindrical ring permanent magnet 9- and differential winding 10, where dots outside the lines show the beginning of coils in the opposite sections 11 and 12 of this winding, the covering pipeline with a certain gap h. The magnitude of the latter is at least 30 mm when installing the sensor on a pipeline of magneto-susceptible pipes, and for control objects with para- or diamagnetic properties, but being electrical conductors, this gap can be reduced to a possible limit, although increasing h to 10 cm and practically does not affect the sensitivity of the sensor, the electrical output of which is proportional to changes in the density of the product moving through the pipeline

FIG. Figure 3 shows one of the typical density variation curves in the form of an alternating electric signal e, measured along the vertical axis, as a function of time t, measured along the horizontal axis. The signal has a dynamic constant, which is indicated by a dotted line and corresponds to a certain time interval At. The latter is chosen within such limits so that it covers several periods of change of the processed signals and allows monitoring the current

five

0

five

0

five

0

five

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information in the process of its registration and processing.

FIG. The same curve of density changes is transferred to the area of absolute values, in which the signal e is represented by rectified, i.e. unipolar (unipolar). The average (effective) value of this curve for the interval Jt is also indicated by the dotted line and has the value

4Pcontrol the true mass concentration of gas by the proposed method is carried out sequentially in two stages. At the first stage, a controlled gas (or air) without liquid is supplied via pipeline 1 (FIG. 1). At the same time, by increasing or decreasing the gas supply (flow), different values of the pressure difference of the AR in the selected section of length 1 are set, if the gas flow is directed along the arrow of the x axis, then Л Р, - Р2. The values of Lp are set from zero to extremely necessary by the technology, for example, with a step of 0.01 MPa, and for each step, according to the signal of density sensor 5, an average absolute value of the increments of the density of gas Afr is determined for a complete cross-section of its flow within equal intervals time, for example / it 1 s. According to the obtained values for given values of A, the functional dependence of the mean absolute increments of the gas density on the pressure difference at two points along the flow axis is found. At the next stage, the average absolute values of density increments of a real gas-liquid mixture Lrs are determined at the full cross section of its flow for the same equal time intervals as in the first stage, also by the output electrical signal of the same density change sensor. At the same time, according to the indications of the recording device 6, for each of the Lrs values, the pressure difference is fixed at the same two points along the flow axis, and each of the density increment values in the controlled gas-liquid flow is compared with the value of the gas flow density increments obtained at the first stage for the same difference pressure (

according to the formula - DRG

(J -str-, M dr

de TS - true mass

 ch

1582076 concentration of gas in the stream;

gaseous-liquid substances

, g

ufr, Afc - the average absolute value of the density increments in the total cross section, respectively, of the gas flow without liquid and gas-liquid mixture for equal time intervals and at the same pressure difference along the flow axis.

The one-to-one correspondence between the scale of conversion of dfr and / grs to analog electrical signals is ensured by the fact that both of these quantities are determined from the output signal e of the same density change sensor (Fig. 2). The effect of the latter is based on the fact that the interaction of the permanent magnet 9 with the body of the pipeline 1 whose density varies under the action of internal pressure; in this field, countercurrent electrical vortex flows occur, which are proportional to the intensity of changes in the density spines and practically do not depend on the magnetic properties of the body, the circulator is separated into adjacent semi-areas of the x-magnetic field that are symmetrical relative to each other. The differential winding 10 performs the role of a physical adder of oncoming electrical vortices, therefore, at the sensor output, when the density of the control object (pipeline) is changed, an electrically signal e is obtained, whose mathematical expression is

e kapVprp,

where k is the dimensional ratio of the electrical connection of changes in the density of the body of the object being monitored and the state of the field;

a is the speed of electromagnetic interactions in the sensor system — the object of control;

 - absolute magnetic permeability;

V is the volume of the object of control, oh-

plugged in by the magnetic field, j - changes in the density of the control object over time, i.e.

Rtr dj rp / dt.

82076 15

ten

Since here k, a, / c are constant, and volume V, encompassing the total cross section of the flow being monitored, due to the continuity of the latter, can be arbitrary in magnitude within a given control object, then ep. In addition, the pulses of motion of the flow of a substance and the pipeline surrounding it are always proportional to each other, i.e. The energy characteristics of the deformation of the pipeline and the flow of matter in it always coincide. Therefore, e Pg / pc, i.e. The signal e is proportional to the change in density of the controlled flow of gas or gas-liquid mixture.

Claims (1)

Invention Formula 20 The method of controlling gas concentrations in the fluid flow, including the determination of the change in density of the gas-liquid flow and the average value of 25 absolute density increments per. certain time intervals, about which, in order to increase the reliability of the control, for equal time intervals determine the average value of the absolute density increments in the full cross section of the gas flow without a liquid by the pressure difference at two points along the flow stream axis then the average absolute density increments are determined at the total cross-section of the controlled gas-liquid flow; at the same time, for each of these values, the pressure difference is fixed at the same two points along the flow axis, and the true mass concentration of gas GM in a controlled gas-liquid flow is found by the formula thirty 35 40 H G1A Јf a7s where pr, / jj) c the average values of the absolute density increments in the total cross-section, respectively, of the gas flow without liquid and gas-liquid mixture for equal time intervals and at the same pressure difference along the flow axis. FIG L FIG. 2 ABOUT Phage.Z FIG A