JPS6128095B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the relative fraction measurement of liquids (non-conductive) and vapors or solids (non-conductive) and gases, such as those occurring in the pumping of fuels or oils or the pneumatic conveyance of solid particles.

The prior art includes many attempts by mechanical and electrical methods to address the problem of inability to effectively deal with the non-homogeneous properties of vapor and liquid or solid and gas in the cross section of a conduit in most practical applications. There is.

It is an object of the invention to provide a measurement of non-conducting gas and solid fractions or of vapor and liquid fractions in a mixed stream which deals effectively with the non-homogeneous cross-section of such mixtures.

Another object of the invention is to perform measurements over relatively short distances of the conduit without being adversely affected by the swirl effects of the annular flow.

It is an object of the present invention to provide a long-life device that handles environmental conditions such as thermal expansion and contraction and pressure in long-term reliable lifetime operation that provides an effective method to meet one or more of the above objectives.

Another object of the present invention is to provide a simple structure that produces minimal disturbances to a measuring device consistent with one or more of the aforementioned objectives.

Another object of the invention is to eliminate sources of incorrect readings that meet one or more of the aforementioned objects.

Yet another object of the invention is to provide an economical device that meets one or more of the above objectives.

According to the invention, capacitance measurements are carried out sequentially on the flow sections to be measured in a distributed and preferably non-overlapping order. Each sequence step then logically counts the capacitance measurement excitation frequency at a large velocity with respect to the flow rate through the sensor so that the solid or liquid is substantially stationary for the purpose of the measurement to be summed. controlled. The excitation frequency used for this capacitance measurement is 10 to 100KHz,
Preferably it is 30KHz (higher than typical power frequencies but lower than radio frequencies). A sensor element consisting of a number of sets of electrodes applies a voltage field to the fluid flow and responds to its capacitance. The summed and changing capacitance response current from the sensor is amplified and converted to a voltage signal displayed on the meter in percent solid or liquid. The electrodes for capacitance measurements are placed on a peripheral plate oriented around the flowing material of the conduit to be monitored, preferably without breaking the conduit or penetrating, disturbing or touching the fluid flow. Preferably in a row.

By using an electrically transparent (non-conductive) portion of the flow tube, the sensor can perform its intended monitoring from outside the flow tube. Preferably, the sensor housing comprises a pair of semicircular tubes that grip around the outer periphery of the flow tube. Each semicircle consists of a laminate assembly having a sensor plate on an inner surface, an intervening insulating layer, and an outer ground plane. This ground plane has a coaxial type connector through which electrical connections to each sensor plate are made.

The sensor is thus easily movable to monitor several locations in the device and to be completely external to the field piping. Mobile functionality is secured and repairs can be made without interfering with on-site operations. Furthermore, this ability to monitor the flow material from outside the flow device provides a sensor that is very economical and reliable in terms of sensor materials and operation.

The invention features a method and apparatus for measuring the phase fraction of a mixed phase non-conductive fluid or mixed stream of non-conductive particles and gas. Phase fraction indicates the relative amount of gas versus liquid phase of a mixed phase fluid being measured, or the relative amount of gas versus solids of a mixed flow of non-conductive particles.

As described below, the measurements are capacitance measurements performed in several overlapping distributed directions within the cross-section of the channel by applying a rotating electric field with an alternating voltage in the range of 10-100 KHz. The capacitance measurement produced by the rotating electric field is proportional to the liquid or solid phase fraction and, by subtraction from the unity, to the gas phase fraction. A rotating electric field is generated by sequentially rotating the electrical positions of six equally spaced plates around the cross section to be measured, the plate structure limiting the flow cross section, and the insulation.

The accompanying drawings show a commercially available Auburn International Model 1000 device.

Referring to FIG. 1, a preferred embodiment of the present invention includes a voltage divider circuit VD, a comparator COMP, and a switching logic X connected through a span control section, in which multiple electrode plates P1 to P6 are connected.
and a sensor assembly S having a sum of Σ
and meter elements. Oscillator O, preferably a Wien bridge oscillator, produces a stable 30KHz sine wave output. 30KHz is given to the span control section and comparator COMP. comparator
The COMP (computational amplifier) produces a rectangular wave output from 0 to 5 volts with a crossover at the intersection of each axis at 30KHz. The output of the comparator is divided by 16 and then converted to a decimal sequence of 6 to 6 in logic X, which in turn controls the switching sequence of the sensor plates via logic Y.

The output of the span control section is switching. It is connected via logic to the appropriate sensor plate and is also provided to a null control with low impedance drive. The output of the zero control section is inverted, the level is reduced, and it is applied to the capacitor CAP as a zeroing current for the addition junction (Σ). The zero control is connected after the span control to minimize interaction between the zero and span adjustments. A suitable sensor plate is also connected to the summing junction. The algebraic sum of currents in the summing junction is exchanged into a voltage by an I/E converter.

Field effect transistors (FETs) are used to block the signal during the transition of the sequence so that the pulses produced during this transition do not saturate subsequent amplifiers. AC amplifier (ACA) amplifies the signal,
The inverter (I) can invert the signal so as to produce a DC signal using synchronous rectification via element SYN.RECT. The output of comparator COMP provides switching and clocking inputs for synchronous rectification. The DC amplifier DCA is proportional to the solid or liquid in the pipe and is connected to the front panel meter M.
Provides 0-10V output to drive. This output is obtained as a result of capacitance measurements made in several overlapping distributed directions within the cross-section of the flow path of the fluid being measured, defining the relative amounts of the gas and liquid phases of the fluid and determining the phase fraction. It is called a signal. For operational convenience, the meter is provided with a time constant decay of 1 second or 2 and a half seconds. DC zero control is used to cancel the DC component present in the signal.

In Figures 2A-2F, the six figures show steps 1-6 of the voltage field rotation sequence. At each step, a voltage of 30KHz is applied to plate "T" and the three opposing plates are connected together to form a common receiving plate "R", which R
A capacitive current proportional to the average dielectric constant inside the sensor is allowed to flow to ground, and the inverting plate is grounded to separate the transmit (T) and receive (R) plates. The jacket on the outside of the sensor is also grounded to act as a shield (guard) around the sensor. Because one position does not provide enough electric field to average the dielectric constant across the entire cross section of the sensor,
The switching logic advances the electrical position of each plate in a sequence of six consecutive steps, thus rotating the electric field for better averaging. The circumferential spread of the electric field in the "R" plate approaches 180 degrees, which is in any case more than about 90 degrees, which is necessary to avoid edge errors that require large correction efforts.

3 to 4, in FIG. 4, the electrode plate of the sensor is connected to the oscillating voltage source O, the addition junction Σ
or a third for selective connection to the ground bus.
Six of the circuits are plate switch circuits, six of which are used in the circuit shown. ``Plate Sequence Logic'' generates Xmit, Gnd and Fec. logic levels for each plate switch circuit from 1 to 6 sequences.

FIG. 4 is a diagram of the "plate switch circuit". The circuit consists of five FET switches, two of which are connected in series with an intermediate load resistor that is grounded to the 30KHz (T) and Σ (R) partners to isolate the plates when unconnected. ing. Ground the plate using the remaining FET switch.

It is desirable that the oscillation action used in the present invention be single-phase and generally have a high frequency. The effective plate area is maximized, as shown in FIGS. 2A-2F, for effective signal strength handling at capacitance values below the microfarad involved. The resulting spatial overlap pattern, as shown in Figures 2A to 2F, must have an arc extending at least 90°, preferably 180°, to the "first capacitance plate" and the "second capacitance plate" on the opposite side. The capacitance plate is limited to less than 90° facing the first plate to avoid the strong electric field in the center and the strong current concentration of the V-channel electric field. A well-defined sequence of commutation steps (with intervening insulation) of rotation of the electric field ensures scanning of the cross-section of the flow, and individual cross-sections of the flow are separated several times during the flow down the axis of the conduit. completely scanned. This rotational scan is similar to the known capacitance vortex sensor meter for measuring the void fraction in the central effective area of the flow channel (the former) and in the fuel line etc. in the effective counter-effect of the annular flow. Contrast with capacitance instruments.

The device of FIG. 1 consists of driver board, switching board and receiver board circuitry. Figure 9A shows the operational amplifier Z of the driver assembly.
1 shows a stabilized Wien bridge (frequency and amplitude stabilized capacitance resistor bridge) oscillator with automatic gain control of 1A and its associated circuit configuration; The output of the oscillator is applied to a comparator Z2A (labeled COMP in FIG. 1), which produces a 0 to 5 V rectangular wave output from the transformation at the point intersecting the coordinate axes of the sine wave produced by the oscillator. The output of the oscillator is also connected to the SPAN control section (FIG. 1). The output of SPAN is connected to the non-inverting input of operational amplifier Z4A (Figure 9A), said amplifier being connected as a non-inverting follower to provide isolation for the SPAN control and switching assembly ( A low-impedance drive is provided to the zero control section (FIG. 1) and the sensor drive section via the zero control section (FIG. 9c, bottom). The output of the null control is inverted, reduced in level by operational amplifier Z3A, and provided to the receiver assembly as the null input. The zero control is connected after the span control to minimize interaction between the zero and span adjustments.

The output of the comparator is provided to the receiver assembly as a switching input for synchronous rectification. This output is also sent to two 4-stage shift registers.
Connected as clock input to counters (Z6A and Z9A). The output of Z6A at terminal SYNC. out will be 30KHz divided by 16 or 1.875KHz, which is also fed to the input of Z9A. The four stages of parallel BDC outputs of Z9A are connected to a binary decimal converter Z10A which is inverted by a Hex, inverter Z11A and then provided to the switching assembly via an electrode select out connection. The seventh count of Z10A is again connected to the "reset" input of Z9A, thus returning the decimal count to position 1 again.

The parallel output of Z6A is decoded by Z7A into decimal counts from 0 to 16. QUADNAND gate Z8
A's NAND gate is connected as a latch. Z
When the count ``15'' from 7A is reached, the latch is set, and when the count ``2'' is reached, the latch is ``reset''. The output of the latch is connected to the Schmitt trigger and the receiver assembly (9th
(see Figure C and description below) produces a gate out which is provided as a rectified blanking gate signal.

Z1A to Z5A amplifiers are National 311
Harris HA2 except Z4A which is a comparator
-2625-5 type operational amplifier is preferable. The other two elements are standard logic chips.

FIG. 9B is a schematic diagram of the switching assembly.
The function of the switching assembly is to connect each electrode plate of the sensor to 30KHZ (XMIT IN), receiver assembly (REC. OUT) or ground (GND). The switching action is performed by QUAD FET switches Z1B-Z7B, Z15B and Z16B. Two switches are cascaded for each send or receive function for sufficient isolation. The selection logic is a triple series of 3
Input NOR gates Z11B to Z14B and Hex
It consists of inverters Z8B to Z10B. The logic is that when one electrode selection line is in the high state, the associated electrode plate is connected to 3KHz for delivery;
The front and rear plates are grounded. The remaining plate is connected to the receiving line since this electrode is automatically connected to the receiving line without any energization from the plate selection line as a ground side send-out. A diode is provided to prevent accidental overvoltage from the sensor connections. 9th
The resistor in figure B is 47K, the diode is IN914,
It is desirable that the FET is Harris HI-1-201-5.

FIG. 9C is a schematic diagram of the receiver assembly. The nulling voltage (Zero In) from the driver assembly (Figure 9A) is connected to an operational amplifier 180° out of phase using capacitive current flowing from the sensor to the summing junction via the switching assembly (REC, In). is applied to a 100 picofarad capacitor that produces a capacitive current in the summing junction of . A capacitor in the Z1C feed back loop converts the summed current to a voltage and phase shifts this voltage using the SYNC.in from the oscillator and driver assembly. FET (E105) is shut off during electrode sequence commutation with the negative gate from the driver assembly. This is done to prevent subsequent saturation of operational amplifier Z2C due to rectification spikes.

Z2C performs voltage amplification, and operational amplifier Z3C acts as a unity gain inverter. The inverted and non-inverted signals are connected through two FET switches of QUAD switch Z5C. This 2
The two switches are turned on alternately by the SYNC signal to perform synchronous rectification of the signals. The third portion of Z5C is connected to provide an inverted SYNC signal to an "inverted signal" switch.

The operational amplifier Z4C provides DC gain and a low impedance output to the rectified signal to drive the meter and produce a 0-10 volt output proportional to the volume of the sensor occupied by the solid or liquid being measured. The on-board zero control is used to eliminate any DC offset components introduced in the circuit, and the meter CAL adjusts all meter readings to exactly 10 volts.

The damping action of the meter is provided by a switch (FIG. 1) at each position with time constants of 0 seconds, 1 second and 2.5 seconds.

Next, in FIGS. 5 to 8, the mechanical configuration of the sensor assembly consists of two semicircular tube stacks 1
This laminated part consists of a conductive ground plane 2, a conductive sensor plate 4 fixed thereto, and an insulated radial connector 6 passed through an insulating layer and fixed to the ground plane. It consists of an insulating surface 3 to which an electrical connection is made by a conductor 5 that connects to and becomes a part of a conductive material.

Two semicircular tube stacks consist of sensors that surround the outer periphery of the electrically transparent (non-conductive) part of the flow channel 7, inside which the substance to be monitored flows.

These semi-circular sections are fixed onto the flow tube using clamps 9, the dimensions of said laminated sections being such that they allow direct contact with the outer surface of the flow tube, with as small a gap as possible between the adjacent edges of each section. Give 10. The mounting position of the sensor plate is symmetrical with respect to the diameter of the flow tube, and its axial length is such that both ends are at a sufficient distance within the protected insulating laminate to eliminate external electrical distribution, i.e. It is designed to be approximately 25.4 mm (1 inch) plus.

These features provide precisely positioned sensor plates needed to perform the aforementioned measurements and to be easy to install and carry.

It will be clear to those skilled in the art that the foregoing disclosure allows other uses and modifications to be made in addition to the specific embodiments herein without departing from the inventive concept. . Accordingly, the invention is to be construed as including all features residing in and processed by the apparatus and method disclosed herein and as a combination of such features as limited only by the appended claims. It is something that should be done.

[Brief explanation of the drawing]

1 is a block diagram of a measuring device according to a preferred embodiment of the present invention; FIGS. 2A-2F are a series of diaphragms showing the sequential rotation of the electric field within the sensor; and FIG. A block diagram illustrating the "switching logic" in Figure 2 in more detail (each sensor plate is connected to 30KHZ ground or summing junction (Σ) via a "brate switch circuit"); FIG. 3 is an enlarged view of the plate switch circuit elements included in the plate switch circuit elements, FIGS. Figures 5 to 8 are
A vertical cross-sectional front view and a side view of the flow conduit used in the apparatus shown in FIGS.
Figure C is a schematic diagram of the main circuit assembly contained in the apparatus of Figure 1; 1... Semicircular pipe laminated part, 2... Ground plane, 3...
...Insulating layer, 4...Sensor electrode plate, 5...Conductor, 6
...Connector, 7...Flow pipe, 9...Clamp,
10... Gap, D1-D2... Electrode plate, VD...
Voltage divider, A, B...Switching logic element, COMP...Comparator, Σ...Summing junction, ACA...AC amplifier, I...Inverter, Z
1A, Z3A, Z4A... Arithmetic amplifier, Z2A...
...Comparator, Z6A, Z9A...Counter,
Z8A...QUAD, NAND gate, Z10A...
Converter, Z11A...Hex, inverter, Z
1B~Z7B, Z15B~Z16B...Switch, Z8B~Z10B...Hex, inverter, Z
11B~Z14B...Input NOR gate.

Claims (1)

[Claims] 1. A method for measuring a phase fraction in a fluid medium containing a mixture of inducers, comprising the following steps. applying a series of periodic electric fields that are relatively displaced across the flow in a distributed, spatially overlapping, and temporally ordered manner, each of the series of electric fields requiring relatively little manual effort. establishing a convergence between an electrode and an opposing relatively wide receiving electrode, created across the flow by the electric field;
and summing capacitive currents affected by the dielectric constant of the flow medium and averaging direction dependent variables to produce a signal correlated with the flow phase fraction. 2. The method of claim 1, wherein said capacitance measurement is provided by a circumferential spread of the electric field of at least 90° in one relatively large electrode. 3. A device for forming capacitor electrodes in a circumferential row around a flow path, a single-phase high-frequency oscillating voltage source, and a periodic device that sequentially applies a voltage to the electrodes to be relatively displaced across the flow path. a non-conductive gas or solid comprising a device for forming a series of electric fields, a device for measuring the current generated in each electrode, and a device for summing the measured currents to produce a phase fraction signal. Or a device for measuring liquid components. 4. The device for sequentially applying voltage to the electrodes is:
4. The apparatus of claim 3, wherein when each electrode is sequentially energized as an input electrode, at least one adjacent electrode is grounded and a number of non-adjacent electrodes are energized as receiving electrodes relative to the sending electrode. 5. Six equally spaced circularly arranged identical circumferential rows with electrodes are provided with three electrodes defining an arc of approximately 180°, said electrodes at any time serving as receiving electrodes. 5. The device according to claim 4, which is energized and faces a delivery side electrode which is energized at the same time. 6. Device according to claim 3, wherein the device for measuring and summing comprises a device for synchronous rectification of the summed currents to produce an AC/DC measurement signal from the high frequency vibrations applied to the sensor. 7. The device of claim 3, wherein the device for sequentially applying voltage to the electrodes includes a device for disconnecting the electrode supply during successive commutations. 8. The device of claim 3, wherein the device for sequentially applying voltage to the electrodes comprises field effect transistors controlled in cascade to separate the electrodes. 9. Apparatus according to claim 3, in which each electrode is attached to a tubular section that can be installed in an electrically non-conductive tubular section of a conduit for the fluid to be measured.