GB1585868A

GB1585868A - Velocity flow measuring apparatus

Info

Publication number: GB1585868A
Application number: GB45543/77A
Authority: GB
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1976-11-30
Filing date: 1977-11-02
Publication date: 1981-03-11
Also published as: JPS5368274A; DE2752328C2; DE2752328A1

Description

(54) VELOCITY FLOW MEASURING APPARATUS (71) We, NISSAN MOTOR COMPANY, LIMITED, a corporation organized under the laws of Japan, of No. 2, Takaramachi, Kanagawa-ku, Yokohama City, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to velocity flow measuring apparatus which measures the drift of ionized fluid mass and more particularly to a velocity flow measuring apparatus which measures the transit time of an ionized fluid mass migrating with the surrounding fluid mass over a predetermined distance between two points in the path of fluid flow.

The reduction of noxious exhaust emissions from an internal combustion engine is achieved when the fuel supply is controlled by a feedback signal derived from an exhaust gas sensor. In designing such feedback control system accurate measurement of fuel quantity supplied to the engine is required.

Specifically, the flow measuring device must be capable of responding to the instantaneous variation of fluid flow. Conventional flow meters are not satisfactory for such purposes.

United States Patent 3,470,741 discloses a flow meter which includes an ionizing means disposed in the path of fluid flow and a pair of opposed ion collecting electrodes spaced from the ionizing means transversely of the direction of fluid flow. With no fluid flow the ions would travel midway between the collecting electrodes. In the presence of fluid flow, the ions would displace from the mid point and there is a difference between the charges collected by the respective electrodes, which difference is detected by a comparator.

The present invention contemplates to utilize the longitudinal migration of ions produced in the path of fluid flow at the same speed with the fluid stream. The migration of the ions over a predetermined distance between a first point and a second point displaced downstream from the first point is detected to measure the transit time of the ions over that known distance. Because of the longitudinal displacement of ions that is utilized, the velocity flow meter of the invention is particularly suitable for high rate flow measurement and is capable of responding to rapid variations of the flow rate.

Therefore, the primary object of the invention is to provide a velocity flow measuring apparatus whose responsiveness to flow rate variations is greatly improved.

The present invention consists in apparatus for measuring the flow velocity of fluids passing through a conduit comprising, means for charging a stream of said fluid to a given potential, a first electrode disposed downstream of said charging means, a source for generating trigger pulses at periodic intervals, means for applying a potential different from said given potential to said first electrode to discharge a portion of the stream of said charged fluid in response to said trigger pulse, a second electrode disposed downstream of said first electrode to detect said discharged portion to generate an output signal, a bistable device for assuming a first binary state in response to said trigger pulse and a second binary state in response to said output signal from said second electrode, and means connected to said bistable device for measuring the length of time between said first and second binary states.

The advantages and features of the present invention will be understood from the following detailed description of the preferred embodiment with reference to the accompanying drawings, in which: Fig. 1 is an embodiment of the present invention; Fig. 2 is an example of ion collecting electrodes employed in the embodiment of the invention; Fig. 3 is a cross-sectional view taken along the line 3-3 of Fig. 2; and Fig. 4 is a circuit arrangement for measuring the variation of electrical conductivity of the mass flow of fluid as a means for detecting the presence or magnitude of the ions migrating with the fluid flow.

A velocity flow measuring apparatus of the invention is shown in Fig. 1 in which fluid is directed to pass through a passage 11 of a hollow cylindrical structure or pipe 10 which is constructed of an electrically non-conductive material. Ionizing means are provided which is formed by two electrodes: a ring Or cylindrically hollow outer electrode 12 and a cylindrical rod or inner electrode 14 having a reduced diameter portion 15. The ring electrode 12 is connected electrically to a first or positive polarity terminal of a high voltage DC power supply 40 or ground by conductors 13 and 18. The cylindrical rod 14 is disposed concentrically with the center axis of the ring electrode 12 and connected electrically to the second or negative polarity terminal of the DC power source 40 to produce a negatively charged continuous fluid stream by conductor 17.An ion collecting electrode 20 is mounted in the cylindrical structure 10 downstream from the ionizing electrodes 12, 14 and connected electrically to a sense amplifier 21 whose output is connected to the reset terminal of a flip-flop 22.

Between the ionizing electrode 14 and the collecting electrode 20 is provided a deionizing electrode 41 which is connected to ground through a switch 42 to establish a conductive path therebetween in response to a control signal supplied from a trigger source 23.

When the deionizing electrode 41 is grounded in response to the trigger signal, the negatively charged ions are collected by the electrode 41 to deionize a portion of the continuous ion stream to form an electrically neutralized region which migrates with the fluid flow. The potential at the collecting electrode 20 which is initially at a negative level is raised to zero voltage level as it is impinged upon by the electrical neutral region. This potential variation is sensed by the amplifier 21. The flipflop-22 is triggered into a set condition by a signal from the trigger source 23. The trigger source 23 generates the trigger pulse at regular intervals to provide measurement of the instantaneous value of flow rate in succession.

An AND gate 25 is connected to the Q output of the flip-flop 22 to pass clock pulses from clock source 26 to a binary counter 27 which is reset by the Q output of flip-flop 22. The counter 27 provides digital output representing the transit time of the flow in the passage 11 over the distance between the deionizing electrode 41 and the collecting electrode 20.

This digital output is applied to a flow rate indicating circuit (not shown) where the input signal is used to arithmetically divide the known distance between electrodes 15 and 20 to compute an instantaneous value of the flow rate.

The voltage and polarity of the DC power source 40 and the shape and size of the inner electrode 14 are so determined as to establish a corona discharge in the fluid passage 11 so that a portion of the fluid is ionized to produce a cloud of oppositely charged ions. The ionizing electrode 14 is at the negative polarity potential and this is preferred because it is found to be advantageous for effecting ionization of the fluid such as gasoline or the like, as compared with the use of positive polarity.

As a result, the positively charged ions are rapidly attracted by the negatively biased inner electrode 14, while the negatively charged ions migrate in the form of a space charge or cloud of ions with the- fluid flow down the passage 11 at the same speed until they are collected by the collecting electrode 20, which is sensed by the amplifier 21. On the other hand, the flip-flop 22 is switched to a first binary state in response to the trigger pulse and AND gate 25 is thus enabled to pass clock pulses to the binary counter 27.

Upon the detection of the negatively charged ions by the collecting electrode 20, the flipflop 22 is switched to a second binary state to reset the counter 27.

It is understood therefore that in response to each of the trigger pulses from the trigger source 23, an electrically neutralized region is produced in the passage 11 and migrates at the same speed as the speed of fluid flow in the passage 11 from the point defined by the deionizing electrode 41 to the point defined by the collecting electrode 20. During the migration of the neutral region the counter 27 is activated to produce an output representative of the transit time of the neutral region over the known distance between the two defined points. Since the neutral region migrates at the same speed as the fluid flow, the digital output from the counter 27 is a measure of the instantaneous value of the flow rate.

The collecting electrode 20 shown and described in the previous embodiments may be formed into a rod or a plate-like member.

However, it is preferable to employ a mesh electrode 90 as shown in Figs. 2 and 3 to increase the ion collecting efficiency. The mesh electrode 90 is formed of a multilayered disc-like mesh structure disposed transversely of the passage 11. This structure increases the surface areas of the collecting electrode while permitting the fluid to pass therethrough.

Another method of detecting ions is illustrated in Fig. 4 in which a pair of electrodes 91 and 92 is disposed in opposed relation to each other and elevtrically connected in a series closed loop including a resistor 93 and a DC voltage source 94 whose one terminal is connected to ground. Since the fluid to be measured is of nonconducting material, there is no current flow when the fluid is not ionized. When a cloud of ions is passed through the electrodes 91 and 92, there is a reduction in resistance between them, and the resulting current will develop a voltage across the resistor 93, which voltage is sensed by an amplifier 95.

WHAT WE CLAIM IS: 1. Apparatus for measuring the flow

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. which is formed by two electrodes: a ring Or cylindrically hollow outer electrode 12 and a cylindrical rod or inner electrode 14 having a reduced diameter portion 15. The ring electrode 12 is connected electrically to a first or positive polarity terminal of a high voltage DC power supply 40 or ground by conductors 13 and 18. The cylindrical rod 14 is disposed concentrically with the center axis of the ring electrode 12 and connected electrically to the second or negative polarity terminal of the DC power source 40 to produce a negatively charged continuous fluid stream by conductor 17.An ion collecting electrode 20 is mounted in the cylindrical structure 10 downstream from the ionizing electrodes 12, 14 and connected electrically to a sense amplifier 21 whose output is connected to the reset terminal of a flip-flop 22. Between the ionizing electrode 14 and the collecting electrode 20 is provided a deionizing electrode 41 which is connected to ground through a switch 42 to establish a conductive path therebetween in response to a control signal supplied from a trigger source 23. When the deionizing electrode 41 is grounded in response to the trigger signal, the negatively charged ions are collected by the electrode 41 to deionize a portion of the continuous ion stream to form an electrically neutralized region which migrates with the fluid flow. The potential at the collecting electrode 20 which is initially at a negative level is raised to zero voltage level as it is impinged upon by the electrical neutral region. This potential variation is sensed by the amplifier 21. The flipflop-22 is triggered into a set condition by a signal from the trigger source 23. The trigger source 23 generates the trigger pulse at regular intervals to provide measurement of the instantaneous value of flow rate in succession. An AND gate 25 is connected to the Q output of the flip-flop 22 to pass clock pulses from clock source 26 to a binary counter 27 which is reset by the Q output of flip-flop 22. The counter 27 provides digital output representing the transit time of the flow in the passage 11 over the distance between the deionizing electrode 41 and the collecting electrode 20. This digital output is applied to a flow rate indicating circuit (not shown) where the input signal is used to arithmetically divide the known distance between electrodes 15 and 20 to compute an instantaneous value of the flow rate. The voltage and polarity of the DC power source 40 and the shape and size of the inner electrode 14 are so determined as to establish a corona discharge in the fluid passage 11 so that a portion of the fluid is ionized to produce a cloud of oppositely charged ions. The ionizing electrode 14 is at the negative polarity potential and this is preferred because it is found to be advantageous for effecting ionization of the fluid such as gasoline or the like, as compared with the use of positive polarity. As a result, the positively charged ions are rapidly attracted by the negatively biased inner electrode 14, while the negatively charged ions migrate in the form of a space charge or cloud of ions with the- fluid flow down the passage 11 at the same speed until they are collected by the collecting electrode 20, which is sensed by the amplifier 21. On the other hand, the flip-flop 22 is switched to a first binary state in response to the trigger pulse and AND gate 25 is thus enabled to pass clock pulses to the binary counter 27. Upon the detection of the negatively charged ions by the collecting electrode 20, the flipflop 22 is switched to a second binary state to reset the counter 27. It is understood therefore that in response to each of the trigger pulses from the trigger source 23, an electrically neutralized region is produced in the passage 11 and migrates at the same speed as the speed of fluid flow in the passage 11 from the point defined by the deionizing electrode 41 to the point defined by the collecting electrode 20. During the migration of the neutral region the counter 27 is activated to produce an output representative of the transit time of the neutral region over the known distance between the two defined points. Since the neutral region migrates at the same speed as the fluid flow, the digital output from the counter 27 is a measure of the instantaneous value of the flow rate. The collecting electrode 20 shown and described in the previous embodiments may be formed into a rod or a plate-like member. However, it is preferable to employ a mesh electrode 90 as shown in Figs. 2 and 3 to increase the ion collecting efficiency. The mesh electrode 90 is formed of a multilayered disc-like mesh structure disposed transversely of the passage 11. This structure increases the surface areas of the collecting electrode while permitting the fluid to pass therethrough. Another method of detecting ions is illustrated in Fig. 4 in which a pair of electrodes 91 and 92 is disposed in opposed relation to each other and elevtrically connected in a series closed loop including a resistor 93 and a DC voltage source 94 whose one terminal is connected to ground. Since the fluid to be measured is of nonconducting material, there is no current flow when the fluid is not ionized. When a cloud of ions is passed through the electrodes 91 and 92, there is a reduction in resistance between them, and the resulting current will develop a voltage across the resistor 93, which voltage is sensed by an amplifier 95. WHAT WE CLAIM IS:

1. Apparatus for measuring the flow

velocity of fluids passing through a conduit comprising, means for charging a stream of said fluid to a given potential, a first electrode disposed downstream of said charging means, a source for generating trigger pulses at periodic intervals, means for applying a potential different from said given potential to said first electrode to discharge a portion of the stream of said charged fluid in response to said trigger pulse, a second electrode disposed downstream of said first electrode to detect said discharged portion to generate an output signal, a bistable device for assuming a first binary state in response to said trigger pulse and a second binary state in response to said output signal from said second electrode, and means connected to said bistable device for measuring the length of time between said first and second binary states.

2. Apparatus as claimed in claim 1, wherein said charging means comprises a source of DC potential, an electrode encircling a portion of said conduit and connected to one terminal of said potential source and a needle electrode aligned to the center of said encircling electrode in said fluid.

3. Apparatus as claimed in claim 1 or 2, wherein each of said first and second electrodes comprises a meshed structure.

4. Apparatus for measuring the flow velocity of fluids passing through a conduit substantially as described with reference to and as illustrated in the accompanying drawings.