Gas bubble detector

• US 5,455,423 A
• Filed: 08/25/1993
• Issued: 10/03/1995
• Est. Priority Date: 08/25/1993
• Status: Expired due to Fees

• Current Assignee: Orbital Sciences Corporation (Northrop Grumman Corporation)
• Original Assignee: Orbital Sciences Corporation (Northrop Grumman Corporation)
• Inventors: Burchfield, David E., Hagey, John M., Mount, Bruce E.
• Primary Examiner(s): FIELDS, CAROLYN
• Application Number:
  US08/112,008
• Time in Patent Office: 769 Days
• Field of Search: 250/343, 250/576, 356/440
• US Class Current: 250/343
• CPC Class Codes: G01N 21/85 Investigating moving fluids or granular solids

Abstract

A gas bubble detector having a modulated IR source focused through a bandpass filter onto a venturi, formed in a sample tube, to illuminate the venturi with modulated filtered IR to detect the presence of gas bubbles as small as 0.01 cm or about 0.004" in diameter in liquid flowing through the venturi. Means are provided to determine the size of any detected bubble and to provide an alarm in the absence of liquid in the sample tube.

Claims

1. An apparatus for detecting gas bubbles in a flowing liquid comprising:

a venturi formed in a tube through which liquid flows,

a modulated IR energy source directed onto the liquid flowing through said venturi,

means for detecting the amount of IR energy absorbed by said liquid and by any gas bubbles in said liquid and providing an output signal proportional to the amount of IR energy absorbed, and

means for processing said output signal to determine the size of any gas bubble in said liquid as a function of the amount of energy absorbed and time.

2. The apparatus as claimed in claim 1 wherein said means for processing said output signal includes alarm means for emitting a signal indicating that a large gas bubble is present or that there is no liquid in the tube or venturi.

3. The apparatus as claimed in claim 1 further including an optical filter which filters the modulated IR energy into wavelengths corresponding to the absorption characteristics of the liquid flowing through the venturi.

4. The apparatus as claimed in claim 3 wherein said optical filter is a bandpass filter.

5. The apparatus as claimed in claim 1 wherein said modulated IR energy source comprises a frequency modulated incandescent lamp operating at a selected duty cycle.

6. The apparatus as claimed in claim 5 further including a reflector for focusing the output of said incandescent lamp onto the liquid within said venturi.

7. The apparatus as claimed in claim 5 wherein the voltage applied to said incandescent lamp is approximately 3.6 v and the duty cycle of said incandescent lamp is approximately 20% when the liquid is water and the gas is air.

8. The apparatus as claimed in claim 1 wherein said means for processing said output signal comprises circuitry which derives a time-varying vector magnitude signal proportional to the size of any detected gas bubble in said flowing liquid.

9. A gas bubble detector which detects bubbles as small as 0.004 inches in a flowing stream of liquid comprising:

a housing,

a source of IR energy,

means in said housing directing said IR energy to a focal point,

means between said source and said focal point for filtering said IR energy to a bandwidth corresponding to the absorption capabilities of said liquid,

tube means in said housing capable of handling said flowing liquid,

a venturi formed in said tube means and located at said focal point,

an IR detector means located so as to detect the amount of IR energy absorbed by said flowing liquid and any gas bubble in said flowing liquid and to provide an output signal, and

means for processing the output signal from said detector means so as to determine the number and size of any gas bubbles in said flowing liquid.

10. The detector as claimed in claim 9 wherein said means directing said IR energy is a parabolic reflector.

11. The detector as claimed in claim 9 wherein the internal diameter of said venturi is approximately 0.015 in.

12. A method of detecting gas bubbles in a flowing liquid comprising the steps of:

providing a flow of said liquid which may contain one or more gas bubbles through a venturi,

directing IR energy towards said venturi so as to illuminate said venturi and the liquid and gas flowing therethrough,

filtering said IR energy as it is being directed toward said venturi to correspond to the absorption characteristics of the liquid and gas flowing through said venturi,

providing detector means for absorbing said IR energy in said venturi and for producing an output signal proportional to the absorption of the IR energy of said liquid and gas flowing through said venturi, and

processing said output signal to determine the size of any detected gas bubble in said flowing liquid.

13. The method as claimed in claim 12 wherein said step of processing said output signal includes the step of determining the size and number of gas bubbles in said flowing liquid.

14. The method as claimed in claim 12 wherein said step of processing said output signal also includes the step of determining when a large bubble or no fluid is present in said venturi.

15. An apparatus for detecting gas bubbles in a liquid flowing through a sample tube comprising:

a sample area comprising a venturi formed in said sample tube through which liquid flows;

an IR energy source directed onto the liquid flowing through said sample area;

frequency modulation means for modulating the intensity of IR energy that is directed onto the sample area by said IR energy source at a selected duty cycle; and

an IR detector for sensing the IR energy incident to said detector and providing an output signal that is proportional to the amount of IR energy absorbed by the liquid flowing through said sample area;

wherein the selected duty cycle of said IR energy source is approximately 20% when said apparatus is detecting air bubbles and said flowing liquid is water.

16. The apparatus as claimed in claim 15 wherein said IR energy source comprises an incandescent lamp.

17. The apparatus as claimed in claim 15 further comprising filtering means for filtering the modulated IR energy into wavelengths corresponding to the absorption characteristics of the liquid flowing through the venturi.

18. The apparatus as claimed in claim 15 further comprising alarm means for emitting a signal indicating that a gas bubble larger than a threshold size is present or that there is no liquid in the tube or venturi.

19. An apparatus for detecting gas bubbles in a liquid flowing through a tube comprising:

a sample area comprising a venturi formed in said sample tube through which liquid flows;

an IR energy source directed onto the liquid flowing through said sample area;

frequency modulation means for modulating the intensity of IR energy that is directed onto the sample area by said IR energy source;

an IR energy detector for sensing the IR energy incident to said detector and providing an output signal that is proportional to the amount of IR energy absorbed by the liquid flowing through said sample area; and

means for processing said output signal to determine the size of any gas bubble in the liquid flowing through said sample area as a function of the amount of energy absorbed by said liquid and time.

20. The apparatus as claimed in claim 19 wherein said means for processing said output signal comprises circuitry which derives a time-varying vector magnitude signal proportional to the size of any detected gas bubble in the liquid flowing through said sample area.

21. The apparatus as claimed in claim 20 wherein said processing means further comprises amplitude demodulation means for processing said output signal for detecting gas bubbles which remain in said sample area for longer than a threshold period of time.

22. An apparatus for detecting gas bubbles in a liquid flowing through a sample tube comprising:

a sample area comprising a venturi formed in said sample tube through which liquid flows;

an IR energy source directed onto the liquid flowing through said sample area;

a frequency modulator circuit for modulating the power supply to said IR energy source at a selected duty cycle; and

an IR detector for sensing the IR energy incident to said detector and providing an output signal that is proportional to the amount of IR energy absorbed by the liquid flowing through said sample area;

wherein the selected duty cycle of said IR energy source is approximately 20% when said apparatus is detecting air bubbles and said flowing liquid is water.

23. The apparatus as claimed in claim 22 wherein said IR energy source comprises an incandescent lamp.

24. The apparatus as claimed in claim 22 further comprising means for processing said output signal to determine the size of any gas bubble in the liquid flowing through said sample area as a function of the amount of energy absorbed by said liquid and time.

25. The apparatus as claimed in claim 24 wherein said means for processing said output signal comprises circuitry which derives a time-varying vector magnitude signal proportional to the size of any detected gas bubble in the liquid flowing through said sample area.

26. The apparatus as claimed in claim 25 wherein said processing means further comprises amplitude demodulation means for processing said output signal for detecting gas bubbles which remain in said sample area for longer than a threshold period of time.