Process and apparatus for ultrasonic measurement of volumeric flow through large-diameter stack
First Claim
1. An apparatus for monitoring volumetric flow rate of gases through a hollow stack having an extended vertical axis wherein the diameter of said stack is greater than about three meterscomprising, ultrasonic transducer means for emitting an ultrasonic beam from a specified vertical position on said stack wall vertically displaced from the bottom of said stack, said ultrasonic beam being emitted with a substantial conical envelope on a central axis of propagation normal to said vertical axis along a diameter of said stack, and for receiving said ultrasonic beam at a vertical position displaced vertically from said specified vertical position by a distance which lies between zero and a fraction of said diameter, not to exceed about two meters, the half angle θ
- h of said emitted beam envelope being such that during volumetric flow a detectable portion of said emitted ultrasonic beam is received, andmeans operative during said volumetric flow for exciting said ultrasonic transducer means in controlled sequence, and for providing as indicative of said volumetric flow rate an output signal indicative of a transit time from the time said ultrasonic beam is emitted from said ultrasonic transducer means until it is received by said ultrasonic transducer means.
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Accused Products
Abstract
An apparatus and method for measuring gas flow velocity through a high stack employs ultrasonic transducers. The transducers are placed on opposite ends of a diameter several hundred feet up, with a small vertical separation L between the transducers. Apparatus for measuring acoustic velocity in the stack gas over short path lengths is also included.
42 Citations
45 Claims
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1. An apparatus for monitoring volumetric flow rate of gases through a hollow stack having an extended vertical axis wherein the diameter of said stack is greater than about three meters
comprising, ultrasonic transducer means for emitting an ultrasonic beam from a specified vertical position on said stack wall vertically displaced from the bottom of said stack, said ultrasonic beam being emitted with a substantial conical envelope on a central axis of propagation normal to said vertical axis along a diameter of said stack, and for receiving said ultrasonic beam at a vertical position displaced vertically from said specified vertical position by a distance which lies between zero and a fraction of said diameter, not to exceed about two meters, the half angle θ -
h of said emitted beam envelope being such that during volumetric flow a detectable portion of said emitted ultrasonic beam is received, and
means operative during said volumetric flow for exciting said ultrasonic transducer means in controlled sequence, and for providing as indicative of said volumetric flow rate an output signal indicative of a transit time from the time said ultrasonic beam is emitted from said ultrasonic transducer means until it is received by said ultrasonic transducer means.
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h of said emitted beam envelope being such that during volumetric flow a detectable portion of said emitted ultrasonic beam is received, and
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2. An apparatus for monitoring volumetric flow rate of gas flowing through a hollow stack having an extended vertical axis wherein the diameter of said stack is greater than about three meters comprising,
a first ultrasonic transducer positioned on said stack wall to emit ultrasonic waves directed on a central axis of propagation along a diameter of said stack in a horizontal plane, normal to said vertical axis, and vertically displaced from the bottom of said stack, a second ultrasonic transducer positioned to receive said ultrasonic waves emitted from said first transducer, said second ultrasonic transducer being displaced vertically from said first transducer by a distance L which is no more than a fraction of said diameter, not exceeding about two meters, the half angle θ -
h of said first ultrasonic transducer emission being such that a detectable portion of ultrasonic waves from said beam emitted by said first ultrasonic transducer directly impinges upon said second ultrasonic transducer, and
means for exciting said first ultrasonic transducer in a controlled time sequence, and for providing an output signal indicative of a transit time of ultrasonic waves from said first ultrasonic transducer received by said second ultrasonic transducer. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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h of said first ultrasonic transducer emission being such that a detectable portion of ultrasonic waves from said beam emitted by said first ultrasonic transducer directly impinges upon said second ultrasonic transducer, and
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33. An apparatus for monitoring volumetric flow rate of gases through a hollow stack having an extended vertical axis wherein the diameter of said stack is greater than about three meters comprising,
a first clamp-on ultrasonic transducer positioned to emit ultrasonic waves propagated from the interior wall of said stack in a direction angled away from a direction normal to said stack vertical axis, a reflecting member mounted within said stack and positioned to intercept ultrasonic waves emitted from said first ultrasonic transducer, a second clamp on ultrasonic transducer positioned at the opposite end of a stack tilted diameter from said first ultrasonic transducer in a location where it receives ultrasonic waves emitted from said first ultrasonic transducer which are reflected from said reflecting member, said second clamp on ultrasonic transducer being oriented to propagate ultrasonic waves to reflect from said reflecting member in a direction where they are received by said first ultrasonic transducer, said second transducer being vertically displaced from said first transducer by a distance L which is a fraction of said diameter, not exceeding about two meters, and means for exciting said first transducer in a controlled time sequence, and for providing an output signal indicative of the transit time from said first transducer of ultrasonic waves reflected by said reflecting member and received by said second transducer.
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34. An apparatus for monitoring volumetric flow rate of a gas flowing through a hollow stack having an extended vertical axis comprising,
a first ultrasonic transducer assembly positioned to direct an ultrasonic beam from said stack wall across said stack at a vertical position displaced from the bottom of said stack, a second ultrasonic transducer assembly positioned to receive ultrasonic waves emitted from said first ultrasonic transducer, said second ultrasonic transducer being displaced vertically from said first ultrasonic transducer by a distance L which is a fraction of said diameter, not to exceed about two meters, said first transducer emission being such that a detectable portion of ultrasonic waves from said beam emitted by said first transducer impinges upon said second transducer, means for exciting said first transducer in a time sequence, and for providing an output signal indicative of a transit time from said first transducer of ultrasonic waves received by said second transducer, and wherein at least one of said ultrasonic transducers comprises a small aperture transducer mounted to direct ultrasonic waves outwardly toward said stack wall and a reflector positioned to receive ultrasonic waves emitted from said transducer and reflect them in a substantially collimated beam back across said stack diameter.
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37. An apparatus for monitoring volumetric flow rate of a gas flowing through a hollow stack having an extended vertical axis comprising,
a first ultrasonic transducer assembly positioned to direct an ultrasonic beam from said stack wall across said stack at a vertical position displaced from the bottom of said stack, a second ultrasonic transducer assembly positioned to receive ultrasonic waves emitted from said first ultrasonic transducer, said second ultrasonic transducer being displaced vertically from said first ultrasonic transducer by a distance L which is a fraction of said diameter, not to exceed about two meters, said first transducer emission being such that a detectable portion of ultrasonic waves from said beam emitted by said first transducer impinges upon said second transducer, means for exciting said first transducer in a time sequence, and for providing an output signal indicative of a transit time from said first transducer of ultrasonic waves received by said second transducer, and wherein at least said first ultrasonic transducer is formed of an array of a plurality of individual ultrasonic transducers, each of said individual ultrasonic transducers having an emitting face in a plane parallel to said extended vertical axis of said stack and, wherein said means for exciting said first transducer includes a variable frequency generator varying its frequency in a predetermined pattern, each of said individual transducers being coupled to said frequency generator through individual phase shift circuits, each phase shift circuit being characterized by a different phase shift response, said predetermined pattern of frequency variation and said individual phase shift circuit characteristic being selected to provide that the composite of ultrasonic waves from said array of individual transducer is steered along an axis which differs from an axis normal to said extended vertical axis of said stack.
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39. A method of monitoring the volumetric gas flow rate through a substantially vertically oriented stack comprising the steps of,
(a) emitting a beam of ultrasonic waves from a first position above the bottom of said stack, across a diameter of said stack, said beam being emitted along a central axis of propagation normal to the vertical axis of said stack; -
(b) sensing said emitted ultrasonic beam at a second position vertically displaced from said emission position by a distance L equal to the stack diameter times the tangent of the half angle, θ
h, of the emitted beam,the variations in the transit time between emitting and sensing in said sensing step providing a measurement of the gas flow velocity along said vertical axis of said stack. - View Dependent Claims (40, 41, 42)
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43. A method of monitoring the volumetric gas flow rate through a substantially vertically oriented stack comprising the steps of,
(a) emitting a beam of ultrasonic waves from a position above the bottom of said stack, across a diameter of said stack, said beam being emitted along a central axis of propagation normal to the vertical axis of said stack; -
(b) sensing said emitted ultrasonic beam at a position at the opposite end of said stack diameter from said emission position, said position being at substantially the same vertical position as said emission position; the variations in the transit time between emitting and sensing in said sensing step providing a measurement of the gas flow velocity along said vertical axis of said stack.
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44. A method of monitoring the volumetric gas flow rate through a substantially vertically oriented stack comprising the steps of,
(a) emitting a beam of ultrasonic waves from a position substantially above the bottom of said stack, across a diameter of said stack, said beam being emitted along a central axis of propagation normal to the vertical axis of said stack; -
(b) sensing said emitted ultrasonic beam at a position vertically displaced from said emission position by a distance L which is a fraction of said stack diameter, not exceeding about two meters, the variations in the transit time between emitting and sensing in said sensing step providing a measurement of the gas flow velocity along said vertical axis of said stack. - View Dependent Claims (45)
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Specification