Measuring and testing – Volume or rate of flow – By measuring vibrations or acoustic energy
Reexamination Certificate
2000-02-02
2002-12-03
Fuller, Benjamin R. (Department: 2855)
Measuring and testing
Volume or rate of flow
By measuring vibrations or acoustic energy
C073S861280, C073S861270
Reexamination Certificate
active
06487916
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for metering flow velocity. More particularly, the present invention relates to a system that measures acoustic pulses in a flowing fluid. In particular, the present invention relates to a velocimeter and a method of comparing acoustic transmission delays between at least two velicometers.
2. Relevant Technology
Many fluid flow applications require real-time evaluation for various reasons such as fluid quality evaluation and process control. Such real-time evaluation allows for dynamic control and monitoring of the fluid flow application. The evaluation of fluid flow in a conduit may be due to the need to control, monitor, or adjust the dynamic volume of fluid being delivered through the conduit. Measuring the flow in a conduit is useful in a number of applications.
One such application is measuring the flow of water through an irrigation pipe, particularly in commercial irrigation applications. Flow measurement is useful for several reasons, including the ability to track the amount of water delivered to a portion of land in order to provide adequate irrigation. Additionally, where irrigation is used, water needs to be employed efficiently. For such reasons, irrigation systems require the ability to monitor the volumetric delivery of water and to measure flow rate.
Another application is measuring the flow of natural gas through a pipe, particularly as it is delivered from the gas fields to metropolitan areas. Measuring both the flow and the concentration of gas is useful for several reasons including the ability to track the total amount of gas being delivered from the gas fields as a response to consumer demand.
Closer to the end use, the monitoring of natural gas as it is mixed with ambient air and charged to a combustion device, may be critical for proper operation of the device. As gas flow meters typically measure a pressure drop such as by using the Venturi principle, the pressure drop may adversely affect the combustion device.
A number of devices for measuring flow rate exist for various applications. The size of the conduit being used, accuracy, cost, and other factors may play a role in determining what type of measuring device will be used for a specific application. One flow metering system uses differential pressures that are detectable with pressure transducers. Measuring flow in this manner requires the conduit to contract. Typical systems for contracting the flow profile include installing a section of pipe which tapers to a significantly smaller diameter.
The contraction of the flow of water through an irrigation pipe is undesirable for a number of reasons. For example, irrigation water often contains debris which can cause an obstruction in a small diameter pipe or which can become caught against a restriction. An obstruction will result in plugging of the pipe, requiring time, energy, and expense to unplug or otherwise repair it. In addition, time required to reverse plugging may jeopardize crops which go unwatered during unscheduled down time.
Another problem with differential pressure producing devices is that there is often significant retrofitting required to incorporate them into the system where flow is being measured. For example, in the case of devices which use a gradual reduction in the diameter of the conduit, a relatively long section of conduit must be removed and replaced with a tapering conduit section.
Another problem with measuring flow in a conduit is that variations in temperature and humidity can adversely affect detection conditions. These are often the types of conditions of commercial irrigation applications. More pronounced is the effect of temperature and humidity variations upon gaseous flow due to the tendency of the gas to expand or contract, and to change in quality where humidity is different between the gas source and the delivery point.
Another approach to measuring flow rate is the so-called elbow flow meter in which a curved section of pipe in the fluid delivery system is fitted with pressure sensors to measure pressure differential in the elbow. In order to measure the flow accurately, the sensors must be precisely placed in both the outer and inner circumferential walls of the elbow, in the same radial plane, and then must be calibrated.
The elbow flow meter itself, however, presents problems of its own. Initially, the mere fact that an elbow must be put into a pipe requires designing the pipe with a bend therein, or removing a section of the pipe to put a first elbow that diverts the flow direction, and a second elbow that restores the flow direction. The elbow flow meter may be configured with pressure transducers that measure the pressure of the fluid both before and after the elbow.
One problem occurs where transducers are located at different elevational levels, particularly for liquids, such that a slight pressure measurement bias is introduced due to the elevation difference. An elevation difference therefore requires calibration of the pressure transducers. Two or more transducers may be placed at each location both above and below the elbow but this requires averaging of the pressure measurements and a single malfunctioning pressure transducer will give a spurious average.
Another problem with elbow flow meters is the disturbance caused by the elbow bend itself that creates eddies, and other turbulence that may cause a spurious pressure reading downstream from the bend. As such, under certain flow regimes such as the laminar flow- to the laminar-to-turbulent-transition region, the disturbance at the bend may require the downstream transducer to be placed at a significant distance, thus complicating configuration of the flow meter. Additionally, where flow velocity variations may vary significantly between laminar and fully turbulent flow, the placement of a downstream transducer at a single location will be inadequate to monitor pressure drop for all flow regimes.
What is needed in the art is a fluid flow meter that avoids the problems of the prior art. Additionally, what is needed in the art is a fluid flow meter that does not require the obstruction or constriction of the flow in the conduit. What is also needed in the art is a fluid flow meter that does not require redirecting the flow of the fluids such as with an elbow and the like.
Such systems, methods, and apparatuses are disclosed and claimed herein.
SUMMARY AND OBJECTS OF THE INVENTION
The present invention relates to a system for measuring fluid flow that avoids the problems of the prior art. The inventive system uses a plurality of “sing-around” circuits that may filter out capacitive couplings for gaseous systems and that filter out electronic noise for fluid systems in general.
The inventive system uses at least two non-intrusive sing-around circuits that send an audio signal through the flowing fluid within a conduit. A first sing-around circuit sends an audio signal in a direction perpendicular to the flow of the fluid. A second sing-around circuit sends an audio signal in a direction that is oblique to the direction of flow of the fluid in the conduit. Although such variables as fluid density, fluid temperature, fluid pressure, and fluid velocity must be monitored during ordinary metering of fluid flow, the inventive combination of the two sing-around circuits eliminates the need to monitor fluid density, fluid temperature, and fluid pressure.
Transit time for a signal to move a known distance between a transmitter and a receiver is determined for two separate sing-around circuits. Thereby, the transit-time shift velocity or sound velocity difference is determinable due to the fluid flow velocity. From the transit-time shift velocity, the flow velocity can be determined by understanding the trigonometric relationship between directional placement of each transmitter and receiver.
In the inventive circuit, an audio signal is generated from a transmitter and detected by a receiver. A portion of the audio signal reaches the receiver. The audio signal is
Gomm Tyler J.
Kraft Nancy C.
Mauseth Jason A.
Phelps Larry D.
Taylor Steven C.
Allen Andre
Bechtel BXWT Idaho, LLC
Fuller Benjamin R.
Workman & Nydegger & Seeley
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