Measuring and testing – Volume or rate of flow – By measuring electrical or magnetic properties
Reexamination Certificate
2003-02-03
2004-06-22
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Volume or rate of flow
By measuring electrical or magnetic properties
Reexamination Certificate
active
06752026
ABSTRACT:
REFERENCE TO FEDERALLY SPONSORED RESEARCH
Not applicable
REFERENCE TO A COMPUTER PROGRAM LISTING APPENDIX
Not applicable
FIELD OF INVENTION
This invention relates to flowmeter and more particularly to electromagnetic flowmeter measurement of either magnetic or non-magnetic, compressible or incompressible fluid flow in a steady or transient fluid state, when fluid flow is characterized as single-phase or multi-phase, including combinations of gases, liquids, vapors, particles, and/or emulsions, and when fluid flow is either forward or backward through a flowmeter, so that obstructionless fluid flow measurements can be made.
BACKGROUND OF THE INVENTION
Fluid flowmeter for many applications already exist. Flowmeter are devices that measure the rate of flow or the quantity of a moving fluid in an open or a closed conduit. They are characterized as consisting of a primary device and a secondary device. The primary device is mounted internally or externally to a fluid conduit. A primary device produces a signal generated by the interaction of the fluid with the physical configurations or manifestations of the device. The secondary device responds to the signal from the primary device and converts that signal into a display or other presentation to indicate flow rate. Flowmeter are fabricated from various materials and constructed in different configurations. Both the primary and secondary devices use a variety of physical means to identify the flow rate of a fluid through a conduit.
Several variables determine how a fluid flowmeter is constructed and used. These variables include, type of fluid; temperature and pressure limits, steady-state, pulsating, or transient fluid flow, range of flow measurement, pipe size; flow conditioner size; length of meter runs to generate stable flow before measurement; surface roughness; number of blades internal to a turbine flowmeter; friction forces; springs; pistons; floats; and other mechanical configurations, such as cones; tubes; and targets. In addition to these variables affecting fluid flowmeter construction and application, costs related to installation and to fluid-flow pressure drop across the meter must be considered. A pressure drop across the meter requires more pumping energy and therefore generates higher fluid pumping costs, especially in large diameter conduits.
There are fluid flow obstruction problems associated with flowmeter applications. These obstruction problems include poorly configured conduit systems, fittings, and other physical devices that may generate an obstruction in the path of a moving fluid. Within the existing range of technologies for fluid flow measurement, most obstructions adversely affect fluid measurement even while generating primary device signals. All obstructions generate a pressure drop within the fluid system.
Fluid flowmeter are also classified as differential producers or linear scale meters. Differential producers include orifice meters, target meters, venturi meters, flow nozzles, low-loss meters, pitot tube meters, and elbows. Linear scale meters include magnetic flowmeter, positive displacement meters, turbine meters, ultrasonic meters, variable area meters, and vortex meters.
The few fluid flow measuring technologies that do not use obstructions include ultrasonic signal and electromagnetic field signal evaluation. Ultrasonic flowmeter that use ultrasonic transmitters and receivers are placed externally to a conduit to sense the change in time of transmitted and received ultrasonic signals within a fluid. The variation in time for the transmitted and reflected signals is translated into fluid flow rate. Doppler flowmeters, another type of ultrasonic flowmeter, reflect the flowing fluid pressure front to a detector by particulate matter in the fluid. The difference in a doppler meters' reflected frequency and fixed frequency is related to the flowing fluid rate. Obstructionless flowmeters also include electromagnetic fluid flowmeters that are based upon the principle of electromagnetic induction. These flowmeters average the velocity of the fluid over the conduit area. Measured fluids must have adequate magnetic properties so that the fluid will support an electromagnetic field.
The measurement of compressible fluids over short time periods when the fluid is in a transient state is an extraordinarily complex problem that is not specifically addressed by existing flowmeter technologies. As a result, both historically and practically, fluid dynamic measurements concentrate on steady-state flow rates where averages of the fluid flow are determined. Instantaneous fluid flow measurements are not often made due to the wide variety of disturbances that can affect the fluid flow rate and due to slow time constants in conventional flowmeters. For example, in most industrial applications, pulsation and transient behavior are considered to be undesirable flowing fluid properties. Pulsation dampeners are often used in fluid systems to decrease pulsation effects and fluid capacitances and fluid accumulators are used to further reduce transient fluid flow behavior. Thus, the measurement of fast-transient fluid flow, and correspondingly, steady-state fluid flow are not dual design parameters in current flowmeters. As a result, current technology is directed to flowmeters that measure average, continuous, steady-state flow rates.
Swirling flow is a common deleterious effect in gas flow measurements. Swirling is caused by elbow fittings out of plane in pipelines. Swirling creates additional measurement problems for common flowmeters such as orifice plate, turbine, and vortex meters, which require relatively undisturbed flow profiles to generate reproducible, reliable, and accurate measurements. Improvement in the measurement of swirling gas flow rates has been reported for the v-cone flowmeter. The v-cone meter is an obstruction, differential pressure, flowmeter in which a cone is placed in the fluid flow path.
The patent literature includes the description of a number of fluid flow measuring devices that address mechanical motion associated with magnetic followers to indicate the conditions of fluid flow. Among the patents is U.S. Pat. No. 3,805,611 to H. A. Hedland (1974) that teaches a single magnetic piston, a conical interior unit to modify fluid flow rate, and a magnetic follower, exterior but concentric and contiguous to the flowmeter housing, to track the mechanical position of the internal magnetic piston and to show flow rate on a mechanical scale. U.S. Pat. No. 3,805,611 represents a beneficial fluid flowmeter with a number of practical advantages. However, the Art taught in U.S. Pat. No. 3,805,611 suggests that fluid flow is not impeded by internal components in the path of a flowing fluid. This description contradicts the known laws of physical science, which require a pressure drop across any passive annular fluid device through which fluid flows. However, this minor discrepancy in description does not affect the practical application of Hedland's flowmeter that has been used in many flow measurement environments in the petroleum industry.
The issue of pressure drop associated with flow rate measurement is an important issue that affects the manner in which flowmeters operate. Pressure drop across a fluid flow rate measuring element is especially important when considering explosive, instantaneous, transient, or fast periodic fluid flow rate measurement.
As a result of the focus of prior Art on steady-state fluid flow measurements, current methods to acquire fluid flow rate data for explosive, fast, non-steady-state, moving fluids suffer a number of disadvantages when addressing fluid flow rate variation, including the disadvantages listed below.
[1] Prior Art in measurement of fluid flow rate focuses upon thermodynamic steady-state conditions of flow and does not specifically address transient and other non-steady-state conditions as the primary focus of fluid flow measurement.
[2] Because existing flowmeters do not focus on explosive, transient, and fast non-steady
Lefkowitz Edward
Miller Takisha
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