Patent Description:
Two of the most important characteristics of a precision flow meter are repeatability and linearity. Repeatability is the ability of a meter to obtain the same results under the same conditions. Linearity is the degree to which a meter's output is linear to the amount of flow being transferred through a pipe or other conduit. <CIT> is related to an inductive flow meter with a probe which is immersed in a liquid and which contains an electromagnet in a housing and has two electrodes which are arranged at a distance from one another on the outside.

It is difficult to make an accurate meter if it is not repeatable. It is also difficult to calibrate and predict performance in various operating conditions (for example, fluids, temperatures, and pipe types) if it is not linear. Insertion flow meters are typically less accurate than in-line meters because they have worse repeatability and linearity than an in-line meter. This is in part because insertion meters by the nature of their design can only measure a point on the velocity profile, or at lease only a small portion thereof, and this measurement must be correlated to estimate the average velocity of flow through the pipe. The shape of the velocity profile changes with flow, pressure, and temperature, among other factors, which affects the translation of this point measurement to total average velocity. Inline meters, on the other hand, measure across the entire velocity profile enabling an accurate direct measurement of the average velocity of flow through the pipe. Consequently, insertion magnetic meters may typically have an accuracy of +/-<NUM>% of reading, whereas in-line meters have accuracies as low as +/- <NUM>% of reading.

However, insertion meters are advantageous as compared to in-line meters because insertion meters are modular and do not require complete system shutdown for installation and repair. In addition, insertion meters cost less and have a lower installation cost. To install an inline meter, the system has to be shut down, a section of pipe cut out, flanges welded in place and then the meter is mounted between the two flanges. Insertion meters can be mounted though a common ball valve.

Any advancement that enables the improvement of either the repeatability of the accuracy of an insertion meter is extremely valuable.

According to the invention, a magnetic insertion meter is disclosed having a sensor head cylinder having a textured front surface and at least two electrodes, wherein the textured front surface is at least one of an abrasive on a substrate, an impregnated abrasive, a deposited abrasive, and/or an abrasive layer. In another aspect of the disclosure, an insertion meter includes a field coil configured to emit an alternating magnetic field when energized with an alternating current. In yet another aspect of the disclosure, a textured front surface is an upstream surface. In one particular aspect of the disclosure, a textured front surface is sandpaper. In another aspect of the disclosure a textured front surface has a higher roughness than a material forming the sensor head tube.

In one aspect of the disclosure, a textured front surface includes at least one groove. In another aspect of the disclosure, a textured front surface includes two grooves extending along the longitudinal axis of the sensor head cylinder. In one aspect of the disclosure, a textured front surface includes dimples. In another aspect of the disclosure, a plurality of dimples is equally spaced apart from each other. In another aspect of the disclosure, a plurality of dimples forms a pattern in which three of the plurality of dimples form an equilateral triangle. In one aspect of the disclosure, a textured front surface includes a plurality of columns of dimples. In one aspect of the disclosure, a textured front surface includes from about <NUM> to about <NUM> columns of dimples. In another aspect of the disclosure a textured front surface includes dimples. In yet another aspect of the disclosure a textured front surface is adapted to alter the boundary layer of a fluid flowing over the sensor head tube as compared to the same sensor head tube without the textured front surface. In another aspect of the disclosure a textured front surface is adapted to move the separation point of a fluid flowing over the sensor head tube towards the front surface as compared to the same sensor head tube without the textured front surface. In one aspect of the disclosure, a textured surface is a surface contour.

According to the invention, a method of measuring flow is disclosed in which the method includes providing a magnetic insertion meter that includes a sensor head cylinder having a textured front surface and at least two electrodes and measuring the output of said electrodes, wherein the textured front surface is at least one of an abrasive on a substrate, an impregnated abrasive, a deposited abrasive, and/or an abrasive layer. In another aspect of the disclosure, a textured front surface includes at least one of dimples and/or grooves.

<FIG> shows a cross section of an insertion meter <NUM>, having the shape of a cylinder, looking down the longitudinal access of an example insertion meter <NUM>. The insertion meter <NUM> may be, for example, part of the example sensor assemblies described in <CIT>, titled "Scalable Monolithic Sensor Assembly, Controller, and Methods of Making and Installing Same," and published as <CIT>. The cross section is taken at electrodes <NUM>.

The insertion meter <NUM>, includes a cylindrical sensor head tube <NUM>, that is inserted into the pipe carrying a suitably conductive fluid <NUM>. In operation, the insertion meter <NUM> generates a magnetic field using field coils energized by an alternating current. The conductor (i.e., the conductive fluid) passing through the magnetic field induces an electric potential and current according to Faraday's law, which is indicative of the flow velocity. The insertion meter <NUM> measures the electrical potential (voltage or "V") generated by the flow velocity between at least two electrodes. Such a potential difference may be measured, for example, between at least one top electrode and at least one bottom electrode.

For example, the insertion meter <NUM> may have <NUM> or more electrodes disbursed from top to bottom of its longitudinal axis. In one particular example the insertion meter <NUM> may include <NUM> or more top electrodes, one or more bottom electrodes, and one or more center electrodes. The center electrodes act as an electrical reference, whereas the voltage potential is sampled between pairs of top and bottom electrodes. The two electrodes <NUM> shown in <FIG> share the same longitudinal height. Thus, the electrodes <NUM>, may each be top electrodes, bottom electrodes, or references electrodes. The electrodes <NUM> shown in <FIG> may be electrically connected to form a single electrode or they be electrically isolated from each other to form two independent electrodes. In an example independent configuration in which the electrodes <NUM> are bottom electrodes, a first potential could be measured between one of the electrodes <NUM> and a respective top electrode and a second potential could be measured between the other electrode <NUM> and a different top electrode.

The repeatability of the fluid flow around previous insertion meters <NUM> can be improved. <FIG> shows insertion meters <NUM> in a flowing fluid <NUM> at an example velocity in the direction of the arrows <NUM>. If, for example, the flowing fluid <NUM> at arrows <NUM> represent a bulk fluid that is turbulent. as shown, the flowing fluid reaches a stagnation point <NUM>, at which the fluid flow is a minimum, when the fluid contacts the front surface <NUM>. The fluid <NUM> also forms a laminar boundary layer <NUM> (or boundary layer <NUM>), which is a transition between the stagnation point and the bulk terminal flow <NUM>, as it contacts the front surface <NUM> facing the oncoming fluid flow. The front surface <NUM>, i.e., the surface facing the oncoming fluid flow, will also be referred to herein as the upstream surface. It should be noted that the if the fluid flow were to reverse directions, the opposing surface would become the upstream surface. The boundary layer <NUM> becomes unstable or otherwise transitions away from the surface of the insertion meter <NUM> as it flows towards the back <NUM>, or downstream surface, of the insertion meter <NUM>. This boundary layer transition is indicated as separation point <NUM>.

The location of the separation point <NUM> is not consistent because fluid flow is chaotic and it is affected by changes in the amount of fluid flow across the insertion meter <NUM>, as well as fluid characteristics, for example, velocity of the fluid, temperature, viscosity, density, and surface finish of the cylinder. In addition, the location of the separation point <NUM> can also change based on whether the flow rate is increasing or decreasing to a given velocity. <FIG> show three different velocities of the same fluid in increasing order, i.e., the <FIG> fluid velocity is higher than the fluid velocity of <FIG>, which is higher than the fluid velocity of <FIG>. In <FIG>, separation point 105a is typically between the electrodes <NUM> and back <NUM>. In <FIG>, the velocity of the fluid is greater than that of <FIG> and less than that of <FIG> and the separation point 105b has shifted to near electrode <NUM>. In <FIG>, the velocity of the fluid is more than that of <FIG> and separation point 105c has shifted closer to the front <NUM> of insertion meter <NUM>, i.e., closer to the direction from which the fluid is flowing. While not being bound by theory, it is believed that the inconsistencies in the boundary layer / separation point <NUM> (105a,105b,105c) location contribute to the decrease in linearity and repeatability experienced with prior insertion meters. That is, an unstable boundary layer at the sensor electrodes <NUM> can prevent accurate and repeatable results as compared to a more stable boundary layer. For example, based on inconsistencies in the fluid flow or changes in the flow rate, at some conditions the separation point 105a is closer to electrode <NUM> (whether downstream or upstream) which, in the right conditions, can cause more variance in the measurements taken at electrode 105a. While the separation point 105c of <FIG> has be shifted towards front surface <NUM>, the variation in the boundary layer shown between <FIG> can cause an insertion meter <NUM> to deviate from calibration.

<FIG> shows example meter outputs (1P-RUN1 through 1P-RUN5) of an example insertion meter <NUM> (<FIG>) as a graph of meter factor expressed as (LPIP Pulse / Isoil Gal) against nominal flow rate expressed in feet per second (ft/s). The meter factor (or correction factor) is normally dimensionless and is calculated as the ratio of the meter output to value determined by a standard reference meter, for example Insertion Meter Pulse/Reference (Ref) Meter Pulse This can be computed from rate measurements or quantity measurements. The different line traces show repeated test runs of the same insertion meter <NUM> under the same conditions. It is shown that both repeatability and linearity can be improved. For the test case shown in <FIG>, the best accuracy achievable using a constant Meter Factor would be +/- <NUM>% of reading. For reference, an ideal sensor would produce a constant meter factor regardless of flow rate being measured (horizontal line) meaning the output of the meter is linear with flow and can be easily corrected by multiplying the meter output by a constant meter factor. While an ideal meter is likely not possible, linearity in the meter factor is desired. Linearity simplifies calibration, that is it is more simple to fit a meter reading to a two-point line as compared to a complex curve fit, e.g. like the complex curve of <FIG>. , which would require multiple characterizations. Linearity also simplifies corrections to other operating conditions, improves reproducibility between meters (unit to unit variation), shortens the manufacturing validation cycle to confirm accuracy of the meter, and limits the need to test multiple meters units to determine characteristic curve, that is, fewer units are required to characterize multiple pipes/sizes. If the meter factor is constant, it is assumed, while the value may change, it will be constant for other fluids or flow conditions. It is much easier to determine corrections for other flow conditions and fluids if the relationship is linear.

Attempts to improve reproducibility have previously been made to change the placement of the electrodes by rotating each electrode towards the front <NUM> of insertion meter <NUM>. This places the electrodes within the laminar boundary layer before it transitions to a turbulent boundary layer. While this could, hypothetically, mitigate some effects of the unstable boundary layer by forcing a consistent velocity profile, it would also result in a decrease of sensor signal, which is not advantageous because it decreases the signal to noise ratio.

<FIG> shows an insertion meter <NUM> having electrodes <NUM>. Insertion meter <NUM> and electrodes <NUM> are the same as insertion meter <NUM> and electrodes <NUM>, respectively, except that insertion meter <NUM> includes textured surface <NUM> on the front <NUM> of insertion meter <NUM>. While the specific configuration of textured surface <NUM> may vary based on the particular operating conditions of the insertion meter (e.g., meter circumference, pipe diameter, pipe flow rate, fluid type, fluid velocity, fluid density, etc.), the textured surface <NUM> should be textured sufficiently to trip or manipulate, the boundary layer such that the separation point (see, e.g., <NUM> , <FIG>) occurs consistently forward (towards front <NUM> of insertion meter <NUM>, i.e., towards the source of the flow) of the electrodes <NUM> for normal operating conditions, and preferably all operating conditions, for the respective insertion meter. In the illustrated embodiment, textured surface <NUM> should be rougher than the remainder of sensor head tube <NUM> of insertion meter <NUM>. For example, in one example, textured surface <NUM> is rougher than the material forming the sensor head tube (e.g., smooth plastic and metal).

As shown in <FIG>, textured surface <NUM> is a sandpaper or other similar abrasive on a substrate adhered to the sensor head tube <NUM>. Example abrasives on substrates include, for example, sand, glass, aluminum oxide, silicon carbide, emery cloth, pumice, crocus cloth, or the like. While this application discusses the use of paper as a substrate, other flexible substrates, for example, cloth, adhesive, or polymer, may also be used as well as inflexible substrates that are formed or machined to the curvature of the outside circumference of the sensor head tube <NUM>. In addition, the abrasives may further be impregnated or deposited into or onto the surface without a substrate as an abrasive layer. The textured surface <NUM> may, in one example, extend the length of the sensor head tube <NUM> or be applied locally in the regions near electrodes <NUM>. The amount of texture will depend on the type of material used, the size and shape of the insertion meter and flow pipe, and the characteristics of the fluid, but should nevertheless be sufficiently textured to manipulate the boundary layer as discussed above.

For example, a sandpaper textured surface <NUM> may include a <NUM>-<NUM> grit adhesive tape having a substrate thickness of about <NUM> inches (<NUM>) and having a width of about <NUM> inches (<NUM>) to about <NUM> inches (<NUM>), inclusive, the width being the dimension which would wrap around the circumference of the sensor head tube <NUM>. The sandpaper textured surface may, in one example, be applied centered on the point of stagnation and along the full length of the meter, or effectively the full length of the sensing portion of the meter sensor head tube <NUM>.

<FIG> shows example meter outputs (SAND1-RUN1-90deg through SAND1-RUN3-90deg) of an example insertion meter <NUM> (<FIG>) as a graph of Meter Factor expressed as (Meter pulse/Ref Meter Pulse) against nominal flow rate expressed in feet per second (ft/s) (<NUM> ft = <NUM>). The different line traces show repeated test runs of the same insertion meter <NUM> in the same conditions. It is shown that both repeatability and linearity are improved over that of insertion meter <NUM> (<FIG>). The improved linearity simplifies calibration and improves performance in different pipes and fluids.

In an alternative example, instead of adding a textured substrate to the surface of insertion meter sensor head tube, the texture is formed directly on the external surface of the sensor head tube. <FIG> shows an example embodiment of an insertion meter <NUM> having electrodes <NUM>. Insertion meter <NUM> and electrodes <NUM> are the same as insertion meter <NUM> and electrodes <NUM>, respectively, except that textured surface of insertion meter <NUM> includes two longitudinal notches <NUM> or grooves within the sensor head tube <NUM> on the front <NUM> of insertion meter <NUM>. The notches <NUM> run along the longitudinal axis of the insertion meters <NUM> between the electrodes <NUM>. The notches <NUM> also serve to manipulate the boundary layer as discussed above with respect to insertion meter <NUM>.

In yet another embodiment, the textured surface includes columns of dimples, for example, those dimples found in typical golf balls. For example, the textured surface may include a plurality of columns of dimples. In one example, the textured surface includes about <NUM> to about <NUM> columns of dimples. In another example, the textured surface includes more than <NUM> columns of dimples. The specific textured surface features discussed above may also be combined. For example, the textured surface may include longitudinal grooves as well as columns of dimples. <FIG> shows an insertion meter <NUM> of similar configuration as insertion meters <NUM>, <NUM>, and <NUM>, including for example a plurality of electrodes including two top electrodes <NUM>, two center or reference electrodes <NUM>, and two bottom electrodes <NUM>. As shown, however, the textured surface of insertion meter <NUM> includes dimples <NUM> formed on or within the sensor head tube <NUM>. The dimples <NUM> of insertion meter <NUM> include <NUM> columns of dimples, with the center column <NUM> being offset longitudinally from the outer two columns <NUM> of dimples <NUM>, which results in a pattern of one by two count rows. i.e. alternating between <NUM> dimple and <NUM> dimple rows. In one example adjacent dimples <NUM> form an equilateral triangle such that gap between any two dimples <NUM> remain consistent. The dimples <NUM> extend the longitudinal length of the sensor head tube beyond the top electrodes <NUM> and bottom electrodes <NUM> in both directions.

The dimples <NUM> may be formed as an additional surface that is added to the sensor head tube <NUM> or may be formed within the sensor head tube <NUM> by, for example, milling or during the formation of the sensor head tube <NUM> itself. While the size and configuration of each of the dimples can be manipulated to depending on the particular sensor installation, as shown in <FIG> as one example, each of the dimples <NUM> have about a <NUM> inch (<NUM>) radius cut with a ¼" (<NUM>) ball end mill that is. <NUM>" (<NUM>) deep into sensor head tube <NUM>. And adjacent dimple has about a <NUM> inch (<NUM>) gap between them. In addition, the arc length between each hole in a specific row (i.e., a dimple in one outer row <NUM> to a dimple in the other outer row <NUM> on the same radial plane) is about <NUM> to about <NUM> degrees, inclusive, or specifically as shown about <NUM> degrees. While the dimples <NUM> are only shown in <FIG> partially surrounding the sensor head tube <NUM>, in an alternative example, the dimples <NUM> may more fully surround, or even completely surround, the sensor head tube <NUM>.

<FIG> and <FIG> are flow velocity stream models comparing insertion sensor <NUM> (<FIG>) with insertion sensor <NUM> (<FIG>) in the same flow conditions. In each of <FIG> and <FIG>, the scales have been normalized to <NUM> in/sec (<NUM>/s). As shown, separation point <NUM> is closer to the electrode <NUM> than separation point <NUM> with respect to electrode <NUM>.

<FIG> shows an increase in linearity in the insertion meters with <NUM> rows of dimples (shown as unfilled purple dots) as compared to the smooth prior meters (shown in filled blue dots). The graph shows the ability to extend the linearity within +/- <NUM>% of reading down to <NUM> ft/sec of nominal flow rate with an example insertion meter with seven columns of dimples <NUM>.

In another example embodiment, the cross-sectional shape of the insertion meter is altered to affect the boundary layer / electrode interaction. For example, the insertion meter cross section can be formed in the shape of an oval or a tear drop to improve linearity and repeatability. In such an embodiment the textured surface is itself a surface contour.

Claim 1:
A magnetic insertion meter (<NUM>; <NUM>; <NUM>) comprising:
a sensor head tube (<NUM>; <NUM>; <NUM>) having a textured front surface (<NUM>); and
at least two electrodes (<NUM>; <NUM>; <NUM>, <NUM>, <NUM>),
characterised in that
the textured front surface (<NUM>) is at least one of an abrasive on a substrate, an impregnated abrasive, a deposited abrasive, and/or an abrasive layer.