Patent Publication Number: US-2023146582-A1

Title: Systems and methods for measuring low speed fluid flow

Description:
TECHNICAL FIELD 
     The present specification generally relates to apparatus and methods for measuring low speed fluid flow and, more specifically, apparatus and methods for measuring for low speed fluid flow in microchannel structures. 
     BACKGROUND 
     Conventionally, fluid flow emanating from microchannel structures may be measured using a pitot tube. The pitot tube allows for a comparison of a total pressure of the fluid flow relative to the static pressure of the surrounding environment to determine a dynamic pressure. The dynamic pressure is then input into Bernoulli&#39;s equation to determine the velocity of the fluid flow. 
     However, pitot tubes have poor accuracy at low velocities due to the slight difference in pressure between the total pressure of the flow relative to the static pressure of the surrounding environment. The friction across a needle of the pitot tube causes too large of a pressure drop for the pitot tube to be accurate. 
     SUMMARY 
     In one embodiment, an apparatus for a fluid flow velocity measurement apparatus includes a pressure transducer and a flexible tube. The pressure transducer is tuned to measure flow speeds having a Reynolds number less than 100 and includes an inlet. The flexible tube has a first end fluidly coupled to the inlet and a second end positioned adjacent to and in fluid communication with a plurality of fluid outlets of a microchannel flow structure. Each of the plurality of fluid outlets has a cross section defining an outlet area. The second end has a cross section defining a flexible tube area that is larger than the outlet area. 
     In another embodiment, methods for measuring fluid flow velocity includes translating a flexible tube to be adjacent to and in fluid communication with a portion of a plurality of fluid outlets. Each of the plurality of fluid outlets have a cross section defining an outlet area. The flexible tube has a cross section defining a flexible tube area that is larger than the outlet area. The method further includes receiving a portion of the fluid flow by a pressure transducer via the flexible tube. The method further includes determining an experimental pressure of the portion of the fluid flow by a pressure transducer via the flexible tube. The method further includes applying a correction factor to the experimental pressure to determine a corrected pressure. 
     These and additional features provided by the embodiments described herein will be more fully understood in view of the following detailed description, in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments set forth in the drawings are illustrative and exemplary in nature and not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which: 
         FIG.  1    schematically depicts an illustrative fluid flow speed measuring system, according to one or more embodiments shown and described herein; 
         FIG.  2    schematically depicts the fluid flow speed measuring system of  FIG.  1    with certain parts omitted for visualization purposes; and 
         FIG.  3    schematically depicts a flow diagram of an illustrative method for determining a flow velocity in a flow measuring system, according to one or more embodiments shown and described herein. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments described herein are directed to a fluid flow speed measuring system that includes a flexible tube for the purposes of determining a corrected velocity of a low speed fluid flow emanating from jets of a microchannel flow structure. As discussed in greater detail herein, the flow measuring system determines the corrected velocity with high accuracy relative to other apparatuses (e.g., an apparatus employing a pitot tube) while also having low complexity and being cost-effective. Various embodiments of the method and apparatus and the operation of the method and apparatus are described in more detail herein. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. 
     Referring now to  FIG.  1   , a fluid flow speed measuring system  100  is illustrated according to one or more embodiments described herein. As discussed in greater detail herein, the flow measuring system  100  is used to determine an experimentally-collected pressure, which is compared to a simulated model of the flow measuring system  100 . This facilitates for a correction factor to be determined and applied to the experimentally-collected pressure. The flow measuring system  100  may be implemented in a production line of a component to determine the spray deposition on the component. 
     The flow measuring system  100  may generally include, for example, a flow meter  102 , an input tube  104 , a flexible tube  112 , a pressure transducer  128 , and/or a signal conditioner  130 . In some embodiments, the flow measuring system  100  may further include a motor assembly  116 , a power supply  118  powering the motor assembly  116 , and/or a controller  125 . The various components of the flow measuring system  100  described herein are generally used and configured to measure the microchannel flow structure  106 , as will be described herein. 
     The flow meter  102  is generally a device that receives fluid flow for the fluid flow speed measuring system  100  from a fluid supply  101  (e.g., pump, compressor) having a valve  101   a  that controls the velocity and pressure of the fluid. The valve  101   a  may be a ball valve, a butterfly valve, a check valve, a gate valve or the like. The flow meter  102  measures the volumetric flow rate of the fluid from the fluid supply  101  before the fluid proceeds through other components of the fluid flow speed measuring system  100 . In this way, the volumetric flow rate of the fluid can be configured by adjusting the valve  101   a  so that the fluid is within a specified range. The flow meter  102  may be a paddlewheel flow meter, a variable area flow meter, an ultrasonic Doppler flow meter, a positive displacement flow meter, or the like. 
     The fluid flow speed measuring system  100  is fluidly coupled to the microchannel flow structure  106  via an input tube  104  and is configured to receive fluid from the input tube  104 . The input tube  104  is positioned between the flow meter  102  and the microchannel flow structure  106  and fluidly couples the input tube  104  to the flow meter  102 . The microchannel flow structure  106  receives the fluid flow from the input tube  104  by a fluid inlet  108  of the microchannel flow structure  106 . The fluid inlet  108  defines a cross-sectional inner diameter having an inlet area. 
     The microchannel flow structure  106  includes a body  105  having at least a first side  107  and a second side  109 . The body  105  of the microchannel flow structure  106  defines a plurality of fluid channels  105   a  (e.g., microchannels), a fluid inlet  108 , and a plurality of fluid outlets  110 . The fluid channels  105   a  fluidly couple the fluid inlet  108  to the plurality of fluid outlets  110 . That is, the fluid channels  105   a  are positioned between the fluid inlet  108  and the plurality of fluid outlets  110 . As the fluid flow progresses through the microchannel flow structure  106 , the fluid is directed by the plurality of fluid channels  105   a  through the body  105 . It should be appreciated that the volume and/or velocity of the fluid flow that is directed by at least a portion of the plurality of fluid channels is dependent on a position of the fluid inlet  108  relative to plurality of fluid channels  105   a  and/or the plurality of fluid outlets  110 . As illustrated in the embodiment of  FIG.  1   , the fluid inlet  108  is disposed on a third side  106   a  of the body  105  the microchannel flow structure  106 . Accordingly, at least a portion of the plurality of fluid channels  105   a  and the plurality of fluid outlets  110  may also be disposed at or near the third side  106   a  of the body  105  of the microchannel flow structure  106  (e.g., positioned closer to the third side  106   a  of the body  105  of the microchannel flow structure  106  relative to a fourth side  106   b ) receive higher levels of fluid flow as compared to the fourth side  106   b  (e.g., axially opposed to the third side  106   a ) of the of the microchannel flow structure  106 . Accordingly, the flexible tube  112  receives higher levels of fluid flow when adjacent to the third side  106   a  as compared to the fourth side  106   b . In embodiments, the flow distribution of the microchannel flow structure  106  may be configured to provide high levels of fluid flow when adjacent to the fourth side  106   b  as compared to the third side  106   a.    
     As illustrated in  FIG.  2   , each of the plurality of fluid outlets  110  define a cross-sectional inner diameter having an outlet area  111 . In some embodiments, the microchannel flow structure  106  may include about 50 to about 150 fluid outlets  110 . In some embodiments, the microchannel flow structure  106  may include about 25 to 50 fluid outlets  110 . In some embodiments, the microchannel flow structure  106  may include about 100 to 250 fluid outlets  110 . 
     The microchannel flow structure  106  further includes a seal  117  which extends along a portion of the body  105 . The seal  117  prevents fluid flow which has entered the fluid inlet  108  from exiting the body  105  except through the plurality of fluid outlets  110 . 
     In some embodiments, the plurality of fluid outlets  110  are in fluid communication with a secondary microchannel flow structure (not shown). In these embodiments, the secondary microchannel flow structure is positioned between the microchannel flow structure  106  and the flexible tube  112 . The secondary microchannel flow structure has a plurality of inlets corresponding to the plurality of fluid outlets  110  and are in line with the plurality of fluid outlets  110 . The secondary microchannel flow structure may be configured to alter the fluid. For example, the secondary microchannel flow structure may be utilized to perform a chemical reaction onto the fluid in the secondary microchannel flow structure. 
     In conventional systems, such as systems that employ pitot tubes or the like, the inner diameter of the tube is about 0.20 mm. For fluid flow having a Reynolds number less than 100, the pressure drop across the length of a needle of the pitot tube results in inaccurate measurements. This pressure drop is a result of the friction of the inner diameter tube being large relative to the low velocity speed of the fluid flow. 
     In contrast, the fluid flow speed measuring system  100  of the present disclosure includes a flexible tube  112  disposed between and fluidly coupled to at least a portion of the plurality of fluid outlets  110  and the pressure transducer  128 . That is, a first end  113   a  of the flexible tube  112  is disposed at or near the plurality of fluid outlets  110  and a second end  113   b  of the flexible tube  112  is spaced a length apart from the first end  113   a  and is fluidly coupled to the pressure transducer  128 . As discussed in greater detail herein, the flexible tube  112  defines a larger inner diameter when compared to tubes (e.g., pitot tubes) used in conventional systems. The larger diameter allows the flexible tube  112  to interact with a greater total pressure from the fluid emanating from the microchannel flow structure  106  relative to the tubes of conventional systems. By receiving a greater total pressure, the fluid flow speed measuring system  100  described herein can determine the average flow velocity over an aggregate of the fluid outlets  110 . As discussed in greater detail herein, a correction factor for the total pressure may be determined to offset the impact of using the flexible tube  112  (e.g., tube friction, obstructing walls). By measuring an aggregate of the fluid outlets  110  and determining an average flow velocity as described herein, the fluid flow speed measuring system  100  is able to calculate low velocity flows (e.g., having a Reynolds number less than 100) that would otherwise not be possible using conventional systems (e.g., systems employing a pitot tube). 
     The flexible tube  112  may be constructed of a plastic material, an elastomer, silicone, a rubber-like material, or any material of the like having the ability to bend and/or compress at nominal forces without experiencing plastic deformation. By being constructed of a flexible material, the flexible tube  112  is able to flex when interfacing with the fluid flow and also to be translated during the measurement process. 
     The flexible tube  112  is separated from the plurality of fluid outlets  110  by a specified distance. In some embodiments, the flexible tube  112  is separated from (e.g., adjacent to) the plurality of fluid outlets  110  such that the first end  113   a  of the flexible tube  112  is spaced a distance of about 0.05 inches to about 0.1 inches. In some embodiments, the flexible tube  112  is separated from the plurality of fluid outlets  110  at a distance of about 0.1 inches to about 0.50 inches. 
     In some non-limiting embodiments, the tube area  114  is about 100 mm 2  and the outlet area  111  is about one-third to one-sixth in magnitude relative to the tube area  114 . In some non-limiting embodiments, the tube area  114  is about 50 mm 2  and the outlet area  111  is about one-eighth to one-twenty-fifth in magnitude relative to the tube area  114 . In some non-limiting embodiments, the tube area  114  is about 25 mm 2  and the outlet area  111  is about one-twentieth to one-fiftieth in magnitude relative to the tube area  114 . 
     The fluid flow speed measuring system  100  further includes a motor assembly  116 . The motor assembly  116  translates the flexible tube  112  relative to the microchannel flow structure  106  during the measurement process. That is, the motor assembly  116  causes lateral movement of the first end  113   a  of the flexible tube  112  relative to the microchannel flow structure  106  such that the first end  113   a  is aligned with a portion of the plurality of fluid outlets  110  at any given point. During the measurement process, fluid exiting a portion of the plurality of fluid outlets  110  and into the flexible tube  112  is measured. The portions may have overlapping plurality of fluid outlets  110  (e.g., different portions share some of the same plurality of fluid outlets  110  similar to a moving average). Further, the same portion may be measured more than once. The motor assembly  116  translates the flexible tube  112  so that it receives fluid flow from varying portions of the plurality of fluid outlets  110 . The motor assembly  116  translates the flexible tube  112  in discrete steps to obtain the experimental measurements across each designated portion of the plurality of fluid outlets  110 . 
     The motor assembly  116  includes a power supply  118  and a motor  120 . The power supply  118  is electrically coupled to the motor  120  and is configured to provide electricity to the motor  120 . The motor assembly  116  further includes a motor track  122  operatively coupled to the motor  120  and a platform  124  positioned on the motor track  122 . In response to the operation of the motor  120 , the motor track  122  repositions the platform  124 . In other words, the platform  124  moves back and forth along a length of the motor track  122  by the motor  120 . 
     The flexible tube  112  is coupled to the platform  124 . In response to the movement of the platform  124 , the flexible tube  112  is also configured to move. In this way, the flexible tube  112  translates along the width of the microchannel flow structure  106  when the fluid flow speed measuring system  100  measures flow across the portions of the plurality of fluid outlets  110 . 
     The motor  120  is communicatively coupled to a controller  125 . The controller  125  may be a control device as is generally understood, and may include processing components such as, for example, a central processing unit (CPU), an electronic control unit (ECU), a digital signal processor (DSP) or the like. During the measurement process, the flexible tube  112  receives a pressure from the fluid flow from a first portion of the plurality of fluid outlets  110 . The velocity of the fluid flow is then determined for a first discrete step of the measurement process. The controller  125  provides a signal to the motor  120  indicative of the distance the flexible tube  112  is to be translated. This distance correlates to a movement of the flexible tube  112  from the first portion of the plurality of fluid outlets  110  to a second set of the plurality of fluid outlets  110 . The velocity of the fluid flow from the second portion of the plurality of fluid outlets  110  is determined for a second discrete step of the measurement process. As will be described in further detail hereinbelow, the controller  125  may also be communicatively coupled to the flow meter  102 , the power supply  118 , and/or any other component of the fluid flow speed measuring system  100  for the purposes of controlling portions of the flow measuring system  100 , receiving measurements, determining flow, and/or outputting results. 
     The fluid flow speed measuring system  100  further includes a pressure transducer  128  (e.g., absolute pressure transducer, gauge pressure transducer, differential pressure transducer) having an inlet configured to receive fluid flow from the second end  113   b . The pressure transducer  128  converts pressure of the received fluid flow into an analog electrical signal. In some embodiments, the pressure transducer may be particularly tuned for flow speeds having a Reynolds number that is less than 100. 
     The fluid flow speed measuring system  100  further includes a signal conditioner  130  communicatively coupled to the pressure transducer  128 . The pressure transducer  128  provides the electrical signal to the signal conditioner  130 . The signal conditioner  130  converts the electrical signal to determine an experimental pressure of the received fluid flow (e.g., the pressure of the received fluid flow from the second end  113   b ). The signal conditioner  130  is communicatively coupled to the controller  125  and is configured to provide the experimental pressure of the received fluid flow to the controller  125 . The controller  125  receives the experimental pressure of the received fluid flow for each discrete step of the measurement process. Using this information, the controller  125  calculates the aggregated average differential pressures of the received fluid flow, as described herein with respect to  FIG.  3   . 
     Referring now to  FIG.  2   , the fluid flow speed measuring system  100  of  FIG.  1    is shown at a perspective angle with certain components omitted. As shown in  FIG.  2   , the microchannel flow structure  106  defines an outlet measuring position  202 . As discussed in greater detail herein, the outlet measuring position  202  is a position in which differential pressure values are measured for the microchannel flow structure  106 . As discussed in greater detail herein, the differential pressure values are adjusted using a correction factor for the fluid flow speed measuring system  100 . 
     The flexible tube  112  further defines a tube measuring position  204 . The tube measuring position  204  is a selected position along the length of the flexible tube  112  in which a pressure of the fluid flow is measured within the flexible tube  112 . As discussed in greater detail herein, the pressure is used to determine a correction factor for the fluid flow speed measuring system  100 . 
     As shown in  FIG.  3   , a method  300  for determining a flow velocity in a flow measuring system (e.g., such as the fluid flow speed measuring system  100 ) is shown, by any device or system configured, programmed, or the like to carry out the steps described herein, such as, for example, the controller  125  described herein with respect to  FIG.  1   . 
     At step  302 , a fluid flow finite element analysis (FEA) sub-model of the flow measuring system is simulated at a selected velocity. The sub-model has a uniform fluid velocity across a plurality of fluid outlets (e.g., such as the plurality of fluid outlets  110 ). A model pressure is determined at a tube measuring position (e.g., such as tube measuring position  204 ) of a flexible tube (e.g., such as the flexible tube  112 ). The model pressure is determined in order to determine the effect of the flexible tube upon the flow velocity in the flow measuring system. 
     At step  304 , using the same sub-model with the flexible tube, a first velocity is determined at an outlet measuring position (e.g., such as the outlet measuring position  202 ) across a cut-line (e.g., a line on a plane extending along a center point of each of the plurality of fluid outlets). The same sub-model is used without the flexible tube to determine a second velocity. The second velocity is also determined at the outlet measuring position across the cut-line. The second velocity is determined in order to determine a reference of the sub-model without the interference of the flexible tube. The second velocity is compared to the first velocity to determine the effect of the tube on the fluid flow field. 
     At step  306 , Bernoulli&#39;s equation is applied using the model pressure with the tube from step  302  to determine a calculated velocity. In the application of Bernoulli&#39;s equation, a static pressure is set to zero. Additionally, a density of the flowing fluid is the density of atmospheric air. 
     
       
         
           
             
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     Due to the fluid flow having a low velocity, the fluid flow recirculates and creates eddy currents. This results in an invalidation of the Bernoulli equation. Accordingly, a correction factor is determined in order to correct any experimental data collected. At step  308 , the correction factor for the selected velocity is determined. The correction factor is dependent on the selected velocity and the configuration of the flow measuring system used (e.g., the size of the flexible tube and the configuration of the microchannel flow structure). 
     The calculated velocity from step  306  and the model pressure from  302  are used in determining the correction factor, as shown below. In the application of determining the correction factor, the static pressure is set to zero. Additionally, the density of the flowing fluid is the density of atmospheric air. Specifically, the corrector factor C f  is determined by adjusting it such that the model velocity prediction using Bernoulli&#39;s equation with the tube matches the model velocity prediction at the cut line without the tube. 
     
       
         
           
             
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     At step  310 , the physical flow measuring system with the flexible tube is utilized at the selected velocity. The flexible tube is placed upon a platform (e.g., such as the platform  124 ) upon a motor track (e.g., such as motor track  122 ) operatively coupled to a motor (e.g. such as the motor  120 ). The flexible tube translates along a width of the flow measuring system at the outlet measuring position. The flexible tube receives fluid flow from a first portion of the plurality of fluid outlets, wherein a first differential pressure is measured. The flexible tube is moved to a second portion of the plurality of fluid outlets, wherein a second pressure is measured. The second portion of the plurality of fluid outlets may overlap with the first portion of the plurality of fluid outlets. In some embodiments, a total of ten to twenty-five portions are tested to determine their pressures. In some embodiments, a total of twenty-five to one hundred portions are tested to determine their pressures. In some embodiments, a total of one hundred to five hundred portions are tested to determine their pressures. 
     After determining the pressures from each portion, the correction factor of step  308  is applied using the experimental pressure to obtain a corrected measurement value. The corrected measurement value is used to determine a corrected flow velocity of the fluid flow in the flow measuring system. 
     At step  312 , it is determined whether there are different velocities of interest (e.g., different selected velocities). If there are different velocities of interest, the process returns to step  302 . The method  300  is repeated to determine a correction factor at a second selected velocity. If there are not different velocities of interest, the method  300  is completed. 
     From the above, it is to be appreciated that defined herein is a flow measuring system that includes microchannel flow structure and a flexible tube in order to determine a corrected velocity of a low speed fluid flow. As discussed in greater detail above, the flow measuring system determines the corrected velocity with high accuracy while having low complexity and being cost-effective. 
     It is noted that the terms “substantially” and “about” may be utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue. 
     While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications may be made without departing from the scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. It is therefore intended that the appended claims cover all such changes and modifications that are within the scope of the claimed subject matter. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the scope of the claimed subject matter. Thus, it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modification and variations come within the scope of the appended claims and their equivalents.