Patent Publication Number: US-2018050347-A1

Title: Fluid Separator Methods and Systems

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application is a divisional of U.S. patent application Ser. No. 15/162,275 filed on May 23, 2016, which is a continuation in part of U.S. patent application Ser. No. 14/310,968, filed on Jun. 20, 2014, which is a non-provisional under 35 USC 119(e) of, and claims the benefit of, U.S. Provisional Application 61/837,745 filed on Jun. 21, 2013. The entire disclosure of each of these is incorporated herein in its entirety. 
    
    
     BACKGROUND 
     1. Technical Field 
     This is related to systems for separating flowing fluid into separate portions, and in particular, to systems for separating solid particles or gases from a liquid or liquids of differing buoyancies. 
     2. Related Technology 
     The separation of mixtures into their component parts for the purposes of clarification, cleaning, and removal of undesirable portions of the mixture is a major function in many industries. In many cases it is desired to perform this function rapidly, at high flow rates and in an “on-line” operating mode. In many applications this function is performed by conventional centrifuges, often augmented with a settling or decanting process to overcome the inherent limitations of current centrifuges to achieve the desired level of end product purity needed. 
     In addition, the removal of air or other gases from fluid flows is widely applicable in cases in which the entrained gases may interfere with the function and performance of equipment. One application is in the removal of air from liquid coolant to improve the heat exchange performance of radiators. Another such application is the removal of air from lubricating fluid to improve the lubrication and cooling performance of the fluid. Yet another application is the removal of air from hydraulic fluid to improve the force transfer of hydraulic actuators. In all of these applications, the separated air or gas is typically removed, since recombination would tend to defeat the purpose of the removal. In these cases, air removal is the primary function and any suspended particles in the fluid are of little or no interest. 
     In other cases, recombination after separation may be desirable, for example, to retain oil fumes that are entrained in the airflow in order to preserve the total oil content of the system. In certain particle monitoring applications, such as that disclosed by U.S. Pat. No. 4,282,016 to Tauber et al., a goal is to remove particles above a certain size for analysis. 
     Real time suspended particle monitors are disclosed in U.S. Pat. No. 5,572,320, U.S. Pat. No. 6,049,381, U.S. Pat. No. 7,921,739, and U.S. Pat. No. 8,056,400. 
     BRIEF SUMMARY 
     A method and system for separating a multicomponent fluid into two or more flow channels, each containing components with different buoyancy. The system includes a housing having a fluid inlet at a first end and at least two outlets; a first member configured to fit within the housing at the first end of the housing and having a passageway from the inlet through the member, the first member having a concave inner surface; a second member having a convex surface at one end that fits into the concave inner surface, the second member having at least one helical channel in an outer cylindrical surface extending from the convex surface to an opposite end of the second member; and a third member having a central fluid passageway for carrying higher buoyancy fluid and extending through the member along a central axis, and at least one other fluid passageway for carrying lower buoyancy fluid with an inlet positioned radially outward of the inlet of the central fluid passageway; the first member, the second member, and the third member configured to fit within the housing and aligned along a central longitudinal axis. 
     A method and system for separating a multicomponent fluid into two or more flow channels, each containing components with different buoyancy. The system includes a housing having a fluid inlet at a first end and at least two outlets; a flow forming member configured to fit within the housing at the inlet end of the housing and having a flow passage therethrough with at least one helical channel in an outer cylindrical surface that directs the fluid into a helical flow direction near the outer circumference of the flow forming member as the fluid exits the flow forming member; and a flow receiving member configured to fit within the housing at an opposite end of the housing, having a central fluid passageway for carrying higher buoyancy fluid and extending through the member along a central axis, and at least one other fluid passageway for carrying lower buoyancy fluid with an inlet positioned radially outward of the inlet of the central fluid passageway; wherein a separation chamber is formed between faces of the flow forming member and the flow receiving member. In operation, the helical flow enters the separation chamber, and more buoyant portions of the flow move toward a central axis of the chamber and enter the central fluid passageway, and less buoyant portions of the flow continue in a helical path near the outer part of the chamber and bypass the entrance of the central fluid passageway and exit the system through the at least one other fluid passageway. 
     A fluid separation method and system for separating a multicomponent fluid into two or more flow channels, each containing components with different buoyancy. The system includes a housing having a fluid inlet at an inlet end, a fluid outlet for heavier fluid at an outlet end opposite the inlet end, and at least one other fluid outlet for lighter fluid; a flow forming member configured to fit within the housing at the inlet end of the housing and having at least one helical channel in an outer cylindrical surface that directs the fluid into a helical flow direction near the outer circumference of the flow forming member as the fluid exits the flow forming member; and a flow receiving member configured to fit within the housing at an opposite end of the housing. The flow receiving member has a first fluid passageway with an inlet positioned at a central axis of the separator to receive lighter fluid, the first fluid passageway extending to the other fluid outlet for lighter fluid, and a second fluid passageway with an inlet positioned radially outward of the first fluid passageway to receive heavier fluid, the second fluid passageway extending to the fluid outlet for heavier fluid. A separation chamber is formed between a face of the flow forming member and the flow receiving member. 
     A cascaded flow separation method and system having at least a first flow separator and a second flow separator arranged in series, each separator having a central axis with both a fluid inlet and a first axial fluid outlet arranged at opposite ends of the separator along the central axis of the separator, each separator having at least a second fluid outlet, the separator configured to separate fluid portions of different buoyancies into channels leading to the first fluid outlet and the second fluid outlet. The separators are operatively coupled together, with the first axial fluid outlet of the first separator aligned with and connected to the fluid inlet of the second separator. Each separator has a flow forming member with a helical channel on the outer surface thereof, a flow receiving member with concentric collectors configured to receive flow portions of different buoyancies, and a separation chamber arranged between the flow forming member and the flow receiving member. 
     Additional features and details will be apparent from the following drawing figures and detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic diagram of a flow separation system for separating a fluid flow into two or more channels based on the fluid buoyancy.  FIGS. 1B, 1C, and 1D  show further detail of some internal components of the flow separation system of  FIG. 1A . 
         FIG. 2A  shows an exploded view of three components of a flow separation system. 
         FIG. 2B  illustrates the three components of  FIG. 2A  with the third component rotated to show the opposite surface. 
         FIG. 3  shows some details of the geometry of one of the components of the flow separation system. 
         FIG. 4A  illustrates an example of a flow separation system as a part of a real time fluid analysis system. 
         FIG. 4B  is a cross sectional view of a viewing window suitable for use in the real time fluid analysis system of  FIG. 4A . 
         FIG. 5  illustrates an example of two flow separators arranged in sequence to create multiple flow channels, each having a fluid component of different buoyancy. 
         FIG. 6  illustrates an example of a fluid separation system as a part of a system for removing foreign material from a fluid reservoir. 
         FIG. 7  illustrates an example of a fluid separation system as a part of a real-time optically based fluid analysis system. 
         FIG. 8A  is a schematic diagram of another example of a flow separation system for separating a fluid flow into two or more channels based on the fluid buoyancy.  FIGS. 8B, 8C, and 8D  show further detail of some internal components of the flow separation system of  FIG. 8A . 
         FIG. 9  illustrates another embodiment of a flow separation system for separating a fluid flow into two or more channels based on the fluid buoyancy. 
         FIGS. 10 and 11  illustrate cascaded fluid separation systems. 
         FIG. 12  illustrates an example of a cascaded fluid separation system in more detail. 
     
    
    
     DETAILED DESCRIPTION 
     The fluid separation systems described herein are suitable for separating fluids or fluids with entrained particles into two or more components based on their densities or buoyancies into separate flow channels. In particular, fluid flow can have entrained or suspended components such as solid particles, gases, or fluids of different densities. The components in either or both channels can be analyzed in real time with an on-line monitor. Alternatively, the entrained components in either of the separated channels can be permanently removed from the flow. Following analysis or removal of the entrained particles, the flows in the two channels can be recombined, allowing reconstitution of the full flow at a downstream location. 
     The fluid separation system described herein can retain the suspended particles in an oil flow while separating the aerated gas. This feature can be an advantageous addition to the operation of real time suspended particle monitors, such as those described in U.S. Pat. No. 5,572,320, U.S. Pat. No. 6,049,381, U.S. Pat. No. 7,921,739, and U.S. Pat. No. 8,056,400, by making these systems operable with aerated flows, thereby expanding their applicability. 
     In general in the following discussion, the term fluid is intended to encompass liquids, aerated liquids, and gases with or without solid particles in the fluid. The liquid can be, but is not limited to oil, hydraulic fluid, or water. The solid particles can be debris from engine wear, such as but not limited to metal shavings, ceramic particles, or non-metallic particles, can be biological contaminants, can be other contaminants or other solid particles. Entrained gas within the liquid can be air or another gas. 
     The system may also be suitable for separating multicomponent gases by separating heavier gases from lighter gases, or by separating one component that is in its gaseous state from another component which is in a liquid state. In one example, the system can strip component gases from liquid air. The centrifugal separation system and method can provide higher efficiency than current air separation methods, including distillation techniques. 
     Entrained solid particles typically are heavier than the liquid in which they are carried. Air or other gases entrained in a liquid are typically lighter than fluid in which they are carried. 
     In some circumstances, it is desired to deaerate a flowing fluid, without discarding the gaseous portion, by separating the flow into a less dense portion containing a high fraction of the gases and into a denser portion containing a low fraction of the gases, then recombining the flows. In some instances, it is desired to separate a flowing fluid into a first portion containing a high portion of entrained solid particles into one portion of the flow, and a second portion containing few entrained solid particles. In other circumstances, it is desired to separate two different fluids, one heavier than the other, that have been mixed together, into two different channels. 
       FIG. 1A  is a cutaway view of a fluid separation system  100  for separating a fluid flow into two or more separate flows based on buoyancy of the flow components.  FIGS. 1B, 1C, and 1D  show further detail of some internal components of the fluid separation system  100 . In this example, the separation system  100  is suitable for separating a flowing fluid that has entrained or suspended components such as solid particles and gases. Thus, the separation system  100  shown in  FIG. 1A  is also suitable for deaerating a fluid, that is, for separating the gases within a liquid from the liquid itself. 
     In the exemplary fluid separation system  100 , a plurality of components are aligned along a common axis and positioned within a housing  110 . In this example, the housing  110  has a generally cylindrical interior surface an approximately constant inner diameter D 3  and an inlet opening  112  at first end along the central axis for receiving the fluid flow to be separated. Note that in the illustration of  FIG. 1A , the half of the housing  110  that faces the viewer has been cut away so that the internal components can be seen. The outer surface of the housing can have various shapes depending on the application, including cylindrical and rectangular. 
       FIG. 2A  and  FIG. 2B  show three components  120 ,  140 ,  160  of the flow separation system  100  that fit within the housing  110 .  FIG. 3  shows some details of the geometry of the member  140 . 
     The first of the three components positioned within the housing  110  is a cup-shaped member  120  having an outer cylindrical surface  121  shaped to fit within the inner diameter D 3  of the housing  110 . A central axial passageway  123  with a diameter D 1  extends from the inlet end  122  that abuts the inner surface of the inlet end  116  of the housing  110  and opens into a concave internal surface  124  that extends to the far end  125  of the member  120 . The internal surface  124  forms a cavity and has a diameter that increases in the flow direction. 
     The cup-shaped member  120  should fit within the housing tightly enough that little or no flow will bypass the passageway  123  by flowing between the outer surface of the member  120  and the inner surface of the housing  110 , but loose enough that it can easily be inserted and removed from the housing  110 . In this example, the cup-shaped member is inserted into the housing  110  through the inlet end  116  of the housing  110  and held inside the housing by an end cap  118 , although other configurations are also envisioned. 
     Also positioned within the housing is a second member  140  having a convex portion  141  with an apex that faces toward the inlet end, and having a generally cylindrical portion  143  with an outer diameter sized to fit within the housing  110 . In this example, the outer diameter of the cylindrical portion is approximately equal to that of the member  120 . When the components are assembled, the convex portion  141  extends at least partially into the cavity of the cup-shaped member  120 , with a gap of a predetermined size between the surfaces  124  and  141 . The convex portion  141  of the member  140  has a maximum diameter that is less than the outer diameter of the member  140 . One or more helical slots or channels  144  and  144 ′ wrap around the cylindrical portion  143  of the member  140 . The fluid can flow from the gap  126  into the channels  144  formed by the side walls  147 ,  148 , the cylindrical bottom surface  149 , and the cylindrical surface of the housing  110 . The channels  144  and  144 ′ are opposite each other, and extend approximately one time around the member  140 , but in other embodiments, the channels could extend several times around the member.  FIG. 3  illustrates the channel geometry. Each of the channels  144  and  144 ′ narrows from the mouth of the channel to a narrower part having a channel width W 1  or W 1 ′, with each narrower channel portion extending at a helix angle A 2  around the member  140 . 
     In one example, the aperture or mouth of each channel  144  and  144 ′ has a width that is almost half the circumference of the cylinder, as seen in  FIG. 2A  and  FIG. 3 , with a small end surface  142  formed between the mouths of the channels  144  and  144 ′. When the member  140  is inserted into the housing  110  the end surface  142  comes into contact with the end  125  of the cup-shaped member  120 , maintaining the desired spacing between the surfaces  141  and  124 . As seen in  FIG. 1A , a gap  126  is formed between the concave internal surface  124  and the convex surface  141 . In this embodiment, the gap  126  extends completely around the convex surface  141  of the member  140 . 
     In operation, fluid flows from the inlet  112  in the inlet end  116  of the housing  110 , through the passageway  123 , and through a gap  126  or space formed between the inner concave surface  124  and the convex surface  141 .  FIGS. 1A and 1B  show the passageway  123  and the gap  126  formed between the members  120  and  140 . The gap between the member  140  and the member  120  is of such dimension that the diameter of the flow area in the gap region is greater than the diameter of the inlet. For example, for any point along the gap  126  in  FIG. 1B , the flow&#39;s radial position, shown in  FIG. 1D , will be larger than flow&#39;s radial position in the inlet passageway  123  shown in  FIG. 1C . The maximum diameter D 2  of the convex portion of the member  140  and the angle A 1  can be determined based on flow rates, allowable pressure drops, mounting space restrictions, and the required amount of separation between fluid components. 
     In this example, both the internal concave surface  124  and the convex surface  141  are cones. Here, the convex portion of the member  140  has a vertex angle A 1 . In this example, the conical surfaces of the member  120  and the member  140  have equal vertex angles, so the gap has approximately the same radial distance between surfaces  124  and  141  over the length of the conical portion  141 . However, the separation between surfaces  124  and  141  could be increased or decreased by setting the vertex angles to be different, depending on the design parameters discussed above. In addition, the surfaces and  141  can be other shapes instead of cones, with constant, increasing, or decreasing gap radial separation. It is suitable to select the shape and dimensions of the surfaces to prevent or minimize increases in turbulence of the fluid flow FL 1  as it moves through this region and approaches the channels  144  and  144 ′. As the fluid FL 1  passes through the passageway  123  and through the gap  126 , it has moved radially outward along the length of the member  120 , and has taken on an annular flow shape. 
     The member  140  should be locked into position to prevent it from moving under the force of the fluid flow. In this example, a pin or protuberance  114  extends outward from the inside cylindrical surface of the housing  110 . The cylindrical portion of the member  140  has a groove  146  that engages the pin or protuberance and prevents the member  140  from moving when the fluid flows through the channel  144 . Other locking mechanisms are also possible. The convex portion  141  of the member  140  collects and directs the flow to enter the helical channels  144  and  144 ′. Each channel has a depth and width DE 1 , W 1 , DE′, and W 1 ′, respectively, that can be different but are typically equal. As seen in  FIG. 3 , one side of a helical channel has a curvature with a radius of curvature R. The channel depths DE 1 , the widths W 1 , and helix angles A 3  can be calculated based on the speed of the fluid flow FL 1  at the inlet and the centrifugal “g-force” to be exerted upon the flow FL 1  needed to create the desired amount of flow separation in the separation chamber  150 . In this example, the depth DE 1  of the channel is defined by the inner diameter of the housing  110  and the cylindrical inner surface of the channel  144 , and is approximately constant throughout its length. However, in other embodiments, the channel depth can be varied depending on the design requirements of the application. 
     A third member  160  is positioned within the housing, with the member  140  being arranged between the member  120  and the member  160 , with a separation chamber  150  between the member  140  and the member  160 . The chamber is defined by the facing surfaces of the members  140  and  160  and the inner surface of the housing  110 . The outer cylindrical surface of the member  160  has a diameter that is approximately the same as that of the members  120  and  140 , so it fits within the inner cylindrical surface of the housing  110 . 
     The member  160  has at least two fluid channels. One channel  161  has a centrally arranged passageway with a wide collector horn  166  facing into the chamber  150 , and another channel  162  has an inlet  163  that is located radially outward and downstream of the collector  166 . 
     The centrally arranged passageway  161  has an inlet that in this example is a horn shaped collector  166  that extends into the chamber  150  and an outlet  169  at the far end  168  of the member  160 . The fluid flow channel  162  has an inlet  163  at the end of the member  160  that faces the chamber  150 , at or near the outer surface of the member  160 . The fluid flow channel  162  can have a bottom surface formed in the member  160 , a top surface defined by the inner surface of the housing  110 , and side walls. In this example, the fluid flow channel  162  extends at least partially around the circumference of the member  160  to a second end  165  positioned to direct the fluid flow through an aperture  113  in the housing  110 . As discussed in later paragraphs, the horn shaped collector  166  receives a portion of the fluid flow passing through the chamber  150 , and the channel opening  163  receives the remaining portion of the fluid flow passing through the chamber  150 . 
     In operation, the fluid with entrained particles or gases enters the inlet passage  123 , and flows through the passage  123 , through the cone shaped gap and over the conical surface  141  of the member  140 . The gap surfaces  124  and  141  direct the fluid into the mouths of the channels  144  and  144 ′, and the fluid continues through the channels  144  and  144 ′. The helical shape of the channels forces the flow into a helical or spiral flow direction, which continues as the fluid moves from the channels into the chamber  150 . The centrifugal force resulting from the spiral flow path of the fluid in chamber  150  causes the heavier, particulate-enhanced portion FL 3 A of the fluid to flow outward toward the cylindrical wall of the chamber  150  while the more buoyant portion of fluid flow (e.g., the gaseous portion) separates and forms gaseous partial flow FL 2 A, which is driven by the generated force toward the center axis  153  of the chamber  150 . In this example, the end of the horn shaped collector  166  is positioned at a distance L from the entrance to the chamber  150 . The horn shaped collector  166  collects the more buoyant portion of the flow FL 2 A that has been driven toward the central part of the chamber. The heavier portion of the flow FL 3 A is collected from the region adjacent to the cylindrical wall of the chamber  150  by the opening  163  of the fluid flow channel  162  in the member  160 . The distance L affects the dwell time of the flow within the chamber  150 , and together with the angle and dimensions of the channel  144  and the helix angle A 3 , affects the amount of separation between the partial flows FL 2 A and FL 3 A. The distance M between the outer rim  167  of the horn shaped collector  166  and the inner wall of the housing  110  affects amount of the more buoyant component in the flow (FL 2 A) collected by the horn-shaped collector  166 , and the amount of the less buoyant component in the remaining flow that enters the fluid flow passage  162  (FL 3 A). 
     In this example, the channels  144  and  144 ′ in the member  140  and the channel  162  in the member  160  can each turn in the same direction. In this example, if viewing the members from the apex end  151  of the member  140 , flow through all the channels will be in the counterclockwise direction and toward the far end  168  of the member  160 . Further, it will be clear that the fluid moves generally in a single direction from the inlet  112  at one end of the system toward the outlets  165  and  169  at or near the far end of the member  160  without reversing course. 
     The spiral shape of the channel  162  can provide a low-resistance flow path to a side outlet in the housing, which can be suitable for a compact particle analysis system discussed in later paragraphs. However, the channel can extend more directly to the side of the housing, or to the end of the housing, and can be a shape other than spiral or curved. 
     In this example, the member  160  is held at the desired axial distance from the member  140  and prevented from moving by an end portion  172  that extends in a radial direction past the inner diameter of the housing, or by another securing mechanism. 
     The design parameters L and M can be selected so the system provides a desired amount of separation efficiency, a desired size range of particles collected in the heavier FL 3 A flow, and concentration efficiency of the FL 3 A flow. Thus, the system is widely applicable for a wide range of values of viscosity, particle density, and sizes. 
     In this example, a single channel  162  is shown radially outward of a single horn shaped collector  166  of a single centrally arranged passageway  161 . In other embodiments, additional horn shaped openings and passageways can surround the first horn shaped collector, to collect intermediate buoyancy flow portions. Further, more channels  162  can be included in the member  160  to collect the heavier portion of the fluid flow. 
     The aperture or mouth of the axial passageway  161  tapers outward, and can be curved in an outward direction as shown in  FIGS. 1A, 2A, and 2B  or can increase linearly in diameter. It may also be suitable to use a straight pipe extending into the chamber in some circumstances, however, such a straight pipe is expected to collect less of the more buoyant flow component. 
     The separated flows FL 2  and FL 3  can be analyzed or processed separately, as discussed in later paragraphs. The flows can then be discarded, maintained separately for further processing, or one or both can be reintroduced into the original system flow path. 
     In this example, the fluids leaving the flow separation system  100  have different buoyancies. For example, FL- 3  can be denser (less buoyant) with more solid particles, while FL 2  can be more buoyant (less dense) due to the presence of more entrained gases. 
     The system  100  can deaerate fluids, that is, can separate most or all of the air or other gases from a fluid flow FL 1  into a flow FL 2  having most or all of the air or other gases and a flow FL 3  having little entrained gas or air. This is suitable for many applications, including particle analysis systems. For example, in some particle sensors the detection sensitivity depends on the pipe diameter of the flow. Deaerating or increasing the concentration of particles in the oil flow allows a smaller diameter pipe and a smaller sensor to be used, providing improved particle detection sensitivity. The deaeration can reduce the noise in the sensor caused by air in the flow. 
     Some presently available real time optical fluid particle analysis systems, e.g., that described in U.S. Pat. No. 5,572,320, are best able to image particles located in the optical near field of the imaging system. For these systems, the conduit size necessary to carry the fluid viewed by that sensor is such that the particles size range is limited. Deaerating the flow with a flow separation system can broaden the applicability and effectiveness of the oil analysis system. 
       FIG. 4A  shows the flow separation system  100  as a part of a larger fluid monitoring system  400 . 
     The flow separation system  100  separates the flow into a denser flow FL 3  containing the majority of the particles in the flow, and a more buoyant flow FL 2 . The particle enhanced flow FL 3  can be introduced into a particle analysis system  410  directly or by way of connecting tubing or other fluid conduits. The particle enhanced flow FL 3  flows through a passageway  420  and past an optional fluid sampling port  440 , and the sample of flow FL 3 B can be extracted through conduit  450 . The remaining flow FL 3 C, which is not removed at the sampling port, can be passed to a real time oil analysis system  430 . In some embodiments, the oil analysis system can automatically analyze the size distribution of particles carried in the fluid. In this example, the flow FL 3 C that has passed through the real time oil analysis system is recombined with the higher buoyancy flow FL 2  in a chamber  460  to form a re-aerated flow FL 4 . In this example, the higher buoyancy flow FL 2  can be transmitted directly from the flow separation system  100  to the chamber  460 , or can be further processed or analyzed by fluid analysis devices before passing into the chamber  460 . The recombined flow FL 4  flows out of the chamber  460  and exits the particle analysis system  410  through an exit port  470 . The flow FL 4  can be reintroduced into the fluid flow system to maintain total system volume, or discarded. 
       FIG. 4B  shows the details of one embodiment of a viewing port as positioned in the flow conduit  420  for the optical analysis system. Here, the heavier fluid flow FL 3 C flows through the conduit  420 . Sets of windows  432  formed of suitably transparent and strong material are aligned opposite each other across the channel  420  in one or more pairs. The windows surfaces  438  are preferably flush with the interior walls of the channel  420  and are secured by a compressing seal system  436  against a lock mechanism  434  such that pressure variations in the channel will not cause the windows  432  to move. In one embodiment, the real time oil analysis system is an optical debris monitor such as that described in U.S. Pat. No. 5,572,320, U.S. Pat. No. 6,049,381, U.S. Pat. No. 8,582,100, or U.S. Pat. No. 8,654,329, and the disclosures of which are incorporated by reference in their entireties. The remaining components of the oil analysis system are not shown. 
       FIG. 5  illustrates a system in which two flow separators  100  are arranged in series. Here, the input flow FL 1  is separated by separator  100  into a denser (less buoyant) flow FL 3  and a more buoyant (less dense) flow FL 2 . In this example, the denser flow FL 3  is then input into a second separator  100 ′, which separates this flow into a denser flow FL 5  and a less dense flow FL 4 . The separators  100  and  100 ′ can have different design parameters. Additional separators can be added in-line with any of the output flows FL 4 , FL 5 , and FL 2  to further separate the fluids. The separated flow channels can be recombined in a chamber or the flow in one or more of the final channels can be permanently isolated, with the remaining flows being recombined and returned to the original fluid system. For example, the most particle-laden flows could be permanently removed from the fluid system. In other examples, the more buoyant flow FL 2  is input to an additional fluid separator. 
       FIG. 6  illustrates a system for removing foreign material from a fluid reservoir contaminated with the foreign material. Here, a positive displacement pump  620  draws contaminated fluid from a reservoir  610 . The contaminated fluid enters the fluid separator  100 , where the fluid is separated into flows FL 2  and FL 3 , with the less buoyant (denser) fluid flow FL 3  containing the particles of foreign material. The cleaned, more buoyant, fluid flow FL 2  is returned to the reservoir by way of conduit  670 . The particle-laden flow FL 3  is directed to a residual slurry separation unit  630  by conduit  660 , and the particles are removed from the slurry separation unit  630  by a foreign material removal unit  640 . The reclaimed fluid from the slurry separation unit  630  is returned to the reservoir  610  via conduit  680 . The particles removed from the flow can be transported to a foreign material compactor and treatment unit  640  for disposal. Fluid from which the particles have been removed is returned to the fluid reservoir  610 . Although only one separation system  100  is shown, more than one separation system can be arranged in the system in series to remove a broader range of particle sizes. Several separation systems  100  can also be arranged in parallel, to clean a high volume of fluid more rapidly. This system  600  provides continuous operation of the separators without loss of fluid from the main reservoir. 
     The fluid reservoir  610  can be, for example, a fuel storage tank. Fuel storage tanks can have a tendency to contain microbial contamination. 
       FIG. 7  illustrates the flow and viewing components of a compact, optical oil analysis system. The flow separation module  700  can be as shown in  FIG. 1A-1D  and  FIG. 2A-2B  above, configured to separate an oil flow FL 1  into a more buoyant flow FL 2  and a more dense flow FL 3 . The more buoyant flow is introduced into a connector module  710 , which physically connects the flow separation module  700  to the viewing and recombination module  720 . 
     The connector module  710  can receive the axial flow FL 2  and redirect it toward another component (e.g., toward an optical viewing and recombination module  720 ). The module can be integral with or affixed to the third member  160 , and its size can keep the member  160  from sliding too far into the housing  110 , thus maintaining the desired distance L between the member  140  and the horn shaped collector  166 . The connector module  710  can be integral with the separation module  700 , with the viewing and recombination module  720 , or can be a separate component. 
     The viewing and recombination module has a passageway  722  that receives the particle laden flow FL 3  and passes it through a viewing window  724 , and subsequently into a recombination chamber  726 . The viewing window  724  can be as shown in  FIGS. 4A and 4B , and can be part of an optical oil analysis system described above. In this example, a passageway  728  transports the lower density fluid FL 2  into the recombination chamber. A passageway  734  and outlet port  732  output the recombined fluid. In real time oil analysis systems, the recombined fluid can be returned to the main fluid reservoir, to avoid loss of system fluid. This embodiment can operate at pressures typical for oil lubrications systems of gas turbine engines, typically 80-150 psi, with an oil flow through the analysis system of approximately 10 gallons per minute. 
     The system  100  can also be considered to include three main components: the housing, a flow forming member, and a flow receiving member, with a separation chamber between the flow forming element and the flow receiving element. The flow forming member takes the input flow and gives it a helical or spiral shape that continues in the separation chamber. The flow receiving member can be considered to be the member  140  or the member  140  together with the member  120 , because it receives the flow from the chamber. It is also noted that the member  120  and  140  do not have to be separate elements, but can be a single unitary element, either integral with each other or formed separately and subsequently joined together. The flow receiving member can be considered to correspond to the member  160 . 
     Thus, the system for separating a multicomponent fluid into two or more flow channels, each containing components with different buoyancy, can comprise a housing having a fluid inlet at a first end and at least two outlets; a flow forming member configured to fit within the housing at the inlet end of the housing and having a flow passage therethrough with at least one helical channel in an outer cylindrical surface that directs the fluid into a helical flow direction near the outer circumference of the flow forming member as the fluid exits the flow forming member; and a flow receiving member configured to fit within the housing at an opposite end of the housing, having a central fluid passageway for carrying higher buoyancy fluid and extending through the member along a central axis, and at least one other fluid passageway for carrying lower buoyancy fluid with an inlet positioned radially outward of the inlet of the central fluid passageway; wherein a separation chamber is formed between faces of the flow forming member and the flow receiving member. In operation, the helical flow enters the separation chamber, and more buoyant portions of the flow move toward a central axis of the chamber and enter the central fluid passageway, and less buoyant portions of the flow continue in a helical path near the outer part of the chamber and bypass the entrance of the central fluid passageway and exit the system through the at least one other fluid passageway. 
     The components of the flow separation system are preferably formed of a strong material that is impervious to corrosion or other degradation from the fluid being carried. Some suitable materials include aluminum, stainless steel, and some plastics. 
     Several flow separation systems or stages may be cascaded to improve separation efficiency and general performance. The systems can be arranged in a stacked or cascaded configuration such that any selected component of the flow may be forwarded into a subsequent stage of a stacked separation system. 
     Further, individual separation systems can be configured to separate the flow into more than two flow portions by incorporating additional collection horns in the separation chamber. 
     These capabilities, when combined together, can broaden the performance envelope of the separator technology to address a wide variety of flow separation applications. 
       FIG. 8A-8D  illustrate an additional example of a flow separation system. The fluid separation system  800  shown in  FIG. 8A-8D  is suitable for a stacked arrangement of several separation systems, or can be used alone. As seen in  FIG. 8A , the separation system  800  includes the same upstream members  120  and  140  as illustrated in  FIG. 1A-1D  and  FIG. 2A-2B , with a different configuration of components downstream of the separation chamber.  FIG. 8A  is a cutaway view of the separation system, with part of the housing removed to show the shape of the interior components.  FIG. 8B  is a sectional view of the separation system, taken at a plane B-B through an outlet channel or passageway  810  and support struts  814 ,  818 , and  819 , looking in the upstream direction toward the separation chamber. 
     In this example, the “flow receiving member”  860  includes a wide collector or “horn shaped” collector  166 , at least one support or strut, and an exit flow adapter module  840 . 
     The horn shaped collector  166  is positioned along the axis of the collector  800  facing the separation chamber  150 , to collect the more buoyant portion of the flow FL 2  that has been driven toward the central part of the chamber. An outlet channel or passageway  810  is positioned downstream of the mouth of the collector  166 . The channel or passageway  810  extends through the wall of the horn shaped collector and extends radially outward to an outlet  812  in the housing  110 . The central passage  161  is closed at the far end  811  that is opposite the horn shaped collector  166 , so the more buoyant fluid FL 2  that enters the collector  166  is forced through the outlet channel  810 , and exits the system  800  through the housing wall at the outlet  812 . 
     The horn-shaped collector  166  is supported by several supports or struts  814 ,  818 , and  819 . Each support or strut is affixed at one end to the horn shaped collector and at the other end to an exit flow adapter module  840 . The struts and the channel or passageway  810  can have low-drag cross sectional profiles such as the oval profiles shown in  FIGS. 8C and 8D , or other low-drag profiles (e.g., an airfoil shape with the leading edge facing into the flow). Other profiles may also be suitable. Note that  FIGS. 8C and 8D  are not to scale. 
     The exit flow adapter module  840  has a cylindrical outer surface that fits closely within the housing, and an inner surface  843  that tapers inward to define a heavy-flow-component axial exit channel  830  with a decreasing cross section along the direction of flow. The diameter of the outlet  820  is D 4 . The decreasing diameter of the inner surface of the exit flow adapter module  840  accelerates the flow through the heavy-flow-component axial exit channel  830 . In addition, the exit flow adapter module  840  can ensure the diameter D 4  of the axial outlet  820  is suitable for connection to the inlet of another fluid separator, as discussed in later paragraphs. However, it is also envisioned that some applications may allow an exit flow adapter module with a constant diameter inner surface, or an inner surface with a different profile. 
     The heavier (less buoyant) portion of the flow FL 3  bypasses the mouth  167  of the horn shaped collector  166  and flows generally axially past the struts toward the axial outlet  820  at the far end of the housing  110 . 
     The flow receiving member  860 , including the exit flow adapter module, one or more support struts, and the horn-shaped collector, is preferably held in position within the housing to maintain the desired separation chamber length L and to align the channel  810  with the opening in the housing. A threaded end cap  850  can maintain the flow receiving member  860  in position. Another option is to use a locking mechanism such as a locking pin, protuberance, or flange to hold the flow receiving member in place. In other embodiments, the flow receiving member can be adhesively attached to the housing. 
     The distance L affects the dwell time of the flow within the chamber  150 , and together with the angle and dimensions of the channel  144  and the helix angle A 3 , controls the amount of separation between the partial flows FL 2  and FL 3 . The distance M between the outer rim  167  of the horn shaped collector  166  and the inner wall of the housing  110  determines how much of the more buoyant flow component will be collected by the horn-shaped collector  166 , and how much of the less buoyant flow component will bypass the collector  166  and exit through the outlet  820 . 
     The axial flow of the less buoyant flow component FL 3  past the collection horn  166 , the struts  814 ,  818 , and  819 , and the wall of the exit channel  810  allows the less buoyant fluid to exit the separator  800  and to be directly input to another separation system arranged downstream of the separator  800 , as is discussed in later paragraphs. 
       FIG. 9  illustrates another example of a fluid separator system. In this example, the flow receiving member  960  includes all the components shown in  FIG. 8 , plus a second collection horn  902  that concentrically surrounds the central collection horn  166  and an exit channel  910  that extends from the second collection horn  902  radially outward through the housing  110 . The second collection horn  902  has a mouth  904  with a larger diameter than that of the central collection horn  166 , and collects fluid FL- 3  that is heavier (less buoyant) than the fluid FL- 2  collected by the central collection horn  166 , but lighter than the fluid FL- 4  that bypasses the second collection horn mouth  904 . Each of the fluid flows FL- 2  and FL- 3  collected by the collection horns is transported to a separate outlet at the outer circumferential surface of the housing  110 . The diameter and position of the mouth  904  of the second collection horn  902  determines how much of the heaviest flow FL- 4  bypasses the collection horns and exits the system at the axial outlet  820 . In this example, the mouth  904  of the second collection horn is slightly downstream of the mouth  167  of the central collection horn  166 , but it could be located at a different axial position depending the desired collection rate and buoyancy of the fluid to be collected by the second collection horn  902 . 
     Instead of outputting the lighter fluids to outlets at the side of the housing, in both of the embodiments shown in  FIG. 8A-8D  and  FIG. 9 , the channels  810 ,  910  could extend through the exit flow adapter module  840  to separate outlets at the outlet end of the separator. 
     The fluid separation systems  100 ,  800 , and  900  described herein rely on the inlet fluid pressure to drive the fluid through the helical spiral channel in the flow forming member, which allows the heavier (less buoyant) fluid and the lighter (more buoyant fluid) to separate in the separation chamber and to be collected by separate collectors in the flow-receiving member. Each of these systems can be configured to operate at a pressure of above about one atmosphere (approximately 14.7 pounds per square inch). The separators can operate at higher inlet pressures, for example, in the range of 80-150 psi, or higher. In one example, the system  100 ,  800 , or  900  has a diameter of about one inch, and operates at an inlet pressure of about 30 psi (approximately 2 atmospheres), with a cone angle A 1  of about 30 degrees. 
     As discussed above, the system geometry can be varied based on the speed of the fluid flow FL 1  at the inlet and the centrifugal “g-force” necessary to create the desired amount of flow separation in the separation chamber. For operation at lower inlet pressures, the system may be configured with a smaller cone angle, longer and thinner helical channels, additional helical channels, and a smaller diameter. 
     Each of the systems illustrated in  FIGS. 1A-1D, 8A-8D, and 9  can be arranged in a cascaded or stacked manner. 
       FIG. 10  illustrates the stacking capability of a separator system by showing three cascaded separators  800 ,  800 ′, and  800 ″″. In this example, the heavier (less buoyant) fluid FL 3  exits the first separator  800  and enters the inlet of the second separator  800 ′. The second separator  800 ′ further separates the flow FL 3  into a lighter (more buoyant) flow portion FL 2 ′ and a heavier flow portion FL 3 ′. The heavier flow portion FL 3 ′ enters the inlet of the third separator  800 ″, and is further separated into a lighter flow portion FL 2 ″ and a heavier flow portion FL 3 ″. In this manner, the cascaded separators separate the flow into separate streams of differing buoyancy, and concentrate the heaviest flow FL 3 ″ at an axial outlet of the final separator. 
       FIG. 11  illustrates three separators  100 ,  100 ′, and  100 ″ arranged in a cascaded or stacked configuration. In this example, and as illustrated in  FIG. 1A , the heavier fluid exits each separator from an outlet port at the circumferential surface of each separator housing, and the lighter fluid exits each separator at the far end opposite the inlet end. Thus, the lightest (most buoyant) fluid FL 2 ″ exits at an axial outlet of the final separator. In each example, there may be more or fewer separators. 
       FIG. 12  illustrates in more detail two axial fluid separators  800  and  800 ′ arranged in a cascaded manner. The first separator and second separator are aligned along the same central axis, and the axial outlet of the first separator feeds the less buoyant (heavier) fluid directly into the fluid inlet of the second separator. A connector  990  joins the outlet end of the separator  800  to the inlet end of the second separator. In this example, the connector includes two flanges or plates  991 ,  992 . Each flange or plate is connected to one of the separators, and the flanges or plates have a planar facing surface held in contact by bolts or screws (not shown) that extending through aligned holes  993 ,  994  that extend through both flanges or plates. In this example, a fluid seal is provided by a compliant sealing member  995  positioned between the flanges or plates in a groove in one of the flanges or plates, and compressed by the bolts, screws, or other clamping device that holds the flanges or plates together. The compliant sealing member can be, but is not limited to, an o-ring, a gasket, or a metal seal. The fluid separators  800 ,  800 ′ can be joined by various other mechanical connectors, or can be adhered or bonded together. 
     In this example, the exit diameter of the axial outlet of the first separator is approximately the same as the inlet diameter of the inlet of the second separator. Because the separators are connected directly together, with no bends in the fluid path between the connectors, the fluid experiences little or no pressure drop as it passes from one separator to the next. Additional separators can be added in a similar or identical manner downstream of the second separator or upstream of the first separator. The maximum number of separators is determined by the pressure drop across each separator and the inlet pressure at the first separator. As shown in this example, no pumps are positioned between the connectors to increase the inlet pressure of the fluid entering the second separator. The cascaded or stacked separators can be considered to be individual stages of a larger separation system. 
     It is also noted that while the description of the separator systems described above identifies a housing with internal components that are separately manufactured and subsequently inserted into the housing, it is also envisioned that the entire separator or subassemblies can be formed integrally by manufacturing processes including, but not limited to, casting, forging, machining, 3D printing, other additive manufacturing processes, or any combinations thereof. In particular, flow separation systems can be formed of a single component. Instead of a separate housing and internal members shown in  FIGS. 1A-1D, 2A-2B, 8A-8D, and 9 , the flow passages can be formed within a single piece of material by one or more of these manufacturing processes. 
     Although the present teachings have been described with respect to various embodiments, it should be realized these teachings are also capable of a wide variety of further and other embodiments.