Patent Description:
Water is not readily available in space. Since the beginning of space travel, there has been a need for smart consumption and recycling and reusing of water. In addition, space environments offer unique challenges of power usage and the space available for these recycling systems. Power must be smartly consumed to power the space environments and ensure power consumption for those environments. Systems and electronics on those space environments may necessitate efficient power consumption and engineering specific to conserve power and consume very little space. Therefore, there is a need for a low-power, low-mass liquid collection apparatus.

An example of collecting water in space is disclosed in <CIT>, California. The '<NUM> patent discloses coating a surface of a spaceship with a drying agent to capture ambient water moisture from space as it impinges on the spaceship. The '<NUM> patent focuses on the external collection of water in space versus the recycling and reusing of water internal to a space vehicle. <CIT> discloses apparatus to separate water droplets from an air stream in accordance with the pre-characterising portion of claim <NUM>. <CIT>, <CIT> and <CIT> are other relevant documents.

In accordance with a first aspect of the present invention, there is provided an apparatus to separate water droplets from an air stream as defined in claim <NUM>.

In accordance with a second aspect of the present invention, there is provided a method of separating water from a stream of water laden air as defined in claim <NUM>.

Embodiments of the first and second aspects of the invention are defined in the dependent claims.

The accompanying drawings and figures illustrate a number of exemplary embodiments and are part of the specification. Together with the present description, these drawings demonstrate and explain various principles of this disclosure. A further understanding of the nature and advantages of the present invention may be realized by reference to the following drawings.

Water is a scarce resource in outer space. It is not readily available and must be mined from extraterrestrial resources if it is to be collected at all in outer space, which is a currently developing technology. Therefore, all water used in spacecraft is carried from earth. As such, the preservation, recycling, and reusing of water in extraterrestrial living systems may reduce the amount of water initially needed at the onset of an extraterrestrial mission. Water may be harvested and recycled from unlikely sources. However, power is also a scarce resource in space and must be used wisely. Therefore, a solution is needed to harvest water from on board resources using as little power as possible. The solution though, must also be lightweight and relatively small as to not encumber the mission or add unnecessary extra weight to the space vessel.

<FIG> illustrates an example of a potential system <NUM> which may utilize a low-gravity water separator <NUM>. The system <NUM> may include the low-gravity water separator <NUM>, an air intake <NUM>, and an air output system <NUM>. The air intake <NUM> may be cabin air intake. The air intake <NUM> may pass air through a filter <NUM>, such as a HEPA filter or the like. After air passes through the filter <NUM>, air may enter a temperature and humidity control device <NUM>. The temperature and humidity control device <NUM> may include a multitude of devices including a heat exchanger. The temperature and humidity control device <NUM> may emit an air stream laden with water droplets along path <NUM>. In some arrangements, the temperature and humidity control device <NUM> may output water laden air using a fan or other device to generate a force on the air. In some arrangements, gravity may alternatively and/or additionally act on the water laden air. The water laden air may enter the low-gravity water separator <NUM>. The low-gravity water separator <NUM> may separate the water droplets from the air stream. The low-gravity water separator <NUM> may then discharge air free of water droplets into the air output system <NUM>. In some arrangements, the air output system <NUM> may include an evaporator <NUM> and one or more fans <NUM> to circulate the air and/or pull the air from the water separator <NUM>. In some arrangements, the air output system <NUM> may output air to a ducting and ventilation system (not shown) along path <NUM>.

The low-gravity water separator <NUM> may additionally incorporate a water-output device <NUM> which may enable water to be discharged from the low-gravity water separator <NUM>. The water-output device <NUM> may incorporate and/or communicate with one or more sensors <NUM> which may enable the water-output device <NUM> to automatically pull water from the low-gravity water separator <NUM>. The water-output device <NUM> may discharge water to a liquid-output system <NUM>. The liquid-output system <NUM> may include one or more pumps and one or more filters. The liquid-output system <NUM> may discharge water to a liquid processing system (not shown) along path <NUM>.

<FIG> is a perspective view of a low-gravity water separator <NUM>. The low-gravity water separator <NUM> may be an example of the low-gravity water separator <NUM> described with reference to <FIG>. The low-gravity water separator <NUM> may include an air inlet <NUM>, an air outlet <NUM>, and a water discharge <NUM>. In some arrangements, the air outlet <NUM> may be cylindrical-shaped and create a sort of chimney for air free of water droplets to be discharged. The air outlet <NUM> may enable air to be discharged from the low-gravity water separator <NUM>. The air outlet <NUM> may be oriented in any desired direction.

<FIG> is a perspective view of the low-gravity water separator <NUM> showing internal features, such as the helix structure <NUM>, shown in broken lines without the chimney air outlet component. <FIG> is another perspective view of the low-gravity water separator <NUM> without the chimney air outlet component. <FIG> is a cutaway view of the low-gravity water separator <NUM> along lines 5A-5A in <FIG>. <FIG> is another cutaway view of the low-gravity water separator <NUM> along lines 5B-5B in <FIG>. <FIG> is a further cutaway view of the low-gravity water separator <NUM> along lines 5C-5C in <FIG>. <FIG> is a still further cutaway view of the low-gravity water separator <NUM> along lines 5D-5D in <FIG>. <FIG> is a view of the helix structure <NUM> of the low-gravity water separator <NUM> of <FIG>.

The low-gravity water separator <NUM> may include an air inlet <NUM>, an air outlet <NUM>, and a water discharge <NUM>. The low-gravity water separator <NUM> may comprise an elongated tube <NUM> (also referred to as a housing or an elongated housing) with an inner wall <NUM> and an outer wall <NUM>. An opening <NUM> to the low-gravity water separator <NUM> may be on a first end <NUM> of the elongated tube <NUM>. The opening <NUM> may be positioned to accept an air stream. For example, the opening <NUM> of the low-gravity water separator <NUM> may be positioned proximate an outlet of a heat exchanger or another device which may output water laden air that includes a plurality of water droplets - also referred to as droplet laden air (see e.g., <FIG>).

A helix structure <NUM> may be positioned within the elongated tube <NUM>. The helix structure <NUM> may guide the droplet laden air from the opening <NUM> at the first end of the elongated tube <NUM> to a second end <NUM> of the elongated tube <NUM>. When the droplet laden air reaches the second end <NUM>, at least some of the water droplets may be separated from the air stream and the water droplets may be captured in a reservoir <NUM> proximate the second end <NUM> of the elongated tube <NUM>. The air stream may continue past the reservoir <NUM> and release into an air output system (e.g., air output system <NUM> shown in <FIG>).

The geometry of the helix structure <NUM> may cause water droplets to separate from the air stream as the air travels through the helix structure <NUM> to the second end <NUM> of the low-gravity water separator <NUM>. In some arrangements, the flow path and velocity of the air stream may cause water droplets to separate from the air stream. Contact between the water laden air and a surface (e.g., helix structure <NUM> or inner wall <NUM>) may create separation of the water droplets from the air as well. The helix structure <NUM> may have an upper surface <NUM> and a lower surface <NUM> arranged opposite the upper surface <NUM>. The helix structure <NUM> may additionally include an outer edge <NUM>. The outer edge <NUM> of the helix structure <NUM> may continuously contact the inner wall <NUM> of the elongated tube <NUM>.

The helix structure <NUM> may have a varying helical pitch as the helix structure <NUM> traverses from the first end <NUM> of the elongated tube <NUM> toward the second end <NUM> of the length of the elongated tube <NUM>. For example, the helix structure <NUM> may have an initial helical pitch p<NUM>, a transitional helical pitch p<NUM>, and a final helical pitch p<NUM>. The pitch of a helix may be defined as the height of a complete turn of a single helix structure, measured parallel to the axis of the helix structure or as the distance between revolutions of the helix. The varying helical pitch of the helix structure <NUM> may increase as the helix structure <NUM> traverses the elongated tube <NUM>. The initial helical pitch p<NUM> may be smaller and/or shorter than the transitional helical pitch p<NUM>, which may in turn be smaller and/or shorter than the final helical pitch p<NUM>.

The initial helix pitch p<NUM> may be governed by an effective flow area of the cross-axial circumferential air stream as it enters the helix structure <NUM>. The pitch p<NUM> may allow an acceptable restriction on the air stream which may cause a desired pressure drop and air speed. If the pitch p<NUM> is too small, the air stream may face an unnecessary restriction which may cause excessive air flow acceleration which may lead to an unnecessary pressure drop and an associated unnecessary increase in fan power. The level of necessary air flow acceleration or peak velocity may be a factor of the size of the water droplets dispersed within the gas stream along with gas viscosity, and a density difference between the liquid and gas phases. In some arrangements, smaller water droplets may require higher peak gas velocities to be spun out of the air stream in the same amount of time that larger water droplets would spin out in lower air flow velocities.

The initial p<NUM> may be a factor of a ratio of gas flow residence time-to-water droplet drift time. The water droplet drift time may be a maximum average time for a water droplet of a specific size to travel from the axis of the device to the inner wall <NUM> of the elongated tube <NUM>. The gas flow residence time may be an average time for the entire gas volume to be completely changed in the low-gravity water separator <NUM>. Another way to describe gas flow residence time is the length of time for air entering the low-gravity water separator <NUM> to exit the low-gravity water separator <NUM>. This may be determined by a volume to volumetric flow rate ratio. The volume to volumetric flow rate ratio may be a ratio of internal air volume to volumetric air flow rate, for example, the amount of volume contained within the low-gravity water separator <NUM> divided by the rate at which the volume of air is exchanged within the low-gravity water separator <NUM> as follows: <MAT>.

The volume to volumetric flow rate ratio may be greater than the water droplet drift time. A ratio as such may enable a water droplet to drift towards and collide with the inner wall <NUM> and/or the upper surface <NUM> before flowing out the air outlet <NUM>. A residence time to drift time ratio may be in a range of the volume to volumetric flow rate ratio of approximately <NUM> based on an initial water droplet size. In some arrangements, an initial helical pitch p<NUM> may be sized approximately between ½ and 1½ times a diameter of the elongated tube <NUM> to achieve this ratio.

The transitional helical pitch p<NUM> may be a portion of the overall length L of the helix structure <NUM> to enable a transition between the initial helical pitch p<NUM> to the final helical pitch p<NUM>. The final helical pitch p<NUM> may transition the gas velocity field at the air outlet <NUM> to a mostly axial air stream. For example, the final helical pitch p<NUM> may reduce and/or remove the tangential air flow velocity component from an initial tangential air flow velocity. The tangential air flow velocity may also include a measure of the air flow rate of revolution about the helix structure <NUM>. In some arrangements, the final helical pitch p<NUM> may comprise most of the length L of the elongated tube <NUM> while maintaining an acceptable initial helical pitch p<NUM>. The final helical pitch p<NUM> may also produce a smooth transition from the initial helical pitch p<NUM> to the reservoir <NUM> and air outlet <NUM>.

The changing helical pitch may also cause an interior angle between the upper surface <NUM> of the helix structure <NUM> and the inner wall <NUM> of the elongated tube <NUM> to change. For example, an initial interior angle α<NUM> between the upper surface <NUM> and the inner wall <NUM> may be less than <NUM>°. In some arrangements, the initial interior angle α<NUM> may be approximately <NUM>° to <NUM>°. The initial angle α<NUM> may change as the initial helical pitch p<NUM> transitions to the transitional helical pitch p<NUM>.

The initial angle α<NUM> may transition to a transitional interior angle α<NUM> between the upper surface <NUM> and the inner wall <NUM>. The transitional interior angle α<NUM> may be sized such that it smoothly and relatively constantly (i.e. linearly) changes the interior angle formed by the upper surface <NUM> and the inner wall <NUM> between reservoir <NUM> and inlet.

The final interior angle α<NUM> may begin at the end range of the transitional interior angle α<NUM> with a range of approximately <NUM>° to <NUM>°. The continuously diminishing interior angles α<NUM>, α<NUM>, α<NUM> may aid in water flow from the air inlet <NUM> of the low-gravity water separator <NUM> to the reservoir <NUM>.

The reservoir <NUM> may collect water droplets as water flows down the helix structure <NUM>. The water droplets, as will be discussed with reference to <FIG>, may be separated from the air stream as the air stream travels through the helix structure <NUM>. The helix structure <NUM> and elongated tube <NUM> may gradually transition into the reservoir <NUM>. For example, the reservoir <NUM> may be located in the second end <NUM> of the low-gravity water separator <NUM> and the transition between the elongated tube <NUM> and the reservoir <NUM> may be a smooth and continuous curved geometry <NUM>.

The reservoir <NUM> may comprise a bulbous cavity <NUM>. The bulbous cavity <NUM> may have an entry point <NUM> which may enable the flow of water from the final interior angle p<NUM> to the water reservoir <NUM>. The water reservoir <NUM> may be bisected by a stabilizing vane <NUM>. The stabilizing vane <NUM> may maintain water within the reservoir <NUM> and may prevent water laden air from being dispersed into the atmosphere. The stabilizing vane <NUM> may additionally guide water droplets towards one or more reservoir vanes <NUM>. The one or more reservoir vanes <NUM> may use capillary action to maintain the water in the reservoir <NUM>. Capillary action, which may arise due to the interaction of surface tension of a liquid and adhesive forces acting between the liquid and adjacent surfaces, may cause the water to minimize its surface area exposed to the air. For example, the water may naturally seek minimum inter-facial energy. In the reservoir <NUM>, the water may pull itself into the series of reservoir vanes <NUM> where the vanes <NUM> are closest together to minimize an exposed water surface. The reservoir vanes <NUM> may be spaced apart such that water, or another liquid, may use surface tension or cohesion and adhesive forces between the liquid and the reservoir vanes <NUM> to maintain the liquid in the reservoir <NUM>.

For example, with reference to <FIG>, the reservoir vanes <NUM> may be arranged at various angles α<NUM>, α<NUM>, α<NUM>, and α<NUM> relative to each other. The angles α<NUM>, α<NUM>, α<NUM>, and α<NUM> may all protrude from a common area or point <NUM>. This point <NUM> is typically contained within the reservoir <NUM> (as shown in the Figures) or may be a point or area located outside the confines of the low-gravity water separator <NUM>. In some arrangements, the various angles α<NUM>, α<NUM>, α<NUM>, and α<NUM> may all comprise the same angle separating each vane <NUM>. In other arrangements, each angle α<NUM>, α<NUM>, α<NUM>, and α<NUM> may be distinct from the others. In some sarrangements, the angles α<NUM>, α<NUM>, α<NUM>, and α<NUM> may be continuous as the vanes <NUM> extend outward from the point <NUM>. For example, the angle α<NUM>, α<NUM>, α<NUM>, and α<NUM> separating adjacent vanes may be constant along a length of each vane <NUM>. In other embodiments, the angles α<NUM>, α<NUM>, α<NUM>, and α<NUM> may be variable as the vanes <NUM> extend away from the point <NUM>. For example, the vanes <NUM> may have a curvature or variable geometry that causes the angles α<NUM>, α<NUM>, α<NUM>, and α<NUM> to change along the length of each vane <NUM>. The angles α<NUM>, α<NUM>, α<NUM>, and α<NUM> may be constant or variable angles in the range of about <NUM> degrees to about <NUM> degrees, and more particularly in the range of about <NUM> degrees to about <NUM> degrees.

The spacing between, the shape and size, and the position within reservoir <NUM> of stabilizing vanes <NUM> may be determined based on a target Weber number. A Weber number is a dimensionless number for analyzing fluid flows at an interface between two different fluids. The Weber number is calculated as a ratio between a dynamic pressure of air and a capillary pressure of the water. A final calculation of the Weber number is indicative of whether the kinetic energy of the air or interfacial energy of the water is dominant. In the current situation, the Weber number should indicate a dominant interfacial energy of the water to indicate the water will remain in a coalesced state in the reservoir <NUM> and not disperse into droplets. The Weber number may also be calculated by either of the following equations: <MAT> <MAT> To achieve water stability, the Weber number may be in the range of about <NUM> to about <NUM>.

In further arrangements, a stability rule may be used to determine a distance between the stabilizing vanes <NUM>. For example, to achieve water stability, a stabilizing calculation may be performed. The calculation may be performed using the following equation for air/water separation: <MAT>.

Vair may be air velocity. D may be distance between the stabilizing vanes <NUM> at the interface between the water and the air. In some arrangements, the reservoir vanes <NUM> may additionally be of sufficient height to maintain an adequate amount of liquid within the reservoir <NUM>. The water discharge <NUM> may be positioned proximate a bottom end <NUM> reservoir <NUM>.

In some arrangements, the water discharge <NUM> may enable water to be drawn from the stabilizing vanes <NUM> within the reservoir <NUM>. In some arrangements, the low-gravity water separator <NUM> may incorporate an automated drain cycle which may utilize liquid level sensing. The water discharge <NUM> may be controlled by sensing an amount of water present in the reservoir <NUM> (e.g., water-output device <NUM> shown in <FIG>). When the reservoir <NUM> is full, a pump (not shown) may be started. The pump may cease operation when the reservoir <NUM> is empty. In some arrangements, capacitive level sensors (e.g., sensors <NUM>, <FIG>) may be used. Capacitive level sensors may be capable of sensing through a wall and may be positioned on an outside of the reservoir <NUM> to determine when the reservoir is 'full' and when it is 'empty.

In some arrangements, the low-gravity water separator <NUM> may include a lip <NUM> proximate the opening <NUM> of the elongated tube <NUM>. The lip <NUM> may mate with another piece of equipment such as a heat exchanger, tube, or other device and/or apparatus which may transfer droplet laden air from a source to the opening <NUM>. The opening <NUM> may additionally and/or alternatively incorporate a multitude of other attachment features such as a male or female threaded end, an interference fit device, or the like.

Likewise, the air outlet <NUM> may comprise an opening <NUM> with a lip <NUM>. The lip <NUM> may provide a clamping surface to attach an apparatus to the air outlet <NUM>. An apparatus may include, for example, a tube or other transfer structure to move and/or guide air to an air output system (e.g., air output system <NUM> shown in <FIG>). The opening <NUM> may additionally and/or alternatively incorporate other connection mechanisms such as threaded ends, interference fits, or the like. The air outlet <NUM> may form a sort of chimney shaped structure with an interior wall <NUM>. The wall <NUM> protrudes into the reservoir <NUM> and may create an interior corner. The interior corner <NUM> may capture any stray wall-bound water droplets and highly wetted liquid films from migrating out of the air outlet <NUM>.

<FIG> is a view of the helix structure <NUM> of the low-gravity water separator <NUM> of <FIG>. In some arrangements, the helix structure <NUM> may have various features on the upper surface <NUM> of the helix structure <NUM>. For example, the helix structure <NUM> may have a groove in the upper surface <NUM> of the first helix turn <NUM>. The second helix turn <NUM> and the third helix turn <NUM> may also have a groove in the upper surface <NUM>. The groove may use surface tension and/or capillary forces to guide the water towards the edge <NUM> of the helix structure <NUM>. This may stabilize the water flow as it transitions towards the reservoir <NUM>. In other arrangements, a tertiary vane may be provided as a protruding feature on the upper surface <NUM> of the helix structure <NUM> to provide a stabilizing force for a water rivulet and/or water droplets. In some arrangements, a water rivulet may be a small stream of coalesced or gather water particles or water droplets. Either feature, a groove or a tertiary vane, may direct water droplets to the outer edge <NUM> of the helix structure <NUM> towards a rivulet. The groove or tertiary vane may provide stability to water rivulets.

<FIG> is a perspective view of an alternative configuration for a low-gravity water separator <NUM>. The low-gravity water separator <NUM> may incorporate similar features as the low-gravity water separator <NUM>, <NUM> discussed with reference to <FIG>. The low-gravity water separator <NUM> may include an elongated tube <NUM>. The elongated tube <NUM> may have a cylindrical shape or may be tapered and/or conical-shaped. The elongated tube <NUM> may include an air inlet <NUM>, an air outlet <NUM>, and one or more water discharges <NUM>. <FIG> is a perspective view of the low-gravity water separator <NUM> with internal features, such as the helix structure <NUM>, shown in broken lines. <FIG> shows a plan view of the low-gravity water separator <NUM>.

<FIG> show cutaway views of the low-gravity water separator <NUM> along lines 9A-9A and 9B-9B as shown in <FIG> and <FIG>, respectively. <FIG> is a view of a helix structure of the low-gravity water capture device of <FIG>. The low-gravity water separator <NUM> includes the helix structure <NUM>. The elongated tube <NUM> may include with an inner wall <NUM> and an outer wall <NUM>. An opening <NUM> to the low-gravity water separator <NUM> may be on a first end <NUM> of the elongated tube <NUM>. The opening <NUM> may be positioned to accept the air stream.

A helix structure <NUM> may be positioned within the elongated tube <NUM>. The helix structure <NUM> may guide an air stream from the opening <NUM> at the first end of the elongated tube <NUM> to a second end <NUM> of the elongated tube <NUM>. By the time the air reaches the second end <NUM>, at least some of the water droplets may be separated from the air stream and captured in a reservoir <NUM> proximate the second end <NUM> of the elongated tube <NUM>. The air stream may continue past the reservoir <NUM> and release into an air output system (e.g., air output system <NUM> shown in <FIG>).

The geometry of the helix structure <NUM> may cause water droplets to separate from the airflow as the air stream travels through the helix structure <NUM> toward the second end <NUM> of the low-gravity water separator <NUM>. In some arrangements, the flow path and velocity of the air may cause water droplets to separate from the air streams. The helix structure <NUM> may have an upper surface <NUM> and a lower surface <NUM> arranged opposite the upper surface <NUM>. The helix structure <NUM> may additionally include an outer edge <NUM>. The outer edge <NUM> of the helix structure <NUM> may continuously contact the inner wall <NUM> of the elongated tube <NUM>.

The helix structure <NUM> may have a varying helical pitch as the helix structure <NUM> traverses from the first end <NUM> of the elongated tube <NUM> to the second end <NUM> of the elongated tube <NUM>. For example, the helix structure <NUM> may have an initial helical pitch p<NUM>, a transitional helical pitch p<NUM>, and a final helical pitch p<NUM>. The initial helical pitch p<NUM>, transitional helical pitch p<NUM>, and final helical pitch p<NUM> may be similar to the initial helical pitch p<NUM> as described with reference to <FIG>. As the helical pitch changes, the upper surface <NUM> of the helix structure <NUM> may maintain a smooth and continuous surface.

The changing helical pitch may also cause an interior angle between the upper surface <NUM> of the helix structure <NUM> and the inner wall <NUM> of the elongated tube <NUM>. For example, an initial interior angle α<NUM>, transitional interior angle α<NUM>, and final interior angle α<NUM> may be sized similarly to the initial interior angle α<NUM>, transitional interior angle α<NUM>, and final interior angle α<NUM> described with reference to <FIG>. The interior angles α<NUM>, α<NUM>, α<NUM> may aid in water flow from the air inlet <NUM> of the low-gravity water separator <NUM> to the reservoir <NUM>.

The reservoir <NUM> in the low-gravity water separator <NUM> may be formed between the inner wall <NUM> of the elongated tube <NUM> and an exterior wall <NUM> of an interior cylinder <NUM> located within the elongated tube <NUM>. The height of the interior cylinder <NUM> may be high enough to hold the water separated from the air entering the opening <NUM>. A connecting wall <NUM> may form a bottom <NUM> of the reservoir <NUM>. The connecting wall <NUM> may connect a bottom of the elongated tube <NUM> to approximately a midpoint of the interior cylinder <NUM>. Dry air may pass through an opening <NUM> formed in the interior cylinder <NUM>. Water collected in the reservoir <NUM> may be extracted from the reservoir via one or more water discharges <NUM>.

In some arrangements, an inlet cap <NUM> may be positioned proximate the air inlet <NUM> (see <FIG>). The inlet cap <NUM> may prevent the formation of a rivulet on an inside edge of the helix structure <NUM>. The inlet cap <NUM> may set a predetermined distance between the inside edge of the helix structure <NUM> and a center axis <NUM> of the low-gravity water separator <NUM>. The inlet cap <NUM> may prevent the air stream from entering the helix structure <NUM> at a trajectory directly down the center axis <NUM>.

In some arrangements, air may enter the reservoir <NUM> at a rapid velocity. The velocity of the air flow entering the reservoir <NUM> may continue to increase after the air has entered the reservoir <NUM> and may turn into turbulent air flow. Turbulent air flow in the reservoir may disrupt a water rivulet or pool of water that may be gather in the reservoir <NUM>.

In some arrangements, air flow to the reservoir <NUM> may be restricted. For example, a baffle (not shown) may sit atop the exterior wall <NUM> of the interior cylinder <NUM>. The baffle may have a donut-like shape or toroidal shape. For example, the baffle may have an interior hole which may allow air to flow out of the low-gravity water separator <NUM> through interior cylinder <NUM>. An outer diameter of the baffle may be smaller than an inner diameter of the inner wall <NUM> of the low-gravity water separator <NUM>. For example, there may be gap or predetermined distance between the inner wall <NUM> and a perimeter edge the baffle. The gap, or space, between the inner wall <NUM> and the baffle may enable the rivulet and water laden air to enter the reservoir <NUM> while reducing the velocity and volume of air flow to the reservoir.

In some arrangements, the exterior wall <NUM> of the interior cylinder <NUM> may incorporate one or more holes along its surface at locations between its open distal and proximal end. The one or more holes may allow turbulent air to exit the reservoir <NUM> while water remains in the reservoir. For example, capillary forces may retain the water inside the reservoir while turbulent air may exit the reservoir <NUM> through the one or more holes.

In another arrangements, one or more fins (not shown) may be incorporated into the reservoir <NUM>. For example, after the helix structure <NUM> enters the reservoir <NUM>, the helix structure <NUM> may terminate near the second end <NUM> of the low-gravity water separator <NUM>. One or more stabilizing fins may wrap around interior cylinder <NUM> and/or connecting wall <NUM>, <NUM>. The stabilizing fins may transition the turbulent, fast airflow entering and swirling in the reservoir <NUM> into smooth and slower laminar air flow. Laminar airflow in the reservoir may reduce or lessen interruptions to the water rivulet formed within the reservoir. Fewer disruptions to the rivulet may enable to the water to stay within the reservoir. Furthermore, the fins may provide the same or similar benefits related to stabilizing the water collected in the reservoir <NUM> as the vanes <NUM> described above with reference to the low-gravity water separator <NUM>.

<FIG> is a side view of the helix structure <NUM> of the low-gravity water separator <NUM> of <FIG>. The helix structure <NUM> may incorporate similar features of the helix structure <NUM> discussed previously. For example, in some arrangements, the helix structure <NUM> may have various features on the upper surface <NUM> of the helix structure <NUM>. For example, the helix structure <NUM> may have a groove in the upper surface <NUM>. The groove may use surface tension and capillary forces to guide or direct the water towards the outer edge <NUM> of the helix structure <NUM>. The groove may help stabilize the water flow as it transitions towards the reservoir <NUM>. In other arrangements, a tertiary vane may protrude from and extend along the upper surface <NUM> of the helix structure <NUM> to provide a stabilizing force for a water rivulet and water droplets. Either feature, a groove or a tertiary vane, may direct water droplets to the outer edge <NUM> of the helix structure <NUM> towards a rivulet. The groove or tertiary vane may provide stability to water rivulets.

<FIG> is a perspective view of a cutaway of an internal portion of a low-gravity water separator <NUM>. The low-gravity water separator <NUM> may include an inner wall <NUM>, an outer wall <NUM> positioned opposite the inner wall <NUM>, and a helix structure <NUM> positioned within the inner wall <NUM>. The low-gravity water separator <NUM> may include one or more secondary vanes <NUM>. The secondary vanes <NUM> may protrude from the inner wall <NUM> towards a centerline of the low-gravity water separator <NUM>. The secondary vanes <NUM> may be of sufficient size to guide water droplets which may be stuck on the inner wall <NUM>. The secondary vanes <NUM> may be formed on the inner wall <NUM>, may be integrally formed as a single piece with the inner wall <NUM>, or may be formed separately and mounted to the inner wall <NUM> in a separate assembly step.

The secondary vane <NUM> may begin at a first location <NUM> at an initial predetermined distance from an upper surface <NUM> of the helix structure <NUM>. A pitch of the secondary vane <NUM> may then be greater than a pitch of the corresponding portion of the helix structure <NUM> such that an end location <NUM> is proximate the upper surface <NUM> of the helix structure <NUM>. In some arrangements, the end location <NUM> may merge into the upper surface <NUM> of the helix structure <NUM>. In another arrangement, the end location <NUM> may not touch or come into contact with the upper surface <NUM>, but rather may be a distance away from the upper surface <NUM>. The secondary vane <NUM> may enable water droplets clinging to the edge of the inner wall <NUM> to be guided down into a rivulet flow as will be discussed with reference to <FIG>.

<FIG> is an example of a low-gravity water separator <NUM>. The low-gravity water separator <NUM> may be an example of one or more aspects of a low-gravity water separator <NUM>, <NUM>, <NUM>, <NUM> described with reference to <FIG>. The low-gravity water separator <NUM> may include an elongated tube <NUM> with a helix structure <NUM>. The low-gravity water separator <NUM> may include an air inlet <NUM>, air outlet <NUM>, and one or more water discharges <NUM>.

The helix structure <NUM> may have a changing helical pitch along its length L. The helix structure <NUM> may have an initial helical pitch p<NUM>, a transitional pitch p<NUM>, and a final pitch p<NUM>, as discussed previously. The helix structure <NUM> may additionally include an initial angle α<NUM>, a transitional angle α<NUM>, and a final angle α<NUM>, as discussed previously.

Air <NUM> laden with water droplets may enter the low-gravity water separator <NUM> through an air inlet <NUM>. The water laden air <NUM> may be forced into an air stream as it enters the low-gravity water separator <NUM> through gravity or an external forcing device such as a fan or the like.

The initial angle α<NUM> combined with the initial helical pitch p<NUM> at the air inlet <NUM> may create an overall angle of an upper surface <NUM> of the helix structure <NUM>. The initial range of the initial angle α<NUM> may drive wall-bound water laden air <NUM> towards an interior corner <NUM> where the upper surface <NUM> of the helix structure <NUM> meets with an inner wall <NUM> of the elongated tube <NUM>. The initial angle α<NUM> may induce a radial velocity of the water laden air <NUM>. The radial velocity may be within a range of <NUM> to <NUM> RPM. The rapid circumferential flow may create a radial acceleration of the water laden air <NUM>, or entrained drops. The radial acceleration may be within a range of <NUM> and <NUM>. The radial acceleration may cause water droplets <NUM> to separate from the air <NUM>.

For example, the helix structure <NUM> may cause a centrifugal, or cyclonic, liquid separation of the water droplets from the air stream. The centrifugal liquid separation may exploit the density difference between the liquid and gas in the air flow to concentrate the water droplets <NUM> on the inner wall <NUM> and upper surface <NUM>. Air <NUM> entering the low-gravity water separator <NUM>, with entrained water droplets, may rapidly change flow direction from an even axial flow to a rapid cross-axial rotating flow. The axial airflow may be airflow mostly perpendicular to an axis of the helix structure <NUM>. This axial airflow may change to cross-axial airflow, or airflow that is aligned with the direction of the helix structure <NUM>. The relatively `lighter' air <NUM> may change direction more easily than the 'heavier' water droplets <NUM> forcing the water droplets <NUM> to drift toward, and eventually collide with, the inner wall <NUM> and upper surface <NUM>.

As the water droplets <NUM> separate from the air <NUM>, the remaining radial velocity of the air <NUM> may drive the water droplets <NUM> into the interior corner <NUM>. The water droplets <NUM> may form a rivulet <NUM>, or a very small stream, of the water droplets <NUM>. For example, a centripetal force acting on the air <NUM> may cause the water droplets <NUM> to drive toward the rivulet <NUM>. Centripetal force may be a force that acts on the air <NUM> as it moves in a circular path down the helix structure <NUM>. The centripetal force acting on the air <NUM> may be directed toward a center of the helix structure. The centripetal force acting on the air <NUM> may be, for example, approximately <NUM>×<NUM>-<NUM> lbf to <NUM>×<NUM>-<NUM> lbf. As described previously, the speed is dependent on the ratio of air residence time to droplet drift time. The physical parameters that influence this are the size of the droplets, gas viscosity, and the density difference between the liquid and gas. Therefore, the centripetal force may change as the mass and acceleration of the droplets change.

As more water droplets <NUM> coalesce with the rivulet <NUM>, the rivulet <NUM> may swell until it fills a gas boundary layer. A gas boundary layer may be a region of air flow near a surface of the inner wall <NUM> or upper surface <NUM> of the helix structure <NUM> over which the gas is flowing, which may move at a lower velocity than the bulk of the freestream air flow. The thickness of the gas, or air, boundary layer may increase as the air flows through the helix structure <NUM>. The size of the gas boundary layer may determine how large the rivulet <NUM> may swell while still maintaining stability of the rivulet. The boundary layer may be defined as the layer of air that is moving at less than <NUM>% of the velocity of the main bulk air stream. In the low-gravity water separator <NUM>, the boundary layer may be approximately <NUM> inches. In some arrangements, the boundary layer may vary along the length of the helix structure <NUM>. The boundary layer may be thinner at the leading edge of the helix structure <NUM> near the air inlet <NUM>. The boundary layer may increase until it exits the low-gravity water separator <NUM>. This natural viscous nature may provide a low velocity zone proximate the inner wall <NUM> and may prevent the rivulet <NUM> from being destabilized even when the bulk of the air is moving rapidly.

For example, the rivulet <NUM> may continue to swell and the rivulet <NUM> may press into a gas velocity stream and the air stream may force the coalesced water droplets <NUM> in the rivulet <NUM> down the interface between helix structure <NUM> and inner wall <NUM>. This may cause a cross-section of the rivulet <NUM> to shrink as the rivulet <NUM> is elongated by the air stream. As more water droplets <NUM> coalesce within the rivulet <NUM>, the rivulet <NUM> may once again swell and repeat the process. The process may repeat as water droplets coalesce within the rivulet <NUM> which may cause the rivulet <NUM> to migrate toward the reservoir <NUM>.

Some water droplets <NUM> may be driven efficiently to the rivulet <NUM>. Other water droplets <NUM> may glide or move along the inner wall <NUM> of the elongated tube <NUM> or the upper surface <NUM> of the helix structure <NUM>. In some arrangements, the water droplets <NUM> may work their way into the rivulet <NUM>. In other arrangements, secondary vanes (e.g., secondary vanes <NUM>, <FIG>) may also guide the water droplets <NUM> to the rivulet <NUM>. In additional and/or alternative arrangements, helical vanes (not shown) may also guide water droplets <NUM> to the rivulet <NUM>. Helical vanes may be similar to the secondary vanes but rather than being located on the inner wall <NUM> of the elongated tube <NUM>, may be located on the upper surface <NUM> of the helix structure <NUM>.

The rivulet <NUM> may be a stable two-phase flow regime. For example, the rivulet <NUM> may form a long connected `string' of water along the interior corner of the intersection between the upper surface116 and the inner wall <NUM> and may remain in that interior corner <NUM>. The flow of the air <NUM> may help stabilize the rivulet <NUM>, but if the air flow exceeds, for example, about <NUM> feet per second, the speed of the air <NUM> may disrupt the rivulet <NUM>. For example, the rivulet <NUM> may experience stable two-phase flow when velocity of the air is not fast enough to pull water out of the rivulet <NUM>.

The decreasing interior angles α<NUM>, α<NUM>, α<NUM> may also stabilize the rivulet <NUM>. The decreasing interior angles α<NUM>, α<NUM>, α<NUM> may induce capillary forces in the water droplets <NUM>. The capillary forces may maintain stability of the rivulet <NUM>. The decreasing interior angles α<NUM>, α<NUM>, α<NUM> also may provide a decreasing potential in the direction of a reservoir <NUM> where the water droplets <NUM> form a collective pool of water <NUM>.

The decreasing interior angles α<NUM>, α<NUM>, α<NUM> may correlate to an increasing pitch of the helix structure <NUM>. As the rivulet <NUM> is formed, the flow of the air <NUM> may be slowed as the transitional pitch p<NUM> increases. The initial helical pitch p<NUM> may initiate a high air flow <NUM> and the transitional pitch p<NUM> may slow down the air flow to, for example, about <NUM> feet per second for the size, shape, and range of flow rates typical for the arrangement shown in <FIG>. The slower air speed in the transitional pitch p<NUM> may stabilize the rivulet <NUM>. The slower air speed may be less rapid axial flow. The less rapid axial air flow may drive the water droplets <NUM> down the rivulet <NUM> and into the reservoir <NUM>. The less rapid axial flow of the air <NUM> may also allow droplet free air to escape the low-gravity water separator <NUM>. A gradual transition between the final pitch p<NUM> and the air outlet <NUM> may maintain the air flow and may enable the droplet free air to be emitted.

<FIG> is a flow chart illustrating an example of a method relating to air and water separation, in accordance with various aspects of this disclosure. The method may include collecting droplet laden air <NUM>. The droplet laden air may enter a water separator <NUM>. The water separator may be a low-gravity water separator. Water droplets may be separated from air stream <NUM>. For example, a variable helix structure within the low-gravity water separator may use air flow and inertial forces to separate water droplets and air stream. The water droplets may be collected in a reservoir for harvesting <NUM>. The droplet free air may be emitted back into the environment or other system <NUM>.

<FIG> is another flow chart illustrating an example of a method <NUM> relating to air and water separation, in accordance with various aspects of this disclosure. The method <NUM> may be performed using any one of the low-gravity water separators <NUM>, <NUM>, <NUM>, <NUM>, <NUM> discussed herein.

The method <NUM> may collect water laden air into a semi-closed environment <NUM>. The water laden air may be forced into the semi-closed environment using a forcing function such as fan and/or gravity. The semi-closed environment may consist of a low-gravity water separator.

The method <NUM> may force the water laden air into a helical-shaped channel <NUM>. The forcing function may cause a turbulent, rapid circumferential flow of the air. The helical-shaped channel may include a variable pitch along its length. The variable pitch of the helical shaped-channel may separate water droplets from the air stream <NUM>. For example, the air stream may contact one or more surfaces of the helical-shaped channel.

A rivulet may be formed with the separated water droplets <NUM>. The water droplets may be stabilized in the rivulet using the air stream. In some arrangements, one or more secondary vanes may guide separated water droplets towards the rivulet. The speed of the air stream may be reduced after the water droplets have been separated <NUM>. For example, the variable pitch of the helical-shaped channel may cause the air speed to decrease. This may cause the turbulent, rapid circumferential air stream transition into less rapid axial flow <NUM>. As the air flow slows, the flow may change from a cross-axial flow perpendicular to the axis of the low-gravity water separator <NUM> into a streamwise flow parallel to the axis of the low-gravity water separator <NUM>. The water droplet from the rivulet flow may then be collected into a reservoir <NUM>. This may include guiding the streamwise driven rivulet flow into the water reservoir. The method <NUM> may then discharge droplet free air <NUM> and may harvest the water <NUM> as necessary.

<FIG> illustrate a low-gravity water separator <NUM> in accordance with a first embodiment of the claimed invention. The low-gravity water separator <NUM> may incorporate similar features as the low-gravity water separators <NUM>, <NUM>, <NUM> discussed above with reference to <FIG>. The low-gravity water separator <NUM> may include various features to help stabilize the collected water within a reservoir portion of the device so that the amount of water that is drawn out of the device with the exiting air flow is minimized. For example, the low-gravity water separator <NUM> may include unique water reservoir features (e.g., shape, size, and location), a helix structure shape and orientation, and air flow paths that provide stabilizing forces for the collected water. Other unique aspects of the low-gravity water separator <NUM> relate to, for example, how various components of the device are assembled together during manufacturing, how airflow is controlled internal the device, and how collected water is directed into and stabilized within the water reservoir.

Referring to <FIG>, the low-gravity water separator <NUM> includes an inlet structure <NUM>, an outlet structure <NUM>, an elongated tube <NUM>, a reservoir assembly <NUM>, and a helix structure <NUM> (see <FIG>). The inlet structure <NUM> is mounted at one end of the elongated tube <NUM>, and the outlet structure <NUM> is mounted to an opposite end of the elongated tube <NUM>.

The inlet structure <NUM> includes an inlet opening <NUM> surrounded by a flange <NUM>. The inlet structure <NUM> also includes a seat <NUM> that provides an interface with the elongated tube <NUM>. The outlet structure <NUM> includes an outlet opening <NUM> surrounded by a flange <NUM>. The outlet structure <NUM> also includes a seat <NUM> to interface with the elongated tube <NUM>. The inlet opening <NUM> is arranged along a side surface and at a radially inward directed orientation relative to a longitudinal axis L. The inlet opening <NUM> is also arranged offset from the longitudinal axis L. This offset radially inward directed arrangement for the inlet opening <NUM> provides a tangential flow of air into the low-gravity water separator <NUM>. This tangential flow facilitates movement of the flow of air into the helical channel defined between the helix structure <NUM> and an inner surface of the inlet structure <NUM> and elongated tube <NUM>. The tangential arrangement for the inlet opening <NUM> also allows the air to begin swirling droplets of water out of the air flow ahead of the entrance into the helical channel defined in part by the helix structure <NUM>. The swirling of the water droplets out of the air ahead of the helix structure causes the droplets to preferentially collide with the walls rather than the helix. Water droplets on the walls are more easily driven to the vertex and into the rivulet.

The outlet opening <NUM> also extends radially relative to the longitudinal axis L. The inlet opening <NUM> and outlet opening <NUM> are arranged in the same direction, which may facilitate easier mounting to other features of the water separator system (e.g., system <NUM> described with reference to <FIG>). In other embodiments, the inlet opening <NUM> and outlet opening <NUM> may be arranged facing in different radial directions, or in longitudinal direction, such as to accommodate the orientation of features to which the low-gravity water separator <NUM> are mounted to.

The elongated tube <NUM> includes first and second ends <NUM>, <NUM>, first and second seats <NUM>, <NUM>, an inner surface <NUM>, an outer surface <NUM>, and an internal cavity <NUM> (see <FIG>). The inlet structure <NUM> is mounted to the first seat <NUM> at the first end <NUM>. The outlet structure <NUM> is mounted to the second seat <NUM> at the second end <NUM>. The seats <NUM>, <NUM> and <NUM>, <NUM> may be formed as spherical structures or having a spherical portion and/or a contoured surface. For example, the seats may form segments of a sphere to allow slight misalignments of the axis of the inlet and outlet structures <NUM>, <NUM> relative to the longitudinal axis L of the elongated tube <NUM> to allow the inlet and outlet structures <NUM>, <NUM> to align with the elongated tube <NUM> even if the components <NUM>, <NUM>, <NUM> have significant dimensional errors. Thus, the joints between the components <NUM>, <NUM>, <NUM> may be able to accommodate relatively large dimensional errors inherent in some types of manufacturing (e.g., additive manufacturing). The spherical shape of the seats <NUM>, <NUM>, <NUM>, <NUM> may provide three rotational degrees of freedom at the joints between the components <NUM>, <NUM>, <NUM>. This allows the flanges <NUM>, <NUM> at the inlet and outlet to be relatively co-planer surfaces so that the interfaces when fastened to a main structure do not experience significant strains and may be able to provide a sufficient air- and water-tight seal. The presence of extra strain at the interface of the flanges to a mating structure resulting from a non-planer inlet and outlet orientation could result in damage to the final assembled low-gravity water separator <NUM>.

Other types of joint structures may be possible for assembling the components <NUM>, <NUM>, <NUM>, <NUM> together. In some embodiments, at least some of the components <NUM>, <NUM>, <NUM>, <NUM> may be integrally formed as single pieces rather than as separate pieces that are later assembled together. Some types of additive manufacturing (e.g., 3D printing) may facilitate creation of the components or combination of components of the low-gravity water separator <NUM> as integral pieces in spite of the relatively complex interior geometries of the various features (e.g., the helical shape of helix structure <NUM>).

In another example, at least some of the components <NUM>, <NUM>, <NUM>, <NUM> may be secured together with a bonding agent such as an adhesive. The components may be bonded by applying uncured resin or other adhesive material to the seats of the joint, following by curing the material using, for example, a suitable ultra-violet (UV) curing light. This method may be particularly useful for the present application because it can eliminate the need to certify additional materials and processes, which may be resourced intensive for items intended for certain applications (e.g., space flight).

The reservoir assembly <NUM> includes an inner reservoir <NUM> (see <FIG>), a reservoir outlet segment <NUM> having a seat <NUM> (see <FIG>), a reservoir chamber <NUM> (see <FIG>), a chamber bottom <NUM> (see <FIG>), a chamber cavity <NUM> (see <FIG>), a water outlet <NUM> (see <FIG>), reservoir return segments <NUM>, <NUM>, <NUM> (see <FIG>), and a plurality of vanes <NUM>, <NUM> (see <FIG>). The return segment <NUM> includes seats <NUM>, <NUM>. The return segment <NUM> includes seats <NUM>, <NUM>. The return segment <NUM> includes seats <NUM>. The seats <NUM>-<NUM> mate with each other and other components (e.g., the sidewall of elongated tube <NUM> and the reservoir chamber <NUM>, etc.).

The inner reservoir <NUM> is defined between the inner surface <NUM> of the elongated tube <NUM> and an interior cylinder <NUM> that defines an outlet from the elongated tube <NUM> into the outlet structure <NUM>. Water collected within the elongated tube <NUM> gathers in the inner reservoir <NUM> where it is directed through the reservoir outlet segment <NUM> into the reservoir chamber <NUM>. A bottom surface of the inner reservoir <NUM> is defined by a connecting helix <NUM> that extends from the inner surface <NUM> of the elongated tube <NUM> to an outer surface of the interior cylinder <NUM>. The reservoir outlet segment <NUM> opens directly into the inner reservoir <NUM> through an opening defined in the wall of the elongated tube <NUM>. The helix structure <NUM> may extend continuously from internal the elongated tube <NUM>, into the inner reservoir <NUM>, through the reservoir outlet segment <NUM>, and into the reservoir chamber <NUM> (see <FIG> and <FIG>).

A plurality of additional vanes <NUM>, <NUM> may also be positioned within the reservoir chamber <NUM> as shown in <FIG>. The position, size, and angle between vanes <NUM>, <NUM> may be designed to stabilize the water based on Weber number, as described above related to separator <NUM>, <NUM>. Furthermore, the angle β between the vanes (~<NUM> degrees, shown in <FIG>) helps to promote passive bubble separation, in the event that bubbles appear, as a result of a disturbance. The position, size and angle of the vanes <NUM>, <NUM> can also be used to remove bubbles form liquid output system <NUM> (i.e., if bubbles are present, liquid can be pumped back into the reservoir, and the capillary forces with these vane angles will cause the bubbles to leave the liquid). The bubbleless liquid can then be recovered from the reservoir back to the liquid output system <NUM> shown in <FIG>. These features and functionality may be applicable for all the reservoir designs disclosed herein.

Vias <NUM> may be formed in the vanes <NUM>, <NUM> and the portion of the helix structure <NUM> positioned within the reservoir chamber <NUM> as shown in <FIG>. The vias <NUM> may be offset relative to each other along the length of the vanes <NUM>, <NUM> and helix structure <NUM>. The offset vias may also be spaced apart from the water outlet <NUM>. This arrangement for the vias may improve stability of the water through the water outlet <NUM> and between the vanes <NUM>, <NUM> and helix structure <NUM> within the reservoir chamber <NUM> along the chamber bottom <NUM> by preventing water from pulling away from the via due to the larger vertex angle if the via were to overlap or coincide on adjacent vanes.

<FIG> shows the edges of the vias <NUM> being radiused or contoured. The radii R<NUM>, R<NUM> of the vias <NUM> may help eliminate pinning edges, which could prevent liquid (e.g., water) from entering the vias <NUM>. The radii R<NUM>, R<NUM> may provide a smoother and/or open path through the respective vane <NUM>, <NUM> and helix structure <NUM> through in which the vias <NUM> are formed. Further, an angle θ from a center of each via <NUM> may be provided to assist with directing air bubbles from the vias <NUM> into spaces between the vanes <NUM>, <NUM>, helix structure <NUM>, and internal walls of the reservoir chamber <NUM>.

<FIG> shows a side view of one of the vias <NUM>. The vias <NUM> may have a length L<NUM> and a height H<NUM>, and have an acute angle α. The length L<NUM> may, in some embodiments, be in the range of about <NUM> in. to about <NUM> in. , and more particularly about <NUM> in. The height H<NUM> may, in some embodiments, be in the range of about <NUM> in. to about <NUM> in. , and more particularly about <NUM> in. The angle α may, in some embodiments, be in the range of about <NUM> degrees to about <NUM> degrees, and more particularly about <NUM> degrees.

The connecting helix <NUM> may have a helical shape as shown in <FIG>. This helical shape may assist with capturing and directing wall-bound water droplets that are not captured by the main helix structure <NUM> toward the reservoir outlet segment <NUM>. Like the main helix structure <NUM>, the connecting helix <NUM> may form an acute angle between the inner surface <NUM> of the elongated tube <NUM>. The size of the acute angle may change as the connecting helix <NUM> approaches the reservoir outlet segment <NUM>.

The reservoir return segments <NUM>, <NUM>, <NUM> provide an air flow path from the reservoir chamber <NUM> back into the main body of the low-gravity water separator <NUM> in the outlet structure <NUM>. The seats <NUM>-<NUM> of the return segments <NUM>, <NUM>, <NUM> may provide a slip joint or other connection that provides some translational flexibility required in the reservoir return tube between the slip joint and the spherical cut ends defined by the seats <NUM>-<NUM> to help maintain an improved alignment between the helix structure <NUM> that passes from the inner reservoir <NUM>, through the reservoir outlet segment <NUM>, and into the reservoir chamber <NUM>. The size and shape of the seats <NUM>-<NUM> may be designed specifically to allow adjustability in both axial and radial placement of the reservoir assembly <NUM> relative to the elongated tube <NUM> and helix structure <NUM>, as well as the outlet structure <NUM> relative to the elongated tube <NUM> and the reservoir assembly <NUM>. The construction of the seats <NUM>-<NUM> may help preserve the ability to more ideally align the helix structure while still securing the components of the reservoir assembly <NUM>. <FIG> illustrate assembly of reservoir return segments <NUM>, <NUM> with a slip joint. Other types of joints and connection features are possible to provide the desired adjustability for the assembly of various components of low-gravity water separator <NUM>.

The reservoir chamber <NUM> may include an enlarged portion along the bottom end thereof that provides for re-circulated flow <NUM>. The re-circulated flow <NUM> is outside of a first flow path <NUM> for air flow passing from the reservoir outlet segment <NUM> to the reservoir return segments <NUM>, <NUM>, <NUM>. The re-circulated flow <NUM> may involve a sudden drop off area that causes an air velocity profile to separate from the vertex, thereby leaving a calm zone immediately above the water outlet <NUM>. The recirculation flow pattern may be set up by drop off and air exit placement. The recirculation sweeps downstream water back towards the water outlet <NUM> to a stagnation zone formed by the opposing stream lines1500, <NUM>. Generally, the dramatic change in depth of the reservoir chamber <NUM> may be referred to as a reservoir boundary layer separator and may cause an air boundary layer in the vertex to largely separate from the vertex as the air passes over the sudden drop off area. This causes a low velocity zone immediately downstream of the drop off where the liquid is especially stable. Additionally, the boundary layer separation promotes a re-circulated flow <NUM> that causes air flow streamlines to collide from opposite directions, which forms a stagnation zone. This creates an air flow pattern that sweeps water into this dead zone from upstream and downstream, which makes it a more ideal location for the water outlet <NUM>.

The reservoir assembly <NUM> may include features that assist in controlling air flow through the air reservoir assembly <NUM>. For example, an orifice plate <NUM> may be positioned in one or more of the reservoir return segments <NUM>, <NUM>, <NUM>. The orifice plate <NUM> may be used to control proper reservoir air flow for a given overall design flow rate. For example, the orifice may be sized such that the air flow velocity in the reservoir is slow enough to maintain a stable reservoir (i.e., the water collected in the reservoir remains stable), even when the overall device volumetric flow is at its design point. The orifice plate <NUM> may be replaceable with orifice plates having different sized orifices to provide the size adjustability. In other embodiments, a single orifice plate may have an adjustable sized opening that is adjustable from exterior of the reservoir assembly <NUM>. Some of the reservoir assembly <NUM> may include multiple orifice plates <NUM> at locations before or after the reservoir chamber <NUM>, or multiple orifice plates within the return channel defined by the reservoir return segments <NUM>, <NUM>, <NUM>.

Water collected in the inner reservoir <NUM> may be inhibited from moving out through the interior cylinder <NUM> and out through the outlet structure <NUM> by features provided on the interior cylinder <NUM>. Any water that ends up inside the interior cylinder <NUM> is lost and represents failure of primary function for the low-gravity water separator <NUM>. Water droplets positioned on the outer wall of the interior cylinder <NUM> may be prevented from traveling up the wall and over the top edge at the proximal end of the interior cylinder <NUM> by a lip <NUM>, as shown in <FIG>. The lip <NUM> may protrude radially outward from the exterior surface of the interior cylinder <NUM>. The lip <NUM> may include an interior angle on the outside of the interior cylinder <NUM> near the top proximal edge. Alternatively, the lip <NUM> may be positioned further along the length of the interior cylinder <NUM> in a distal direction spaced away from the proximal edge and inlet opening <NUM>. Water being driven up the outside surface of the interior cylinder <NUM> will encounter this lip <NUM> to be prevented from migrating over the top edge and through the opening <NUM> where it can escape through the outlet opening <NUM>.

The helix structure <NUM> may include an upper surface <NUM>, a lower surface <NUM>, and an outer edge <NUM>, as shown in <FIG>. An inlet cap <NUM> may be positioned at the upper end of helix structure <NUM> near the inlet opening <NUM> (see <FIG>). The helix structure <NUM> may have a variable pitch along its length as described above with reference to low-gravity water separators <NUM>, <NUM>, <NUM>. Generally, the helix structure <NUM> may have many of the same or similar features and functionality of the other helix structures described with reference to <FIG>.

The helix structure <NUM> may extend continuously through the inner reservoir <NUM>, through the reservoir outlet segment <NUM>, and into the reservoir chamber <NUM>, as shown in <FIG>. The helix structure <NUM> may define a reservoir vane and provide a single connective capillary path between the inlet of the helical channel open to the inlet opening <NUM> where the swirl and separation of water droplets happens, and the bottom of the reservoir chamber <NUM>. Additionally, the helix surface and surface of the reservoir vane may be completely enveloped into the secondary annular water pick-up area between the interior cylinder <NUM> and the interior wall or inner surface <NUM> of the elongated tube <NUM> at an entrance to the reservoir component positioned external to the elongated tube <NUM>.

The helix structure <NUM> may be divided into different segments along its length. For example, the low-gravity water separator <NUM> may be divided into different components (e.g., components <NUM>, <NUM>, <NUM>, <NUM>), and the helix structure <NUM> may be divided into segments 1410A, 1410B at the interface between the elongated tube <NUM> and the reservoir assembly <NUM>, as shown in <FIG>. This interface may be an angled interface <NUM>. The angled surface joint at interface <NUM> may provide a pinning edge that stray droplets on the surface of the helix structure <NUM> will encounter. The stray water droplets on the helix surface will typically migrate along the helix surface without moving towards the vertex. The interface <NUM> (also referred to as a joint) in the helix surface may be angled such that when droplets encounter the interface <NUM> and pin to its edge, the air flow will drive the droplets along the pinning edge toward the vertex where it will be carried into the main rivulet in the chamber bottom <NUM>. Thus, the interface <NUM> may provide both an interface or connection point between segments 1410A, 1410B of the helix structure, as well as provide a feature to help direct the water droplets to the primary rivulet for collection within the reservoir chamber <NUM>.

In other embodiments, the helix structure <NUM> may be formed as a single unitary piece along its entire length, such as when the entire low-gravity water separator <NUM> is formed from an additive manufacturing method, or at least the elongated tube <NUM>, reservoir assembly <NUM> and helix structure <NUM> are formed integrally as a single piece. A pinning feature, groove, vane or similar feature may be formed in the helix structure <NUM> to mimic the interface <NUM>. Other types of joints may be used in other embodiments for connecting various segments of the helix structure <NUM> to each other. In one example, UV curable material may be used to provide a positive connection between the helix segments 1410A, 1410B, or other segments or portion of the helix structure.

The water outlet <NUM> may join the spaces between the vanes <NUM>, <NUM> together to draw water evenly from each channel within the reservoir chamber <NUM>, as shown in the cross-sectional view of <FIG>. The channels within reservoir chamber <NUM> (e.g., those channels defined between the vanes <NUM>, <NUM>, the helix structure <NUM>, and walls of the reservoir chamber <NUM>) are joined together in a manner such that only two flow paths are joined together at a time. Flow path bifurcation promotes even distribution of flow, whereas joining three or more paths together simultaneously can cause uneven flow distribution. <FIG> shows flow paths C<NUM>, C<NUM> joining to form flow path B<NUM>, flow paths C<NUM>, C<NUM> joining to form flow path B<NUM>, and flow paths B<NUM>, B<NUM> joining to form flow path A, which then exits out of the water outlet <NUM>.

The water outlet <NUM> may have different shapes, sizes and connecting features based on a number of criteria, such as the device to which the water outlet <NUM> is to be connected. While any number of fitting choices were available to connect to the water outlet <NUM>, such as numerous standard tapped thread styles or an integrally printed barb fitting, a fitting geometry for water outlet <NUM> consisting of a flanged double o-ring face seal may be selected that is compatible with a commercial KF style vacuum fitting clamp. A KF style vacuum clamp may help eliminate the need to do any post machining of threads required for other types of connection. The KF style clamp may also provide a quick and secure connection that does not involve transfer of any appreciable torque or force to the rest of the low-gravity water separator <NUM>, for example, during installation or removal of a liquid drain line from the water outlet <NUM>. This means there is a reduced risk of damaging the hardware by, for example, over tightening a threaded connection, or snapping off a barb fitting while trying to install or remove tubing. Additionally, use of a KF style clamp may have advantages over embodiments that include machined threads in an additive manufacturing application (e.g., the 3D printed material of the remaining portions of the low-gravity water separator <NUM>), in which threads could create micro cracks that may propagate to complete failure under the vibrations present in some types of environments (e.g., launch of a spacecraft).

Referring to <FIG>, air flowing into the low-gravity water separator <NUM> through the inlet opening <NUM> may pass into the helical channel between surfaces <NUM>, <NUM> of the helix structure <NUM> and the inner surface <NUM> of the elongated tube <NUM> along the length of the elongated tube <NUM>. At the bottom or distal end of the helix structure <NUM>, the air flow in the helical channel is divided into first and second air flows that are directed along first and second flow paths <NUM>, <NUM>. The first flow path <NUM> passes from the helical channel into the inlet opening <NUM> of the interior cylinder <NUM>. A significant portion of the air flow that enters into the inlet opening <NUM> is typically directed into the first flow path <NUM> due to the size, shape and orientation of the inlet opening <NUM> provided by the interior cylinder <NUM>. The remainder of the air flow passes into the second flow path <NUM>: first into the inner reservoir <NUM> and then through the reservoir outlet segment <NUM> into the reservoir chamber <NUM> and through the reservoir return segments <NUM>, <NUM>, <NUM> back into the outlet structure <NUM> downstream of the interior cylinder <NUM>. The air flows through first and second flow paths <NUM>, <NUM> recombine at the outlet opening <NUM> provided by the outlet structure <NUM>.

The splitting of the air flow passing through the helical channel into the first and second flow paths <NUM>, <NUM> may be referred to as a split air flow path or the creation of parallel air flow paths. The splitting or providing of parallel air flow paths may allow air velocity over the collected water within the reservoir chamber <NUM> to be locally reduced without the need to expand the flow area of the entire low-gravity water separator <NUM>. Expanding the flow area of the entire device may not be feasible in some scenarios due to volume constraints for the size of the entire low-gravity water separator <NUM>.

<FIG> illustrate a low-gravity water separator <NUM> in accordance with a second embodiment of the claimed invention. The low-gravity water separator <NUM> may incorporate similar features as the low-gravity water separators <NUM>, <NUM>, <NUM>, <NUM> discussed above with reference to <FIG>. The low-gravity water separator <NUM> may include various features to help stabilize the collected water within a reservoir portion of the device so that the amount of water that is drawn out of the device with the exiting air flow is minimized. For example, the low-gravity water separator <NUM> may include unique water reservoir features (e.g., shape, size, and location), a helix structure shape and orientation, and air flow paths that provide stabilizing forces for the collected water. Other unique aspects of the low-gravity water separator <NUM> relate to, for example, how various components of the device are assembled together during manufacturing, how airflow is controlled internal the device, and how collected water is directed into and stabilized within the water reservoir.

A plurality of additional vanes <NUM>, <NUM> may be positioned within the reservoir chamber <NUM> as shown in <FIG> and <FIG>. Vias may be formed in the vanes <NUM>, <NUM> and the portion of the helix structure <NUM> positioned within the reservoir chamber <NUM> (e.g., the vias <NUM> shown in <FIG>). The offset vias may be spaced apart from a water outlet <NUM>. The water outlet <NUM> may be positioned at an opposite end of the reservoir chamber <NUM> as compared to the location of the water outlet <NUM> of the separator <NUM> shown in <FIG>. The size, shape and orientation of the vanes <NUM>, <NUM> and helix structure <NUM> within the reservoir assembly <NUM> are comparable to the vanes <NUM>, <NUM> and helix structure <NUM> shown in, for example, <FIG> and <FIG>.

The low-gravity water separator <NUM> may have only two revolutions of helix surface for the helix structure <NUM>. The two revolutions may be distinct from other designs such as the low-gravity water separators <NUM>, <NUM>, <NUM>, <NUM> discussed above with reference to <FIG> for at least the reason that they have three full revolutions of helix surface for their respective helix structures.

The low-gravity water separator <NUM> may also have a configuration for the reservoir chamber <NUM> that is different from reservoir <NUM> described above, specifically related to the size, shape and orientation of vanes <NUM>, <NUM>. Low-gravity water separator <NUM> may have a single vane that provides a continuation of the helix structure <NUM> with a pair of vanes <NUM>, <NUM> positioned to a side of the continuous helix structure <NUM>. With the design of low-gravity water separator <NUM>, the only way for water to access the areas between the two side vanes <NUM>, <NUM> is through the vias <NUM>. In the low-gravity water separator <NUM>, a vane in the reservoir <NUM> is also a continuation of the helix structure <NUM>, but the other two vanes <NUM>, <NUM> extend upward from a vertex formed on either side of the continuous helix structure <NUM> within the reservoir chamber <NUM>.

The vanes <NUM>, <NUM> may grow from the vertex formed on either side of the helix <NUM>, thereby bifurcating the rivulet in each vertex to evenly divide the flow across the separate channels between the vanes <NUM>, <NUM> and helix structure <NUM>. Furthermore, the vanes extending out from the vertex provides a sudden decrease in the interior angle of the capillary corner. This design helps pin water within the reservoir where the angle is smallest, and prevent water from wicking from the reservoir back up toward the elongated tube <NUM>, particularly in the event that airflow is interrupted.

Additionally, the reservoir chamber <NUM> does not employ a significant depth change that creates boundary layer separation as in the reservoir chamber <NUM> described above, and thus the water outlet <NUM> is positioned as far downstream as practical.

Referring to <FIG>, an example method <NUM> related to assembly or manufacture of a low-gravity water separator is shown and described. The method <NUM> may include, at block <NUM>, the step of providing a water capture device having an elongated tube, an inlet structure position of the first end of the elongated tube and defining an inlet opening configured to receive a stream of water-laden air into the water capture device, an outlet structure positioned at the second end of the elongated tube and defining an outlet opening, a helical structure positioned internal the elongated tube, and a reservoir configured to collect water that has been separated from the stream of water-laden air within the elongated tube.

At block <NUM>, the method <NUM> may include securing the inlet structure to the elongated tube at a first joint, and securing the outlet structure to the elongated tube at a second joint, wherein in the first and second joints each have at least one contoured surface. The contoured surface may include a spherical portion, a hemispherical portion or an arc portion. The method may include forming the elongated tube, inlet structure and/or the outlet structure using 3D printing or other additive manufacturing process. The water capture device may further include first and second air flow paths coupled inflow communication with the outlet opening, the second air flow path being defined at least in part by the first and second tube segments, the method including securing the first and second tube segments together with a slip joint. The water-capture device may further include at least one vane positioned in the reservoir, and the first and second tube segments may be adjustable relative to each other and relative to the elongated tube to align at least one vane with the helical structure. The water-capture device may further include first and second air flow paths coupled in flow communication with the outlet opening, the second air flow path including an orifice, the method including adjusting the size of the orifice to control a rate of air flow through the second air flow path. The first and second joints may be formed in part by applying uncured base material resin to the contoured surfaces, and then curing the resin, such as by using ultraviolet (UV) light.

<FIG> illustrates an example method <NUM> of separating water from a stream of water-laden air. The method <NUM> may include, at block <NUM>, a step of delivering the stream of water-laden air into a helical-shaped channel of a water capture device, the helical-shaped channel having a variable pitch along its length. Block <NUM> may include separating water from the air flow within the helical-shape channel. Block <NUM> may include collecting the water into a reservoir, the reservoir including a plurality of vanes. Block <NUM> includes dividing the air flow into a first air stream and a second air stream, the second air stream passing through the reservoir. Block <NUM> includes combing the first and second air streams after the second air stream has passed through the reservoir. The method <NUM> includes, at block <NUM>, passing the combined air streams out of the water-capture device. Block <NUM> includes removing the water from the reservoir.

The method <NUM> may also include separating water droplets from the air flow by contacting the air flow against one or more surfaces of the helical-shaped channel, and collecting the separated water droplets from the one or more surfaces of the helical-shaped channel in the reservoir. The method may include stabilizing the water within the reservoir using the second air stream. The water capture device may include a helical structure that defines in part the helical-shaped channel, the helical structure extending continuously into the reservoir. The water capture device may include an elongated tube housing the helical-shaped channel, and a portion of the reservoir extends outside of the elongated tube, the portion of the reservoir defining an air channel through which the second air stream passes out of the elongated tube at a tangential angle. Delivering the stream of water laden air into the helical-shaped channel may include delivering the stream of water laden air at a tangential angle relative to a longitudinal axis of the water capture device.

Claim 1:
An apparatus (<NUM>)(<NUM>) to separate water droplets from an air stream, the apparatus (<NUM>)(<NUM>) comprising:
an elongated housing (<NUM>)(<NUM>) defining a longitudinal axis and having a first end, a second end and an inner surface;
an inlet structure (<NUM>)(<NUM>) positioned at the first end and defining an inlet opening (<NUM>) configured to accept the air stream;
an outlet structure (<NUM>)(<NUM>) positioned at the second end and defining an outlet opening (<NUM>);
a reservoir assembly (<NUM>)(<NUM>) positioned at the second end of the elongated housing (<NUM>)(<NUM>), the reservoir assembly (<NUM>)(<NUM>) configured to collect water;
a helix structure (<NUM>)(<NUM>) positioned within the elongated housing (<NUM>)(<NUM>);
a first air flow path (<NUM>) coupled in flow communication with the outlet opening (<NUM>);
a second air flow path (<NUM>) separate from the first air flow path (<NUM>) and coupled in flow communication with the outlet opening (<NUM>), the second air flow path (<NUM>) defined in part by the reservoir assembly (<NUM>)(<NUM>);
characterised in that:
the inlet structure (<NUM>)(<NUM>) is mounted to the first end of the elongated housing (<NUM>)(<NUM>); and
the inlet opening (<NUM>) is arranged along a side surface and at a radially inward directed orientation relative to the longitudinal axis; and
in that the reservoir assembly (<NUM>)(<NUM>) comprises:
a reservoir outlet segment (<NUM>) extending outwardly from a sidewall of the elongated housing (<NUM>)(<NUM>);
a reservoir chamber (<NUM>)(<NUM>) positioned outside of the elongated housing (<NUM>)(<NUM>) and in flow communication with the reservoir outlet segment (<NUM>); and
a reservoir return tube positioned external of the elongated housing (<NUM>)(<NUM>) and in flow communication with the reservoir chamber (<NUM>)(<NUM>), the reservoir outlet segment (<NUM>), reservoir chamber (<NUM>)(<NUM>) and reservoir return tube each defining a portion of the second air flow path (<NUM>).