Concentric split flow filter

A concentric split flow filter may be configured to remove odor and/or bacteria from pumped air used to collect urine and fecal waste products. For instance, filter may be designed to effectively fill the volume that was previously considered wasted surrounding the transport tube of a waste management system. The concentric split flow filter may be configured to split the air flow, with substantially half of the air flow to be treated traveling through a first bed of filter media and substantially the other half of the air flow to be treated traveling through the second bed of filter media. This split flow design reduces the air velocity by 50%. In this way, the pressure drop of filter may be reduced by as much as a factor of 4 as compare to the conventional design.

FIELD

The present disclosure relates to a filter and, more specifically, an axial flow filter.

BACKGROUND

Conventionally, in the Space Shuttle and International Space Station (ISS), the Waste Collector System (WCS) has used air flow to entrain waste. Urine is collected in a funnel held in close proximity to the urethra. Fecal material is collected separately by air flow entrainment. For instance, air may enter in a fairly uniform radial direction under a seat of the WCS. Air drag then helps separate the fecal bolus and draw it into a tank or fecal collection bag. Air is separated from the urine and fecal material, treated for odors, and returned to the spacecraft cabin.

Successful capture and ease of use for simultaneous urination and defecation for mixed gender crews have been consistent limitations of the Space Shuttle and ISS WCS. Additionally, these systems are sensitive to crew alignment on the seat and can result in inadvertent fouling of the collection hardware with fecal material.

The ISS WCS shared many features of the Space Shuttle WCS, but modified the fecal collection from a large storage tank to a removable fecal canister. Using plastic lids, a compactor compressed each individual fecal bag to reduce storage volume. After about 21 uses, the canisters are removed, and stored. To improve air flow predictability, a fan was included for the urine separator, and a separate fan was provided for fecal collection. The toilet on the Russian Soyuz vehicle (Soyuz ACY) is smaller than the Space Shuttle WCS and the ISS WCS. It pulls cabin air through the urine funnel and fecal collector before passing through a static separator, where the urine is stored. The saturated air travels through an odor filtration device before the urine and cabin air are separated by a centrifugal unit. The fecal collection bag is designed for a single use, and the urine tank is limited to 10.2 liters. Urine collection is considered acceptable, whereas fecal collection did not receive favorable review.

The Russian Module toilet (SM ACY) for the ISS has provided long-term WCS use since the ISS was first inhabited. It uses air to assist fecal and urine collection. A centrifugal urine separator removes air from the urine stream. The air flows to a charcoal filter prior to reentry back into the cabin. This unit has an air ring under the seat, similar to the two American designs discussed, to control odor and assist in fecal capture. The fecal canister holds one bag that is pushed into a collection tank after each use. This tank can hold about 21 defecations before removing and replacing the canister. From a crew-satisfaction perspective, the WCS is one of the most personal and intimate systems on the spacecraft. Crew consensus is paramount regarding which elements are needed and which would benefit from improvement.

SUMMARY

According to various embodiments, a filter unit is described herein. The filter unit may comprise a housing having a first outlet, a second outlet and an inlet plenum there-between. The housing may be generally hollow cylinder shaped. The filter unit may comprise a first filter media positioned within the housing between the inlet plenum and the first outlet. The filter unit may comprise a second filter media positioned within the housing between the inlet plenum and the second outlet. The first filter media and the second filter media may be disposed axially on opposite sides of the inlet plenum.

According to various embodiments, a method of treating air through a waste collector system comprises receiving via an air flow inlet air flow to be treated by a filter system. The method may include passing the air flow to be treated from the air flow inlet to an inlet air flow plenum of the filter system. The method may include reducing air flow velocity of the air flow to be treated through the inlet air flow plenum by about 50% by passing a first portion flow of air to be treated from the inlet air flow plenum to a first bed of filter media and passing a second portion flow of air to be treated from the inlet air flow plenum to a second bed of filter media of the filter system. The method may include delivering the passed first portion flow of air to be treated to a delivery location via a first outlet. The method may include delivering the passed second portion flow of air to be treated to the delivery location via a second outlet.

DETAILED DESCRIPTION

The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration and their best mode. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it should be understood that other embodiments may be realized and that logical changes may be made without departing from the spirit and scope of the disclosure. Thus, the detailed description herein is presented for purposes of illustration only and not of limitation. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step.

According to various embodiments and with reference toFIGS. 1 and 2, a diagram of a concentric split flow filter100(e.g., filter unit) is presented. Concentric split flow filter100may be designed for use with a universal waste management system (UWMS). Air is pulled from a commode and delivered to an odor/bacteria filter to capture odor-causing molecules and bacteria. The filter media of concentric split flow filter100comprises activated charcoal, for example, activated charcoal developed for use on the ISS WCS. To reduce system volume, the UWMS concentric split flow filter100surrounds a commode transfer tube which is the conduit between a seat and a fecal collection canister (not shown). The transfer tube is concentric to the split flow filter100and may be located closely adjacent to an interior surface5of concentric split flow filter100. Concentric split flow filter100may be utilized as an orbital replacement unit, for example, to support longer-duration missions

In a traditional configuration of a WCS, air to be filtered enters through a central plenum and traverses radially through the filter media. Prior art odor/bacteria filters were cylindrical in form and were housed separately. However, present and future space vehicles designs demand a significantly reduced overall WCS volume, such as a reduction of about 80% from conventional systems. The conventional cylindrical filter did not support this volume challenge. The conventional WMS had a central cylinder, commonly referred to as the transport tube, acting as a conduit to translate fecal matter to a fecal can. The conventional design left an empty volume around transport tube and as such, occupied excessive volume.

According to various embodiments, the concentric split flow filter100may be designed to effectively fill the volume that was previously considered to be underutilized space surrounding the transport tube. The concentric split flow filter100is configured to remove odor and/or bacteria from pumped air used to collect urine and fecal waste products. Further, the design of concentric split flow filter100splits the flow, with substantially half of the air flow to be treated traveling through a first bed of filter media25(FIG. 2), and substantially the other half of the air flow to be treated traveling through the second bed of filter media50. This split flow design reduces the air velocity by 50%. Since the pressure drop can be as much as a squared function of air velocity, the pressure drop of concentric split flow filter100may be reduced by as much as a factor of 4 as compared to the pressure drop in conventional filter designs since the air velocity is substantially split in half.

According to various embodiments, concentric split flow filter100is designed to utilize an axial flow pattern. As used herein, an axial flow pattern refers to an air flow that flows generally parallel to the axis of the cylinder, such as axis A-A′. As used herein, a radial flow refers to an air flow which is substantially perpendicular to the axis of the cylinder, such as perpendicular to axis A-A′. As used herein, air flow may be measured by the volume of air per unit of time that flows through a particular point.

In space applications such as the ISS, a pressure drop may be a limiting design constraint. Thus, a pressure drop through a filter may be a design defining parameter. Because pressure drop (i.e., head loss) is a function of velocity squared, doubling the flow rate doubles velocity which quadruples pressure drop. For instance, the Darcy-Weisbach equation:

Δ⁢⁢p=fD·LD·ρ⁢⁢V22
where the pressure drop (or loss) due to friction Δp (Pa) is a function of: the ratio of the length to diameter of the pipe, L/D; the density of the fluid, ρ (kg/m3); the mean velocity of the flow, V (m/s); and the Darcy Friction Factor, a (dimensionless) coefficient of laminar, or turbulent flow, fD.

In operation, according to various embodiments, and with continued reference toFIGS. 1 and 2, air to be filtered may be introduced to air flow inlet75via inlet port73. Air to be filtered may pass through air flow inlet75and flow into inlet air flow plenum30. The inlet port73diameter “D” may be substantially equal to the height of inlet air flow plenum30. Inlet air flow plenum30may be hollow cylinder in shape. This air flow to be filtered enters inlet air flow plenum30which is a hollow cylinder. Since fluid flow, such as air, travels the path of least resistance, after filling the cylinder, the air substantially splits equally since each bed of filter media25,50has a very similar flow resistance (i.e., the air splits into air flow portion101and air flow portion102) as it travels through a first perforated plate40and a second perforated plate45to enter the first bed of filter media25or the second bed of filter media50, respectively. The inlet air flow plenum30may be positioned sustainably equidistant between top perforated plate90and bottom perforated plate95. Stated another way, inlet air flow plenum30may be positioned in the mid-point of concentric split flow filter100. First bed of filter media25may be hollow cylinder in shape. First bed of filter media25may be internal to housing1. Thus, substantially half the air flow to be treated travels into the first bed of filter media25and substantially half the air flow to be treated travels into the second bed of filter media50. In this way the velocity of the air flow to be treated is effectively reduced by 50%. Thus, one fourth of the previous pressure drop may be experienced, which as described above is desirable.

According to various embodiments, air may be drawn through the transport tube300(FIG. 1) towards a fecal bag (not shown) to control odor and to assist with the collection of feces. The transport tube300may be a tube concentric to and/or interior to a cylindrical shaped housing1surface, e.g., interior surface5. Though they may be any shape, interior surface5and exterior surface15of housing1may be substantially parallel. Interior surface5and exterior surface15may be made from any desired material. However, interior surface5and exterior surface15may be advantageously made from a material that is able to house corrosive ammonia without decreased product life. Exemplary materials include for example, fiberglass, steel, stainless steel, titanium, and/or a polymeric material. Interior surface5and exterior surface15of housing1may span between a top perforated plate90and a bottom perforated plate95. Interior surface5, exterior surface15, top perforated plate90and bottom perforated plate95may form a torrid, such as a hollow cylinder. Similarly, air may be drawn through a hose to assist with the collection of urine. These air flows, e.g., air flow through the transport tube and air flow through the urine collection hose may be jointly plumbed. This air flow may become the air flow to be treated by the split flow filter100. Air flow to be treated may be introduced, via a fan and/or impeller, to air flow inlet75via a hose73and enter into inlet air flow plenum30. Air flow inlet75may be one or more pass-through voids through exterior surface15. Back pressure and/or the resistance of the charcoal on the top22and the bottom27cause the air flow to be treated to equalize inside inlet air flow plenum30substantially around the diameter of concentric split flow filter100. Thus, a relatively even distribution of air is achieved from inlet air flow plenum30to the first bed of filter media25and the second bed of filter media50(e.g., the air splits into air flow portion101and air flow portion102). Based on this design, treatment surfaces near air flow inlet75tend not become overworked or clogged.

Air flow to be treated within inlet air flow plenum30travels through first perforated plate40and the second perforated plate45to enter the first bed of filter media25or the second bed of filter media50such as via apertures35that pass through first perforated plate40and the second perforated plate45. The first perforated plate40and the second perforated plate45may be hollow cylinder in shape. As previously mentioned the air flow will generally take the path of least resistance.

A layer of a first retaining substance20, such as felt, may be substantially adjacent to and/or between the first bed of filter media25and the first perforated plate40. The layer of the first retaining substance20may span the diameter of concentric split flow filter100and/or a portion thereof, as desired. Stated another way, the layer of the first retaining substance20may be hollow cylinder in shape. The first retaining substance20may be configured to retain the filter media25in position and/or act as a first barrier to filter out any particulates so that they cannot re-enter the cabin. The filter media25may be any desired filer media configured to control odor and assist in waste capture; however as noted above, as the velocity of the air flow traveling through this media is a limiting design constraint, since it is accounts for a considerable impact in determining the fluids pressure drop through the filtering system, care must be taken in in both filter media selection and when determining the needed amount of media. The flow of air to be treated passes through the retaining substance20to the filter media25, such as a charcoal based media. Instead of being a hollow cylinder, as shown, the filter media25may be any desired shape within interior surface5and exterior surface15of housing1. The filter media25may be configured to absorb odor causing constituents in the air flow, such as methane and/or ammonia. A second retaining substance65, which may comprise the same materials as retaining substance20, may be positioned adjacent to and/or between the first bed of filter media25and the top perforated plate90. In response to traveling through filter media25the air to be treated may be transformed into treated air flow. A treated air flow plenum55may be situated between the second retaining substance65and the top perforated plate90. Treated air may return to the cabin by traveling through the treated air flow plenum55and out aperture92.

According to various embodiments, the operation of concentric split flow filter100is generally equivalent on top and bottom; however for completeness, the second bed of filter media50will be briefly described blow. A layer of a first retaining substance10, such as felt, may be substantially adjacent to and/or between the second bed of filter media50and the second perforated plate45. The layer of the first retaining substance10, such as felt, may span the diameter of concentric split flow filter100and/or a portion thereof, as desired. The first retaining substance10may be configured to retain the filter media50in position and/or act as a first barrier to filter out particulates so that they cannot re-enter the cabin. The flow of air to be treated passes through the first retaining substance10to the filter media50, which may be, for example, a charcoal based media. Filter media50may be hollow cylinder in shape. Filter media50may be internal to housing1. The filter media50may be configured to absorb odor causing constituents are in the air flow, such as methane and/or ammonia. A second retaining substance60, which may comprise the same materials as retaining substance10, may be positioned adjacent to and/or between the second bed of filter media50and the bottom perforated plate95. In response to traveling through filter media50the air to be treated may be transformed into treated air flow. A treated air flow plenum70may be situated between the second retaining substance60and the bottom perforated plate95. Treated air may return to the cabin by traveling through the treated air flow plenum70and out aperture92. A retention structure85, such as a bolt, working with a retention mechanism87, such as a threaded chamber, may couple the elements of concentric split flow filter100together, such as top perforated plate90, interior surface5, exterior surface15, bottom perforated plate95and/or the elements within these structures together. A spacer86, such as a washer, may assist with retaining elements of the filter unit in position and maintaining the shape of treated air flow plenums55,70.

The top portion22and bottom portion27of concentric split flow filter100comprising the first bed of filter media25and the second bed of filter media50are configured to act in tandem, such as substantially simultaneously as a single filter structure. The top portion22and bottom portions27of concentric split flow filter100are configured to have similar operational life spans. The volume of filter media25within first bed of filter media25is substantially equivalent to the volume of filter media50within the second bed of filter media50.

According to various embodiments and with reference toFIG. 3a method of using concentric split flow filter100may comprise receiving, via an air flow at inlet75, air flow to be treated by a filter system (step310). Air flow to be treated may be passed from the air flow inlet75to a radial inlet air flow plenum (step320). The volume of the air flow to be treated may be substantially evenly split into a first portion101flow of air to be treated and a second portion102flow of air to be treated. (step330). The first portion101flow of air to be treated may be passed from the radial inlet air flow plenum to a first bed of filter media25(step340). The second portion102flow of air to be treated may be passed from the radial inlet air flow plenum to a second bed of filter media50(step350). The method may include axially filtering the first portion101flow of air to be treated to create first portion101flow of treated air and axially filtering the second portion102flow of air to be treated to create second portion102flow of treated air (step360,370). The first portion101flow of treated air and the second portion102flow of treated air may be transferred to receiving location, such as back to the cabin of an aerospace vehicle (step380).

Concentric split flow filter100may be configured for use within the ISS, low earth orbit (LEO) aircraft, crew exploration vehicle (CEV), and/or a space hotel. Stated another way, concentric split flow filter100may be an element of an aerospace waste collector system. Similarly, as filters may be used throughout most chemical processing plants and a variety of filtration needs, due to the volume savings concentric split flow filter100affords, this solution is applicable on most vehicles and other systems that have “high density” packaging needs.