Abstract:
An air filtration system is described that is suited for CBRN and ColPro applications, and has an integrated inertial particle separator (IPS) and scavenge fan blower as a pre-dust/particle filter, a variable speed fan blower, and a filter housing that mounts two gas-particulate filter sets. The variable speed fan blower, managed by a motor control unit and motor speed algorithm, automatically adjusts its speed to maintain constant air flow regardless of its altitude.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application Ser. No. 62/351,268 filed Jun. 16, 2016 entitled Portable, Low-Power Air Filtration System, which is hereby incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to efficient, low power air filtration for Chemical, Biological, Radiation and Nuclear (CBRN) applications and especially for Collective Protection (ColPro) applications. Filtering for CBRN and/or ColPro applications typically involve the utilization of modular fan blower assemblies that deliver a light-weight, low-power, weather-proof, stackable air filtration system. This system is typically used to pressurize a Toxic Free Area (mobile or permanent shelters) or Chemical Biological liner, which may be placed outside a military shelter to prevent the infiltration of chemical or biological vapors and liquids. 
         [0003]    Existing air filtration systems are typically not capable of meeting the performance requirements for the above application, for example, because they are unable to operate at high air flow and static pressure, (400 cfm/15 iwg), or are unable to maintain the low power draw. Hence, an improved air filtration system is needed to address the shortcomings of present systems. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention is generally directed to an air filtration system that can meet or exceed the above noted limitations, and therefore is better suited for CBRN and ColPro applications. In one embodiment, the air filtration system consists of an integrated inertial particle separator (IPS) and scavenge fan blower as a pre-dust/particle filter, a variable speed fan blower, and a filter housing that mounts two gas-particulate filter sets. The variable speed fan blower, managed by a motor control unit and motor speed algorithm, automatically adjusts its speed to maintain constant air flow regardless of its altitude. When dust accumulates on particulate filters during extended use, a pressure transducer detects increased filter pressure drop, and motor rotational speed automatically increases to maintain the required air flow. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    These and other aspects, features and advantages of which embodiments of the invention are capable of will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which: 
           [0006]      FIG. 1  is an airflow diagram of a fan blower according to the present invention. 
           [0007]      FIG. 2  is a functional diagram of a fan blower assembly control according to the present invention. 
           [0008]      FIG. 3  is a perspective view of a fan blower assembly according to the present invention. 
           [0009]      FIG. 4  is a perspective view of a fan blower assembly according to the present invention. 
           [0010]      FIG. 5  is a bottom view of a fan blower assembly according to the present invention. 
           [0011]      FIG. 6  is a perspective view of a fan blower assembly according to the present invention. 
           [0012]      FIG. 7  is a perspective view of a fan blower assembly according to the present invention. 
           [0013]      FIG. 8  is a cross sectional view of a fan blower assembly according to the present invention. 
           [0014]      FIG. 9  illustrates a view of a fan assembly according to the present invention. 
           [0015]      FIG. 10  illustrates a view of a fan assembly according to the present invention. 
           [0016]      FIG. 11  illustrates a view of a fan assembly according to the present invention. 
           [0017]      FIG. 12  illustrates a view of a fan assembly according to the present invention. 
           [0018]      FIG. 13  illustrates an inertial particle separator according to the present invention. 
           [0019]      FIG. 14  illustrates a view of a scavenger fan according to the present invention. 
           [0020]      FIG. 15  illustrates a view of a scavenger fan according to the present invention. 
           [0021]      FIG. 16  illustrates a cross sectional end view of a fan blower according to the present invention. 
           [0022]      FIG. 17  illustrates a cross sectional end view of a fan blower according to the present invention. 
           [0023]      FIG. 18  illustrates a cross sectional end view of a fan blower according to the present invention. 
           [0024]      FIG. 19  illustrates a fan blower control system according to the present invention. 
           [0025]      FIG. 20  illustrates a view of a portion of the inertial particle separator according to the present invention. 
           [0026]      FIG. 21  illustrates a view of a remote control for a fan blower according to the present invention. 
           [0027]      FIG. 22  illustrates a graph representing a relationship between atmospheric pressure and elevation. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0028]    Specific embodiments of the invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements. 
         [0029]    In one embodiment, the present invention is directed to an air filtration system comprising a fan blower  100  that, among other uses, is especially capable of CBRN and/or ColPro applications. As seen in  FIG. 1 , outside air enters the fan blower  100  around the air inlet shroud  102 . Next, it enters the inertial particle separator  104  to remove relatively large particle from the outside air. Next, the air passes through the fan blower  106 , which is responsible for pulling in the outside air and pushing it through the blower  100 . The air then moves through one or more replaceable air filters  108 , and finally out through output ports  110 . 
         [0030]    The fan blower  100  is controlled by the fan blower control system  111 , which is depicted in the functional diagram of  FIG. 2 . Power is supplied to the control system  111  via an AC power supply  114  (e.g., 208 VAC, 3 Phase, 60 Hz) and power cable  116 , which passes through an EMI filter  118  and circuit breaker  120  to the microcontroller  112  (powered by a DC power supply  122 ). The microcontroller  112  includes software/firmware logic/algorithms that monitor sensor readings, such as those from the pressure transducer  124  (that measures static pressure within the fan blower  100 ) and from the altitude sensor  126  (that measures the altitude of the fan blower, or alternately may be measured indirectly using an atmospheric pressure sensor), and then controls the main fan blower assembly  128  and scavenge fan blower assembly  130 , accordingly. Additionally, the microcontroller  112  accepts local input to control the operation of the fan blower  100  via the local motor control  132  or the remote control  134 . 
         [0031]      FIGS. 3-5  illustrate various external views of one embodiment of the fan blower  100 . The fan blower  100  generally includes a tubular or cylindrical body  140  with two air output ports  110  along its side ( FIG. 3 ). As seen best in  FIGS. 3 and 5 , an air inlet shroud  102  is positioned on a first end of the tubular body  140 , leaving a gap  103  that the air can enter or be sucked into the fan blower  100 . A second end of the tubular body  140  includes an air filter access door  148  (selectively attached via a hinge and wingnuts  150 , and a fan blower control system housing  146 , in which the fan blower control system  111  is located (se also  FIG. 19 ). Attached to the fan blower control system housing  146  is wire conduit  152 , which includes power and sensor wires connected at other locations on the fan blower  100 . 
         [0032]    The tubular body  140  is preferably fixed or supported by a framework comprising two generally square or rectangular support members  142  located along each side of the tubular body  140 , and a plurality of perpendicular cross beams  144  (e.g., two top and two bottom) that connect to the support members  142  at both of their ends. Preferably, each of the cross beams  144  have a curved portion with a curvature matching the sides of the tubular body  140 , thereby mating with and engaging the tubular body  140 . 
         [0033]    The top cross beams  144  may include horizontal apertures  144 A aligned on their left and right sides, sized to allow the prongs of a forklift to pass through and thereby easily lift the fan blower  100  as necessary. The support members  142  may also include pivotally mounted handles  142 A (e.g., two on each corner) that can allow several people to carry the fan blower  100 . 
         [0034]    The fan blower  100  is also preferably configured so that multiple fan blowers  100  can be stacked on to each other. As seen in  FIG. 5 , the top and bottom cross beams  144  can include vertical apertures  144 B (e.g., one on the left and right). When stacked, the vertical apertures  144 B of the bottom cross beams can be aligned with the vertical apertures  144 B of the top cross beams of the lower fan blower  100 . The attached stacking pins  142 B can be placed through the aligned vertical apertures  144 B, locking the two fan blowers  100  together. 
         [0035]    As seen in  FIGS. 6 and 7 , the air filter access door  148  can be opened to expose an interior of the fan blower  100 , thereby allowing the user to install desired air filters  108 . For example, and outer gas filter  108 A and inner particulate filter  108 B can be used. When the air filter access door  148  is closed, an air filter support structure  148 A engages an end of the filters  108  to help maintain their positions within the fan blower  100 . 
         [0036]    As previously described, air is sucked into the fan blower  100  through the circular gap  103  formed between the air inlet shroud  102  and the first end of the tubular body  140 , as seen in  FIGS. 8, 16, and 17 . From there, air enters the inertial particle separator  104 , which is also seen in  FIG. 13 . The inertial particle separator  104  includes a circular or tubular shape and a plurality of passages  104 A along its forward face. As seen in  FIG. 20 , the passages  104 A include helical fins  104 C, which cause the air to spiral. This rotational motion causes the relatively larger particles in the air to move to the outer diameter of the passage  104 A. A nozzle  104 D is positioned at the end of the passage  104 A, and includes an outer ramped surface that ejects the particles in a relatively tangential trajectory, while a central passage of the nozzle  104 D allows the relatively particle free air to pass along a straight trajectory. 
         [0037]    The reduced-particle air continues relatively straight through the inertial particle separator  104  and the tangentially ejected particle-containing air is moved towards the circular walls of the inertial particle separator  104 . As best seen in  FIGS. 13, 14, and 17 , the inertial particle separator  104  includes a lower exhaust port  104 B that is connected to an inlet  130 D of a scavenge fan blower assembly  130 . The scavenge fan blower assembly  130  includes a motor  130 A that drives rotation of a fan  130 C, thereby sucking out the particle-containing air from the inertial particle separator  104  and ejecting it through the particle exhaust tube  130 B to an exterior of the fan blower  100 . 
         [0038]    As seen in  FIG. 17 , the positioning of the scavenging fan blower assembly  130  allows for its particle exhaust tube  130 B to eject particles early in the intake pathway, reducing any wear and increasing filter life that they may otherwise cause if filtered later in the process. Optionally, the particle exhaust tube  130  may be fitted with a noise suppressor on its end to decrease added noise. 
         [0039]    The reduced-particle air continues is then sucked into and through the variable speed fan assembly  106 , which is located inwardly adjacent to the inertial particle separator  104 , as best seen in  FIG. 8 . 
         [0040]    Preferably, the variable speed fan assembly  106  is a mixed flow fan assembly, seen best in  FIGS. 9-12 . The fan assembly  106  includes a forward, first fan  162  (i.e., closest to the inertial particle separator  104 ), a middle, stationary member  166 , and a rearward, second fan  164 . The first and second fans  162 ,  164  are fixed on an axle  171  and thereby rotate together, while the stationary member  166  remain stationary. The vanes or fins  166 A of the stationary member  166  help to create relatively higher pressure and redirects the air flow along a more efficient, linear trajectory. Hence, the air is moved by a combination of aero-dynamic and mechanical pushing force, and the centrifugal action of spinning the air against the outer fan housing  160 . The configuration of the fan assembly  106  may also provide negligible stall characteristics and therefore is well-suited for systems having high or variable resistance, such as filters. 
         [0041]    Generally, axial flow fans have various blade shapes including Aerofoil, Sickle, Paddle, and Variable pitch. Axial fans are used for relatively high flow rates and low pressures with flow parallel to the axis of fan and are often selected for simple extraction or cooling applications with very low system resistance, such as moving air from one large space to another (i.e. from factory to outside), desk fans and condenser cooling in refrigeration. 
         [0042]    Centrifugal flow fans have relatively low flow rates and high pressures with flow perpendicular to blower axis. Air enters around center of the fan and exits around the outside. Fans with backward curved blades produce less air volume than axial fan, but generate considerably more pressure and are the least hungry for power in the centrifugal range. Typical applications for centrifugal fans include air handling units, process heating and cooling, electronic cooling and boiler combustion air. 
         [0043]    Mixed flow fans combine the high flow of an axial fan with the high pressure of a centrifugal fan. It provides a solution where combined high pressure and flows are a requirement. It consists of two spinning fan blades at two ends and a stationary vane in the middle. The stationary vane creates higher pressure and adds efficiency by redirecting the air flow created from the spinning fan blade. They may be considered vane-axial fans, but the impeller is shaped like a bevel gear, where the fan blades are designed with an angle. This means the air is moved by a combination of aero-dynamic/mechanical pushing of air, and the centrifugal action of spinning the air against the housing. Mixed flow fan tends to be quieter than other types because of their efficiency and that their moving parts are partially blocked by the shroud. 
         [0044]    In one embodiment, the first fan  162  and the second fan  164  have fins that are substantially angled, relative to an axis of the fan assembly  106 , in a first angular direction. In one embodiment, the fins  166 A of the stationary member  166  have a concave shape oriented in a first radial position. In another embodiment, the first and second fans  162 ,  164  are about  6  inches in diameter, as opposed to about  20  inches or more on prior art designs, due to the efficiency of the mixed flow fan design. 
         [0045]    Motors in prior art air filters/blowers have utilized AC induction motors, likely due to several limitations inherent in permanent magnet motors. For example, permanent magnet motors can exhibit “cogging” at startup from the interaction of the rotor magnets and stator windings due to harmonics. This cogging, in turn, causes noise, vibration, and non-uniform rotation, which is undesirable for fan blowers, and especially those that vary their fan speed. Additionally, high current or operating temperatures can cause the magnets of the motor to lose their magnetic properties permanently. 
         [0046]    The variable speed fan assembly  106  preferably uses a permanent magnet motor by at least partially addressing the above limitations and therefore taking advantage of other advantages these motors have over their AC induction counterparts. Specifically, the motor can include a relatively high number of poles than an equivalent AC induction motor to help overcome the cogging-related issues. Further, by using a more efficient mixed flow fan  106 , less current is required than with an equivalent AC induction motor. In contrast, the use of the permanent magnet motor allows for greater efficiency than an AC induction motor, lower operating temperatures, reduced wear, and a smaller physical size (i.e., due to the higher flux density of permanent magnets vs. AC windings). 
         [0047]    Power to the fan assembly  106  is supplied though a wire conduit connected to port  160 A on the outside of the fan housing  160  from inductors  137 . As seen in  FIG. 11  (with the stationary member  166  removed), power is supplied to the windings of the stator  168  (from port  160 A to the stator pins  168 A), held in place by the motor bushings  172 . When power is supplied to the stator  168 , it generates a magnetic field that acts on the magnets in the rotor and magnetic retention band  170  (seen in  FIG. 12  with the stator  168  removed). Since the rotor  170  is fixed to the axle  171 , it causes the axle  171  and fans  162  and  164  to rotate. 
         [0048]    As best seen in  FIGS. 11 and 12 , the fan assembly  106  further includes a magnetic encoder ring  176  and a magnetic encoder reader  174 . The reader  174  monitors the rotational speed of the ring  176  and relays that information back to the microprocessor  112  to ensure the fan assembly  106  is operating at the desired speed. 
         [0049]    Once the air passes through the fan assembly  106 , it enters into the space  117  within the filters  108  ( FIG. 7 ). The continued pressure from the fan assembly  106  forces the air through the filters, which provide additional filtering, and finally through the air output ports  110 , which are connected to various tubes and ventilations passages, depending on their use. 
         [0050]    As previously discussed, the microcontroller  112  compensates for different elevations by increasing or decreasing the speed of the fan assembly  106 . In one embodiment, the sensor  126  is a barometric pressure transducer. As seen in  FIG. 22 , there is a general correlation between the barometric pressure and elevation, allowing for a rough altitude estimate to be generated. That altitude can then be used to determine the speed of the fan assembly (e.g., via a predetermined equation) and thereby provide a consistent air flow through the blower  100 , regardless of altitude. 
         [0051]    As previously discussed, the microcontroller  112  can be controlled via a local user interface  132  on the fan blower  100  itself or via a remote control  134  (e.g.,  FIG. 21 ) that connects to the fan blower control system  111  via an external port on the fan blower control system housing  146 . In one example, these controls include Start, Stop, Flow Rate, Configuration (thresholds for chemical/biological sensor alerts), and Saturation Warning (the maximum fan speed reached without meeting the desired flow rate). 
         [0052]    In one embodiment, the fan blower  100  includes one or more chemical and/or biological detection sensors in communication with the fan blower control system  111 . For example, the fan blower  100  may include a sensor upstream of the inertial particle separator  104  to monitor incoming air, downstream of the filters  108  and near the air outlet ports  110  to monitor outgoing air, or at both locations. In this regard, the fan blower control system  111  can determine if contaminated air is entering the blower  100 , if contaminated air is exiting the blower  100 , and if the blower  100  is filtering air properly. Similarly, a non-hazardous chemical agent (e.g., R134a refrigerant gas or DMMP gas) can be intentionally introduced near the fan blower  100  to test if various components are installed/functioning properly (e.g., filter installation) and to measure how much of the chemical is being removed. The control system  111  may issue an indication (e.g., sound, light) via the remote control  134  and user interface  132  to alert a user to a filtering problem and/or can immediately cut power to the fan blower  100  (or to the fan assembly  106 ) to prevent downstream contamination. 
         [0053]    In one embodiment, the sensors are any of those found in U.S. application Ser. No. 13/468,945 entitled System and Method for Chemical and/or Biological Detection, and is herein incorporated by reference. 
         [0054]    Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.