Patent Application
20150336653
The present invention relates generally to devices for providing active control of the aerostatic lift of an aerostat or balloon and, more particularly, to a device for actively controlling the static lift of an aerostat or balloon by altering the ratio of air to lifting gas contained within the aerostat or balloon via pneumatic means. The present invention relates generally as well to forced air devices such as heating and cooling systems that require forced air.
Balloons and aerostats employ a lifting gas, such as helium, to fill an envelope and create static lift. Early balloons and aerostats were single envelope designs, i.e. designs which featured a single envelope for the lifting gas. These craft had no ability to control the amount of static lift and hence had no ability to control their rate of ascent or to descend, other than by means of carrying ballast which could be jettisoned during flight to increase lift and by venting lifting gas to the atmosphere to decrease lift.
Additionally forced air is used to pump ambient air through radiators to add or remove heat from a source such as heating and air conditioning devices. These devices often have non-linear flow across their surfaces reducing the overall efficiency of the system. Radiator systems typically have fans central to the square configuration of the cooling fins. This leaves the corners with much lower and turbulent air flow resulting in lower overall heat removal capacity. Efficient and linear forced air for use in heating, cooling and industrial systems improves total energy consumption. In the event that uniform airflow is required across the face area of a large heat exchanger, for example, a plurality of fans may be arranged into an array, with each having either separate and individual control, such as variable speed, on/off, etc., or they may alternatively be controlled as a group. If fans in such an array are used to pressurize a plenum, and individual control means is also desired, then the individual fans must also include means of providing unidirectional flow, known otherwise as backflow prevention in the art.
These early methods of altitude control quickly proved to be problematic. The carrying of ballast to increase lift through subsequent jettisoning reduces initial payload capacity, and once jettisoned the ballast, generally, cannot be recovered. The release of lifting gas to the atmosphere to reduce lift is likewise disadvantageous because, once released, the lifting gas cannot be recovered and subsequent increases in altitude are no longer possible without the further jettisoning of ballast. Moreover, the only commercially available non-flammable lifting gas, helium, is a relatively expensive commodity which further makes atmospheric venting unattractive.
Subsequent balloon and aerostat designs adopted the use of duel envelopes, i.e. envelope within an envelope designs to provide for buoyancy control. In dual envelope balloon and aerostat configurations, an outer envelope is inflated with a lifting gas, typically helium, while an inner envelope or ballonet, is inflated with a higher density gas, typically air, to provide ballast. In a dual envelope design, buoyancy control is accomplished by increasing or decreasing the volume of the inner envelope which increases or decreases the mass of the inner envelope. Decreasing the volume of air in the inner envelope reduces the mass of heavier gas and thus increases static lift. Conversely, increasing the volume of air in the inner envelope increases the mass of heavier air and thus decreases static lift for the combined envelope. The advantage of a dual envelope design is that bi-directional altitude control of the balloon or aersostat may be achieved without the need to either carry and jettison ballast or vent lifting gas to the atmosphere.
Through use of smart controls, dual envelope craft are able to repeatedly gain or reduce altitude, or loiter at a fixed altitude, at will. Such altitude control is highly desired in station-keeping missions where solar heating causes significant day/night temperature differentials which in turn create substantial altitude variations. Similar conditions may arise when, for example, navigation is dependent upon the prevailing patterns of high altitude winds, and where altitude control must be used in order to position the craft within the desired wind pattern at the appropriate time.
Prior art ballonet or inner envelope inflation systems, typically utilizing stored compressed gasses, and/or compression systems and relatively complex valve arrangements, have been proposed. All such systems are believed to have drawbacks with the principle drawback being excess weight, which reduces payload capacity. The art of ballonet inflation systems is presently undergoing change in response to new design concepts for lighter than air craft. At the present time, no particular inflation system has proven to be superior and the industry has yet to settle on a standardized design. Thus, there remains room for improvement in the art.
It is desirable for a ballonet inflation system for use on a lighter than air craft to be as compact, efficient, and lightweight as possible. This is due to the fact that such equipment consumes a portion of the available payload in a parasitic manner. Further, such equipment may rely upon photovoltaic power generation and battery energy storage. Inefficient equipment requires that power generation and storage equipment be upwardly scaled to account for such inefficiencies which adds yet more parasitic weight.
It is an object of the present invention to present an improved air pumping device for buoyancy control of lighter than air craft.
It is another object of the present invention to minimize the weight and packaging volume of such an improved buoyancy control system.
It is a further object of the present invention to maximize the operating efficiency and hence minimize the power consumption of such an improved buoyancy control system.
It is a further object of the invention to present an improved air pumping device for use in residential and commercial heating and cooling systems and other industrial systems which require forced air flow or a controllable source of high volume, pressurized air.
The air pumping device of the present invention solves many of the problems associated with prior art lighter than air craft buoyancy control systems by providing a high volume compressor and a particularly efficient electric motor design, integrated within a single housing, wherein all rotating components of the compressor and motor are mounted on a single common rotating shaft. The compressor portion of the air pumping device includes a compression chamber featuring a plurality of one-way flow control or check valves, as well as a plurality of selectively controllable, electrically actuated, two-way flow control valves, where the two-way flow control valves allow for the backflow of air through the housing—a desirable characteristic in buoyancy control applications.
The electric motor portion of the device is a direct current (“DC”) motor design featuring two magnetic rotors with a stator assembly disposed there between. The rotors include magnetic faces formed from a permanent magnet material which are spaced equidistant from the stator assembly, thereby defining an air gap between the rotor faces and the stator assembly. The stator assembly is a printed circuit board which includes an “ironless” stator coil, as well as all power, communications and sensor electronics needed to operate the motor, all of which are integrated on the single, common printed circuit board. The air pumping device of the present invention, exhibits exceptionally high operating efficiency and power density, which are highly desirable in lighter than air craft applications.
This same invention with changes to the flow control valves can be utilized in forced air systems where the flow control is limited to a single direction and the flow control valves are used to prevent the reverse movement of air i.e. one-way or check valves.
The above and other features of the invention will become more apparent from the following detailed description.
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. The invention may, however, may be embodied in many different forms and should not be construed as being 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. Like numbers refer to like elements throughout.
With reference to
The centrifugal compressor assembly 12 includes the shroud 16, the housing 18 having an air compression side 56 and an air discharge side 26, the housing cover 74 and an impeller 20. The housing 18 and housing cover 74 support the common shaft 60 via anti-friction radial ball bearing assemblies 48 and 50 mounted in the housing 18 and housing cover 74, respectively. Mounted on the common shaft 60 is the impeller 20, which is secured to the common shaft 60 via a nut 22 and a threaded portion 24 of the common shaft 60. Mounted to the housing 18 and enclosing the impeller 22 is the shroud 16 which features an air inlet 52. Formed between the shroud 16 and a compression side 56 of the housing 18 is an air compression chamber 54, which includes an upper portion 58.
Incorporated into the housing 18 are a plurality of openings 28 into which are mounted one-way flow control or check valves 30A through 30K. Mounted to the air discharge side 26 of the housing 18 are valve assemblies 32 and 34. Each of the valve assemblies 32 and 34 include a plurality of electrically operated linear actuators 36A through 36C and 38A through 38C. The linear actuators 36A through 36C operate corresponding valves 40A through 40C which control airflow through certain of the plurality of openings 28 in the housing 18. Similarly, the linear actuators 38A through 38C actuate a plurality of valves 42A through 42C which likewise control airflow through certain of the plurality of openings 28. The flow control valves 30A through 30K, 40A through 40C, and 42A through 42C, are in fluid communication with the compression chamber 54 and an ambient environment external to the compression chamber.
With reference to FIGS. 1 and 3-6, the axial gap motor 14 is enclosed within a singular cavity 76 within the housing 18. The cavity 76 is closed-out by the housing cover 74. (See
The magnetic rotor assemblies 62 and stator assembly 68 are each mounted on the common shaft 60. Each of the pair of magnetic rotor assemblies 62 has a magnetic side 64 having a magnetic face 78, and an iron side 66. The magnetic rotor assemblies 62 are mounted on the common shaft 60, such that each of the magnetic faces 78 bear against a shoulder 70 of the common shaft 60. (See
Referring now to
The iron side 66 of the magnetic rotor assembly 62 is populated with a plurality of thin laminar layers 90 and 92 of ferrous material, formed in the outer web region 88. This laminar construction more optimally shapes the amount and location of the ferrous material in order to provide an efficient magnetic circuit function for the axial gap motor 14, while eliminating ferrous material where it is of little to no use. The laminar layers 90 and 92 are arranged so that the thickest portion of the stacked layers lies directly behind a line at which the permanent magnet (i.e. magnetic face 78) changes pole direction, i.e., from north to south. The point at where the magnet poles reverse being also the point at where magnetic flux in the back iron (i.e. layers 90 and 92) is maximum, and therefore the location at where the maximum amount of back iron is required.
The laminar layers 90 and 92 are bonded to the outer web region 88 of the core 80. Each laminar layer 90 and 92, may consist of one or more layers with a greater number of thinner material layers inuring to a more optimal shape. The layers 90 and 92 are preferably formed using stamped or die cutting processes of low cost sheet material, making for an easily manufacturable, low cost construction.
Referring now to
In lieu of connecting wires, drive power for the axial gap motor is conducted via PCB traces at 96A, 96B, and 96C. DC power and all low-level logic control and communication for the air pumping device 10 are secured at electrical connector 98. Connector 98 is accessible from the aft end of the first embodiment 10 of the air pumping device via slot 100 (see
Referring now to
With reference to
Referring now to
With, reference to
Bi-directional flow control through the first embodiment 10 of the air pumping device is necessary if the high altitude balloon is intended to have the ability to both increase and decrease in altitude at will. Increasing the volume of the ballast envelope 6 causes a corresponding increase in the total system mass which thereby causes the balloon 4 to lose static lift and decrease in altitude. Decreasing the volume of the ballast envelope 6 on the other hand, reduces the total system mass which therefore increases static lift and allows the balloon 4 to gain altitude. (A dual envelope balloon may increase in altitude up to its pressure height, i.e. the point at which the volume of the ballast envelope is zero.) Therefore, in order to achieve bi-directional altitude control, the ballast envelope 6 must be controllably inflated with pressurized air, and exhausted, as needed.
In the first embodiment 10 of the air pumping device of the present invention, exhaustion of pressurized air from the ballast envelope 6 is accomplished by allowing the air to back flow through the first embodiment 10 of the air pumping device. Valve assemblies 32 and 34 provide this function. Valve assembly 34 is replicated by assembly 32, so description is limited to this one case. In the exemplary embodiment, the linear actuators 36A through 36C are of the self-locking type, i.e. power is only required to move the actuator to a new position, and no power is required to hold at any given position. The valves 42A through 42C are attached to actuator rods of the linear actuators 38A through 38C, and are shown in the closed position. This position is desired when pumping up the ballast envelope 6 to reduce altitude. Conversely, when altitude gain is desired, actuators 36A through 36C, and 38A through 38C are energized, opening valves 40A through 40C and 42A through 42C. The impeller 20 (see
It should be additionally noted that the actuated valve assemblies 32 and 34 may also be operated when the air pump is active and filling the ballast envelope 6, and thereby increase the overall air flow passage area by 60%. For example, more rapid inflation of the ballast envelope 6 may be desired in some situations and the valve assemblies may therefore be activated to allow for increased air flow rate.
With reference to
In the exemplary second embodiment 11 of the air pumping device, the one-way check valves 111 are duckbill style check valves. Duckbill style check valves are elastomeric check valves that allow forward air flow in response to a positive differential pressure. Conversely, in response to a negative pressure differential, reverse airflow or backflow is prevented or checked. Duckbill check valves are commercially available and can be designed to open over a wide range of positive pressures depending on valve size, geometry, and elastomeric compound characteristics.
The plurality of one-way check valves 111 are inserted in the plurality of openings 28 in the housing 18. (See
With reference to
The Impeller 20 must be operated at relatively high speed and, in the exemplary embodiment, shaft speeds of 30,000 RPM or greater are both possible and required. Shaft speeds of 30,000 RPM or greater are necessary to produce a discharge pressure of the air pumping device 10 in a desired range of about 15%-35% above the ambient air pressure at the air inlet 52, or a pressure ratio of 1.15-1.35. The axial gap motor 14 is directly mounted to the common shaft 60 as is the impeller 20, and therefore must operate at the same rotary speed. In traditional permanent magnet motor designs, high speed operation results in significant loss in the stator iron structure. These are termed “iron losses” and become dominant at the speeds of interest. Therefore, an iron-less core construction will eliminate these dominant high speed losses, as no ferrous material exists in the stator structure, and the axial gap motor can attain high speed operation at extremely high efficiency, with minimal thermal load. Such efficiency is highly desired for lighter than air craft as operating power during extended deployments is often reliant upon photovoltaic solar cells and batteries. Maximizing the operating efficiency of the buoyancy control air pump device therefore will minimize the photovoltaic and battery capacity needed, and associated parasitic payload.
Another advantage of the iron-less core axial gap motor 14 is extreme power density. Ironless core axial gap motors of greater than 8 kW/kg have been demonstrated in the literature, and this level of power density is far greater than that attainable by traditional, slotted coil construction designs. Such performance is extremely important for lighter than air craft applications to further reduce the parasitic payload component. Further reducing mass is the integration of the power, communications and sensor electronics (94A through 94C) onto the PCB of the stator assembly 68 (
Another advantage which may be of particular value in heat exchanger applications regards the ability to tailor the discharge air flow characteristics of the air pumping device. Depending upon the needs of any particular application, flow control valves may be selected that control both the volume of air flow and the characteristics of the discharge air. For example, in heat exchanges applications, the ability to uniformly distribute large volumes of air over the face of a radiator would likely prove advantageous. This uniformity of air distribution provides for higher utilization of the radiator surface area extracting a maximum heat over the entire surface.
The above described advantages result in an air pumping device exhibiting exceptional operating efficiency and power density. The exemplary embodiment described herein for example, results in a 300-watt class machine a total mass of approximately 1700 grams (3.75 pounds).
This application claims the benefit of U.S. provisional patent application No. 62/002,856 filed on May 25, 2014, the entirety of which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 62002856 | May 2014 | US |
| Child | 14717732 | US |
