Transportation system and vehicle for supersonic transport
1. A transportation system comprising:
- a substantially enclosed conduit provided between a first geographic location and a second geographic location, the enclosed conduit having a cross-section of a fluted tube and being provided with an atmosphere that allows a vehicle traveling within the enclosed conduit to achieve aerodynamic tunneling, the cross-section having a curve outlining one or more lobes and one or more waists, the cross-section being defined by a polar-coordinate equation r=a+b cos2 ct, wherein r is a distance of a point on the curve from a pole, t is an angle in a polar coordinate system, c is an integral multiple of ½
, and a and b are real parameters, wherein none of a, b and c is zero, and wherein the atmosphere inside the enclosed conduit has a density such that a speed of sound is greater than a speed of sound of atmospheric air outside of the enclosed conduit.
A transportation system for supersonic travel including a conduit containing an atmosphere that exhibits high aerodynamic tunneling performance, or high gas efficacy, and a vehicle designed to operate within the conduit. The vehicle traveling within the conduit along a support and guide structure that is complementary to a support and guidance system of the vehicle. The vehicle being propelled through the conduit via a propulsion system that includes contra-rotating propellers.
|Transport system with a minimum of two supporting points disposed on opposite sides of inter-connected ring frames|
Patent #US 5,275,111 A
Current AssigneeMilorad Saviccevic
Sponsoring EntityMilorad Saviccevic
|High speed transport system|
Patent #US 5,282,424 A
Current AssigneeGerard K ONeill
Sponsoring EntityGerard K ONeill
|Operating system for high speed tunnel trains|
Patent #US 4,881,469 A
Current AssigneeHelmut Hirtz
Sponsoring EntityHelmut Hirtz
|Pneumatic mass transportation system|
Patent #US 8,146,508 B2
Current AssigneePatrick Joseph Flynn
Sponsoring EntityPatrick Joseph Flynn
|CONVERTIBLE RAIL-HIGHWAY VEHICLE|
Patent #US 3,730,103 A
Current AssigneeGeorge D. Weaver
Sponsoring EntityGeorge D. Weaver
|TRANSPORTATION SYSTEM FOR HOSTILE ENVIRONMENTS|
Patent #US 3,861,319 A
Current AssigneeGunkel H. Rudolf, Egon Gelhard
Sponsoring EntityGunkel H. Rudolf, Egon Gelhard
|High-speed ground transportation systems|
Patent #US 3,404,638 A
Current AssigneeLawrence K. Edwards
Sponsoring EntityLawrence K. Edwards
- 1. A transportation system comprising:
a substantially enclosed conduit provided between a first geographic location and a second geographic location, the enclosed conduit having a cross-section of a fluted tube and being provided with an atmosphere that allows a vehicle traveling within the enclosed conduit to achieve aerodynamic tunneling, the cross-section having a curve outlining one or more lobes and one or more waists, the cross-section being defined by a polar-coordinate equation r=a+b cos2 ct, wherein r is a distance of a point on the curve from a pole, t is an angle in a polar coordinate system, c is an integral multiple of ½
, and a and b are real parameters, wherein none of a, b and c is zero, and wherein the atmosphere inside the enclosed conduit has a density such that a speed of sound is greater than a speed of sound of atmospheric air outside of the enclosed conduit.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
This application is a continuation of U.S. Nonprovisional application Ser. No. 14/015,796 entitled “Transportation System and Vehicle for Supersonic Transport” filed on Aug. 30, 2013, which is a continuation-in-part and claims priority to U.S. Nonprovisional patent application Ser. No. 12/698,887 entitled “Supersonic Hydrogen Tube Vehicle” filed on Feb. 2, 2010, now U.S. Pat. No. 8,534,197 issued on Sep. 17, 2013, which claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 61/695,983 titled “Tube Vehicle for Supersonic Transport,” filed Aug. 31, 2012, and U.S. Provisional Patent Application No. 61/840,232 titled “Tube Vehicle for Supersonic Transport with Wheels and Balancing System,” filed Jun. 27, 2013, all of which are hereby incorporated by reference in their entirety for all purposed.
There are many ways to transport both people and goods, including airplanes, automobiles, and trains. The length of time that a trip may take is often a determining factor for the type of transportation that may be used, and there is a demand for shorter travel times between destinations. In addition to travel time, many consumers choose their method of transportation based on cost and consumers will often choose one airline carrier over another based on ticket price. The efficiency of a method of transportation plays a big role on costs passed on to consumers. For instance, when the price of aviation fuel increases, some airlines also increase the cost of tickets. Additionally, consumers are more environmentally conscious and are looking to alternative energy modes of transportation when making their transportation decisions.
Business travelers are primarily concerned with speed, and automobiles are not the first choice for long distance travel. Such consumers really have only one travel option: flying. The speed of commercial aircraft, however, is practically limited by the speed of sound, because as an airplane speeds up and begins to approach the speed of sound, it enters a speed region known as the transonic region. When the airplane enters the transonic region, parts of the airflow over the airplane'"'"'s surface are subsonic and parts are supersonic. Air is strongly compressible near the speed of sound and the supersonic parts emanate shock waves that are approximately normal to the surface of the airplane. The shock waves increase drag (wave drag) and decrease lift. Thus, as the speed of the aircraft varies as it accelerates through the transonic region, movement of the waves on the surface causes buffeting. The wave drag gives rise to a power peak at Mach 1 called the “sound barrier.” After the airplane passes through the transonic region, the stability of the vehicle improves and the power requirement drops temporarily below the power peak of the sound barrier. Nonetheless, the power continues to rise with speed and, due to wave drag, is much higher than at subsonic speeds. Indeed, the power in the supersonic region rises at more than the third-power of speed. The additional power requirements make supersonic airplanes prohibitively expensive to build and operate, especially for commercial use. This means that in order to increase their speed past the speed of sound, aircraft must use significantly more fuel, charge higher prices for either passengers or cargo in order to make up for the increases in fuel usage, and will expel more emissions into the environment.
The foregoing examples of the related art and limitations therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.
Aspects of the present disclosure involve a transportation system including a substantially enclosed conduit. The conduit is provided between a first geographic location and a second geographic location. The conduit has a cross-section of a fluted tube and is provided with an atmosphere that allows a vehicle traveling within the conduit to achieve aerodynamic tunneling.
Another aspect of the disclosure involves a vehicle including at least one source of power and a motor operably coupled with the at least one source of power and configured to receive power from the at least one source of power. In one specific example, the at least one source of power includes at least one fuel-cell stack that uses a gas from an atmosphere included in the enclosed structure in which the vehicle travels as a fuel source. The vehicle includes a propulsion system supported on the outside portion of the vehicle body and configured to move the vehicle through the enclosed structure. The propulsion system being operable coupled to the motor. The propulsion system, in one implementation, includes at least one propeller supported at one end of the vehicle. The propeller being configured to operate within an atmosphere of the enclosed structure that allows the vehicle to achieve aerodynamic tunneling.
The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools, and methods that are meant to be exemplary and illustrative, and the embodiments and aspects described and illustrated are not intended to be limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other improvements. In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following descriptions.
Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than limiting. The use of the same reference numerals in different drawings indicates similar or identical items.
Aspects of the present disclosure involve a vehicle capable of supersonic travel (relative to air outside the conduit) that “flies” in a substantially enclosed conduit provided with an atmosphere that exhibits high aerodynamic (tunneling) performance, such as a hydrogen atmosphere. The conduit is intended to be enclosed and its interior isolated from air outside the conduit as completely as is practicable, up to, for example, flaws in manufacturing or fabrication (e.g., pinholes in welds). The conduit may be of various configurations capable of supporting either unidirectional or bidirectional transit. The vehicle includes one or more fuel cells, rechargeable batteries, an electrical catenary, an electrical bus running parallel to the centerline of the conduit, or other sources of power that power the vehicle. In the case of fuel cells, a gas within the conduit, such as hydrogen or other gases can be used as a fuel source. The fuel cell, rechargeable battery, or other source of power drives a propfan or other propulsion system to propel the vehicle within the conduit. Further, by traveling in an atmosphere with a more aerodynamically favorable performance than air allows the vehicle to travel faster than the speed of sound with respect to the air outside the conduit without exceeding the sound barrier within the atmosphere. Thus, for example, in a hydrogen atmosphere, which has a higher speed of sound than air by a factor of 3.8, a delay in the onset of the sound barrier is observed. Mach 1.2 in air corresponds to only Mach 0.32 in hydrogen. Hence, the vehicle may reach Mach 1.2 (with respect to air) while remaining subsonic in the hydrogen atmosphere. To “fly” the vehicle will involve utilization of a levitation apparatus or a similar type of apparatus that supports and guides the vehicle that cooperates with a guideway or support and guide structure within the conduit such that the vehicle levitates above the guideway or travels along the support and guide structure within the conduit. The levitation or support and guidance apparatus may, for example, include aerostatic gas bearings, magnetic levitation, wheels, or small-diameter rollers, like the rolling elements of roller bearings, or the like. In the case of aerostatic gas bearings, a gas pump may be used to force gas through the bearings to allow the vehicle to hover so that the system does not depend on vehicle-guideway relative velocity to provide gas pressure. At least one embodiment of magnetic levitation, for example, AC-electromagnet levitation, can analogously hover.
Alternatively, as shown in
Referring again to
The wheel system 103, in one particular implementation, may include one or more wheels 107 longitudinally aligned along the bottom portion of the vehicle. The wheels are positioned and configured to interact with the support and guide structure provided within a conduit. In the specific example shown in
Alternatively, as shown in
As shown in
In general, the design of the propeller arrangement 105 may be optimized for the environment in which it will operate. In particular, the propeller arrangement may be designed in accordance with the size of the conduit and/or the atmosphere within the conduit, among other parameters. For example, the diameter of the propeller arrangement 105 may be a function of the size of the conduit and may be increased or decreased as the conduit diameter or size is increased or decreased. Furthermore, for a given operating atmosphere, rotational frequency, number of blades in the propeller arrangement, and/or diameter may be optimized to achieve satisfactory propeller static thrust, power loading, and efficiency.
In one particular example, propeller arrangement design may involve optimizing rotating frequency of the blades and the number of blades for a given propeller diameter. In general, propeller efficiency is defined as:
where T is thrust, V is the velocity of the vehicle, and Ps is the shaft input mechanical power. For a single propeller, the Rankine-Froude momentum theory of propulsion assumes that the operating gas is accelerated by an infinitely thin “actuator disc” of area S that provides energy to the gas but offers no resistance to gas as it passes through it. In unit time, the mass of gas passing through the actuator disc is:
where ρ is density of the gas, and Vo is the gas velocity at the immediate rear of the disc. The increase of momentum of the mass of fluid, and hence the thrust T on the disc is
where V is the gas velocity far ahead of the disc, Vs the gas velocity far behind the disc. Therefore, after several steps of derivation, the ideal efficiency (ηi) of the actuator disc is given by:
Similarly, the Rankine-Froude momentum theory when applied to contra-rotating tandem propellers assumes that the propeller be an ideal actuator disk with an infinite number of blades which exhibits no resistance to gas flow, transfers all mechanical energy to the gas, and experiences a uniform distribution of gas pressure and velocity over its surface. With the flow velocity Vf through the front disk being defined as:
where V is flow velocity far ahead of the disk (i.e., vehicle velocity, or initial inflow velocity, within the vehicle-fixed frame of reference) and Vs is the fully-developed slipstream velocity far behind the disk, the mass flow through the front disk, in unit time increment, becomes:
where ρ is density of the gas and S is an area of the disk. Thus, thrust provided by the front disk of tandem pair is:
and the power required by the front disk being given by:
Because for the rear disk in the tandem configuration the initial inflow velocity V′ may be greater than V, and its final slipstream velocity Vs′ may be greater than Vs, the thrust and power for the rear disk differ from those for the front disk. Taking this into consideration and after several steps of derivation it can be shown that for a rear disk the thrust is given by:
and power by:
where ω is the probability that a streamline in the slipstream from the front disk will intersect the rear disk defined by ω=A/At where A is the area of the rear actuator disk and At is the cross-sectional area of the tube. Extending the Rankine-Froude propulsive efficiency to contra-rotating tandem propellers, thus, results in the propulsive efficiency for the tandem pair configuration being defined as:
where V is vehicle velocity, Tf and Tr are the thrust provided by the front and rear disks, respectively, and Pf and Pr are the slipstream power required by the front and rear disks, respectively. Substitution of the power and thrust required by the front and rear disks, Pf,Pr,Tf and Tr gives:
as the propulsive efficiency for tandem disks in a tube. Additional details related to propeller design discussed herein may be found in “Hydrogen tube vehicle for supersonic transport: 4 Hydrogen propeller” by Arnold Miller published in the International Journal of Hydrogen Energy 37 (2012) 14603-14611, which is hereby incorporated by reference herein.
An important fact shown by these equations is that the propeller efficiency is independent of gas density. Thus, the efficiency of the propeller will not necessarily be changed by operating in hydrogen or any other atmosphere rather than in air. However, a different propeller diameter, rotational frequency, wider and/or more blades may be required to attain the same efficiency and thrust as a propeller operating in air. Hence, for example, in case of a hydrogen atmosphere, a different (larger) propeller diameter, higher rotational frequency and/or more blades may be required to attain the same efficiency and thrust as a propeller operating in air. One specific hydrogen propeller design may employ 14 contra-rotating blades, 4.11 m diameter, and rotational frequency of 40.4 s−1 at translational velocity of 970 m/s. The same is true for water propellers compared to air propellers: waterborne ship propellers are of similar efficiency but are smaller and slower-turning than comparable-power airplane propellers.
Additionally, from consideration of the kinetic-energy imparted to the slipstream, which preferably is minimized, the larger the diameter of propeller arrangement 105, the greater the potential propeller efficiency. However, as the diameter increases for a given rotational frequency (speed), the propeller tips will eventually enter the transonic region, and the considerations discussed above regarding dynamic instability and high power associated with the transonic region will apply to the propeller blades. Moreover, because the propeller traces out a helix as the vehicle advances, a vector component of rotational velocity should be added to vehicle translational velocity, and hence the blade-tip velocity exceeds the vehicle velocity. It is for this reason that propeller tip speed limits the speed of a propeller-driven vehicle, and a higher propeller diameter may require a lower rotational frequency.
Although the propulsion system may include a propeller arrangement 105, other forms of propulsion may be used in place of the propeller arrangement 105. For instance, the vehicle 100 may be powered by a motor, engine, and the like. If the vehicle 100 uses magnetic levitation, then the vehicle 100 may alternatively be propelled by a linear synchronous or linear induction motor. The stator of such a linear AC motor may be either on the vehicle 100 or on the guideway 302 (see
According to another implementation shown in
In yet another implementation, the vehicle 100 may travel through the tube 406 while supported by magnetic levitation, with appropriate magnetic system components included on the vehicle as well as the guideway 302. The tube 406 will have an appropriate guideway, generally analogous to the above-described vee-way for aerostatic gas-bearing levitation, and the vehicle 100 levitates above the guideway on a magnetic field rather than a fluid film. In these embodiments, the guideway includes magnetic material and the vehicle 100 has magnetic materials installed on the bottom of the vehicle 100, for instance, where the levitation system 303 is located. The guideway 302 may, for example, include tracks that have wires, solenoids, conducting materials, magnets, or may otherwise produce a magnetic field in order to produce levitation and/or propulsion of the vehicle 100.
The guideway 302 or any other similar support and guide structure may be used to support a track or other guidance system for the vehicle 100. In some embodiments, the guideway or any other similar support and guide structure may be located at the bottom of the tube 406, in other embodiments the guideway 302 or any similar support and guide structure may be located on the sides or top of the tube 406. In some embodiments, the guideway or any other similar support and guide structure may be used to support a rail system and may provide a track or tracks to support and guide the vehicle 100. The guideway 302 may be shaped in any manner, however in some embodiments the guideway 302 may be shaped as the letter “V” or as the letter “U”.
The embodiment employing AC electromagnets is similar to the aerostatic gas-bearing embodiment. Alternating current in the solenoids of the AC electromagnets induces alternating same-polarity magnetic fields in metal sheets 701, 703. The same-polarity (N-N or S-S) of the electromagnet fields and induced fields produces levitation of vehicle 100. Like the aerostatic gas bearings discussed above, the AC magnetic levitation allows the vehicle to hover because the magnetic fields induced in the conductive sheets 701, 703 are due to the alternating current in the solenoids of electromagnets 702, 704 rather than relative motion of the vehicle. The AC-electromagnets 702, 704 may use feedback control of AC-solenoid current to control the gap height between magnets 702, 704 and the conductive sheets 701, 703 and hence the height of the vehicle above the sheets.
There is a type of DC magnetic levitation that can also provide hovering. In such an embodiment, the vehicle could be suspended below a ferromagnetic rail and an appropriate gap between the rail and DC magnets on the vehicle 100 would be provided through feedback control of the solenoid DC current. While this embodiment could require a very different design of the guideway—namely, a ferromagnetic rail rather than aluminum sheets on a vee-way—this is also a viable embodiment for magnetic levitation of vehicle 100.
The vee-way, with attached, conforming metal sheets or alternatively a ferromagnetic rail, then guides the vehicle 100 through the tube 406. The magnetic levitation apparatus conforms generally to the shape of the vee-way or ferromagnetic rail so that the vee-way or rail can guide the vehicle 100 through tube 406.
Although, as discussed above, the conduit may be configured as a tube with a circular cross-section, alternatively the conduit may have a “waisted circle” configuration with a cross-section of a fluted or grooved tube as shown in
One method of forming a fluted tube configuration may involve joining two or more separate, circular-section tubes, along their length to form a single fluted tube with grooves or waists along its length. In the specific example shown in
Regardless of the tube configuration, the tube is built to the appropriate dimensions such that the vehicle 100 (or vehicles in case the tube is designed to support a bidirectional transit) can fit completely inside the tube. The tube may be constructed similarly to a pipeline for natural gas, oil, or water. For instance, the tube may be constructed of concrete, metal or other suitable materials. The tube may also include various types of seals to prevent the gas 407 filling the tube from escaping the tube. The seals may be any type of conventional material used to prevent air/gas from escaping an enclosed area. For instance, sealing may be provided by elastomers, concrete layers, rigid panels, or the like. The tube may inherently have sufficient gas-tight properties (e.g., a welded metal tube) so as to not require additional/separate seals. In some embodiments, the tube may be sealed in order to create a consistent environment for the vehicle 100 to travel, as well as to prevent impurities from entering the tube. Furthermore, in these embodiments, the tube may also contain air locks or other sealed entryways that allow the tube and vehicle 100 to be accessed from different locations.
In addition, the tube may also include a purification system to remove impurities, such as water that inadvertently slips through the vehicle water-collection system when, for example, hydrogen is used as the tube atmosphere or air that escapes around the air-lock seals, as well as any other unwanted materials, from the atmosphere 407 within the tube. In case of a hydrogen atmosphere, the purification system may utilize conventional purification hardware, such as pressure-swing-absorption, hydrogen palladium filters, or hydrogen catalytic combustors, through which the tube hydrogen may slowly pass. Analogous purification systems may be used for any of the other gases disclosed below.
The operating atmosphere inside the tube is selected to achieve aerodynamic tunneling that has the potential of enabling high-efficiency, quiet, supersonic transport. In particular, the atmosphere is selected to increase the speed of sound so that, although it is not necessary for the vehicle to travel at supersonic speed, its speed at a given Mach number will correspond to a higher absolute speed (ms−1). The selected atmosphere will also have a lower gas density and/or viscosity so that drag is reduced. In other words, the ideal properties of such a gas are that the absolute speed be higher and density be lower than that of air at a given Mach number and pressure: The speed of sound in a gas increases as the density decreases, and the drag decreases as the density and viscosity decrease. Also, the potential operating atmosphere may be able to serve as a fuel for the propulsion fuel cells for vehicle 100 operating inside of the conduit. One method of determining the potential operating atmosphere for use inside the conduit may involve determining aerodynamic (tunneling) performance of the atmosphere and energy density of the tube vehicle with the product of the two parameters determining the rank of atmospheric merit. Alternatively, the potential operating atmosphere may be determined based on gas efficacy (Γ), with higher efficacy indicating higher speed and/or reduced drag. In particular, the higher the efficacy, the more the gas increases the Mach 1 speed or reduces drag. Based on the criteria of speed and drag, gas efficacy can be defined as:
where c is speed of sound (m s−1) in the gas and D is drag (N) on an ideal flat plate used as an aerodynamic test body in the tube atmosphere. An important fact to note from this equation is that the efficacy Γ increases as the first power of absolute speed at Mach 1, and varies inversely as the first power of skin-friction drag for laminar flow over the plate. With the speed of sound for the ideal gas given by:
where γ is the ratio of specific heats, p is constant tube pressure, and ρ is tube gas density. Friction drag on either face of a rectangular flat plate of infinitesimal-thickness is given by:
where C is the friction drag coefficient, V is speed of the plate (or of the flow), b is width of the plate, and L is the length parallel to the flow, the gas efficacy Γ after several steps of derivation, can be shown to be equal to
where μ is gas viscosity. Substituting thermo-physical properties of various gases into the above equation provides ranking of the gases for their potential use as a conduit atmosphere based on the gas efficacy parameter. Examples of potential conduit atmosphere gases ranked using gas efficacy parameter are shown in Table 1. Although gases listed in the table can be used individually, use of a mixture of any of the listed gases as the tube atmosphere is also contemplated. Additional information on the methods for determining potential gases for tube atmosphere can be found in the “Aerodynamic Tunneling” article by Arnold Miller submitted to and accepted for presentation at the World Hydrogen Technologies Conference, to be held in Shanghai, China, from 25-28 Sep. 2013, as well as “Hydrogen tube vehicle for supersonic transport: 3. Atmospheric merit” article by Arnold Miller published in International Journal of Hydrogen Energy 37 (2012) 14598-14602, which are hereby incorporated by reference herein.
In one specific implementation, the conduit atmosphere may contain hydrogen that was determined as having both highest overall merit as well as gas efficacy. In the particular embodiment discussed herein, this hydrogen gas environment provides the vehicle 100 with its fuel, and the tube hydrogen consumed by the vehicle is replaced from a source of hydrogen outside the tube. Hydrogen 407 is used within conduit 406 as the vehicle 100 can travel within the hydrogen atmosphere at supersonic speed with respect to air outside the tube while remaining subsonic inside the tube; the low density and viscosity of hydrogen results in lower drag for the vehicle relative to the outside air; and the high thermal conductivity of hydrogen facilitates heat rejection from the vehicle compared to heat rejection to atmospheric air and especially to reduced-pressure air.
The hydrogen 407 within the tube 406 may be maintained at a pressure slightly above atmospheric pressure. For example, the pressure within the tube may be maintained at about 0.05 bar above ambient atmospheric pressure. The relatively higher pressure inside of the tube assures that hydrogen 407 would leak out of the tube through any inadvertent breach (e.g., crack, pinhole leak in a weld, or similar breach) in the tube, rather than have the outside air atmosphere and other elements leak into the tube, thereby maintaining a safe working environment for vehicle 100. An objective of not allowing air to leak into the tube is that by keeping the concentration of hydrogen at or above 75% (by volume), the hydrogen 407 will be held above the upper flammability limit of hydrogen and the hydrogen 407 will be too rich to burn. This method of safety also applies to any of the other flammable gases (see Table 1 above) that may be used as tube gases because of increased gas efficacy, although the upper flammability limit will vary for each gas.
One embodiment of an atmosphere alternative to hydrogen is methane, or natural gas, which is substantially methane. The density of methane at a given pressure is about half the density of air at the same pressure, and methane can be used as a fuel for fuel cells. As for hydrogen above, the pressure of the methane within the tube may be maintained slightly above air pressure outside the tube, and thereby any inadvertent leakage through tube would be leakage of methane to the outside of the tube rather than leakage of air into the tube. Analogous to the substantially hydrogen-filled tube, an objective of not allowing air to leak into the substantially methane-filled tube is that by keeping the concentration of methane at or above about 17% (by volume), the methane will be held above the upper flammability limit of methane and the methane within the tube will be too rich to burn. The methane breathed by the vehicle 100 may be converted to hydrogen onboard the vehicle 100 by a steam reformer, or similar chemical processor, and the hydrogen then supplied to the fuel cell to provide propulsion power; alternatively, some fuel cells, for example, solid-oxide fuel cells, may operate directly on methane. In this embodiment using methane as the atmosphere within the tube, the products of the chemical processes onboard the vehicle 100 are substantially both water and carbon dioxide, and in one embodiment, the carbon dioxide may be chemically trapped onboard the vehicle 100 and thereby not released into the tube 406. The technique may use any method of trapping carbon dioxide, for example, converting it to a liquid or solid or chemically trapping it as a product such as a carbonate. In the case of trapping the carbon dioxide as a carbonate, the carbon dioxide may be readily reacted with a strong base such as calcium hydroxide to give the solid calcium carbonate. In this embodiment, the trapped carbon dioxide may be stored onboard the vehicle 100 until the end of a run, at which time it would be removed from the vehicle 100 to make room for more trapped carbon dioxide on a subsequent run of the vehicle 100.
Another possible gas for use within the tube is helium. Having a density twice that of hydrogen but about seven times less than air and having a viscosity about the same as air, it would provide a lower operating gas density than air for the vehicle 100 and would thereby give a higher sonic speed and lower drag than air outside the tube. However, it would not be as good in this regard as hydrogen, and because helium is an inert gas, it would not be useable as a fuel for the onboard propulsion fuel cells of the vehicle 100.
While the use of a single high-efficacy gas for the tube atmosphere is desirable in order to achieve higher speed and/or reduced drag, in some instances these gases may provide relatively low thrust for a propeller and therefore possibly result in low acceleration of the vehicle. The same consideration applies to braking of the vehicle by the propeller. This is due to the fact that the propeller thrust is a function of the first power of gas density as shown and discussed above. Low acceleration could limit the system to long-range applications (thereby allowing sufficient distance to accelerate to cruise speed), or limit the weight of the vehicle, or limit the achievable speed of the vehicle. One possible method for overcoming this potential limitation of the high-efficacy gases is to utilize gases with different densities in different parts of the tube so as to create “density stages.”
The schematic in
As an example of the operation of density stages, consider that the tube vehicle commences its transit from the left-most part of the three-stage tube shown in
In another implementation, Iris 1 and Iris 2 are each comprised of a pair of irises. The first pair of irises may straddle the location of Iris 1 in
Table 2 set forth below gives a numerical example of the benefits of multiple stages. In this example, which is not intended to be restricting in any manner, assume that the limiting speed in each stage is Mach 0.74, and the acceleration in the hydrogen stage is 2.4 m/s2 which may be constant. The accelerations in Stages 1 and 2 are also constant and are proportional to their respective gas densities (see Table 2) compared to hydrogen; thus, the acceleration in Stage 1 is (6.27/0.0824) 2.4 m/s2=182.6 m/s2, and the acceleration in Stage 2 is (0.6556/0.0824) 2.4 m/s2=19.1 m/s2. With these parameters, the time and distance to traverse each stage, as well as the total time and distance (the sums of the times and distances in the separate stages), are calculated from the standard equations in physics for acceleration of masses and are given in Table 2.
If the tube included only a single gas, such as, for example hydrogen, the time required to reach 969 m would be 404 s, and the distance required to reach this speed would be 195,778 m. Thus, using the three stages in the example results in substantial reductions in the vehicle'"'"'s total time and distance: Time is reduced from 404 s to 278 s, and distance is reduced from 195,778 m to 85,843 m. Reduced time would result in faster service for passengers or cargo; in some implementations, reduced distance to reach cruise speed allows the vehicle more length of its tube for cruise speed and braking, as well as reduces the mass and cost of the dense gases of the acceleration stages. The greater the number of stages in the method of density stages, the larger the reduction of time and distance.
The discussion will now turn to some of the functional components of the vehicle 100.
Another possible propeller arrangement may include contra-rotating, tandem propellers, with one contra-rotating propeller assembly located at each end of the vehicle. The propeller arrangement according to this embodiment, similar to the contra-rotating propeller discussed above, helps to reduce energy losses and is more efficient than propellers having a single set of non-contra-rotating blades. Additionally, the contra-rotating, tandem propeller helps the vehicle achieve higher speeds as compared to the vehicle equipped with either a single set of non-contra-rotating propellers or a single contra-rotating propeller located at only one end of the vehicle.
The blades of each of the first and second blade set 109, 110 are connected to the body of the vehicle 100 at the tip region 101 of the body 102. The blade arrangements 109, 110 may be provided with more or fewer blades, and in some instances more blades (e.g., 7 instead of the 6 shown in
In addition to driving or propelling the vehicle 100, the propeller blades 109, 110 may be used to brake and stop the vehicle 100 or reverse the direction of the vehicle 100. When used for braking of the vehicle, pitch of the blades may be reversed so that the propellers are running as turbines whose electric power is dissipated in a resistor or used to regenerate rechargeable batteries. That is, braking of the vehicle 100 may be accomplished by increasing the pitch of the propeller blades 109, 110 beyond the feathered position. Alternatively, the vehicle could use a “gas brake” wherein one or more plate-like structures are extended to increase the aerodynamic drag on the vehicle, or the vehicle could use an eddy-current brake wherein eddy currents are induced into a metal structure along the rail, or into the rail itself, by one or more electromagnets carried on the vehicle.
Reversal of the vehicle may involve rotation of the blades 109, 110 by 180° around their radial axes, followed by reversal of rotational direction of the propellers 109, 110. Once the vehicle 100 is slowed (braked) by changing the propeller pitch, as described above, the method of reversing vehicle 100 may include rotation of the blades 109, 110 by 180° around their radial axes, followed by reversal of rotational direction of the propellers. This feature allows the vehicle 100 to levitate within the tube 406 and still be able to stop without relying on friction brakes, which can produce significant amounts of heat and suffer wear. However, friction brakes, or an equivalent mechanical form of braking, may be used to hold the vehicle 100 in place on the guideway once it has been braked and stopped by the propellers 109, 110. For instance, the vehicle 100 may use friction brakes, magnets, or the like placed on the levitation system 303 or on the bottom of the vehicle 100, to stop the vehicle 100. Similarly, the vehicle 100 may use a second propeller located at the rear of the vehicle 100, which propeller set is normally configured to provide propulsion supplementing the front propulsion system but may separately be used for braking. In any case, the vehicle 100 may be stopped or put in reverse in any manner.
The motor 1004 drives the propeller arrangement 105. The motor 1004 is powered by a fuel-cell stack 1012. It is possible to use other power sources or supplement the fuel-cell stack 1012 power output. However, in the implementation discussed herein, the fuel-cell stack 1012 synergistically “breathes” the hydrogen 407 (or other gas) within the tube 406 as its fuel source. The motor 1004 may be any device capable of using energy or electricity to drive the propeller 104. For example, the motor can be an alternating-current (AC) motor, a direct current (DC) motor, a hydraulic motor, and the like. In one embodiment, the motor 1004 is an AC induction motor.
When the vehicle operates in a tube filled with hydrogen, to collect hydrogen gas 407 (or other gas) from the tube 406 for use in the fuel cells of the vehicle 100, an intake scoop 1006 is provided on the vehicle 100 near the propeller arrangement 105. The intake scoop 1006 collects hydrogen 407 from the tube 406 and directs it into the fuel-cell stack 1012 in a flow-through manner. To exhaust excess hydrogen from the vehicle 100, an exhaust scoop 1007 is provided, in one embodiment, on the diametrically opposite side of the vehicle 100. The diametric disposition of scoops 1006, 1007 is illustrative and not intended to be limiting, and any angle formed between scoops 1006, 1007 and the vehicle centerline 112 may be used. The exhaust scoop 1007 releases excess hydrogen 407 not consumed by the fuel-cell stack 1012 from the vehicle 100 to the tube 406. Each scoop may be rotated by 180° when the vehicle 100 reverses direction of travel. That is, in order to maintain hydrogen flow in a fixed direction through the fuel-cell stacks, if scoop 1006 is the intake scoop in one direction, it may be rotated by 180° when the vehicle 100 reverses direction, and thereby it will continue to be the intake scoop. It will continue to be the intake scoop because the direction of the hydrogen airstream relative to the vehicle 100 has changed by 180°.
The intake scoop 1006 and the exhaust scoop 1007 are oriented in opposite directions. The intake scoop 1006 faces the front of the advancing vehicle and hence hydrogen 407 is rammed into the scoop and delivered to the fuel-cell stacks. The exhaust scoop 1007 faces toward the rear of the advancing vehicle 100 and hence the relative motion of the vehicle 100 and hydrogen 407 tend to suck the hydrogen flowing through the stacks 1012 into tube 406. The effects of ramming and sucking work together to distribute hydrogen through the fuel-cell system in a passive manner. The intake scoop 1006 and the exhaust scoop 1007 may be constructed out of suitable material for withstanding the high gas pressure of high speeds. The intake scoop 1006 and the exhaust scoop 1007 may be any shape capable of receiving and dispersing hydrogen 407 to and from the tube 406. In some embodiments, the intake 1006 and the exhaust 1007 may be shaped as open rectangular vents. For the combined ramming and sucking effects to work in each direction of vehicle 100 travel, the intake 1006 and the exhaust 1007 are designed to rotate by 180° when the vehicle 100 changes direction from forward to reverse.
A fan 1008 assists the intake 1006 in pulling hydrogen 407 from the tube 406. For example, when the vehicle 100 is not moving or is moving slowly, the intake 1006 may not be able to passively breathe as much hydrogen 407 as is necessary to operate the fuel cells 1012. In these instances, the fan 1008 turns on and pulls hydrogen 407 through the intake 1006 using suction or other means. The fan 1008 is located in a duct system 1010 that channels hydrogen from the intake 1006 to the fuel-cell stack 1012. The fan 1008 may be an axial fan, a squirrel-cage fan, a pump, or the like. In some embodiments, the fan 1008 may only operate when the vehicle 100 is traveling at low speeds or is stopped. In other embodiments, the fan 1008 may operate at all vehicle 100 speeds, such that the hydrogen 407 intake flow through scoop 1006 is maximized or otherwise controlled.
The duct system 1010 transports gas 407 from the intake 1006 to the fuel cells 1012 and from the fuel cells 1012 to the exhaust 1007. The duct system 1010 may involve piping, tubing, or any suitable conduit that transports the hydrogen 407 from within the tube 406, to within the vehicle 100 and then directs the unused or excess hydrogen 407 back into the tube 406. However, the duct system 1010 may be omitted, for instance, the intake 1006 and exhaust 1007 may directly connect to the fuel cells 1012 and to the tube 406 environment, without the additional piping or tubing.
As discussed above with respect to the motor 1004, the fuel-cell stack 1012 supplies power to drive the motor 1004. A fuel cell may use hydrogen and oxygen to generate electricity. The fuel cells in stack 1012 receive hydrogen 407 from the tube 406 via the intake 1006 and receive oxygen from an oxidant storage container 1014 onboard the vehicle. In some embodiments the fuel cells 1012 are an acid-electrolyte proton-exchange membrane type, wherein liquid oxygen provides oxygen (the oxidant) to the fuel cells, and the fuel-cells'"'"' fuel, hydrogen (the reductant or reducer), is breathed from the tube 406. In these embodiments, hydrogen flows through the fuel-cell stacks, in the manner described above by the action of the scoops 1006, 1007, and oxygen is dead-ended. The fuel-cell stack 1012 produces electricity when hydrogen at the anode gives up electrons to an external circuit plus positively charged hydrogen ions that move through an electrolyte (not illustrated) within the fuel cells of stack 1012 and combine with the oxygen to produce water at the cathode. As the oxygen is dead-ended, water is produced at the cathode as a waste product of the electricity production of the fuel cells 1012. This embodiment allows the water produced by the fuel-cell stack 1012 to be stored onboard in a waste storage container 1024, versus being exhausted into the tube 406. Excess hydrogen gas that is not used in the energy conversion process is expelled back into the tube 406 via the exhaust scoop 1007. However, the fuel cells of stack 1012 may be any fuel-cell type that uses hydrogen and oxygen as fuel sources. More generally, the fuel cells may use any gaseous fuel that provides the atmosphere within tube 406, for example, methane. Examples of fuel-cell types are proton-exchange membrane fuel cells, alkaline fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, solid oxide fuel cells, and the like. There may be any number of fuel cells within stack 1012. For instance, to increase the power of the vehicle, more fuel cells may be added to stack 1012, or the size of the fuel-cell electrodes in stack 1012 may be increased, depending on the power requirements of the vehicle 100.
The oxidant storage tank 1014 holds the oxidant required to operate the fuel cells of stack 1012. The oxidant storage tank 1014 may be any type of storage device suitable for storage of a compressed gas, a cryogenic liquid, a chemical oxygen source such as hydrogen peroxide, or the like. In one embodiment, the fuel storage tank 1014 holds liquid oxygen in a vacuum-insulated storage tank; however, the oxidant storage tank 1014 may be used to hold oxygen gas, chemical precursors of oxygen, or other desired oxidant capable of reacting with hydrogen. The fuel cells 1012 combine oxidant from the oxidant storage tank 1014 with the hydrogen 407 collected from the tube 406 via the intake scoop 1006.
A water separator 1016 may separate water from cathodic oxygen and remove traces of water from the hydrogen exit stream through scoop 1007. For instance, in some embodiments, the separator 1016 separates water from cathodic oxygen and runs the separated water to storage tank 1024. The separator 1016 may also function to condense unwanted materials and thereby prevent them from entering the tube 1006. For instance, the separator 1016 may also remove traces of water from the hydrogen exiting the fuel-cell stack 1012. One embodiment of the separator is also used as an evaporator to convert liquid oxygen stored onboard to gaseous oxygen used by the fuel cells; the cold liquid oxygen on one side of a heat-exchange surface causes freezing of the impurities, for example, water, on the other side of the heat-exchange surface.
A set of coolant lines 1030 supply waste heat from the fuel cells and other components to the liquid-oxygen evaporator within separator 1016 and then expel the excess heat to the hydrogen 407 via a liquid-gas heat exchanger 1020. The source of waste heat is primarily from the fuel cells, the propulsion motor(s), and the power electronics.
A heat exchanger 1020 is connected to the coolant lines 1030 and may be used to reject excess heat from the fuel cells, the propulsion motor(s), and the power electronics to the hydrogen atmosphere in the tube 406. Because of the high thermal conductivity of hydrogen (seven times greater than air), the heat exchanger in one embodiment is simply a thin shell on the outside of the body 102. In contrast, liquid-air heat exchangers, for example, the radiator of an automobile, require a greater surface area than this embodiment because of the seven-fold lower thermal conductivity of air versus hydrogen.
The power electronics subsystem 1022 changes and controls the voltage of the DC output from the fuel cells 1012 to the voltage, DC or AC, as required by the propulsion motor 1004, vehicle communications systems, vehicle control systems, passenger-car HVAC and lighting systems, and all other electrical components on the vehicle 100.
Waste water produced from the reaction of hydrogen and oxygen within the fuel cells is directed towards a water storage container 1024. The water storage container 1024 is connected to the separator 1016. The waste storage container 1024 may be constructed out of any type of material suitable to store water, for instance, plastic, metal, or the like. Waste water storage, in one embodiment, is provided by a horizontally oriented cylinder and may have a volume of about 1500 liters. However, depending on the desired trip length of the vehicle 100, the size of the vehicle 100, the type of fuel cells used, etc., the waste storage container 1024 may be designed to hold more or less volume.
The levitation system 303 according to the embodiment shown in
A coupler 1026 is used to connect multiple vehicles together, as well as connect the vehicle 100 to passenger or cargo cars. For instance, as illustrated in
The segments 1102-1105 include four segments for each bearing surface, but any number of segments may be used. The segments 1102-1105 are included both on vehicles acting as locomotives, as well as passenger and cargo cars. Referring now to
Referring still to
The vehicle 100 may also include ailerons 111 toward the middle of the vehicle that function to balance the vehicle when the vehicle is operated above a certain minimum speed (Vmin). As shown in more detail in
The vehicle 100 may further include a landing gear assembly 1206 that allows for the vehicle to take off and to stop and to be held upright when the speed of the vehicle falls below a minimum speed (Vmin) or when the vehicle is at rest. The vehicle includes longitudinally arranged wheels that may not balance the vehicle at slow speeds or at rest; therefore the vehicle includes landing gear to allow the vehicle to reach the proper speed for the ailerons to balance the vehicle, after which the landing gear may be retracted. In particular, the landing gear is designed to grasp two faces of the rail to steady the vehicle. As shown in more detail in
Although one or more of the embodiments disclosed herein may be described in detail with reference to a particular vehicle, the embodiments should not be interpreted or otherwise used as limiting the scope of the disclosure, including the claims. In addition, one skilled in the art will understand that the following description has broad application. For example, while embodiments disclosed herein may focus on certain vehicles, such as a propeller-driven vehicle, it should be appreciated that the concepts disclosed herein equally apply to other transportation methods. For example, the concepts disclosed herein may be employed in automobiles, trains, and aircraft. In addition, it should be appreciated that the concepts disclosed herein may equally apply to non-transportation related items, such as manufacturing and scientific laboratory apparatus. Furthermore, while embodiments disclosed herein may focus on a gas-filled operating atmosphere, the concepts disclosed herein equally apply to other operating atmospheres, such as air. Accordingly, the discussion of any embodiment is meant only to be exemplary and is not intended to suggest that the scope of the disclosure, including the claims, is limited to these embodiments.