U.S. patent application number 12/586187 was filed with the patent office on 2010-07-01 for device for the efficient conversion of compressed gas energy to mechanical energy or thrust.
Invention is credited to Henry M. Gerard.
Application Number | 20100162681 12/586187 |
Document ID | / |
Family ID | 36600383 |
Filed Date | 2010-07-01 |
United States Patent
Application |
20100162681 |
Kind Code |
A1 |
Gerard; Henry M. |
July 1, 2010 |
Device for the efficient conversion of compressed gas energy to
mechanical energy or thrust
Abstract
A mechanical device efficiently converts energy stored in a
highly compressed gas, such as air in a pipeline or SCUBA tank, to
mechanical energy, such as might be used to drive an electrical
generator or to propel a water craft.
Inventors: |
Gerard; Henry M.;
(Capistrano Beach, CA) |
Correspondence
Address: |
LEONARD TACHNER, A PROFESSIONAL LAW;CORPORATION
17961 SKY PARK CIRCLE, SUITE 38-E
IRVINE
CA
92614
US
|
Family ID: |
36600383 |
Appl. No.: |
12/586187 |
Filed: |
September 18, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11215983 |
Aug 31, 2005 |
7066890 |
|
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12586187 |
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61192645 |
Sep 20, 2008 |
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Current U.S.
Class: |
60/221 ;
60/407 |
Current CPC
Class: |
A61B 5/6897 20130101;
A61B 5/02241 20130101 |
Class at
Publication: |
60/221 ;
60/407 |
International
Class: |
B63H 11/02 20060101
B63H011/02 |
Claims
1. Apparatus for converting energy from a compressed gas into
propulsion of a non-compressible fluid; the apparatus comprising: a
housing having a first flow path in which said compressed gas is
introduced and a second flow path in which said non-compressible
fluid is introduced, said first and second flow paths being
isolated from one another; at least one rotatable member having
blades in said first flow path and having fluid propulsion units in
said second flow path, interaction between said blades and said
compressed gas causing said member to rotate and causing said
propulsion units to rotate and impart propulsion to said
non-compressible fluid.
2. The apparatus recited in claim 1 wherein said compressed gas and
said non-compressible fluid flow in opposed directions.
3. The apparatus recited in claim 1 comprising at least two of said
rotatable members.
4. The apparatus recited in claim 3 wherein said at least two
rotatable members rotate concurrently in opposite directions.
5. The apparatus recited in claim 1 wherein said compressed gas is
air and said non-compressible fluid is water.
6. Apparatus for converting energy from a compressed gas into
electrical energy; the apparatus comprising: a housing having a
flow path in which said compressed gas is introduced; at least one
turbine having blades in said flow path for rotating said turbine;
said turbine having an electrical generator responsive to rotation
of said turbine for producing electrical energy.
7. The apparatus recited in claim 6 comprising at least two of said
turbines.
8. The apparatus recited in claim 7 wherein said at least two
turbines rotate concurrently in opposite directions.
9. The apparatus recited in claim 8 wherein each of said at least
two turbines having oppositely oriented blades.
10. The apparatus recited in claim 6 wherein said compressed gas is
air.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application takes priority from U.S. Provisional
Application Ser. No. 61/192,645 filed Sep. 20, 2008.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to the field of energy
conversion and specifically to the use of compressed gas (e.g.,
air) to transmit energy to a non-compressible fluid (e.g., water),
or to an electrical generator.
[0004] 2. Background Art
[0005] The use of gas compression is a known method for storing
energy as in, for example, the application to air-brake systems.
This mode of energy storage has at least two important advantages
over other mechanical modes, e.g., using springs or flywheels;
namely: [0006] 1. The compressed gas stored energy system is
relatively safe because the accidental release of the stored energy
is less likely to cause harm by hurling a massive, mechanical
projectile. [0007] 2. The compressed gas storage system is
comparatively lightweight and inexpensive because, being hydraulic;
it is relatively easy to manipulate forces.
[0008] While it is quite easy to store energy compactly by
compressing a gas, it is relatively difficult to efficiently
recover this stored energy to perform useful work. This difficulty
arises from the same aspect that makes compressed gas safe for
energy storage; namely, that while high gas velocities may readily
occur accidentally, as through a leak, there is a relatively
insignificant amount of mass in the high velocity gas, itself, with
which to do work, or damage.
[0009] This invention utilizes well-known gas turbine techniques
with fluid propulsion techniques to efficiently extract energy from
the high pressure gas and transfer it to the fluid. This is of
major significance because the configuration facilitates the
gradual, controlled extraction of the compressed gas energy in
sequential stages. Furthermore, it also facilitates the gradual,
controlled transmission of this energy to a non-compressible fluid,
or to integral electrical generators. The stored energy is,
thereby, rendered readily available to perform useful mechanical
work.
[0010] Unlike gas, the non-compressible fluid has significant mass.
Consequently, by being transferred to the fluid, the (potential)
energy stored in the compressed gas becomes more easily used to
perform further mechanical work, such as driving the rotating
shafts of electrical generators or to propel a vehicle.
Historical Background:
[0011] Roughly 20 years ago, the inventor herein was asked to
develop a practical means of powering a small recreational
watercraft, such as a surfboard. Because the product drivers for
this application include low cost, simplicity, durability and
effective propulsion, this problem proved quite formidable.
Solutions based on mechanical energy storage or employing
reciprocating pistons proved impractical because they typically
involve valves, (often) electronics and frequently the consumption
of fuel. All of these factors pointed toward an inappropriate level
of weight, complexity, cost and risk. For example, the mechanical
storage of sufficient energy to propel the mass of a person on a
surfboard would require a massive spring or flywheel that would be
large, heavy, expensive and, most troubling of all, unrealistically
dangerous for a toy. Storing and extracting the fuel to energize
such a mechanical apparatus also seemed rather impractical and
risky for a compact mobile lightweight sea-going platform,
particularly one destined for use in the random and forceful
environment of breaking waves!
[0012] After the mechanical approach was rejected, several years
passed before the inventor noticed a neighborhood boy playing with
a toy rocket powered by compressed air. The body of the rocket was
an inverted plastic pop bottle which was partially filled with
water. Air was pumped in through a hole in the cork stopper, which
bubbled up through the water and was trapped and compressed in the
bottle. At the appointed time, the cork was pulled, allowing the
compressed air to push water downward from the now open bottle. In
reaction to the expulsion of the water, the bottle shot high into
the air until all the water was expelled. This was a remarkable
example of compressed air energy being transferred to water to
produce safe, simple, inexpensive and significant kinetic energy.
It was also quite clear that without the use of water, the
compressed air energy could barely lift the rocket from the
ground!
[0013] The combination of compressed air and water made a
sufficiently impressive demonstration to motivate the application
of the configuration to the surfboard-propulsion problem. In
running the applicable equations, however, it quickly became clear
that this approach was not effective because it required
transporting too much water (in addition to the weight of a
passenger) for compressed air to accelerate. Too much energy was
simply wasted in accelerating the water before it was "pumped" out
to drive the vehicle; there was insufficient energy to move the
passenger fast enough or far enough. Clearly, a better method was
needed which utilized water for producing thrust, but did not
require carrying and accelerating the water!
[0014] Recently, it became clear that the compressed gas could be
made to drive water that was not onboard only if the water and
compressed gas were confined to separate chambers. In this
configuration, compressed, low mass gas could readily be carried
on-board as the energy storage medium, while the necessary, more
massive water, could be readily acquired from and expelled to the
environment, as needed.
SUMMARY OF THE INVENTION
[0015] This invention utilizes few moving parts, no inputs of
electricity and does not require chemical fuel. Though the design
optimization of the turbine and impeller blades is technically
challenging, both technologies are understood. However, the novel
combination of these in the sequential turbine/impeller sections is
a key attribute of this invention. The configuration is rugged in
construction and the manufacturing is relatively simple and
inexpensive. Because this invention may be constructed entirely
from non-metallic materials, the characteristics of the material(s)
from which the component parts are fabricated are also a critical
element of the invention. For the use as a propulsion engine, the
configuration of the underwater housing is also a key
attribute.
[0016] In researching issued U.S. patents for fluid propulsion
systems that employ energy from turbines as a source, several
disclosures were found in which hot gas turbine exhaust was the
source of energy that created pressure in the fluid. This invention
differs in principle from those. This invention does not involve
mixing (or contact) between the high-pressure gas and the
non-compressible fluid.
[0017] In the preferred embodiment hereof, the high-pressure gas is
controlled by a pressure regulator and used to drive blades of a
turbine, causing a rotation which then drives attached impeller
blades that are integral to the turbine section.
[0018] The high-pressure gas and the non-compressible fluid are
confined to separate chambers.
[0019] The impeller blades are driven by the rotation of the
turbines and thereby transmit energy to a non-compressible fluid,
such as water, thereby increasing the fluid pressure along the
axial direction toward the fluid jet outlet.
[0020] This invention includes the use of several turbine/impeller
sections in sequence, (as well as only a single section, if
desired) that are directly coupled by gas and fluid flows so as to
enable efficient energy extraction from the compressed gas to the
fluid. As the gas pressure drops after transferring energy to one
turbine section (and thereby, coupling some energy to the pumped
fluid) the lower pressure gas out-flow then drives the subsequent
turbine/impeller section (and thereby, contributing more energy to
further increase fluid pressure).
[0021] Through the action of one or more turbine/impeller sections,
energy extracted from the high pressure gas flow produces a jet of
high pressure fluid that is ejected at the fluid outlet to produce
thrust or to drive another energy-consuming machine, e.g., an
impact turbine, positioned at the high pressure fluid output.
[0022] A principal feature of this invention is that the mass of
the ejected fluid is far greater than the mass of the compressed
gas that stores the energy. Thus, the resulting thrusting force is
correspondingly far greater than if the compressed gas is directly
ejected to generate a reactive thrust.
[0023] A second important feature of this invention is that it
contains multiple turbine/impeller sections thereby permitting
concurrent extraction of energy at different compressed gas
pressures.
[0024] A third important feature of this invention is that the
turbine/impeller sections are configured to permit independent
rotation of the sections; thereby allowing the sections to have
different rotational velocities. This facilitates the design
optimization of each section (and all sections) so as to extract
maximum energy from the gas and couple it to the fluid, thus
maximizing the conversion efficiency.
[0025] A fourth important feature of this invention is that the
principles of operation remain unchanged if combustion of fuel is
utilized as a source of the high-pressure gas, so as to increase
the "on-board" energy beyond the constraints of passive compressed
gas.
[0026] In summary, high-pressure gas is caused to flow past a
series of optimally designed turbine sections causing these
sections to rotate. This rotation causes the rotation of optimally
designed impellers that are integral to each section, which, like
pump stages, increase the pressure of the non-compressible fluid
stream flowing through them. The overall effect is that
"environmentally clean" low pressure (spent) gas is expelled to the
atmosphere, while a high pressure fluid jet, carrying the energy
extracted from the gas is ejected for propulsion, or supplies
mechanical energy, in a more useful and practical form, for other
work-performing purposes.
[0027] One application for this invention is in enabling the use of
a low-cost, environmentally safe readily renewable, relatively
physically small-sized and lightweight energy source (e.g., high
pressure gas) to propel a craft through a relatively dense fluid,
such as water.
[0028] Another application is as a novel and efficient means for
the transfer of energy stored in a compressed gas to a denser
medium, whereby the energy becomes more practically available to
perform work.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The aforementioned objects and advantages of the present
invention, as well as additional objects and advantages thereof,
will be more fully understood herein after as a result of a
detailed description of a preferred embodiment when taken in
conjunction with the following drawings in which:
[0030] FIG. 1A illustrates a configuration of this invention, which
is intended for the production of thrust, and identifies the
principal elements;
[0031] FIG. 1B illustrates a configuration of this invention, which
is intended for the production of electricity, and identifies the
principal elements;
[0032] FIG. 2 shows the Gas Expansion Cavity which must be
analytically designed to result in optimum energy conversion
efficiency;
[0033] FIG. 3, comprising FIGS. 3A and 3B, illustrates a preferred
implementation of the mechanism by which rotational energy of a
turbine/impeller section is converted to increase pressure of the
non-compressible fluid; and
[0034] FIG. 4 shows one technique, namely reversing blade curvature
for adjacent turbines that may be employed to preserve laminar
(i.e., non-turbulent) flow in the gas region.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0035] FIGS. 1A and 1B illustrate the configuration of this
invention and identify principal elements.
[0036] FIG. 1A shows a housing 10 with two cylindrical chambers 14
and 18 through which pressure regulated (throttled) compressed gas
flows from a High Pressure Inlet 16, through a gas distribution
manifold in the outer chamber 18, to a Low Pressure Outlet 20; and
non-compressible fluid (that provides the thrust) flows from a Low
Pressure Inlet 22 through the inner chamber 14 to the fluid output
24. Subsequently, the housing design was modified to its current
configuration which is streamlined. In this configuration, the
rotating element is called the Turbine/Impeller Section.
[0037] FIG. 1B also shows a housing 30 with two cylindrical
chambers 34 and 38 through which pressure regulated (throttled)
compressed gas flows from a High Pressure Inlet 36, through a gas
distribution manifold in the outer chamber 38, to a Low Pressure
Outlet 40. Here, however, the inner chamber 34 houses electrical
generators 35, one per turbine section, that are driven by the
rotating turbines. No non-compressible fluid is involved; instead,
the electrical power produced by each generator is fed by cables 42
to an electrical power-combining network 44. In this configuration,
the rotating element is called the Turbine/Generator Section.
Turbine/Impeller Section (External Surface) (FIG. 1a):
[0038] Within the chamber 14, two turbine/impeller sections are
shown which are representative of a series of such sections. The
outer surface of the toroidal section contains turbine blades 25
that are shaped to efficiently extract energy from the gas stream
using conventional aerodynamic principles, such as those commonly
used to design an airplane wing or a boat sail. Critical elements
of this design include "angle of attack" and radius of curvature;
and it is well-known that high-energy extraction, or "lift", is
achieved in a high-velocity stream, when the angle of attack and
curvature are relatively small. Similarly, for low velocity
streams, greater angle of attack and curvature provides for better
energy coupling. Thus, it is desirable for improved energy
extraction as the gas pressure drops along the direction of gas
flow owing to the extraction of energy by the preceding sections,
to modify the blade shape for each section. It is worth noting that
the force on the (Reaction-Type) turbine blade, as illustrated, is
produced as a reaction (per Newton's Third Law) to the streamline
gas flow over the curved turbine blades. With respect to pumping
the fluid, where a second turbine is working with a flow of more
massive molecules such as water or pressurized steam, alternative
(Impulse-Type) turbine blade designs (whereby the force may be
produced by the direct impact of the fluid stream against the blade
surface, per Newton's Second Law) may transfer energy more
efficiently. Depending on the intended use, either a propeller
(which is a Reaction-Type turbine) or an impeller (which is an
Impact-Type turbine) method, or a combination of both, may be used
for optimization of the turbine blade design for increasing the
pressure of the fluid stream. Thus impellers may be used in this
invention to pump the non-compressible fluid through turbine
action, while propeller type turbine blades are preferable for
extracting energy from the compressed gas.
[0039] Turbine/Generator Section (external surface): The outer
surface of the Turbine/Generator Section of FIG. 1B is the same as
that described, above, for the Turbine/Impeller Section of FIG.
1A.
Gas Expansion Cavity:
[0040] FIG. 2 shows the Gas Expansion Cavity which must be
analytically designed to result in optimum energy conversion
efficiency. In general, the geometry of the Gas Expansion Cavity is
related to the details of desired working pressure range and the
configuration and dynamics of the turbine blades and impellers. Two
basic principles guide the design; namely
[0041] 1. The need to conserve mass and non-turbulent flow, as the
gas interacts with the turbine blades; and
[0042] 2. The compressed gas and non-compressible fluid both
interact efficiently with the turbine blades and the impellers, as
they flow through their respective cavities, as illustrated, inside
the Housing.
[0043] While the compressed gas tank pressure may be well over 200
atm, the gas flowing into the gas expansion chamber may be
regulated by means of a pressure regulator (not shown) to limit the
working pressure to a lesser range. For purposes of discussion, we
consider the case of a design for operation over a pressure range
of 20:1; i.e., the regulator might be set for about 20 atm so that
when fully-expanded, the gas would have about 1 atm pressure and,
in principle, have little energy remaining for further extraction,
before the gas was vented to the atmosphere. The regulated
compressed gas experiences a pressure-drop as it couples
(interacts) with the High Pressure Turbine Blades (see the FIG. 2
illustration). The pressure reduction is a manifestation of the
energy extracted, and coupled to the non-compressible fluid by the
rotating turbine/impeller section. Having lowered pressure, the
compressed gas exiting from the first section must flow into a
greater volume of cavity (shown by increased cross-sectional area),
to ensure conservation of mass-flow of the gas. The amount of the
volume increase is related to the aerodynamics of the blades and
the loading corresponding to the impeller action. Similar
considerations apply as the compressed gas interacts with
subsequent turbine/impeller sections while flowing toward the final
section of low pressure (see FIG. 2). Because the compressed gas is
transformed from high pressure to low, the gas expansion cavity is
shown to increase in cross-sectional area along the direction of
gas flow, and the turbine blades are shown to increase in blade
area in this direction. With sequentially diminishing gas pressure,
the progressive increase in blade area works to improve the energy
extraction efficiency of the lower pressure sections. Well-known,
but relatively complex aerodynamic formulas can be employed to
determine the effect of each turbine section upon the gas flow, and
to ensure that gas pressure and energy remains at appropriate
levels (described by the well-known Bernoulli's equation) to ensure
laminar flow through the gas expansion cavity. In principle, the
force on the turbine blades decreases with gas stream velocity,
which itself, decreases as gas pressure drops. Therefore, there is
usually a point of diminishing returns, beyond which it is not
practical to employ additional turbine/impeller sections. Based on
this consideration and that of the hydrostatic pressure at the
Housing surface, the "spent" compressed gas may well be at some
pressure above or below atmospheric when vented (thereby, possibly
sacrificing or saving some energy conversion efficiency).
Turbine/Impeller Section (Internal Surface):
[0044] The interior of each turbine/impeller section contains
impellers that are driven by the rotation of the section. As is the
case for turbine design, the impeller design should be optimized
using conventional hydrodynamic techniques to maximize the
efficiency of converting the rotational energy to pressure of the
non-compressible fluid flowing along the axis of the section. The
objective of this transfer of energy to the fluid is to increase
the pressure of the fluid as it passes through the section by the
process of "pumping". In broad generality, a propeller may be used
to replace the impeller. In such case, the design optimization of
turbine blade and propeller are similar in that angle of attack and
curvature are optimization parameters that change as pressures and
velocities vary along the axial direction of the invention.
[0045] It is possible that interchanging the outer (gas) and inner
(non-compressible fluid) chambers may offer an advantage in
optimizing for efficient energy conversion and/or economical
manufacturing. Indeed, it is also possible that improvements may be
achieved, from an increase in complexity, by utilizing more than
one chamber for gas and/or non-compressible fluid flow. These
alternatives are within the scope of this disclosure.
Fluid Impeller Pumping:
[0046] FIG. 3, comprising FIGS. 3A and 3B illustrates a preferred
implementation of the mechanism by which rotational energy of a
turbine/impeller section is converted to increased pressure of the
non-compressible fluid. Other means for such conversion of
rotational energy include the use of propellers, such as are
commonly used to power watercraft, instead of impellers. As
mentioned earlier, the impeller implementation being an impact
class of turbine may be superior to the propeller, a reactive
class, because of the sensitivity of efficiency of the latter to
preservation of laminar flow. Thus, it may be possible to readily
achieve higher conversion efficiency using the impeller than with
the propeller.
[0047] FIG. 3A illustrates a representative turbine/impeller
section 50, shown in both isometric (FIG. 3A) and cross-sectional
views (FIG. 3B). Also shown in both views are representative
turbine blades. Support/bearings 53, are structures that provide
support for the turbine/impeller sections. These hold the sections
in place with respect to the housing 10 and allow them to rotate
independently with low friction and prevent mixing (leaking)
between the gas and fluid streams. The cross-sectional view (FIG.
3B) illustrates the fluid path from the Fluid Inlet, through the
input orifices 55 and into the impeller chambers 54. Centrifugal
force in the rotating section forces the fluid outward toward the
exit orifices of the impeller chambers 56; through the space
between sectors and into the input orifices of the subsequent
impellers. The rotating impellers pump the fluid from the Fluid
Input to the Fluid Output Jet, sequentially increasing fluid
pressure in each rotating section.
Structural Support:
[0048] The turbine/impeller sections are typically held in place
while permitting their free rotation by means of support rings 53
in FIG. 3B. The cylindrical section of the ring is fitted into
circular slots in the two adjacent turbine/impeller sections with
sufficient clearances to permit axial rotation with minimal
frictional loss, but not excessive clearances that may cause
leakage. The cylindrical supporting rings are held in place by
their connection to the internal surface of the outer chamber of
the housing.
Other Hydrodynamic Considerations for Achieving Efficient Energy
Transfers:
[0049] A fundamental principle which guides the design of all
elements of this invention, including the gas and fluid chambers,
the multiple turbine/impeller sections and the supported
cylindrical rings, is the need to preserve non-turbulent flow in
the compressed gas and in the non-compressible fluid. If either
flow is permitted to become turbulent, the ability of the gas to
transfer energy to the turbine blades and/or the ability of the
impellers to increase the fluid pressure is reduced! The
illustration in FIG. 4, shows one technique, namely reversing blade
curvature for adjacent Reaction-Type turbines, that may be employed
to preserve laminar (i.e., non-turbulent) flows.
Preserving Streamlined (Laminar) Flow:
[0050] In the example shown in the FIG. 4, the direction of angle
of attack and curvature of the turbine blades is reversed for
adjacent turbine/impeller sections. This change causes the
direction of rotation to alternate for the adjacent sections, and
may necessitate corresponding changes in the impeller configuration
so that the efficiency of fluid pressure increase is maintained for
each section. The alternating of turbine blade curvatures is used
to compensate for the changes in gas stream direction caused by
action of the up-stream turbine blades, and serves to bend the gas
stream back toward the axis of the assembly.
[0051] A second aspect of the illustrated configuration that is
intended to comply with aero- and hydrodynamic flow constraints is
the selective placement of the high speed and the high torque
turbine/impeller sections. The larger turbine blades are positioned
to drive the impellers of the lower pressure region of fluid flow.
Thus, the pressure in the non-compressible fluid increases as it
moves toward the smaller sections. In this manner, the opening of
the compressed gas pressure regulator valve (not shown) acting as a
throttle, causes low velocity gas to flow past the "up-stream"
turbine blades, that could be designed to best couple only to high
velocity flow. There, the angle of attack and blade curvature is
relatively flat so as not to cause turbulence in the low velocity
gas as it bypasses blades and flows on toward the blades of the
lower pressure sections that are designed to match the aerodynamics
for lower velocity gas flow. Similarly, the impellers that are
"upstream" (with respect to the gas flow) are designed to
efficiently pump the relatively low-pressure fluid arriving from
the lower gas velocity sections. As gas pressure is throttled up,
the blades of the high pressure sections start to couple more
efficiently and, by action of their impellers, begin to produce
increased pressure all along the fluid stream. At full throttle,
all turbine/impeller sections are efficiently driven because of
progressive energy extraction from the gas flow, which
progressively reduces gas velocity to match the design ranges of
"down-stream" turbine blades, and maximum fluid pressure is
achieved in the sequence of impeller pumps.
[0052] Other elements (not shown) can be included to maintain
laminar flow in the gas and, if needed, in the fluid streams. These
include non-rotating vanes, called "stators", which are positioned
between the rotating turbine/impeller sections. The stators help to
deflect the gas and fluid flows back toward the axis of the
channels, and thereby inhibit turbulent flow.
[0053] Also not shown, is the ability to vary the width and
impeller length along the non-compressible fluid chamber (i.e.,
cavity cross-section), as an additional design variable that can be
used in the optimized embodiment to adjust gas flow velocity and
fluid pressure at each turbine/impeller section.
Turbine/Generator Section (Internal Surface):
[0054] The exterior of the section contains turbine blades that are
identical to those in the Turbine/Impeller configuration, but the
interior employs a conventional electrical generator instead of the
Impeller used in the alternative configuration. The generators
provide loading on the rotating turbine sections in the same manner
as described for the Impellers. The design optimization
requirements for the turbine blades are analogous to those
described for the Turbine/Impeller configuration.
[0055] Because the individual sections rotate independently, the
use of Direct Current (DC) generators may be advantageous compared
to Alternating Current (AC) generators as DC provides the
simplification of eliminating the need for phase and frequency
matching in the Electrical Power-Combining Network.
Electrical Power-Combining Network:
[0056] The electrical power-combining network uses conventional
circuit design techniques to conduct and combine the electrical
power, generated by the individual rotating Turbine/Generator
sections, to a common output for delivery to the user.
Applications:
1. Recreational Propulsion (Turbine/Impeller Configuration):
[0057] a) Powered Surfboard: This invention, (along with compressed
air storage tanks), may be integrated into the design of a
surfboard, or smaller "Boogie" board. The rider controls the speed
of the board through the water by adjusting the (regulated) air
pressure at the `High Pressure Inlet`. The benefits of this
compressed air powered propulsion include aiding the recreational
user in effortlessly moving further and more quickly through the
water. The limitations of paddling, the need for fins and even for
beginning the ride from a prone position, are eliminated.
[0058] b) SCUBA Propulsion: This invention may be integrated into
the design of a harness which permits the diver to route a portion
of the `on-board` compressed air supply for use in underwater, or
surface, propulsion. This, for example, might enhance the
underwater dive experience and also provide a useful aid for
returning to the beach, or dive boat, at the end of a dive.
[0059] c) Small Craft Propulsion: The invention may be fitted to a
small boat or float-craft, along with an (electrical) solar cell,
an (electrical) air compressor, and a storage tank for the
compressed air. After several hours of floating off-shore, the
solar cell, driving the air compressor, builds up a charge of
compressed air in the storage tank. This collected energy is then
fed into this invention and used to propel the craft back to shore.
Such an assembly would be particularly useful in remote locations,
or other places where the management of combustible fuel is
problematical.
2. Energy Retrieval Form Compressed Air Energy Storage (CAES) in
Solar Energy System (Turbine/Generator Configuration):
[0060] There is a concept for storing solar energy for use during
the night by compressing it into vast underground caverns. Recovery
is implemented, by the use of a pair of turbines; paralleling the
configuration disclosed herein, in that the sequential turbines are
built for "High Pressure" and "Low Pressure, respectively. It is
worth noting that there is "pre-heating" of the compressed gas
prior to injection into the turbines. The present invention
eliminates this wasteful use of energy by requiring that the
turbine blades, themselves, be designed to couple (match) the
pre-existing pressure of the compressed gas. The Turbine/Impeller
Configuration of this invention is a critical component for
enabling the wide-spread adoption of Solar Energy as a replacement
for power generation from fuels that are in dwindling supply, which
also produce the undesired by-products of Greenhouse gases.
3. Spark-less Propulsion (Turbine/Impeller Configuration):
[0061] a) Explosion-Sensitive Marine Environments: Similar to SCUBA
Propulsion application, described above.
[0062] b) Submarine Stealth Drive: Through the use of compressed
air as an energy source, combined with a non-metallic
implementation of this invention, The present `non-reciprocating`
form of engine, driving an internally-powered jet of (propulsion)
water, could provide a quiet `Stealth-Drive` for a submerged
vehicle.
[0063] c) Light Weight, Low Cost Torpedo Drive: Similar to `Stealth
Drive`, described above.
Sample Stored Energy Calculation:
[0064] Two important questions bearing on the effectiveness of this
invention as a means of marine propulsion using a compressed air
tank as the source of stored energy are:
[0065] 1. How much energy can safely stored in a practical-sized
tank?
[0066] 2. How much transport can this energy provide?
Calculation of Stored Energy:
[0067] We will use a modern High Pressure SCUBA tank as the
reference for the safe storage of compressed air. This tank is
certified for storing 107 cubic feet (volume at 1.0 atmosphere
pressure) at a pressure of 3442 psi (234.2 atmospheres). This tank
has a volume of 0.457 cubic feet. (Recent H.sub.2 powered vehicle
technology has increased max. pressure limit by about
3.times..)
[0068] Fundamental Equation for Stored Energy: The energy in a
closed system is calculated as the sum of differential amounts of
energy, dU, where,
dU=.delta.q-.delta.W
Where, .delta.q is the infinitesimal amount of heat added to the
system and SW is the infinitesimal amount of work done by the
system.
[0069] Converting to Extensive Variables: The symbol, ".delta.",
denotes an intensive variable; that depends on the detailed
properties of the system. The symbol, "d", denotes an extensive
variable; one that depends on the overall state of the system. For
a reversible process,
.delta.q=TdS
Where, T is the system temperature (Kelvins), and S is the entropy.
dU can be written in terms of extensive variables as,
dU=TdS-PdV
Where P is the pressure and V is the volume.
[0070] To solve for the total energy added to a tank by compressed
gas, we will assume that heat flow into or out of the tank accounts
for a negligible amount of energy. This adiabatic assumption
means,
.delta.q=TdS=0;
Leaving,
dU=-PdV.
[0071] Equation for Total Energy: The total energy change in terms
of work done by the system is calculated by integrating the
differential, dU, contributions from the start, to the end of the
process. The total energy change is thus,
.DELTA.U=-.intg.PdV. Equation 1
[0072] Pressure-Volume Equation for an Ideal Gas: To a close
approximation, most gasses follow a pressure, volume, temperature
equation (the Ideal Gas Law) given by,
PV=nRT. Equation 2
[0073] Here, n is the number of moles of gas and R is a universal
gas constant.
Inserting Equation 2 into Equation 1 leads to,
.DELTA.U=-nRT.intg.(dV/V);
[0074] This integrates to,
U.sub.f-U.sub.i=nRT.sub.vi.intg..sup.vf(dV/V)=nRT ln(Vf/Vi),
or
U.sub.f-U.sub.i=-nRT ln(Vi/Vf). Equation 3
U.sub.i and U.sub.f are the initial and final energies,
respectively.
[0075] Evaluation of Work Done by the System: We can now calculate
the work done by the system when 107 cubic feet of gas is
compressed into the 0.457 cubic foot tank. This is the negative of
the work done on the system in this compression process; and (by
the conservation of energy), this is equal to the amount of energy
that can be delivered from the compressed gas tank when the ejected
gas returns to the state of P=1 atmosphere and V=107 cubic feet.
From Equation 3 we find that the work done by the system (during
compression) is,
U.sub.f-U.sub.i=-nRT ln(107/0.457).
[0076] Substituting from Equation 2 leads to:
U.sub.f-U.sub.i=-PV ln(107/0.457),
[0077] Which we can evaluate using P and V as the initial pressure
and volume of the uncompressed gas; namely, 1 atmosphere and 107
cubic feet, respectively; leading to,
U.sub.f-U.sub.i=-107 ln(107/0.457)cubic foot atmospheres.
[0078] By transforming to metric units we get,
U.sub.f-U.sub.i=-107.times.28.3 ln(107/0.457)liter atmospheres.
In still more familiar units of energy we find that the work done
by the system is,
U.sub.f-U.sub.i=-107.times.28.3.times.74.7 ln(107/0.457)foot
pounds. Equation 4
[0079] Total Stored Energy: Finally, we evaluate Equation 4 to
calculate the available energy, U.sub.a, that can be delivered from
the compressed gas tank to perform work; namely,
U.sub.a=-(U.sub.f-U.sub.i)=1,244,095 ft pounds.
[0080] To get a better feel for this amount of energy, we can
convert to still other units; namely,
U.sub.a=0.628 horsepower hour;
[0081] Or, U.sub.a is the total amount of energy that can be
supplied by the combustion of 1.5 fluid ounces of gasoline!
[0082] Estimation of Maximum Range of Marine Craft: In the ideal
case where we ignore the actual energy conversion loss in this
invention (which is, as yet, unknown) and the energy loss to drag,
or friction with the water (also unknown), we can estimate the
maximum range, d.sub.max, by hypothesizing that the invention is
used to deliver, for example, 20 pounds of thrust, f.sub.t. This is
perhaps approximately what a passenger could deliver by using swim
fins for propulsion. For this example, the range, given by,
U.sub.a=f.sub.t.times.d.sub.max, and
d.sub.max=Ua/f.sub.t
[0083] For f.sub.t=20 pounds, d.sub.max=62,205 feet or 11.8
miles!
[0084] Conclusion: While ignoring the actual energy conversion
efficiency that this invention can achieve, as well as drag force
(that varies with design of he craft), the potential achievable
range at 20 pounds thrust is sufficient to strongly suggest that
this invention can be an effective source of propulsion for a small
watercraft (e.g., a surfboard), or a SCUBA diver returning to his
boat.
[0085] In both the propulsion and generator applications, it is
desirable to maximize the conversion of energy taken from the
compressed gas. For a practical turbine design, this implies: (1)
that the gas temperature is not changed in the energy extraction
process; and (2) that the system is designed for minimal stream
velocity of the exhausted gas.
[0086] Having thus disclosed embodiments of the present invention
in the form of a propulsion device and in the form of an electrical
generator for use with compressed air or other gases, it will now
be evident that the invention has a number of novel aspects that
provide useful and advantageous results. Therefore, such aspects
are recited in the following claims and may be protected by the
scope thereof which may exceed the limited examples of the provided
description.
* * * * *