U.S. patent application number 10/421813 was filed with the patent office on 2004-10-28 for low cost heat engine which may be powered by heat from a phase change thermal storage material.
Invention is credited to Gould, Len Charles.
Application Number | 20040211182 10/421813 |
Document ID | / |
Family ID | 33298748 |
Filed Date | 2004-10-28 |
United States Patent
Application |
20040211182 |
Kind Code |
A1 |
Gould, Len Charles |
October 28, 2004 |
Low cost heat engine which may be powered by heat from a phase
change thermal storage material
Abstract
This invention is an engine where the working fluid may be in
either a closed circuit or an open circuit. The engine may be
powered by heat stored in an easily rechargeable high temperature
phase change system or by heat of combustion directly. Also
disclosed is a portable device incorporating the engine optionally
as a) an electrical generator b) a source of refrigeration in
remote environments c) a source of rotating mechanical power in
remote environments. Also disclosed is a stationary device
incorporating the engine and phase change thermal storage system as
a co-generating heating and refrigeration system for widespread
application. Also disclosed is a vehicle catalytic converter
pre-heater incorporating a phase change thermal storage system and
engine.
Inventors: |
Gould, Len Charles;
(Brampton, CA) |
Correspondence
Address: |
Mr. Leon C. Gould
43 Copeland Road
Brampton
ON
L6Y 2S5
CA
|
Family ID: |
33298748 |
Appl. No.: |
10/421813 |
Filed: |
April 24, 2003 |
Current U.S.
Class: |
60/643 ;
60/645 |
Current CPC
Class: |
F01K 13/00 20130101 |
Class at
Publication: |
060/643 ;
060/645 |
International
Class: |
F01K 001/00; F01K
013/00 |
Claims
I claim:
1) A gerotor machine having the outer rotor supported by two
journal bearings surrounding the outer rotor
2) A gerotor machine as in claim 1 where lubricant to the journal
bearings is oil pumped by a purpose-built additional gerotor pump
which is driven from the common shaft of the main gerotor
machine.
3) A gerotor machine as in claim 2 where Coolant passages are
provided between any lubricated element and any hot gas chambers of
the gerotor machine for the purpose of cooling the lubricant.
4) A gerotor machine as in claim 1 where lubricant to the journal
bearings is an engine fuel pumped by a purpose-built additional
gerotor pump which is driven from the common shaft of the main
gerotor machine.
5) A gerotor machine as in claim 1 where lubricant to the journal
bearings is a gaseous working fluid pumped by a gerotor compressor
which is driven from the common shaft of the gerotor machine.
6) A gerotor machine as in claim 5 where lubricant to the journal
bearings is further compressed by a purpose-built additional
gerotor pump which is driven from the common shaft of the main
gerotor machine. the lubricant is compressed to a pressure above
its critical point pressure to become a supercritical fluid.
7) A gerotor machine as in claim 1 where the outer rotor is
substantially surrounded be a sealable case the sealable case is
separated into two or more chambers by fixed seals provision is
made to pressurize the resulting several chambers to differing
pressures to reduce unbalanced loads on the journal bearings
8) A gerotor machine as in claims 1 to 7 where thermal energy to
operate the gerotor machine as a heat engine derives substantially
from a phase change Thermal Store. the heat storage phase change
material is one of aluminum, zinc, copper, lead, barium, tin,
silver, silicon, boron oxide, lithium iodide or any alloy composed
substantially of one or more of these.
9) A heat engine as in claim 8 where the engine drives an
electrical generator as its primary load provision is made for the
engine to drive other loads mechanically the thermal storage
container is attached to the engine by one or more insulated
structural shafts said shafts are designed to house and protect the
conduit tubes which transport the engine working fluid to and from
the said thermal storage. said shafts are designed to allow the
thermal storage container to be suspended over a substantially open
fire or other general purpose heat source for collection of heat.
the thermal storage container is shaped to provide for additional
thermal storage containers to be placed in close thermal contact
with it to provide additional thermal storage capacity.
10) A heat engine as in claim 9 where the engine working fluid is
air the engine working fluid operates in an open cycle with
additional heat energy supplied by a burner oxidizing part of the
working fluid.
11) A heat engine as in claim 8 where the engine working fluid
operates in a closed cycle the thermal storage is part of a
stationary space conditioning electrical co-generation system
12) A heat engine as in claim 8 where heat is provided by a solid
fuel burning system disposed to supply heat primarily to the
thermal storage
13) A heat engine as in claim 8 where heat is provided by a sollar
collector system disposed to supply heat primarily to the thermal
storage
14) A heat engine as in claim 8 where heat is provided by the fuel
burner of a second heat engine as in claim 8 with the working fluid
operating in an open circuit the fuel burner is disposed to supply
heat primarily to the thermal storage the exhaust of the fuel
burner drives the second engine
15) A heat engine as in claim 13 where heat is provided by a
decorative fireplace
16) A heat engine as in claim 8 where the thermal storage surrounds
the catalytic converter of a motor vehicle the thermal store is
normally heated by the exhaust of the vehicle engine the heat
engine working fluid operates in a closed cycle the heat engine
drives an auxiliary compressor to operate a refrigeration circuit
providing space cooling to the vehicle cabin
17) A heat engine as in claim 16 where an auxiliary fuel burner is
disposed to provide heat to the thermal store
18) A heat engine as in claim 17 where the thermal store or engine
exhaust is also used to provide space heating to the vehicle
cabin
19) A heat engine as in claim 17 where the thermal store or engine
exhaust is also used to provide heating to the engine prior to
startup of the vehicle engine
Description
FIELD OF THE INVENTION
[0001] This invention relates to heat engines and heat engines
powered by heat stored in a phase change material.
BACKGROUND OF THE INVENTION
[0002] Designing an engine and generator machine for dedicated use
in as a cogenerator to supply electrical needs to an off-grid
single family dwelling or small commersial establishment presents
some unique problems not commonly encountered in engine design. The
first problem is that the generator must be very large to carry
peak loads, yet operate efficiently at an average load of less than
10%. For example a home which can demand 20+ Kw at peak will likely
consume only 1000 Kw hr per 720 hr month, meaning the 20 Kw
generator is only required to produce 6.94% of its capability. A
strategy of battery storage of electricity can work but batteries
are expensive or short lived, and require costly inverters to
re-convert their output for use, among other problems. Also the
engine generator should be capable of producing a fairly broad
range of output power at a fairly low fixed rpm, since current 50
or 60 hz systems require that even a two-pole alternator cannot
synchronize above 3000 or 3600 rpm, and corrective electronics are
very expensive. A further problem is the timing of the electrical
load versus the thermal load. Thermal losses occur at a fairly even
and continuous rate so the recovered waste heat from a cogeneration
unit which experiences short daily peaks must be stored for later
use.
[0003] There is thus a need for an engine which can be constructed
at low cost and operate efficiently at low speed over a wide range
of power outputs.
[0004] In current heat engines where the products of combustion are
also the engine working fluid, much design effort and construction
expense is devoted to allowing the fuel to be burned at high
temperatures in order to gain maximum efficiency from the burning
of the fuel. However this entails employing either exotic materials
to survive the resulting temperatures, or external circuit cooling
of operating parts which drains efficiency from the engine circuit
In many applications where the balance of heat unused by the engine
can be effectively employed for space heating purposes, notably
small co-generating electrical systems or generating systems
intended for use with solid fuels, the criterion of maximum
efficiency should be secondary to the criterion of low cost. It is
a benefit of the present invention to provide an engine which
employs a novel combination strategy of "topping" of the fuel
burner with a temperature mediating storage medium, combined with a
compressor and expander incorporating a novel combination of
bearing systems and optional regenerating cooling systems which can
be constructed at low cost.
[0005] Burning a typical engine fuel such as gasoline, natural gas
etc. at near stoiciometric ratios in a continuous flow will result
in working fluid temperatures of 1400 C or above, at which
temperatures standard steels loose strength or worse if continualy
exposed uncooled. Ceramics can be created to withstand the higher
temperatures, but costs are high, particularly when complex parts
with additional materials or surface requirements above high
temperature withstand are involved.
[0006] In U.S. Pat. No. 4,782,252, Meijer et al describe employing
a phase change material to store heat for cabin heating of a
vehicle, but do not contemplate then using the heat to power an
engine.
[0007] In U.S. Pat. No. 4,586,334, Nilsson et al describe employing
a phase change material to capture solar heat for operation of a
stirling engine but no consideration is taken of the use of the
storage to mediate the combustion temperature of hydrocarbon fuels,
capture heat from fuels difficult to manage such as wood, or of
constructing an affordable engine to employ the stored heat. Indeed
Nilsson recommends converting part of the engine generator
electrical output to hydrogen for storage and provision of heat
when the sun doesnt shine. The costs of such a system are
prohibitive.
[0008] In U.S. Pat. No. 5,871,041 among others is revealed a means
of employing liquid to solid phase change materials to directly
supply heat for environmental heating. No provision is made to then
use the heat to operate an engine.
[0009] It is known to employ a gerotor machine as a heat engine.
Holtzapple et al in U.S. Pat. No. 6,336,317 teach the use of a
complex gerotor compressor and gerotor expander in a specifically
open circuit brayton cycle engine. High temperatures in the
combuster, heat exchanger and expander are still a source of
materials problems in this design, and no consideration is given to
thermal storage to mitigate the problem or to achieve load
levelling or turndown rates.
[0010] It is known to construct heat engines to extract significant
mechanical work from fairly low temperature differences. Many
ingenious designs have been taught in patents to this purpose,
among them many turbine engine and compressor combinations. Also
U.S. Pat. No. 5,444,981 by Kakovitch. The key element to all of
these designs is the minimizing of parasitic losses expecially into
bearings, pumping losses and working fluid flow losses. However,
turbine engines typically operate at very high speed, employ exotic
materials and loose efficiency very rapidly with reductions in
load.
[0011] It is known to employ the heat of fusion of a material to
store large amounts of thermal energy in relatively small masses.
The benefit to a small co-generation system of doing this is that
it separates the timing dependence of the burning of the fuel from
the generating of the electricity. The thermal storage system is
essentially operating as a battery. It is easily shown that the
amount of heating fuel such as natural gas normally burned at 70%
efficiency to provide heat and hot water to an average home in a
temperate climate, could also provide nearly all the home's
electricity requirement if the higher quality part of the heat is
used in an efficient engine-generator and the lower quality exhaust
heat is recovered to 90+% and used to supply the heating
requirement. The problem is that the heat load will not occur at
the same time as the electrical load, which has meant that small
systems require relatively large chemical battery storage of the
electricity, the costs of which make such a system prohibitively
expensive.
[0012] There is thus a need for a low-cost system to separate the
timing of burning of the fuel from the generating of the
electricity, and a means to convert the stored heat into useful
mechanical energy when required.
SUMMARY OF THE INVENTION
[0013] It is therefore a primary object of the present invention to
provide a means of powering any engine capable of operating on a
relatively low temperature difference, from the heat stored in the
heat of fusion phase change of a solid material which melts at the
hot side temperature of such an engine.
[0014] It is a second object of the present invention to provide a
new means of extracting useful rotating shaft work from a
relatively low temperature difference heat source/sink using a
novel compressor expander machine which may operate using a variety
of working fluids from air and products of combustion in an open
circuit; to a variety of gases, for example carbon dioxide, in a
closed circuit; to a variety of fluids such as water or a
refrigerant which themselves undergo a phase change through the
engine cycle.
[0015] It is a further object of the present invention to provide a
method of constructing a very compact, efficient and low cost
compressor expander machine which can be used in such a thermal
engine.
[0016] It is a further object of the present invention to show a
method of constructing a very compact, efficient and low cost
compressor expander machine which can be employed without damage to
its materials or its lubricants in a fairly high temperature
thermal engine such as one partly driven directly by the heat of
combustion.
[0017] It is a further object of the present invention to show a
method of constructing a novel heat engine, generator and phase
change thermal storage machine which can be carried hot or cold to
locations where electricity may not be available, and then also
re-charged locally using simple heat sources.
[0018] It is a further object of the present invention to show a
method of constructing a catalytic converter incorporating a novel
heat engine, generator and phase change thermal storage machine
which can provide hot or cold space conditioning and auxiliary
electrical power to the vehicle in which it is installed. The
thermal storage material ensures that the catalyst is more often at
working temperature, even at vehicle startup, while significant
mechanical energy is recovered from low value exhaust gases
normally wasted.
[0019] In a first preferred embodiment of the present invention,
the first object is met by providing a hollow container constructed
of a material which can withstand fairly high temperatures. A loop
of thermally conductive tubing of similarly high temperature
material is placed within or in intimate thermal contact with the
said container with both ends protruding to the container's
exterior via sealed openings. The container is then filled with a
material which has a high heat of fusion and a melting temperature
at the design hot circuit operating temperature of a heat engine.
The coefficients of thermal expansion of the container material and
the phase change material should match as closely as possible. One
good pair of materials are a T S20000 Series Stainless Steel from
e.g. Carpenter Steels as the container, and pure Aluminum casting.
The aluminum melts at 660 degrees C. absorbing 389,000 J/kg in the
heat of fusion. For aluminum metal as the phase change material,
the container needs to provide at least 9.25 kg of this phase
change material per kilowatt hour thermal required of the storage
system. Other useful materials include, but are not limited to,
zinc, lead, copper, barium, boron oxide, lithium iodide, and a wide
variety of alloys and/or chemical combinations of these and other
elements. Selection is based on cost and operating temperature
required, though alloys need to be carefully evaluated for
likelihood of separation at melting, with a resulting change of
operation.
[0020] If the system should be portable, then handling means are
provided in order to enable one to place the said container in way
of a heat source, e.g. a camp stove or even a good wood campfire
possibly within a portable ceramic or other container also
provided. Alternatively a designed burner may be provided for any
of a variety of fuels which can supply heat to the storage
container at at least the melting temperature of the phase change
material chosen. Obviously precautions must be taken such as
thermal containment covers etc. for protection of any person who
may inadvertently contact a hot surface.
[0021] The further objects of the present invention are met by
providing an expander and working fluid compressor or pump which
can operate on either a closed or open working fluid circuit, said
engine comprising a single housing containing gerotor compressor or
pump and expander means with a mechanical gear mechanism disposed
between the compressor or pump and the expander within the housing.
The said housing is supported externally on 2 lubricant film
bearings which provide close tolerance, e.g. clearances of 0.05 mm,
radial and axial alignment of the housing relative to a stationary
container. Said gear mechanism is designed to enforce precisely
synchronized rotation of the inner gerotor member with the outer
gerotor member of both the compressor if present and the expander,
eliminating any sliding contact between the rotating members. The
gear housing is separated from each working chamber by a solid seal
plate pierced for passage of the shaft. Said stationary container
supports at each end of the rotating members valve plates
containing inlet and outlet ports for the expander and, if
provided, the compressor. Also supported at each end are bearings
which support the shaft through the inner rotating gerotor member.
The shaft also may drive a small lubricant pump for bearing
lubricant, a fuel pump for a burner, a working fluid pump if the
working fluid undergoes a liquid phase, and any loads driven by the
engine. The pressurized lubricant which may be a hydrocarbon or
synthetic fluid, or a gas, is supplied by tubing or by drilled
passages to each bearing, and possibly by a passage drilled into
the center of the shaft to the central gear mechanism. If a liquid
lubricant is used, a collection sump or other means is provided to
collect spent lubricant from all points and recirculate it possibly
through a cooler to the lubricant pump inlet.
[0022] In one preferred embodiment of the present invention the
engine working fluid is carbon dioxide (CO2) which operates in a
closed circuit at normal compression pressure of 851 kpa. A small
secondary gerotor compressor driven by the common shaft is then
used to further compress a small amount of the compressed CO2 above
7395 kpa, the critical point pressure of CO2, at which point it
becomes a supercritical fluid particularly suitable for use as a
bearing lubricant. This lubricant is supplied by tube to the outer
rotor bearings, thus providing lubrication and seal pressure to the
interface between the outer rotors of both gerotors and the
stationary end plates. The bearing leak-down simply re-joins the
high pressure compressor output flow as it enters the expander
cooling circuit or is re-collected to the main compressor outlet.
The extent to which high pressure leakdown from the bearings is
maintained for re-collection, is controlled by two fixed
longitudinal sealing members attached to the stationary outer
housing. The two internal spaces created by these seals, the
stationary outer housing, and the rotating outer gerotor element
allow for maintaining an unbalanced fluid pressure within these two
chamber sufficient to counteract the unbalanced fluid pressures
within the gerotor machine itself, or the unbalanced forces created
by the synchronizing gear mechanism. In this way the load on the
outer rotor bearings can be reduced to the point where the size and
cost of the gas bearings which support them can be greatly
reduced.
[0023] In the first, second and third preferred embodiments of the
invention a heat exchanger is provided to transfer thermal energy
from the expander exhaust flow to the compressor output flow. The
compressor output flow is then connected to the the engine heat
source. If operating conditions warrant, the flow is then connected
to the tube which was disposed in the phase change container
described previously and then optionally to a fuel burner. The
outflow of the heat source is further connected by tube to the
expander inlet port, thence to the regenerater hot exhaust inlet
port. If a closed circuit is used then the exhaust flow from the
heat exchanger is connected by tubing to a cold side heat
exchanger, possibly a length of tubing disposed within a container
designed to hold water or ice. The cold flow from this heat
exchanger is then connected by tubing to the compressor inlet. Two
valves in the high pressure circuit provide to shut the engine off
while trapping high pressure working fluid for re-starting the
engine. A third valve may be provided at the compressor inlet as a
throttle which provides a simple though inefficient means to
manually or automatically regulate the engine power. For a closed
circuit, a more efficient regulation means can be provided by
employing a storage container connected by two valves between the
compressor outlet and inlet. Valving high pressure working fluid
into the storage container reduces the total mass of working fluid
in the engine circuit and thus the power of the engine. Valving
working fluid from the tank into the compressor inlet will increase
the said total mass of working fluid in circuit and thus the power
of the engine.
[0024] The complete engine assembly may be semi-hermetically sealed
within a container defined by the stationary container or fully
hermetically sealed within a further container which may also
contain the load machine. If a closed circuit is used, a working
fluid can be selected according to requirements from many stable
liquid or gaseous material, such as water, a standard refrigerant,
carbon dioxide, air, helium, argon etc.
[0025] The invention as described needs little or no exotic
materials or fabrication methods. A portable machine with separable
phase change thermal storage containers may be designed to be
carried on camping trips with the containers re-heated on hot
campfires. A stationary system of similar design incorporated into
a home or commercial heating system could provide significant
electrical or refrigeration output from just topping the fuel
normally used for space heating or hot water heating, as well as
providing economically a means of storing energy for load leveling
and emergency use without the need for expensive short-lived
batteries.
[0026] A mobile closed circuit engine designed to provide heating
and air conditioning for a vehicle cabin may have its phase change
storage container with an auxiliary burner deployed to
substantially surround the catalytic converter of the main vehicle
engine exhaust system, in order to bring the catalyst temperature
into working range prior to engine start and then to collect heat
from the engine exhaust.
DESCRIPTION OF THE DRAWINGS
[0027] In drawings which illustrate embodiments of the
invention:
[0028] FIG. 1 is a schematic circuit of the simplest embodiment of
the invention.
[0029] FIG. 2 is a cross section view of a basic compressor and
expander which form part of the engine.
[0030] FIG. 3 is a section view axially at 3-3 through the expander
of FIG. 2 further illustrating a basic compressor expander which
form part of the engine.
[0031] FIG. 3A is a plan view of the gear elements at 3A-3A of FIG.
2 which synchronize the compressor and expander rotors.
[0032] FIG. 4 is a cross section view of a compressor and expander
which might form part of the engine where the expander is provided
with forced cooling by the compressed working fluid.
[0033] FIG. 5 is a section view axially at 5-5 through the expander
of FIG. 4 illustrating the bearing cooling passages and thermal
barrier which may be formed into the expander, as well as the
bearing unloading seals.
[0034] FIG. 6 is a plan view of an embodiment of the invention
illustrating one possible physical relationship of the parts used
for the portable version.
[0035] FIG. 7 is a side view of FIG. 6.
[0036] FIG. 8 is a schematic circuit of the dual engine embodiment
of the invention as is used in a stationary cogeneration
installation using a closed circuit engine powered by the heat
stored in a thermal store where the thermal store is heated by the
exhaust of an open circuit engine employing the compressor and
expander of the invention fueled by a gaseous or liquid fuel.
[0037] FIG. 9 illustrates an alternative heat source for the
cogeneration installation of FIG. 8 where the thermal store heat
source is a simple burner rather than an open circuit engine, said
burner fueled by wood or any other fuel.
[0038] FIG. 10 is a plan layout of a motor vehicle where the
invention is used partly to pre-heat the catalyst of the catalytic
converter.
[0039] FIG. 11 is a detail of FIG. 10
DETAILED DESCRIPTION OF THE DRAWINGS
[0040] In the preferred embodiments of the invention shown in
Figures similar parts are referred to on all drawings by the same
numbers.
[0041] In FIG. 1 is the simplest schematic of the engine
incorporating the thermal storage system. A primary thermal storage
container 1 and secondary thermal storage containers 2 are filled
with the selected phase change material. Heat collection tube coils
3 are deployed within or in close thermal contact to the primary
thermal storage container. The said tubes are connected to a
compressor 4 and an expander 5 which are connected by a shaft 6 or
similar means. The exhaust from the expander is led by tubes to a
waste heat exchanger 7 and then back to the compressor intake.
Provision is made to remove waste heat from the exhaust flow, as
indicated at 8. A regenerative heat exchanger may be deployed to
conduct heat from the expander exhaust gas flow into the compressor
output flow, as indicated by dashed arrow 9. A means of employing
the excess rotational energy of the expander is deployed, such as
an oversized compressor to produce compressed working fluid or a
machine such as a generator 10 connected by a shaft to the
expander.
[0042] Heat is applied to the primary and possibly also the
secondary thermal storage units as indicated at 11 either prior to
or during the operation of the engine. Part or all of the applied
heat is stored in the heat of fusion of the phase change material
contained within the containers. The thermal storage units may then
be insulated for efficiency and safety and left for later use or
transported to a location where creating the required heat is not
convenient, at which time the stored heat may be employed to drive
the engine expander. The heat stored in the primary container may
be used directly, while that stored in the secondary containers is
accessed by physically moving said secondary containers into close
thermal contact with the primary container as required.
[0043] In FIG. 2 is illustrated one preferred embodiment of a
compressor and expander machine for use in an engine as described.
The compressor is formed of an inner gerotor element 20 and outer
gerotor element 21. The outer gerotor element is machined into the
outer rotating housing 22 or formed separately and keyed into outer
rotating housing 22. The compressor gerotor valve plate 23 carries
the stationary side of gas bearing 24 which mounts one end of the
outer rotating housing, providing both radial and axial location of
the rotating housing. Valve plate 23 also carries the compressor
outlet port and supply tube 25 and the compressor inlet port and
supply tube 26. At the center of valve plate 23 are machined
openings for 2 additional complete gerotor machines which are
possibly fabricated from a self-lubricating ceramic material such
as boron/silicon nitride etc, labeled items 27 and 28. Inboard
machine 27 is supplied at it's inlet port from the outlet of the
main compressor. It is designed to draw a small proportion of the
output gas flow from the main compressor and to further boost the
pressure until it is sufficient to support gas bearings 24a and
24b. Supply to these bearings is carried by tube 29 from the outlet
of gerotor 27 to the bearing inlets. If the shaft bearings are
sealed ball or roller bearings and the gears 33 and 34 are machined
or moulded from a self-lubricating ceramic, then the problem of
temperatures being too high for any fluid lubricant to withstand
are resolved. Alternatively, as shown in FIG. 2, gerotor machine 28
may be provided at the outboard position as an oil pump sized to
provide lubricant to bearings 30a and 30b which support shaft 31
radially and axially, and to gears 33 and 34. Fluid lubricant is
drawn from sump 32 by tube 33 into gerotor machine 28 which pumps
it at bearing pressure into bearing 30a via a short passage. Part
of the lubricant flow then enters a passage to the centre of shaft
20 and exits through gear 34 to lubricate the gear pair. A further
part of the lubricant fluid continues along the passage in the
centre of shaft 20 through a section which may be lined with a
ceramic thermal barrier material 36 to isolate the lubricant from
the heat within expander 37, and exits to lubricate bearing 30b.
Alternatively a separate tube may follw an external path from
lubricant pump 28 to bearing 30b, reducing the complexity and
thermal gain of the centre shaft passage. Passages are provided to
return bearing lubricant to sump 32 which operates normally in
contact with the engine working fluid and at or near compressor
inlet pressure. In closed circuit engines it may be advantageous to
remove sump 32 and lubricant inlet tube 33 to the lowest and
coolest point in the exhaust waste heat exchanger where
temperatures may provide improved oil separation from the working
fluid. The gas bearing pressure flow would be sufficient to
transport all lubricant to that point, at which the two could be
readily separated and re-used. The gear case is separated from the
compressor and expander by solid plates 38 and 39 which are round
and keyed to rotate with the rotating outer rotor housing 45. Plate
39 may be formed partly or entirely from a thermally non-conducting
material in order to isolate the gear case from the expander
temperatures. The expander is comprised of an outer gerotor gear 40
and an inner gerotor gear 37 having one less radial projection than
outer gear 40. Both are formed from any suitable material which can
withstand the engine design temperatures and mechanical loads and
working fluid corrosion characteristics. Valve plate 41 mounts
expander inlet port and tube 42, and expander exhaust port and tube
43. Bearing mounting plate 44 is provided to separate and isolate
bearing 30b from the high temperatures within the expander.
Enlarged holes for tubes 42 and 43 are provided in plate 44 to the
same purpose. The majority of the assembly is contained within
casing 45 which can be semi-hermetically sealed using standard
shaft seals and end plates not shown.
[0044] Fixed chamber separation seal plates 47 are provided to
maintain a pressure differential on the outer surface of outer
rotor housing 45, the pressure differential being designed to
partially balance the load from pressures within the outer rotor on
the bearings 24a and 24b. The pressure differentail may be
maintained by trapping the leak-down gas pressure from the bearings
at regulated outlets not shown, or any other convenient means. When
the high pressure side of the external rotor is maintained at or
near compressor outlet pressure and the opposite side is maintained
at or near compressor inlet pressure, the widths of bearings 24a
and 24b can be reduced to arbritarily small dimensions making them
very low-cost to manufacture.
[0045] It is to be understood that persons skilled in the art could
propose modifications to this embodiment without altering the
essential concept. For example if this compressor and expander were
deployed in an open circuit, a designer might consider eliminating
the gas bearings in favor of simply burning any evaporated
lubricant supplied to the hottest points, in a manner similar to
current two-cycle otto cycle engines. Several fuels, e.g. diesel
oil might also serve to lubricate the bearings and/or the gears
prior to being burned. The gears might be formed from a
self-lubricating ceramic. The choice of bearing types for each
location can be altered depending on operating conditions, design
life, construction costs or available maintenance inter alia. All
wall thicknesses shown are for illustrative purposes only and
whould be evaluated for volume production.
[0046] In FIG. 3 is illustrated a cross section through the
expander of FIG. 2 at 3-3. The several bolt holes used to assemble
all outer rotor parts are showed as 46. These through bolts connect
together all rotating elements of the outer rotor of the expander
and compressor during assembly, which progresses from left to right
in FIG. 2. The line labels 50 to 55 mark significant radii of the
expander. Line 50 is only a construction line used to locate holes
46. Line 51 is the outer radius of the expander outer rotor insert
and of the outer gear and the gear case separator plates. Line 52
is the outer radius of the rotating outer rotor housing. Line 53 is
the line separating the rotating bearing face from the fixed
bearing face. Line 54 is the radius of the inner wall of the fixed
casing. Line 55 is the radius of the outer wall of the fixed
casing. The linear seals used for bearing load balancing are showed
at 47.
[0047] FIG. 3a is a sketch drawing of the inner and outer gears at
3A-3A of FIG. 2, which gears synchronize the rotation of the inner
and outer rotors.
[0048] FIG. 4 illustrates a second preferred embodiment of a
compressor and expander for use in this invention. In order to
reduce the temperature of the bearing supporting the expander, the
said expander outer rotor is either comprised of or surrounded by a
material of low thermal conductivity and which is constructed
having longitudinal ridges on its outer surface. These ridges form
a series of passages 61 surrounding the said expander outer rotor
when it is assembled into the rotating outer rotor housing 45. An
additional separator plate 62 is placed between the expander and
the gear case and a series of drilled holes 63 are provided in the
outer case 45 If the outer bearings are not gas bearings then a
simple labyrinth seal 64 is provided to separate the lubricant flow
from the compressor flow supplied by tube 25 which conducts all or
part of the flow from the compressor into the newly formed chamber
between the gear casing and the expander. If the bearing load
balancing system described in FIG. 3 is used here, then the seal
plate will need to be pierced to enable rotation of this labyrinth
seal mechanism, and its sealing clearances reduced. From there the
compressor flow travels along the passages 61 surrounding the
expander to be collected again into channel 65 which is machined in
the entire circumference of valve plate 41 and from there to
compressor flow tube 25. Using the compressor output flow for
cooling in this manner, bearing temperatures may be reduced
suffiently to allow standard lubricants to be used in bearing 24b
while the heat lost to cooling may be carried by the working fluid
back into the engine circuit, thus reducing the negative impact on
efficiency.
[0049] Also illustrated in FIG. 4 is the addition of gaseous fuel
gerotor pump 66, a valuable addition if the engine must operate in
an open working fluid circuit on a low pressure fuel supply.
Commercial pumps capable of raising natural gas pressure to the 7+
bar pressures required in an open circuit engine burner are
extremely expensive. Using a simple fuel throttle valve and/or
dedicated regulator and a backflow preventer on the inlet of pump
66 will provide for an accurate and consistent fuel/air ratio
throughout the entire rpm range of the compressor, while the tube
path from the fuel pump to the burner can be very short, improving
the system safety.
[0050] In FIG. 5 is illustrated a cross section through the
expander of FIG. 4 at 5-5. All is the same as FIG. 3 except for the
addition of the thermal barrier layer 60 and the longitudinal
ridges which form cooling passages 61 for working fluid.
[0051] FIG. 6 is a plan view of one embodiment of the present
invention as a portable engine which can be powered by a variety of
heat sources. A container 70 which is filled with a thermal storage
phase change material is suspended by thermally insulated
structural tubes 72 and vertical supports 73 over thermal source
81. The shape of container 70 is modified by indentations such as
at 71 to improve heat collection from both the primary thermal
source and additional auxiliary thermal storage containers of
similar shape as at 82. Persons skilled in the art may see
additional modifications which may be made to the container shape
for a variety of purposes without altering the essential design.
Primary container 70 contains within it a heat exchanger means for
transferring the thermal energy of the phase change material into a
working fluid which is supplied from and returned to
compressor/expander 75 by tubes thermally isolated within
structural tubes 72. A regenerative heat exchanger is provided at
74. Waste heat exchanger 77 is deployed within a container 78 which
is designed to hold cooling water poured into container 78. A
throttle valve means is provided at 80. A mechanical load such as a
generator or mechanical drive means may be provided at 79. A
variety of starting means may be provided to bring the hot side
tubes up to pressure, some of which are a recoil rope starter such
as at 76, or one or more valves designed to supply pressurized
working fluid from a storage container, or an electrical source
which could drive a generator at 79 as a motor for starting
purposes. An automatic control system may be included employing any
of a variety of feedback mechanisms to automatically modulate the
output of the engine either by throttling, by varying the working
fluid pressure within the engine circuit, by varying the efficiency
of any of the heat exchangers provided, or by varying the
compression and expansion ratios of compressor/expander 75 using
port position adjustment means not shown.
[0052] If the working fluid is a material such as water which
undergoes a phase change in the waste heat exchanger 77, then the
compressor is replaced by a working fluid liquid pump, and the
configuration is slightly modified so that container 78 is at a
greater height than the expander. An appropriate means of power
control such as a working fluid liquid container which is sealed to
the circuit, capable of containing all the engine working fluid in
the liquid phase and connected by a branch fitting and a rotatable
elbow to the lowest point between said waste heat exchanger 77 and
said working fluid pump may be provided. Power control is then
provided by the degree of rotation of this container. If it is
positioned so that the condensate preferrably flows into it than
into the pump inlet, then the amount of working fluid in the engine
circuit is reduced or the engine is shut off. Alternatively, if the
container is positioned so that the condensate preferrably flows
into the pump inlet rather than the container, then the amount of
working fluid in the engine circuit is increased, increasing the
engine output. Other possible means of power control, such as a
manual or automatic flow bypass valve conecting the pump outlet
back to its inlet, are also apparent to those skilled in the
art.
[0053] For further clarification, FIG. 7 is a side view of the
portable engine embodiment shown in FIG. 6, all reference numbers
the same.
[0054] An alternate preferred embodiment of the present invention
is shown schematically if FIG. 8. In this embodiment three separate
phase change thermal storage containers are deployed. At 70 is a
hot thermal storage container constructed of steel or a ceramic
material capable of safely containing a material such as zinc,
lead, copper, barium, boron oxide, lithium iodide, or one of a wide
variety of alloys and/or chemical combinations of these and other
elements. The key criteria in the selection of the material are the
temperature of the input heat source, and the desired temperature
input to the next heat consumer in the hot circuit. At 100 is an
intermediate temperature thermal storage container designed to
store large amounts of low quality heat. This container may be
designed to store thermal energy in the phase change of a material
which melts at a temperature just below the boiling point of water
at atmospheric pressure. Many useful materials to this purpose are
well known in the art, including glaubers salt, many other hydrated
salts of lithium, sodium and potassium, tars, pitches, resins etc.
This phase change material may be sealed into containers 101
deployed within the intermediate temperature thermal storage
container. At 102 is a low temperature thermal storage container
designed to store large amounts of refrigeration, in the chilled
working fluid contained within tank 102 and possibly in the heat of
fusion of a third phase change material such as water ice or a
hydrate such as CO2: H2O sealed within containers 103 deployed
within the low temperature thermal storage container. Pump 104 is
installed to circulate a working fluid such as a water/glycol mix
from either the intermediate temperature thermal storage container
or the low temperature thermal storage container into space
conditioning units 105 depending on the settings of three-way
valves 106. A domestic hot water heating coil not shown may also be
deployed within intermediate thermal storage container 100. All
three thermal storage containers are suitable insulated for
efficiency.
[0055] A closed circuit engine, possibly using the compressor
expander set illustrated in FIG. 2 above, is then deployed at 75.
Its regenerative heat exchanger is showed at 74. Heat collection
tube coils 107 are deployed within hot storage container 70, and
the main waste heat rejection heat exchanger 77 is installed as
convenient. If efficient and useful, a heat recovery indoor air
heat exchanger, not showed, may be provided prior to outdoor heat
exchanger 77. Provision is made using three way valve 108 for the
control system to optionally route the exhaust flow from this
engine into a heat exchanger coil 109 installed within intermediate
thermal storage container 100. If it is installed, provision may
also be made using three way valve 110 for the control system to
optionally route the waste heat exchanger return flow from this
engine into a heat exchanger coil 111 installed within cold thermal
storage container 102 for the purpose of occasionally increasing
the power output of the closed circuit engine for load leveling
purposes etc. The loads on the closed circuit engine may be a
generator 79 and/or an air conditioning circuit compressor 112. If
the air conditioning circuit is installed then secondary waste heat
rejection heat exchanger 113 is installed as convenient to reject
the heat. Thermal expansion valve 114 is then installed just before
the return flow from this heat exchanger enters cooling circuit
heat exchanger 115 installed within cold storage container 102. The
refrigerant is then routed back to air conditioning compressor
112.
[0056] If the fuel for the system is to be one which can usefully
operate an open circuit engine, such as natural gas, propane,
hydrogen or any of the pumpable hydrocarbon fluids, then a second
compressor expander set as illustrated in FIG. 2 or FIG. 4 above
may be installed as showed at 116 in FIG. 8. A regenerative heat
exchanger 117 may be installed in the expander exhaust flow
depending on the efficiency required and the system materials and
lubricants temperature withstand abilities. The exhaust flow is
then further routed into hot thermal storage unit 70 where a large
portion of the exhaust thermal energy above the melting temperature
of the hot phase change material, e.g. 660 degrees C., is collected
and stored. From there the exhaust flow is routed into the
intermediate thermal storage container 100 via tube 118 where a
large portion of the remaining exhaust thermal energy above the
melting temperature of the intermediate phase change material, e.g.
80 degrees C., is collected and stored. The exhaust is then routed
to atmosphere at a safe location by tube 119. If efficient and
desirable and the pressure drop on the engine is acceptable, a
final indoor condensing air heat exchanger not shown may be
provided in tube 119, since this is a pressurized flow. In any case
care must be taken to ensure that continuous or occasional
condensation in the exhaust circuit does not cause problems for the
system. A fuel supply pump 120, possibly as illustrated in figures
above and driven by engine 116, is connected to burner 121 which
also is supplied compressed air from inlet air filter 123 by the
compressor. The heated output of burner 121 is tempered to a
temperature which the expander can handle, e.g. 900 C to 1000 C, by
transferring part of the heat of combustion into hot phase change
thermal storage unit 70. The burner output is then fed into the
expander to drive mechanical loads such as a generator 124. Fuel
shutoff valve 122 controls fuel supply to the burner. A well known
variety of other controls implementing a variety of control
strategies and auxiliary functions such as burner ignition etc. are
assumed but not showed in figures.
[0057] FIG. 9 illustrates an alternative source of thermal energy
for the system in FIG. 8. If the fuel source should be a solid fuel
such as wood etc., then the open circuit engine within the dotted
box in FIG. 8 is replaced with the burner system of FIG. 9. Hot
thermal storage container 70 contains closed circuit engine heat
exchanger 107 which is heated by burning fuel 125. Hot exhaust gas
then enters tube 118 and proceeds as in the previous discussion. In
the case of wood fuels or others where the exhaust may contain
condensible and flammable materials, care must be taken to ensure
the exhaust tube remains sufficiently hot to safely discharge them
completely. It is also apparent that the burner showed in FIG. 9
may be a decorative fireplace fueled by any fuel and deployed all
or partly within a residential or commercial building in a
fireplace insert or stove designed for the purpose.
[0058] FIGS. 10 and 11 show schematically another alternate
preferred embodiment of the present invention. In this embodiment a
container 70 which is filled with a thermal storage phase change
material is installed surrounding the catalytic converter 130 of a
motor vehicle. The shape of container 70 is designed to optimize
heat collection from both the primary thermal source, the vehicle
engine exhaust, and additionally from an auxiliary fuel burner such
as at 121 supplied air by a pump within a heat engine 116 of type
as shown in figures above. A fuel supply pump not detailed,
possibly as illustrated in figures above and driven by engine 116,
is connected to burner 121 which also is supplied compressed air
from inlet air filter 123 by an auxiliary compressor. The output of
burner 121 is simply used to pre-heat thermal storage container 70
if the vehicle exhaust is insufficient to do so. A starter
motor/generator and/or air conditioning circuit compressor 112 is
driven by engine 116. If the air conditioning circuit is installed
then secondary waste heat rejection heat exchanger 113 connected to
supply tube 131 is installed as convenient to reject the heat. A
thermal expansion valve not shown is then installed just before the
return flow from this heat exchanger enters a cooling circuit heat
exchanger installed within the vehicle cabin. The refrigerant is
then routed by tube 131 back to air conditioning compressor
112.
[0059] Fuel shutoff valve 122 controls fuel supply to the burner. A
well known variety of other controls implementing a variety of
control strategies and auxiliary functions such as burner ignition
etc. are assumed but not showed in figures.
[0060] Container 70 contains within it a heat exchanger means for
transferring the thermal energy of the phase change material into a
working fluid which is supplied from and returned to
compressor/expander 116 by tubes 132. A regenerative heat exchanger
is provided at 74. Waste heat exchanger 77 is deployed at a
convenient location in the vehicle for cooling, possibly adjacent
the engine cooling water heat exchanger 133. The waste heat
exchanger is connected to the compressor/expander by tubes 134 A
throttle valve means under automatic control is provided at 80. A
generator as an additional mechanical load is provided at 79.
Starting is provided to bring the hot side tubes up to pressure,
preferably using the vehicle electric battery which can drive the
generator at 79 as a motor for starting purposes. An automatic
control system not shown is included employing any of a variety of
feedback mechanisms to automatically modulate the output of the
engine either by throttling, by varying the working fluid pressure
within the engine circuit, by varying the efficiency of any of the
heat exchangers provided, or by varying the compression and
expansion ratios of compressor/expander 75 using port position
adjustment means not shown.
[0061] It is understood that those skilled in the art may propose
other variations and modifications of the preferred embodiments
described above without departing from the scope of the
invention.
* * * * *