Note: Descriptions are shown in the official language in which they were submitted.
NATURAL GAS ENGINE
Field of the Invention
This application relates to a system and method that improves the overall
energy efficiency of
mobile units operated on pressurized or liquefied gas, in particular mobile
units and vehicles
operated on compressed natural gas or liquefied natural gas.
To concentrate the gas fuel significant amount of energy is invested into the
gas phase to
increase its pressure so significant amount can carried by the vehicle fuel
tank or in liquefaction.
Typically in the prior-art this invested energy is wasted when the fuel is
used as a combustion
fuel. The present invention is a system and method to recover this compression
invested energy
with the use and recovery of additional energy from the combustion waste
energy for the re-
heating of the expansion fuel gas in a single stage or multiply stages. This
invention will
minimize the amount of fuel required to operate an internal combustion engine
and by that
increasing the range of the vehicle, reducing the fuel consumption and as a
result, reduce the
CO2 gases generated by the vehicle.
BACKGROUND OF THE INVENTION
Natural gas is used as a fuel in internal combustion motors and turbines in
various types of
vehicles. To maintain sufficient fuel on the mobile vehicle, the gas has to be
compressed or
liquefy and maintained in insulated tank. Synthetic gas with combustion
properties also have to
be compressed to high pressures to archive sufficient energy per volume unit.
To archive such
energy concentration either by compression or liquefaction, significant amount
of energy is
invested into the compressed gas. This compression energy is lost in the
process on both ends ¨
the compression and the decompression prior to the combustion. There is a need
to recover the
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invested compression energy carried in the mobile vehicle tank to increase the
overall efficiency
that can be reflected in decreasing the fuel consumption, increasing the
travel range and
decreasing emissions on the mobile side.
The use of the pressurized gas is combined with the use of the flue gas
combustion heat where
the expanding gas is re-heated prior to expansion to increase the recovered
energy during the
expansion process.
Various patents have been issued that are relevant to this invention. For
example:
U.S. Patent Pub. No.: US 2013/0199500 Al Published on Aug. 8, 2013 by Matos-
Cuevas
describes a modification of an internal combustion engine so that it can be
operated using
compressed air instead of fuel
Canadian Patent No. 2716283, issued on July 30, 2013 to DUNN et al. describes
a system for a
gaseous fuelled two engine system comprising a high pressure direct injection
engine as the main
power source and an auxiliary fumigated engine that can be fueled with vapor
removed from a
storage tank that stores the gaseous fuel in liquefied form at cryogenic
temperatures. The fuel
supply system comprises a cryogenic pump for raising the pressure of the fuel
to the injection
pressure needed for the high pressure direct injection engine, and the
cryogenic pump is powered
by the auxiliary fumigated engine. In Dunn invention the energy invested in
the liquefaction is
lost.
Canadian Patent application No. 2762697, by to Melanson et al. published on
June 22nd 2013
describes supplying gaseous fuel from a tender car to an internal combustion
engine on a
locomotive comprising storing the gaseous fuel at a cryogenic temperature in a
cryogenic storage
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tank on the tender car; pumping the gaseous fuel to a first pressure from the
cryogenic storage
tank; vaporizing the gaseous fuel at the first pressure; and conveying the
vaporized gaseous fuel
to the internal combustion engine; whereby a pressure of the vaporized gaseous
fuel is within a
range between 310 bar and 575 bar.
WO 2015/159056 A3 of SEALY et. al. published 22 October 2015 describing a
system for an
engine comprises a heat recovery system and a gaseous fuel supply system. The
heat recovery
system comprises a first reservoir for fluid, at least one evaporator for
transferring heat from an
engine to the fluid, a vapour expander for converting fluid vapour energy into
motive power, and
a condenser. The gaseous fuel supply system comprises a second reservoir for
liquefied gaseous
fuel and a fuel evaporator for expanding liquefied gaseous fuel into gaseous
fuel for the engine.
The objects and advantages of the present invention will become apparent from
a reading of the
attached specification, drawings and appended claims.
BRIEF SUMMARY OF THE INVENTION
The method and system of the present invention for high efficiency combustion
of compressed
fuel gas includes the following steps: (1) Heating pressurized fuel gas with
combustion gas heat.
(2) Expanding the heated fuel gas and recovering at least a portion of the
expansion energy. (3)
combusting the lowered pressure fuel gas in an internal or external combustion
engine to
generate energy and combustion exhaust gas (4) recovering heat from the
combustion gas to heat
the compressed fuel gas prior to the expansion stage.
The present invention method to operate a mobile gas combustible engine with
the use of
pressurized fuel gas comprising the following steps: concentrating fuel gas
into a container
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where said concentrated fuel gas is selected from a group containing:
compressed natural gas,
compressed produced gas, liquefied natural gas and condensed light
hydrocarbon; heating said
concentrated fuel gas in heat exchanger with combustion flue gas to generate
high pressure hot
fuel gas; expanding said high pressure hot fuel gas while generating work
energy and medium
pressure fuel gas; heating said medium pressure fuel gas in heat exchanger
with combustion flue
gas to generate medium pressure hot fuel gas; expanding said medium pressure
hot fuel gas
while generating work energy and low pressure fuel gas; combusting said low
pressure fuel gas
in an engine to generating work energy and combusting flue gas and recovering
heat from said
generated hot flue combustion flue gas for heating said high pressure and
medium pressure fuel
gas.
The present invention system to operate a mobile gas combustible engine with
the use of
pressurized fuel gas comprising the following components: a combustion engine
combusting low
pressure fuel gas for generating work energy and combustion flue gas; a
container with
concentrating fuel gas where said concentrated fuel gas selected from a group
containing:
compressed natural gas, compressed produced gas, liquefied natural gas and
condensed light
hydrocarbon; a heat exchanger in a fluid connection to said concentrating fuel
gas and engine
exhaust gas for heating said concentrating fuel gas for generating hot high
pressure fuel gas; a
high pressure expansion apparatus recovering energy from said hot high
pressure fuel gas while
generating medium pressure fuel gas; a heat exchanger in a fluid connection to
said high pressure
expansion apparatus and engine exhaust gas for heating said medium pressure
fuel gas with heat
from said engine exhaust gas for generating hot medium pressure fuel gas; a
medium pressure
expansion apparatus recovering energy from said hot medium pressure fuel gas
while generating
low pressure fuel gas in fluid connection to said combustion engine.
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BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a schematic view of the current invention for a single stage
expansion.
FIGURE 2 is a schematic view of the current invention for a double stages
expansion.
FIGURE 3 is a schematic view of the current invention for a triple stages
expansion.
FIGURE 4 is a schematic view of the current invention for a double stages
expansion piston with
an engine.
FIGURE 5 is another schematic view of the current invention for a double
stages expansion
piston with an engine.
FIGURE 6 is a schematic view of the current invention for a double stages
expansion piston with
compressed air vessel.
FIGURE 7 is a schematic view of the current invention for a double stages
integrated
combustion and expansion piston with pressurized crankcase.
FIGURE 8 is a schematic view of the current invention for an integrated V type
integrated
engine and expansion pistons.
FIGURE 9 is a schematic view of the current invention for a combustion engine
piston that
perform both the expansion cycle and the standard combustion cycle with heat
exchanger and
medium pressure fuel gas tank.
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DETAILED DESCRIPTION OF THE INVENTION
FIGURE 1 shows an embodiment of the current invention for recovering energy
from a source of
a concentrated fuel gas. A pressurized or liquefies hydrocarbons like
compressed natural gas or
LNG is stored in vessel 3. The pressurized gas is fed into a heat exchanger /
evaporator 1 where
the pressurized gas is heated with the heat from a combustion exhaust gas 12
of an internal
engine or gas turbine 11. The heated gas 5 is expanded on an expander 6 with
energy recover 7
to generate mechanical rotating energy that can be used to operate a vehicle
through a gear
system or generate electric energy that can be used for charging batteries or
operate an electric
motor. The expander 6 can be a turbine expander, a piston expander or any
other compressed gas
engine that can recover the compression gas enthalpy to a mechanical energy.
The lower
pressure fuel gas 8, after portion of its energy was recovered on the expander
6, is fed into engine
11 for combustion. In the engine it is combusted with oxidizer like air 9. The
air flow 9 can be at
an atmospheric pressure or at high pressure with the use of turbo or
supercharger. The engine 11
is a piston internal combustion engine, a wankel type engine or a gas turbine.
Heat is recovered 1
from the exhaust gas 12 generated by the engine 11. The lower temperature
exhaust gas 2 is
discharged from the system.
FIGURE 2 shows another embodiment of the current invention.
A pressurized or liquefies hydrocarbons like compressed natural gas, LNG or
pressurized
synthetic gas is stored in vessel 1. The pressurized gas 2 is fed into a heat
exchanger / evaporator
7 where the pressurized gas 2 is heated with the heat from a combustion
exhaust gas 11 of an
internal combustion engine or gas turbine 12. The heated gas 3 is expanded on
a high pressure
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expander 3 with energy recover 5 to generate mechanical rotating energy that
can be used to
operate a vehicle through a gear system or generate electric energy that can
be used for charging
batteries or operate an electric motor. The expander 3 can be a turbine
expander, a piston
expander or any other compressed gas engine that can recover the compression
gas enthalpy to a
mechanical energy. The lower pressure fuel gas, after portion of its enthalpy
was recovered on
the expander 3, is fed into a second heat exchanger 8 and heated with heat
from combustion gas
11. To increase the efficiency, the heat exchangers 8 and 7 can be a counter
flow heat exchangers
operated in a row where the lower pressure fuel gas is heated first with the
combustion flue gas
11 heat, and the higher pressure fuel gas 2 is heated second. The low pressure
fuel gas is
expanded on a second expander 4 to recover portion of its enthalpy in the form
of a mechanical
or electrical energy. The further lower pressure fuel gas 9 is mixed and
combusted with air 10 to
generate mechanical or electrical energy 13. The mixture and combustion can be
performed in a
gas turbine or internal combustion engine like piston engine or wankel type
engine operating at
Otto or Atkinson cycle.
FIGURE 3 shows a schematic visual illustration of the present invention.
A pressurized fuel gas like natural gas or produced gas like synthetic gas is
contained in
longitude pressure vessel 21. The pressure vessel can be composed from few
longitudes vessels
in side by side arrangement connected to a manifold. This arrangement can
reduce the pressure
vessels wall thickness and limit the energy stored in each unit like 21. A
compromising of one
unit will only release the amount of stored energy in this particular unit,
and by that limit the
potential explosion risk. Liquefy natural gas or other light hydrocarbon in
the form of liquid can
be supplied 23 by a pump pressurizing the liquid as well. The pressurized
fluid 13 is heated in a
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non-direct heat exchanger 11 where any liquid evaporates to gas and the gas
specific weight
decreases due to the increase in the gas temperature. The high pressure heated
fuel gas 4 is
expanded at a first stage high pressure expansion piston 1 where portion of
the supplied gas 4
enthalpy is recovered in a form of mechanical energy. The fuel gas is then
discharged at a
medium pressure 5 toward the second expansion step. The medium pressure fuel
gas 5 is heated
in a heat exchanger to generate a medium pressure heated fuel gas 6. The
medium pressure
heated fuel gas is expanding in the second stage piston 2 where additional
energy is recovered
from the expanding fuel gas. The low pressure fuel gas 7 is heated with
combustion heat to
generate heated low pressure fuel gas 8. The heated low pressure 8 is
expanding in a third stage
expansion piston 3 to recover additional energy in the form of mechanical
energy. The lowest
fuel gas 9 is discharged from the 3111 stage piston to be used in an internal
combustion engine 19.
The discharge lowest gas 9 is flow through an accumulator vessel (not shown).
It is then mixed
15 with air 16 and combusted at an internal combustion engine to recover the
chemical energy
within the fuel gas13. The hot exhaust gas discharged from the combustion
piston can be used to
operate a turbocharger (not shown) to increase the pressure of the air 16. The
hot flue exhaust
gas 14 is fed to the heat exchangers to heat the fuel gas during the 3 stages
expansion. The
combustion flue 14 can be used to operate a turbocharger to compress the
intake air 16 (not
shown) for the combustion piston engine. The piston engine includes at least
one cylinder with
reciprocating piston19. The discharged hot combustion flue gas discharged from
the engine 20
and is flow through heat exchangers to heat the fuel gas 13 during its
expansion and pressure
reduction stages. First heat exchanger recover heat from the combustion gas to
the low pressure
fuel gas 7 supplied to 3rd expansion cylinder 3. Additional heat exchanger is
recovering heat
from the flue gas to heat the medium pressure fuel gas 5 supplied to the 2nd
expansion cylinder.
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Additional heat exchanger is recovering heat from the flue gas to heat the
high pressure fuel gas
13 supplied to the 1nd expansion cylinder. The cold combustion flue gas is
discharged 12. The
heat exchangers in Fig. 3 are arranged in a serial arrangement, however any
other arrangement.
Like a parallel arrangement can be used as well. Parallel arrangement will
reduce the potential
flow resistant of the discharged combustion flue gas 14. The work generated by
the engine and
the expansion stages can use to mobile a vehicle or operate an electric
generator.
FIGURE 4 shows a schematic visual illustration of the present invention.
A pressurized fuel gas like natural gas is contained in pressure vessel 21.
The pressure vessel can
be composed from few longitudes vessels in side by side arrangement connected
to a manifold.
Another option is to store the gas in a liquid state, like LNG. For that
option the storage tank 21
will be an insulated tank and the liquid supplied under pressure by a pump to
the 1st heat
exchanger where it is evaporated to a pressurized gas phase. The pressurized
fuel gas 13 is pre-
heated with heat from the second expansion piston 2 in heat exchanger 26. The
low pressure fuel
gas 7 discharging from the second expansion piston is cooled at the heat
exchanger and its
specific volume is decreased 9. This can increase the power efficiency
generated by the internal
combustion piston engine 19 as it allows for more fuel to be combusted at the
piston engine. The
high pressure fuel gas 25, after it cooled the low pressure fuel gas 8, is
heated at heat exchanger
11 with heat from the engine discharged flue combustion gas 8. The heated high
pressure fuel
gas 4 is expanded in a first high pressure expansion cylinder 1. The medium
gas pressure leaving
the first small expansion cylinder 5 is heated in heat exchanger 10 with flue
exhaust gas from
engine 19 to generate heated medium pressure fuel gas 6. This medium pressure
fuel gas 6 is
expanding in the medium pressure expanding piston 2, which is larger in volume
then the 1st
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high pressure piston due to the gas expansion with the drop in pressure. The
low pressure fuel
gas discharging g from the 2nd larger cylinder is fed to heat exchanger 26 to
reduce the low
pressure gas temperature and increase its density. The system can operate
without this low
pressure fuel gas cooling at heat exchanger 26. The low pressure fuel gas,
after the physical
energy was recovered in the two expansion stage is fed in a controlled manner
to a internal
combustion engine 19. The control can include a accumulator 27 to overcome the
pressure
changes in the fuel gas leaving the cylinder 27. Flow control device 29 can be
added to control
the fuel gas injected to the internal combustion engine like piston engine 19.
The low pressure
controlled fuel gas 9 is mixed with air 16 from turbo charger 28. The turbo
charge is design to
increase the power output from the combustion piston engine 19. It is an
optional design feature,
and it is possible to avoid the use of turbocharger 28, where in that case the
combustion air will
be an a atmospheric pressured air, possibly after dust removal with the use of
filter (not shown).
The combustion flue gas discharged from the engine 19 through the exhaust
valve 20 is directed
to first heat exchanger 10 where it heats the medium pressure fuel has 5
discharged from the first
step expansion piston 1. The heated fuel gas 6 expands in the medium pressure
expansion
cylinder 2. The heated combustion gas then flow through heat exchanger 11
where it heats the
high pressure fuel gas 13 to generate the heated high pressure fuel gas 4
before it expand in the
first high pressure expansion cylinder 1. The cold combustion gas 12 is then
expands in a turbo
charger 28 to direct additional air 16 to the combustion engine. The
turbocharger 28 is less
efficient than a standard turbocharger as it is operated on a colder exhaust
gas, so the amount of
energy it recovers in generating flow 16 is relatively lower. A potential
advantage in this
configuration is improved in the heat exchangers 10 and 11 efficiency due to
the fact that more
enthalpy in the discharge combustion gas 14 and the slightly higher pressure
due to the
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turbocharger 28. Turbocharger 28 should be evaluated from the extra cost
perspective and might
be eliminated without significant affecting the overall system performance.
Another option is
avoiding heat exchanger 26. This is done by line A40 for directly connecting
the supplied high
pressure fuel gas 13 to heat exchanger 11 and by line A41 for directly
connecting the low
pressure expansion gas 7 from the medium pressure expansion cylinder 2 to 9
where it is directed
to the combustion engine 19.
FIGURE 5 shows another schematic visual illustration of the present invention.
The system includes 3 blocks: Block 42 include a pressurized fuel gas like
compressed natural
gas. Block 41 include 2 expansion and heating stages to recover physical
energy in the
compressed fuel gas while generating mechanical energy and low pressure fuel
gas flow. Block
41 recovers additional heat energy from the combustion flue gas heat the
compressed and
expanded fuel gas. Block 40 include an internal combustion engine for
combustion of low
pressure natural gas while recovering the chemical energy within the fuel gas
while generating
mechanical energy and flue gas flow.
A pressurized fuel gas like natural gas 22 is contained in pressure vessel 21.
Another option is to
use a pressurized LNG 23. The fuel gas can be pre-heated with heat from the
combustion engine
liquid cooling fluid 52 which is circulated into heat exchanger 53 where the
high pressure fuel
fluid 56 is pre-heated to generate high pressure fuel gas 55. This heat
recovery reduces the heat
loss through the standard engine air radiator 50. To reduce the system
complexity and if the heat
within the glycol cooling liquid 52 is limited, it is possible to avoid the
glycol pre-heating stage
where the high pressure fuel fluid from the fuel vessel bypass the heat
exchanger 53 and flows
54 to the combustion gas heat exchangers for the expansion process as
describes in Fig. 3 and 4.
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The high pressure fuel fluid 13 is heated with combustion gas heat in heat
exchanger 11. The
heated high pressure fuel gas 4 is expended in 1st stage high pressure
expansion cylinder 1. The
medium pressure fuel gas 5 released from cylinder 1 is heated in heat
exchanger 10 to generate
heated medium pressure fuel gas 6 that is expand in the 2nd stage medium
pressure expansion
cylinder 2 to recover additional enthalpy within the pressurized fuel gas into
a useful mechanical
energy form. The discharged low pressure fuel gas 7 is supplied 9 to an
internal combustion
engine. To regulate the fuel gas supplied to the engine, accumulator vessel 27
and a controller 29
can be added. The engine in block 40 is an internal combustion piston engine
operates on Otto or
Atkinson cycles. Air 16 is mixed with the low pressure fuel gas 9 and
combusted in engine 19.
The flue gas 14 discharged from engine 19 through the discharged exhaust valve
20. The
discharge gas 14 can operate a turbocharger 28 to compress air 24 and supply
the compressed air
16 to the engine, while improving the engine performance. The exhaust gas 8
leaving the
turbocharger 28 is supplied to heat exchanger 10. The turbocharger is an
option, where without a
turbocharger the exhaust hot flue gas 14 is supplied 31 to block 41 as flow 8
for heat exchanger
10. Heat exchanger 10 heats the medium pressure fuel gas 5 before it expanded
in medium
pressure expansion piston 2. The flue gas is then heating the high pressure
fuel gas 13 before it
expanded in piston 1. In one embodiment, the low pressure fuel gas discharged
from the 2' stage
expansion 2 is cooled in heat exchanger 26 with the high pressure gas flow
before it is heated in
heat exchanger 11. The low pressure cold fuel gas 7C is directed to the
combustion engine block
40 where it is mixed with air and combusted. The mechanical energy generated
in Block 41 and
the mechanical energy generated in Block 40 by the combustion engine is
combined and coupled
together 30. It is also possible to generate electricity energy in both blocks
40 and 41 separately
by two electricity generators or connect them together directly or through a
controlled gear ratio
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to control the amount of low pressure fuel gas 9 generated by block 41 to fit
the combustion
engine block 40 requierments.
FIGURE 6 shows another schematic visual illustration of the present invention.
The system includes 3 blocks: Block 42 include a pressurized fuel gas like
compressed natural
gas and a pressurized oxidizer like air. Block 41 includes 2 expansion and
heating stages to
recover physical energy in the compressed fuel gas and compressed air with
additional heat
energy from the combustion flue gas heat. Block 40 includes an internal
combustion engine for
combustion the compressed air and fuel gas. Pressure vessel 21 includes a
compressed fuel gas,
like natural gas. Pressure vessel 22 includes compressed oxidizer like air.
The fuel gas 24 flows
though a controller 17 that includes a check valve 26. The compressed air 23
flows through a
controller 16 that includes a check valve 25. The compressed gases are mixed
together 23 at a
stoichiometric ratio and heated in a first heat exchanger 11 to a safe
temperature lower than the
auto-ignite temperature. The high pressure heated mixture 4 expands in a 1st
stage high pressure
expansion stage 1 where physical pressure energy is recovered without
combusting the mixture.
The discharge flow of medium pressure gas mixture 5 is heated in heat
exchanger 10 to a safe
temperature lower than the auto ignite temperature 6 and expand in a 2nd stage
expansion stage 2.
The discharged low pressure stoichiometric gas mixture 7 is fed to combustion
engine through
regulator 27 and intake valve 18. The engine recovers the chemical energy in
the fuel and
generates hot flue combustion gas 8. The combustion gas flows thorough heat
exchanger 10 and
11 where portion of its energy is recovered into the compressed stoichiometric
gas in 2 stages.
The cooled combustion gas is discharged 12.
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FIGURE 7 shows another schematic visual illustration of the present invention.
Compressed fuel gas 2 like natural gas is maintained in a pressure vessel 1.
It is also possible to
use a LNG insulated vessel and pump the LNG under pressure 2 to the first heat
exchanger 3
where it will evaporate into a pressurized gas 6. The heated pressurized gas
is supplied to the
crank case of an internal combustion piston engine 12 during the compression
or discharge
stages where the fuel gas pressure pushes the cylinder when it moves upward.
When the piston
reached the dead top point the fuel gas from the 12 crank case are discharges
at medium pressure
as they contribute portion of their enthalpy to the first high pressure
expansion cylinder and are
flowing 7 to heat exchanger 8 where they are heated to generate a medium
pressure heated fuel
gas. The medium pressure gas 9 is injected to a cylinder crank case 13 during
the piston upward
movement where the medium pressure compressed gas pushes the piston 14 upwards
while
generating mechanical energy. The low pressure fuel gas in the 2nd stage is
discharge when the
piston moves down from the crank case 11. The low pressure fuel gas is
combusted with air at
the engine, pushing pistons 15 and 14 downward in a standard Otto cycle or
Atkinson cycle. In
Figure 7 only 2 pistons were presented, however it is possible to use engine
with more pistons
that can work in additional stages or in parallel by incorporating few pistons
in a single
compression / expansion stage. The engine can incorporate a turbocharger 16 to
recover energy
from the exhaust gas 17 for compressing air 25 before the internal combustion
step.
FIGURE 8 shows another schematic visual illustration of the present invention.
The figure shows a piston configuration that can be used to execute the
present system and
method. The engine presented is a V engine with two sections ¨ Section 1
includes the
combustion pistons design to recover the chemical energy within the fuel for
generating work.
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Section 2 designs to recover the physical energy within the compressed fuel
gas and heat
recovered from the combustion gas in section 1 for generating additional work.
The pistons are
connected to a central crank case 4 which is connected to the combustion
cylinder 12 and
combustion piston 13 and to the expansion cylinder 5 ad expansion piston 6.
The angle between
the pistons is ranging form 180 degrees (a typical opposite flat engine)
through 90 degrees (a
typical V engine) and up to 0 degrees (which is inline engine). Heat exchanger
9 is located in
close proximity to both the expansion cylinders 5 and the combustion cylinder
13. Flue gas
discharge 11 is directed in heat exchange 9 to heat the expanding pressurized
fuel gas 7. The
colder flue gas, after portion of its energy was recovered into the
pressurized fuel gas, is
discharged 10. The high pressure and medium pressure fuel gas are heated on
heat exchanger 9
with the combustion gas heat. View A shoes a side view. A common crank is
connected to the
combustion piston 17 and the expansion pistons 15 and 16. High pressure fuel
gas 25 is heated in
heat exchanger 22 and expands in high pressure expansion piston. The medium
presser fuel gas
21, after the first expansion stage, is heated in heat exchanger 23 and the
heated medium pressure
gas expands in the medium pressure expansion cylinder 16. The low pressure
fuel gas 18 is used
as a fuel in the combustion piston 17 where the fuel gas is compressed and
combusted with air in
a standard Otto or Atkinson cycle. The engine can include multiple pistons
working in parallel in
2 states or in serial arrangement where the expansion stage will be composed
from multiply
stages one after the other.
FIGURE 9 shows another embodiment of the present invention with a common
expansion and
combustion gas chamber. The system and method include a high pressure fuel gas
tank 1, A
medium pressure accumulate gas tank 7 and a low pressure gas thank 8. The
operation is
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composed of the following stages:
High pressure expansion: the high pressure fuel gas 2 from tank 1 flows
through open valve 3
through heat exchanger 25 where it is heated by a counter flow to combustion
gas 24 to become
heated fuel gas 19 and through open valve 17 and intake valve 21 into chamber
27 and expands
inside while pushing piston 28 and generating work.
Medium pressure discharge: After the expansion stage the medium pressure flows
from cylinder
27 through intake valve 21 and open valves 17 and 4 through heat exchanger 25
in a parallel
flow relation to the combustion gas 24 to generate medium temperature medium
pressure flow
into medium pressure vessel 7.
Medium pressure expansion: Medium pressure medium temperature fuel gas 5 flows
from the
medium pressure tank 7 through valve 4 through heat exchanger 25 where it is
further heated and
flow through valve 17 and the intake valve 21 and into cylinder 27 where it
pushes piston 28.
Low pressure discharge: The low pressure fuel gas, after energy is recovered
from the medium
pressure expanding gas is discharged from cylinder 27 by the piston traveling
upwards through
the intake valve 21 and through valves 17 and 18 and through line 9 into low
pressure vessel /
accumulator 8.
For the engine combustion cycle, low pressure fuel gas flowing through valve
11 and line 12
where it mixed with air 13 and flows through valve 15 and intake valve 21
where it is combusted
in a standard Otto or Atkins combustion cycles. The combustion flue gas is
discharged from the
exhaust valve 22 and through heat exchanger 25 where it heats the pressurized
fuel gas and
discharged from the system 26.
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