Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to internal combustion engines comprising a
cornbustion chamber, delivery means to deliver inert carrier gas, combustion
supporting gas and fvel into the combustion chambler, means to cause the fuel
to combust in the combustion chamber and means to exhaust exhaust gas
from the combustion chamber. More particularly, the invention relates to
engines which are capable of operating efficiently where free-atmospheric
air is not available, for example under water or where
communication/connection with the atmosphere is undesirable such as in
certain types of mine.
For ex~mple, in the operation of a diesel engine, a mixture of an inert
carrier gas and a combustion supporting gas such as oxygen is delivered
through an inlet valve to a combustion chamber in a cylinder of the engine
and the mixture within the cylinder is compressed, producing a rise in
temperature of the mixture which is sufficient to cause the fuel to combust,
the fuel is then injected into the cylinder whereupon it cornbusts. Thereafter
products of combustion of the fuel comprising, mainly, carbon dioxide and
water vapour, are exhausted from the cylinder with the inert carrier gas and
residual combustion supporting gas. The rise in temperature produced is
dependent upon the compression ratio of the engine and on gamrna, the ratio
of specific heat at constant pressure (Cp) to the specific heat at constant
volume (Cv~. A normal diesel engine uses air, the nitrogen of the air
constituting a majority of the inert carrier gas and the oxygen of the air
constituting the combustion supporting gas and gamma is approximately 1.4.
Difficulty is encountered where atmospheric air is not freely available.
In such circumstances the delivery of combustion supporting gas must be
provided for from a contained supply thereof, such as oxygen $rom a bottle.
It is also necessary to provide for delivery of the inert carrier gas but the
delivery of carrier gas by such a means is preferably dispensed with.
Suggestions have been made (R. Thompson and A. Fowler of Newcastle
University) initially to introduce air into the combustion chamber and then to
remove from the exhaust aas the excess carbon dioxide produced by
combustion of the fuel by the use of potassium hydroxide and to use the thus
treated exhaust gases comprisinq essentially nitrogen, as the inert carrier gas
with oxygen added thereto to provide the required proportion of combustion
supporting gas, which is introduced into the cornbustion chamber in a
subsequent cycle(s) of the engine.
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However, the quantity of potassium hydroxide required to treat the
exhaust gas to achieve a suf~iciently high carbon dioxide removal rate can,
under certain operating conditions, present a serious problem.
An object of the invention is to overcome this probiem.
According to a first aspect of ~he invention, there is provided a method
of operating an internal combustion engine in which there is introduced into a
combustion chamber, inert carrier gas, combustion supporting gas and a
monatomic inert gas, to provide a mixture thereof in th~: combustion
chamber, the monatomic gas being introduced into the combustion chamber
in an amount controlled such that said mixture has a gamma value Iying in a
predetermined range, and fuel is introduced into the combustion chamber, the
fuel is caused to combust in the combustion chamber and exhaust gas is
exllusted from the combustion chamber, at least part of the exhaust gas is
treated to remove from the exhaust gas an amount of carbon dioxide
generally equal to the quantity of carbon dioxide added by said combustion,
and the thus treated exhaust gas is returned to the combustion chamber to
provide the carrier gas.
Preferably said at least part of the exhaust gas is treated with water to
remove from the exhaust gas and absorb in the water s~lid amount of carbon
dioxide.
This solves the problem mentioned above (which arises by using
potassium hydroxide to treat the exhaust gas~ by treating wi~h water.
One of the criteriq governing the quantity of carbon dioxide soluble in
water is not the total pressure at which the exhaust gas is treated but the
partiai pressure of each gas in the mixture. For example, in the case of a
normal diesel engine, the partial pressure of the carbon dioxide content is
about 10% of the total pressure, and it has been calculated that to remove
most of this carbon dioxide, at a pressure of, for example, five atmospheres,
the weight of water which would be needed would be about 500 times the
weight of carbon dioxide and more at lower total pressure. This would
present a serious difficulty in that the power requirements of the water
management system anà the size of the absorber would be high. Thus, we
prefer to use a carrier aas which comprises a significant proportioll of carbon
dioxide so that the parti~l pressure of the carbon dioxide in the exhaust gas isincreased to an exten~ where the remov~l of carbon dioxide by absorption
water is practicat.
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Whilst the carrier gas may be "primed" with carbon dioxide, it is
envisaged that the carrier gas will be initially unprimed, i.e. without any
significant proportion of carbon dioxide, and thus initially may be inert
components of air, but the proportion of carbon dioxide in the carrier gas will
increase ontil equilibrium conditions are established in which the proportion
of carbon dioxide will be dependent upon the quantity of water utilised and
the pressure (3nd temperature at which absorption takes place.
By a significant proportion of carbon dioxide, we mean more carbon
dioxide than is present in air and preferably at ieast 2û% carbon dis~xide by
volvme of the total volume of carrier gas introduced into the combustion
chamber.
It is preferred that the proportion of carbon dioxide in the carrier gas
introduced into the combustion chamber when equilibrium conditions have
been established will be in the range 35% to 50% by volume of the total
volume of carrier gas, the proportion increasing in the exhaust phase,
depending upon the fuel input to and load carried by, the engine (lower power
lower extra C02), so that the absorption operation is carried out on gas
containing carbon dioxide in the range 45% to 60% by total volume of carrier
gas being absorbed. As the carbon dioxide content increases, the efficiency
of operation of the engine decreases and the maximum carbon dioxide
content is typically 60% by volume of the total weight of carrier gas
introduced into the combustion chamber.
Prçferably the exhaust gas is cooled prior to absorption in order to
achieve good solubility of the carbon dioxide. The exhaust gas may be cooled
with the solvent water used for absorption, or may be cooled in a separate
pre-cooler.
Preferably, the absorption takes place at a pressure greater than
atmospheric to reduce the amount of water required, preferably in the range
two to thirty atmospheres.
The engine may be aspirated at atmospheric pressure, i.e. a pressure of
one atmosphere and the exhaust gas compressed prior to said treatment with
water.
Alternatively, the engine may be aspirated at an elevated pressure
above atmospheric pressure and the exhaust yas treated with said water at
said elevated pressure.
Where the exhaust gas is treated at high pressure, typically above five
to ten atmospheres, pre-cooling is necessary.
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The engine may be operated in an open cycle by directing the exhaust
gas to atmosphere and drawing the gas to be introdvced into the combustion
chamber from atmosphere.
Where the engine is aspirated at a pressure of one atmosphere to
change the engine from closed to open cycle operation, the exhaust is
directed to atmosphere ancl the gas to be introduced into the combustion
chamber is drawn from atmosphere.
~ lowever, when the engine is aspirated at an elevated pressure above
atmospheric pressure, to change the engine from ciosed to open cycte
operation, initially the exhaust is directed to atmosphere to reduce the
pressure in the circuit to atmospheric pressure and then the gas to be
introduced into the combustion chamber is drawn from atmosphere.
In either case, after open cycle operation, the engine may be changed
to closed cycle operation by directing the exhaust gas to be treated with
water and isolating the exhaust gas and gqs to be introduced into the
combustion chamber from atmosphere. Where no compressor is provided7 the
pressure obtaining in the closed circuit will be equal to the total pressure
which results in the partial pressure of carbon dioxide being equal to that at
which an amount of carbon dioxide equal to that produced by the engine is
absorbed.
Where the engine is normally aspirated, i.e. aspirated at atmospheric
pressure, the circuit advantageously comprises a compressor by which the
exhaust gas is compressed on leclving the combustion chamber so that the
exhaust gas is treated with water at a pressure greater than one atmosphere,
for exampie five atmospheres, to reduce the amount of water required to
absorb tile excess carbon dioxide, and an expander within which the exhaust
gases are permitted to expand after treatment with water and before being
returned to the combustion chamber.
It is preferred, however, to provide means so that the engine is
ass~irated at an elevated pressure above atmospheric pressure, for example
two atmospheres, and the pressure in said circuit is likewise at said elevated
pressure.
In this case, the same amount of fuel is delivered to the combustion
chamber as if the engine were run at one atmosphere and so the amount of
combustion supporting gas required to be fed to the combustion chamber can
be reduced compared with that required when operating at atmospheric
pressure. This is siynificant because it avoids any excessive loss of oxygen
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despite operat;on at above atmospheric pressure. More particularly, if the
engine were run wifh 21% of oxygen, i.e. the norrnal oxygen content of free
atmospheric air, then at full torque the residual oxygen in the exhaust would
be about 12% of the exhaus7 gas. Since most natural sea water will already
contain oxygen in solution equivalent to 21% of atmospheric pressure, i.e.
0.21 atmospheres, then 12% by volume of oxygen at two atrnospheres is
equivalent to 0.2 atmospheres partial pressure and hence only a small amoun
of oxyaen would dissolve in the sea water and be lost.
However, if the engine is run at, for example3 25% of maximum torque,
the oxygen content of the exhaust would be about 19% which, at two
atmospheres, would produce C1 partial pressure of .38 atmospheres and hence
considerable oxygen wouid ~dissoive in the sea water and be lost.
To reduce this loss to a small value, the engine is run at or near a
constant oxygen exhaust concentration, for example 12%, which would
involve negligible oxygen loss.
Accordingly, we prefer to provide an oxygen content control means to
maintain a predetermined oxygen content in the exhaust gas. Thus,`at low
torque only relatively little oxygen is delivered to the combustion chamber,
for example an oxygen content oF approximately 14%, whilst at full torque
more oxygen would be delivered to the combustion chamber, for example up
to 21%, whi Ist maintaining a predetermined exhaust oxygen content of
approximately 12%. Thus, delivery of combustion supportina gas to the
combustion chamber may be controlled to maintain a predeterrnined content
of combustion supporting gas in the exhqust gas to achieve a partial pressure
of the combustion supporting gas in the exhaust gas approximately equal to
the partial pressure of combustion supporting gas in the treatment water.
Alternatively9 particularly where the engine is aspirclted at atmospheric
pressure, the oxygen content of the gas introduced into the combustion
charnber may be controiled to provide a desired combustion supporting gas
content in the inducted gas.
The amount of water available for treatment of the exhaust gas may be
controlled in dependence Upoh the total pressure of the gas to be treated with
water to control the amount of carbon dioxide removed from the exhaust aas.
It is desirable to provide an engine which is capable of operating uncler
conditions in which free atmospheric air is not available with an efficiency
similar to that achieved when operating normally.
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The gamrna value may be approximately that of air, pre~erably Iying in
the range 1.3 to 1.5.
The monatomic inert gas may be one, or a rnixture of at least two, of
xenon, crypton, neon, heliumt argon but advantageously is orgon aione.
According to a second aspect of the invention3 there is provided an
internal con-,bustion engine comprising:-
An internal combustion engine comprising:
(a) a combustion chamber;
(b) delivery means to deiiver inert carrier gas9 combustion supportinggas and a monatomic inert gas, to provide a mixture thereof in the
combustion chamber;
(c) delivery means to deliver fuel into the combustion chamber;
(d~ means to cause the fuel to burn in the combustion chamber;
(e) means to exhaust exhaust gas from the combustion chamber;
(f) a circuit through which the exhaust gas is ducted from the
combustion chamber and returned to the combustion chamber, the
circuit including an absorber in which at least some of the exhaust
gas is treated to remove carbon dioxide from the exhaust gas; and
(g) control means to control the amount of the monotomic inert gas
supplied by the delivery means such that said rnixture of gases has
a gamma value Iying in a predetermined range.
Preferably, said absorber is adapted to treat said at least some of the
exhaust gas with water.
Said delivery means for said monotomic inert gas may comprise a
reservoir of one9 or a mixture of at least two of, xenon, crypton, neon,
helium, argon.
Said control means may be to control the amount of monotomic inert
gas such that said gamma value lies in the range 1:3 to 1:5.
The circuit may include a cooler in which the exhaust gas is cooled.
The circuit may include means to cause the exhaust yas to be treated at
a pressure greater than atmospheric pressure.
Preferably said delivery means is adapted to deliver combustion
supporting gas to a manifold where combustion supporting gas is mixed with
the treateà exhGust gas prior to passage into the combustion chamber.
The engine may be aspirated at atmospheric pressvre, the circvit
comprising a compressor by which the exhaust gas is compressed on leaving
the combustion chamber so that the exhaust gas is treated with water at a
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pressure greater than one stmosphere, and an expander within which the
exhaust gas is permitted to expand after treatment with water and before
being returned to the combustion chamber.
Alternatively the engine may be aspirated at an elevated pressure
above atmospheric pressure, and the pressure in said circuit is likewise at
said elevated pressure.
Said delivery means may be adapted to deliver combustion supporting
gas to a rnanifold where combustion supporting gas is mixed with treated
exhaust gas prior to passage into the combustion chamber and the delivery
means delivers the monotomic inert gas to said manifold to be mixed with the
combustion supporting aas clnd the treated exhaust gas prior to passage into
the combustion chamber.
The engine may comprise a sensor means responsive to a property of
exhaust gas returned to the combustion chamber (which property may be a
physical property or may be the composition of the gns) and me~ns adapted to
vary the rate at which the monotomic inert gas is delivered by the delivery
means under the control of the sensor means to control the proportions of the
inert carrier gas and the monotornic inert gas such that the gamma value of
the gas delivered to the combustion chamber equals the predetermined value.
Preferably the sensor means is adapted to control the rate at which the
monotomic inert gas is added to the exhaust gas to provide, when combustiorl
supporting gas has been added thereto, a gas having a gamma value
approximately that of air.
The engine may be a diese! engine or a gas turbine, and in each case,
particularly when the engine is operating at relatively high pressure in closed
cycle, i.e. above about five to ten atmospheres, the engine may comprise a
heat exhanger by which heat is extracted from the exhaust gases leaving the
combustion chamber and returned to the treated exhaust gases which
comprise the carrier gas prior to re-entering the combustior. chamber.
There will now be given a detailed description, to be read with the
reference to the accompanying drawing, of three internal combustion engines
which are preferred embodiments o~ this invention, and which have been
selected for the purposes of illustrating the invention by way of example. In
the accompanying drawings:
FIGURE I is a schematic illustration of a first embodiment of the
;nvention, as applied to a diesel engine;
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FIGURE 2 is a schematic iilustration similar to Figure I but showing a
modification of the engine shown in Figure l; and
FIGURE 3 is q schematic illustration cf a third embodiment of the
invention, as applied to a gas turbine.
The internal combustion engine which is the first embvdiment of this
invention has been devised for operating both under conditions of normal
aspiration at atmospheric pressure cnd in environments where communication
with free-atmosphere is undesirable, or under water, in which latter context
the engine will here;nafter be descr;bed. The engine comprises a
piston/cylinder unit 6 designed to operate on diesel cycle and hence having a
combustion chamber and an inlet valve or valves through which a mlxture of
gases containing oxygen are admitted to the cylinder, and an exhaust vqlve or
valves through which exhaust gas is ducted from the cylinder. The engine
also comprises means 7 to inject fuel into the cylinder, and a circuit C
through which some at least of tlle exhaust gas is ducted from the combustion
chamber and returned to the cylinder, said circuit including a heat exchange
unit 8, first and second cooling units 10 and 12, a compressor unit 14, an
absorber unit 16, an expansion unit 18, and a cooler 24.
In the operation of the engine in a non-atmospheric or closed cycle,
oxygen from a high pressure store thereof is delivered to a manifold 2û at
utmospheric pressure, and is ducted into the engine cylinder together with
carrier gas. The gas charge is compressed within the engine cylinder, causing
the temperature of the gas to increase, and fuel is ;njected, producing
combustion of the fuel. Exhaust gas is ducted from the combustion chamber
through the heat exchange unit 8, in which the temperature of the exhaust
gases is reduced, and through the first cooling unit 10 to the compressor unit
14, at which the pressure of the exhaust gases is increased. The compressed
exhaust gases are passed through the second cooling unit 12 to the absorber
unit 16, in which the exhaust gases are treated with sea water, at a pressure
of nbout five atmospheres. The absorber may be of any suituble type but
prefer(lbly comprises a rotor provided with wire mesh or other material
having a high surface area to volume ratio through which the water is thrown
radially outwardly by centrifual fQrce whilst the exhaust gas is caused to pass
therethrough in counterflow. This absorber achieves rapici absorption into the
sea water and is comp~ct. The absorber unit 16 is provided with a level
control 17 to ensure that the absorber is not flooded or run below a
predetermined water levei.
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The thus treated exhaust gas is passed throu~h the heat exchange unit
8, at which the temperature of the gas is increased, and through an expansion
unit i8 within which the exhaust gas is permifted to expand, through a sensor
unit 22 in which the composition of the gas is measured, through a third
cooling unit 24, and back 1nto the manifold 2~ in which argon and oxygen are
added to the treated exhavst gas from reservoirs 2~, 26 respectively.
The sensor unit 22 is arranged to provide a control signal to a metering
valve 28 which meters the amount of argon fed to the manifold 20 from the
reservoir 25 to ensure that the proportion of argon in the inducted gas
provides the desired ratio of specific heats gamma. In the present example,
the sensor 22 comprises a compressor having a pressure ratio greater than 2:
I in which the exhaust gas is compressed followed by means to pass the
compressed exhaust gas through a convergent/divergent p~ssage, together
with means to measure the inlet pressure and throat pressure in the pnssage.
Changes of gamma changes the ratio of these two pressures (absolutely) and
comparison means are provided to compare the two pressures and to produce
an output in relation thereto which controls the valve 28.
The change of ratio which occurs is very small and thus high1y accurate
transducers and comparison electrical circuits are provided.
During an initial stage in the operation of the engine on closed cycle,
the proportions of carbon dioxide and argon in the circulating gas will
increase, and the proportion of ni~rogen will decrease until an equilibrium
con~ition is established ~dependent upon the characteristics of the absorption
process~ in which the rate at which carbon dioxide is removed by absorption
in the wqter is equal to the rate at which carbon dioxide is added during the
combusfion process.
The supply of air for the initial charge for closed cycie operation may
be achieved by supplementary supply bottles, or air may be ducted from
available free-space in the engine compartments, of course once closed cycle
ooperation has started, further air is not re~uired but only a continua! supply
of oxygen. If engine is shut down from a closed cycle system in balanced
operation, the initial charge is suitable for another start-up without
addit ions.
Alternatively and preferably operation of ~he engine is initiated in the
atmosphere on "open cycle", in which the exhaust gases are vented to
atmosphere via two-way valve E, and air is drawn into the maniFold from
atrnosphere via two-way vcllve 1, clnd then switched over to closed cycle, in
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which an increasing proportion of exhau~t gas is clucted to the absorber by
progressively closing valve E to atmosphere, causing, in conseauence, an
increasing proportion of treated exhaust gases to be returned to the manifold
through the expander with a corresponding closing of valve I to atmosphere.
When change over to closed cycle has been ccmpleted, the engine may be
submerged to its intended location. The rate of switch-over is limited by the
rate at which argon can be fed in to maintain the desired 5: 3 volume ratio
of argon to carbon dioxide, otherwise the ignition can be affected in a diesel
engine, and it could stop. Therefore, the change-over rate is afFected by
power demand during the operation until the argon level car- reach that
desired.
When it is desired to terminate closed cycle operation, exhaust valve ~
is opened to atmosphere and then inlet valve 1, if desired both valves rnay be
opened at the same time.
Because the carrier gas is rich in carbon dioxide, it is possible, and may
be desirable, to pass only a proportion of the cooled exhaust gas through the
compressor absorber and expander and still have the correct mixture enterina
the engine, by absorbing a greater proportion of carbon dioxide from the
smaller quantity of exhaust gas. Thus a duct 27 may be provided (shown in
dotted lines in Figure 1) between the cooler lû and the sensor unit 22. In
this rnanner a reduction in compressor and expander size and weight may be
obtained.
Both the compressor unit 14 and the expander unit 18 are drivingly
connected to a driveshaft 29 driven by the engine, which driveshaft 29 also
drives a generator 30, through a gearbox 31, conveniently through a
releasable covpiing (not shown). Power may be derived from the engine,
either directly by a power take-off ~not shown), or in the form of electr;city
from the generator. Conveniently the generator 30 is connected to a battery
32, and may be operated as a starter motor. Pumps 33 for the absorber unit
16 are also driven from the engine driveshaft 29 via the gearbox 31 and a
shaft 34.
In order to control the amount of water circulated through the absorber
16 by the pumps 33, a motorised by-pass valve 19 is provided which is
adjusted in accordance with a signal provided alona a line 21 from a further
sensor 23 through which the treated exhaust aas is passed after leaving the
expander 18. The sensor 23 measures the total pressure in the gas circuit C
and increases the water flow through the absorber 16 if the pressure exceeds
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a predetermined pressure and reduces the water flow if the pressure falls
below a predetermined pressure so as to control the amount of carbon dioxide
removed from the exhaust gas.
The gas leaving the manifold 20 to enter the cylinder 6 passes through a
third sensor unit 35 which provides a control signal via line 36 to a metering
valve 37 which controls the amount of oxygen fed to the manifold 2û from
the reservoir 26 to meter the correct amovnt of oxygen into the carrier gas.
The sensor unit 35 comprises a conventional sensor for detecting oxygen
content and may be provided with means to adjust the oxygen supply in
accordance with operating parameters of the engine. Alternatively, the
sensor may be positioned to sense the oxygen content of the exhaust gas and
control the valve 37 to provide a desired oxygen content in the exhaust gas as
to be described with reFerence to Figure 2.
The engine which is the first embodiment of this invention is designed
to operate in air, or a charge which simulates air, that is w;th a mixture of
charge gases having a gamma ratio oF approximately 1.4.
Figure 2 shows a second embodiment of the invention, which is
preferred and is a modification of the first embodiment of the invention. The
same reference numerals have been used in Figure 2 as are used in Fi~ure I
~or corresponding paris.
In this embodiment, the engine is operated so that the pressure in the
closed circuit is above atmospheric pressure. This permits of elimination of
the heat exchanger 8, the compressor 14, the expander 18 and the cooler 24.
In other respects, the second embodirnent is as the first embodiment except
that during operation of the engine in the non-atmospheric cycle, the gases
delivered to the combustion ehamber are delivered thereto under pressure
which is above atmospheric pressure, in the present example, at a pressure of
two atmospheres.
Assuming that the engine is operating on an atmospheric cycle, drawing
charge from atmosphere which is introduced into the combustion chamber at
atmospheric pressure, then, when it is desired to initiate ciosed cycle
operation, the exhaust vulve E is operated to direct exhaust gas to the
absorber 16 and to close the exhaust to atmosphere, and then the valve I is
operated to ciose the inlet to atmosphere. The pressure in the system
increases due to carbon dioxide generation until the pressure attains the
desired operating pressure at which the partial pressure of the carbon dioxide
in the exhaust gas is such that the carbon diox;de is absorbed at the same
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rate as it is generated, thereby preventing further pressure increase. The
rate of pressure increase in the closed circuit depends upon the rate of
carbon dioxide generation and so will be high when the engine is operating at
high load and vice versa.
When it is desired to terminate closed cycle operation, the exhaus7
valve E is opened to atmosphere thus droppina the pressure in the circuit C to
atmospheric pressure and then the valve I is opened.
The exhaust gas is ducted from the combustion chamber directly to the
cooler 10 and into the absorber 16 at a pressure of two atmospheres so that it
is treated with sea water at this pressure which, whilst requiring more water
than is required in the case of the first embodiment where the exhaust gas is
treated at a pressure of five atmospheres, still permits of a practical size of
absorber 16. Problems of oxygen loss are avoided by controlling the oxygen
content so tha~ the partial pressure of the oxygen in the exhaust gas is
approximately equal to the partial pressure of oxygen in the water used for
treating, for example sea water, where the engine is used in a marine
application. The treated exhaust gas is then returned to the engine cylinder
at a pressure of two atmospheres via the sensor units 22, 23 and 35.
The sensor units 22 and 23 work as described above in connection with
the first embodiment except that in this embodiment, the sensor unit 23 is
arranged so that the predetermined pressure is two atmospheres absolute.
In this embodiment, the sensor unit 35 is positioned to sense the oxygen
content of the exhaust gas and provides a control signal to ensure that a
(variable) amount of oxygen is added to the carrier gas so that the proportion
of oxygen in the exhaust is maintained substantially constant at the desired
level to avoid excessive oxygen solution in the water in the absorber i6. In
the present example, the sensor unit 35 controls the vaive 37 to ensure that
the proportion of oxygen in the exhaust gas is approximately 12% which, as
mentioned above, at an operating pressure of two atmospheres provides a
partial pressure of oxygen of approximately .24 atmospheres which in view of
the oxygen content of the sea water in which the engine is intended to
operate corresponding to an atmospheric oxygen partial pressure of 0.21
atmospheres ensures that there is relatively little oxygen loss.
A third embodiment relates to the application of the present invention
to a gas turbine, comprising compressor means, heat exhanger means,
combustion means, turbine expander means, heat exchanger means, and
cooler rneans in ~low sequence. The compressor means may be multistage
with intercooier, and the heat exchanger means is optional. Such a system
normally draws in atmospheric air and rejects the exhaust gases~ typically
containing some 6% of CO2 to atmosphere. Such devices are primarily
suitable for large power units of 10,000 hp plus, where the weights of large
diesel engines become relatively excessive.
For example in gas turbine engines utilised In submarine environments
one requirement is that the engine should be capable running on atmospheric
air.
Thus in the application of the present invention, the exhaust from the
turbine or its following heat exchanger (if fitted) is cooled by indirect
thermal contact with sea water, and returned to compressor inlet, at which
point oxygen needed to continue combustion, and argon to control the argon
content are conveniently added through metering valves VO~ Va from
reservoirs Ro, R3. The excess carbon dioxide must be rejected, and this is
done by separating part of the gas flow at the outlet of the gas compressor,
which part is then passed through a heat exchanger to conserve heat, and
exposed at full compressor pressure to sea water in the absorber. The
carbon dioxide dissolves preferentially in the sea water, and the remainder of
the gas is pumped back through the pump heat exchanger to rejoin the main
flow prior to the main flow heat exchanger (if fitted), or if not, to the inlet
of the combustion chamber.
Thus, by adding a monatomic gas (such as argon) to the circuk~ting flow
such that ~ is argon and ~ is carbon dioxide~ together w;th oxygen for
combustion, then both the gamma ratio and heat capacities by volume of the
circulating gas is close to the values for air, and the engine will run equaily
well on the carbon dioxide/argon mixture, so that a change over is simple and
the engine compressors and turbines are unchanged. It should also be noted
that the carbon dioxide absorber is run at full compressor pressure and only a
part of the circulating flow needs to pass through the absorber.
A gas turbine may run at twelve to twenty atmospheres for absorption
without increasing the inlet pressure above one atmosphere, i.e. its normal
condition.
Thus as illustrated in Figure 3, the engine 100 comprises a compressor
means 101, which may consist of one or two sections 102 and 103
advantageously with an optional intercooler lû4, which is drivingly connected
by a shaft IOS to a high pressure turbine or turbines 106. The gas flow from
turbine I û6 is ducted to a power turbine 107 and through a circuit C
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comprising a duct lû8 to an optional heat exchanger lû9t by which some
exhaust heat is removed, and then to a cooler 110 where it is cooled to near
sea water temperature by sea water pumped through the cooler 110 by pump
111. The cooled gas then enters the compressor means lûl and emerges at
high pressure at the exit 11 2 where a proportion passes throvgh duct or
rnanifold 11 3 to the high pressure inlet of heat exchanger 1 09, where it
absorbes heat from the exhaust gases, and passes into a combustion chamber
114, wherein fuel is injected and burned, and passes to the Inlet high pressure
turbine 1060
The other fraction of gas ernerging from compressor 101 at exit 112
passes to another heat exchanger 115 which reduces the temperature further,
and is then injected into the bottom of the absorber 116, where it is brought
into int;mate contact with sea water to dissolve out the carbon dioxide. The
gas is cleaned from salt water in a cleaner/scrubber 117, and is then returned
to the circuit by compressor 118, and passes back through the opposite paths
of the heat exchanger 11 5 to the engine where this fraction rejoins the
fraction of the gas flowing through duct or manifold 113 to the high pressure
entry to heat exchanger 109. Alternatively all the gas may pass through the
absorber.
The absorber 116 is also provided with a level control 127 corresponding
to the level control 17 of the first two embodiments.
Sea water is pumped through the absorber 116 by a pump 119 which
collects power from the high pressure sea water in its pressure reductlon,
passes through the absorber water distribution systern shown as sprayers 122,
collects at the bottom of the absorber, and is pumped away by a pump 120.
Sensor units 124, 126 and 128 are provided corresponding to the sensor
units 22, 23 and 35 of the first two embodiments to control argon supply,
water supply and oxygen supply respectively as previously described in
connection with the first two embodiments. Except, of course, the oxygen
supply is controlled to maintain a desired oxygen proportion at the inlet to
the gas turbine analogously to fhe oxygen control afforded ;n the first
embodiment.
Alternatively, the reservoir Ro and valve Vo may l~e positioned as
shown in chain dotted line and oxygen fed directly into the combustion
chamber. In this case, the oxygen content in the closed circuit can be low,
consistent with permitting sensing of the oxygen content.
31D
- 16 -
Further alternatively, the sensor 128 can be positioned in the duct 113
upstream of the return line from the absorber 116 and be arranged to control
an oxygen control valve, similar to the valve Vo, but positioned downstream
of the return line from fhe absorber 116, for example where the sensor 128 is
shown in Figure 3.
The engine is controlled in conventional manner by altering fuel flow
inlet to the combustion chamber 114 to provide the desired power, this flow
being limited as required by, for example, speed governors of known type.
Change over between open and closed cycles operation is as described
for the first embodiment.
In all the embodiments described above, the water vapour generated at
combustion is condensed in the absorber and/or cooler, where provided and so
is removed from the exhaust gas.
In all the embodiments described above, the ratio of argon to carbon
dioxide is calculated to have the same ratio of specific heat as air in the
relevant temperature range of compression in the engine cylinder, i.e.
between I OûC and 5ûOC. For example, in practical terms 3 moles of
carbon dioxide to S moles of argon or helium make 8 moles of a mixture
which, when oxygen is added, behaves in all practical respects like air.
The ratio of the partial pressures of carbon dioxide to argon is the
molar ratio, i.e. 3:S. The ratio of carbon dioxide removal to argon removal
is equal to the solubility ratio x 3/5, i.e. ~ x 3 = 19.1.
Thus the ratio of argon to carbon dioxide in the treated gas is 5: 3,
equal to the rate at which argon and carbon dioxide is delivered to the
combustion chamber. In other words, the carbon dioxide added to the carrier
yas by the conlbustion process has been removed.
Whilst the desired ratio of argon to C02 is 5: 3 for best
operation, other ratios are acceptable depending on the engine design and
fuel quality for lower ratios, and depends on the ruggidness of construction
and pressure operating levels of the engine for higher ratios.
In general the operation of the power unit is self-regvlating, dependent
upon the operation of the absorber unit, in as much as, if the proportion oF
carbon dioxide in the carrier gas increases, the partial pressure of the carbon
dioxide in the exhaust gas increases commensurately, increasing the rate at
which carbon dioxide is removed by the absorbing process.
However some argon will be removed by the absorber, and desirably
means are provided to apply argon at a small rate, conveniently entering the
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- 17 -
manifold 20, to replace this lost argon. Advantageousiy the rate of such
addition of argon to the manifold is controlled by the sensor unit 22 to a
desired rate.
Although argon has been described above as the inert gas, the inert gns
may comprise one, or a mixture of at least two of, xenon9 crypton, neon,
helium, argon.
Whilsf the invention has been described above in relation to diesel
engines and gas turbines, it is to be appreciclted that the invention is not
limited in this respect, and may be used to advantage in other types of
engine. Furthermore, the exhaust gas may be treated at any desired pressure
which in practical terms can lie between atmospheric pressure ~nd thirty
atmospheres.
If desired the composition of the inducted ~as may be such as to
achieve any desired ratio gamma including ratios gamma outside the range
1.3 to 1.5 The above described embodiments may be modified by omitting
the above described menns for removing carbon dioxide with water. If
desired, carbon dioxide may be removed by other means, for example with
potassium hydroxide.
If desired, gas other than oxygen may comprise the combustion
supporting gas, for example hydrogen peroxide, or a mixture of suitable
combustion supporting gas may be provided with suitable supply and control
means analogous to those described above for oxygen.
In this description and claims the proportion of carbon dioxide in the
carrier gas is expressed in % by volume of the total volume of carrier gas.
The features disclosed in the foregoing description, or the following
claims, or the accompanying drawings5 expressed in their specific forms or in
terms of a means for performing the disclosed function, or a method or
process for attaining the disclosed resvlt, or a class or group of substances orcompositions, as appropriatej may, separately or any combination of such
features, be utilised for realising the invention in diverse forms thereof.
L3~
- 18 -
If desired the composition of the inducted gas may be such as to
achieve any des;red ratio gamma including ratios gamma outside the range
1.3 to 1~5~ Thus a further componen~ is selected to be of appropriate
atomicity relative to the other component(s) to achieve the desired gamma is
introduced into the combustion chamber. For example, where nitrogen is the
main component of the carrier gas, then when it is desired to raise gamma a
monatomic gas, such as argon etc., is added and when it is desired to iower
gamma, a gas of higher atomicity than diatomic, for example a triatomic gas,
such as water vapour or a quadratomic gas or other polyatomic aas is added.
Where according to the second and fourth aspects of the invention the
proportions of the components of the gas introduced into the combustion
chamber are controlled to provide a modified gamma value, the above
described embodiments may be modified by omitting the above described
means for removing carbon dioxide with water. !f desired, c~lrbon dioxide
may be removed by other means, for example with potassium hydroxide.
Alternatively, the exhaust gas may be exhausted to atmosphere.
If desirecl, gas other than oxygen may comprise the combustion
supporting gas, for example hydrogen peroxide, or a mixture of suitable
combustion supporting gas may be provided with suitable supply and control
means analogous to those described above for oxygen.
In this description and claims the proportion of carbon dioxide in the
carrier gas is expressed in % by volume of the total volume of carrier gas
The features disclosed in the foregoing description, or the following
ciaims, or the accompanying drawings, expressed in their speci~ic forms or in
terms of a means for performing the disclosed function, or a method or
process for attaining the disclosed result, or a class or group of substances orcompositions, as appropriate, may, sepcrately or any combin~tion of such
features, be utilised for realising the invention in diverse forms thereof.
.
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