Note: Descriptions are shown in the official language in which they were submitted.
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Internal combuQtion engine having an extended operating
cycle
The invention relates to internal combustion
engines according to the precharacterizing clause of
Claim 1.
Such internal combustion engines play a major role
in modern industry. While internal combustion engines,
for example steam turbines and nuclear reactors
combined with turbines, make up a considerable
proportion of electrical power generation, they are
limited to large installations and represent only a
small portion of the installed power capacity.
Environmental activists are very strongly in favour of
the Stirling engine, but, although this is regarded as
favourable from the thermodynamic stand point, at the
moment it cannot compete with the engines mentioned
above in terms of mechanical efficiency or power
density.
Present-day internal combustion engines can be
operated only within a very narrow range of power
density, efficiency and engine life. They are heavily
dependent on engine size (power, cylinder volume),
engine speed, fuel type and the materials used. Piston
engines with self-ignition (diesel) or external
ignition by means of spark plugs (Otto-cycle engines)
or turbine engines (Rankine, Brayton or mixed cycle) or
a combination of these are preferably used depending on
the application, for example motor vehicle propulsion,
boat propulsion, aircraft propulsion, drives for
electrical power generation, pump drives or the like.
Each type of machine has its own, narrow operating
envelopes and its preferred operational envelopes.
Extension of these operating conditions or of the
operational envelope has been the subject of extensive
investigations and developments since the invention of
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internal combustion engines. In this case, progress
has been achieved on the basis of further developments
in the materials used, improved combustion control,
more effective fuels, weight reductions, better engine
cooling, streamlined flow paths, improved valve control
and, recently, computer-aided engine control. Seen
overall, however, development progress with regard to
increased power density, efficiency and engine life has
remained relatively modest. The maximum efficiency of
commercial engines, at the moment, is about 44% at
2 300 rpm or 8.2 MJ/kWh or 144 g Gasoil/Hph or 192 g
Gasoil/kWh (10200 cal/g - 42.707 J/g). Maximum
efficiencies which can be achieved at the moment with
slow-running engines (for example Sulzer two-stroke
diesel at 76 rpm) are in the order of magnitude of 50%.
The use of water in conjunction with ethanol was
investigated, with limited success, by Gunnermann (WO
91/07579). Gunnermann used aqueous alcohols with 40
and 60% water dilution. He found that an expensive and
complex platinum catalytic converter was required
inside the combustion chamber in order to assist the
initiation of combustion, in that the hydrogen bonds in
the fuel mixture were activated. Gunnermann
incorrectly interpreted the high fuel efficiency as
additional release of heat, which was caused by
dissociated water. A simple heat balance shows that
this does not occur since the heat released from the
combination of hydrogen and oxygen is equal to the heat
which is absorbed in the dissociation. Only the Pt
value allows ignition in mixtures which would otherwise
be too damp for ignition. However, Gunnermann's engine
had problems with regard to its stability, reliability
and costs, and was limited to a water:fuel ratio of
1.5:1.
The use of a cycle extension fluid has been
practised to a limited extent in gas turbines. The
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injection of steam into the combustion chamber, which
was originally intended in order to reduce soot
formation and to promote the combustion process,
resulted in increased power emission from the turbine,
and an improvement in efficiency. Further
investigations by a large number of inventors lead to
the so-called SAGT or Steam Augmented Gas Turbine. The
SAGT operates with steam injection downstream of the
combustion chamber. In this way, the temperature after
combustion can be raised to a considerably higher level
than the expansion turbine can withstand, and steam
injection reduces the temperature back to a level which
is acceptable for the expansion turbine, and converts
the heat into a large volume. The SAGT has been
improved further and a "CHENG point" has been defined
at which the efficiency of the SAGT reaches a maximum
by injecting exactly the amount of saturated steam
which can be produced by heat recovery from the exhaust
gases. However, the CHENG point does not correspond to
stoichiometric combustion, since excess oxygen is
present.
A further step was taken by Urbach & Knauss, who
brought the SAGT to stoichiometric combustion
conditions, and accepted a higher power density at the
expense of slightly reduced efficiency. Urbach &
Knauss achieved this by operating a first combustion
chamber at high pressure, followed by steam injection
with subsequent expansion to an intermediate pressure.
In this way, the combustion gases were cooled both by
steam injection and by partial expansion. A second
combustion chamber consumed the remaining oxygen, and
this was followed by steam injection and final
expansion. However, Urbach & Knauss did not go beyond
this development stage.
The cycle extension fluid can advantageously be
used as a carrier for chemicals which promote
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combustion. Additives of peroxides to the fuel were
already known from Lindstrom (WO 88/03550) in order to
reduce the content of CO and HC residues in the exhaust
gases. The addition of peroxides to the cycle
extension fluid eliminates mixing, storage and shelf-
life problems with fuels which are otherwise doped with
peroxide.
DE 21 27 957 B2 discloses a system for the
injection of an anti-knock fluid, which may be water,
in order to reduce the combustion temperature. The
fluid is injected before the compression stage, so that
compression energy can be saved and the risk of
premature ignition (knocking) is reduced by decreasing
the temperatures after compression (that is say before
ignition). This contains no reference to the possible
introduction of more fuel into the same cycle or to
isochoric combustion. Such an engine is a conventional
internal combustion engine, irrespective of stratified
charging, turbo charging, an Otto-cycle, diesel cycle
or comparable cycle, or whether secondary or multiple
fuel injectors are present.
DE 43 01 887 A1 states, in particular, that the
addition of water or some other secondary fluid is
based on the use of waste heat from the traditional
method for vaporization, leading to a general reduction
in temperatures and thus to a reduction in the
contamination with, for example, NOx. In this case,
the water must either be preheated or converted into
steam by reusing waste heat from the exhaust gases
(which is possible within very narrow limits with gas
turbines, but is in practice impossible with piston
engines owing to the very high pressures and the time
available for injection), or the water has to be
applied in liquid form to hot surfaces within the
cylinder, but without taking any heat from the burnt
fuel/air mixture (also, only a very small amount).
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This shows that no consideration was given to the
possibility of injecting more fuel per cycle.
The use of more than one fuel injector in a
combustion chamber is known in the prior art, but
always for purposes other than that in the present
invention. Multiple injectors are typically used for
pistons with very large bores, in which the aim is to
reduce the size of the mixing region. According to the
present invention, the reason for optionally using
multiple fuel injectors is that a step-by-step
combustion sequence may be desirable, which is
difficult or impossible to achieve and/or to control if
a single injector is used. According to the invention,
different fuels may be used in different injectors so
that, for example, combustion is initiated by using a
high-quality fuel in the first injector, with this
being followed by combustion of lower-quality fuels, or
fuels mixed with water or with other chemicals, in the
other injectors. The invention relates to the use of
the injectors.
US 54 00 746 A discloses the use of hydrogen
peroxide as an additive to conventional fuel in order
to reduce the peak combustion temperature. This is
necessary here since it has not been recognized that it
is possible to improve the efficiency of combustion by
the injection of sufficient fuel and by the timing of
injection of water. This known method leads to the
flame being extinguished when water is injected. The
only option is oxygen enrichment or oxygen addition by
the use of hydrogen peroxide. This does not cover the
teaching of using additional oxygen, which is available
in order to inject more fuel and to obtain more power
from each cycle.
In contrast, the object of the invention is to
expand the range of power density, efficiency and
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DE 29 25 091 A1 discloses an open-circuit internal combustion engine, in which the
combustion air is isothermically compressed within a compressor, is burnt with
injected fuel, and the combustion gases are isothermically expanded before they are
released isothermically. Water is injected in such a manner and in such quantities that
it is evaporated during the compression of the combustion air. Injected water is not
used for decreasing the combustion temperature and for increasing the amount of fuel,
which is transformed by air unit; rather, water is injected concerning the amount and
the manner as part of the compression cycle so that partial isothermic compression will
be obtained. This is followed by an adiabatic isotropic compression up to extremely
high pressure values so that the heat generated by compression will reach temperatures
of more than 800~ C. Then, combustion will be carried through continuously during
the expansion phase so that an approximate isothermic expansion will be obtained,
whereby this part of compression corresponds to the Carnot portion of the cycle.
BE17834.DOC
1.2.991:01PM
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engine life beyond the levels of conventional motors
and engines.
This is achieved according to the invention, in
the case of an internal combustion engine of this
generic type, by the features in the characterizing
part of Claim 1, and by a method having the features in
the characterizing part of Claim 9. Further
refinements of the invention are the subject matter of
the dependent claims.
In principle, the proposal in the present
invention is to use water or some other fluid which is
chemically inert or can be decomposed endothermically,
and to pass said fluid into the combustion chamber or
chambers in order to make a greater amount of fuel
available per cycle and thus to improve the operating
power of internal combustion engines. The fluid used
for this purpose is a secondary fluid, which is called
a cycle extension fluid (CEF). This fluid makes it
possible to use a similar or higher fuel/air ratio
without any disadvantageous effects on the
temperature/pressure graph for the engine, which is the
critical factor for long engine life. In this case,
high temperature is exchanged for increased pressure
and/or increased volume, in that an additional
substance is vaporized and/or endothermically
decomposed. This substance is preferably water, since
any required amounts of water are available, it is easy
to handle, and presents no environmental problems
whatsoever. However, other fluid additives may also be
used for specific applications.
While the use of combustion air enriched with
oxygen, or even of pure oxygen, or the use of
secondary, oxidizing substances, such as nitro or
peroxy components gives only limited advantages since,
owing to the temperature limits, only a small portion
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of the oxidizing substance can be utilized and
stoichiometric operation is precluded, the use of a CEF
achieves a major improvement since, in comparison with
conventional applications, up to five times the amount
of energy can be converted per cycle. An engine
operating with pure oxygen can be operated without any
NOX emission and with easily controllable CO2 output,
which can be cleaned in a simple manner for subsequent
industrial use.
According to the invention, water is injected in
liquid or gaseous form into the combustion chamber in
order to increase the pressure and/or the volume while
the rise in the temperature of the operating fluid is
slowed down, or the temperature is stabilized or
reduced. This allows higher fuel/air ratios, which
would otherwise lead to excessively high temperatures
in the operating fluid, to the detriment of long
machine life. In this case, gas, solid material or a
liquid other than water may also be injected into the
combustion chamber, in order to achieve the same effect
as water. Such a medium should either vaporize and
convert heat into a large volume or high pressure, or
should result in endothermic dissociation in order to
achieve a large volume or partial pressure of
decomposition products. In the case of a gas turbine,
the combustion takes place isobarically, and the fluid
produces a large volume. In the case of a piston
engine, combustion takes place partially isochorically,
and the fluid produces a high pressure.
The amounts of water injected may be up to twenty
times the amount of fuel used. This means that a large
water reservoir or a system for recovering water from
the exhaust gases is used. Since the exhaust gases are
considerably cooler than was previously the case, this
can be achieved using very simple means, preferably by
cooling close to the dew point using dried exhaust
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gases in a heat exchanger, followed by wet washing with
further cooling in the washing water cycle. Recovered
water holds a large amount of residual impurities,
which can be introduced into the cycle once again, and
can be burnt.
This technique allows very high power densities to
be achieved since more energy can be introduced into an
operating cycle for an equivalent or lower theoretical
cycle efficiency, to be precise with a comparatively
equivalent or better overall efficiency for conversion
into mechanical energy. In the case of an engine with
spark-plug ignition, a small range of materials may be
used in order to achieve power densities which at the
moment can be achieved, for example, only in expensive
racing-car engines, with engine lives which far exceed
those of conventional designs. This technique also
makes it possible for engines with self-ignition to
achieve equivalent or higher power densities than
engines with external ignition, since the upper
temperature limit is raised. In the case of gas
turbines, this technique makes it possible to increase
the power densities by a factor of 5 or more, since the
upper temperature limit is raised (WO 94/28285). In
the case of steam-augmented gas turbines, SAGT,
improved efficiency can be achieved and, with engines
according to Urbach & Knauss, increased power density
can be achieved. The latter engines have brought the
conditions for SAGT turbines up to stoichiometric
combustion, but options for operating at reduced
temperatures (in order to achieve the advantage of
lengthened engine life) are not recognized, nor is the
potential for operation with oxygen augmentation or
pure oxygen exploited. Limiting the peak temperature
when using fluids is important from the environmental
aspect, in terms of reducing NOX emissions.
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g
Minor added amounts of water with, for example,
0.01~ H2~2~ O3, organic peroxides or other oxidizing
substances are sufficient to clean residual CO and
residual HC from the exhaust gases. The addition of
peroxides to the water base overcomes storage and
shelf-life problems of fuels doped with peroxide in
some other way. Minor additions of H2O2 or O3 can be
achieved simply by on-line electrolysis of water.
Stronger concentrations of peroxide can be used in
order further to increase the power density, in that a
portion of the oxidizing substance is supplied.
Engines can be operated with air enriched with
oxygen or even with pure oxygen. The latter would
result in no NOX whatsoever being formed, and in the
exhaust gases being composed exclusively of CO2 and
water. Water can be condensed and recycled, and CO2
can be used for industrial processes or for addition to
the air in greenhouses or the like.
Water can also be mixed with water-soluble fuels
or fuels which can be dispersed in water. The ignition
process is achieved by a concentrated fuel charge, and
the fuel diluted with water can then be burnt in an
aqueous environment. This application is limited by
the situation in which all the fuel is supplied in an
aqueous base, this being equivalent to Gunnermann's
proposal, which proposed aqueous alcohols in 40 and 60~
aqueous solution and required an expensive platinum
catalytic converter in the combustion chamber in order
to assist the initiation of combustion, in that the
hydrogen bonds in the fuel mixture were activated. The
high fuel efficiency for additional release of heat,
which was caused by dissociated water, was not
identified by Gunnermann. A simple heat balance shows
that this is not true, since the heat released from the
hydrogen/oxygen combination is equal to the heat
absorbed in the dissociation. The Pt allows only one
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ignition in mixtures which would otherwise be too wet
for ignition. In this case, Gunnermann's engine ran
into stability, reliability and cost problems, and was
limited to a water:fuel ratio of 3:2, while
considerably higher levels could be achieved with the
present invention.
The invention results in the capability to operate
an internal combustion engine of this generic type in a
region of power density, efficiency and machine life
which until now has not been feasible. This is
achieved in that a fluid which extends the cycle is
added, and either the amount of fuel added per cycle is
increased or the cycle is modified towards higher
pressures.
The invention is explained in the following text
with reference to exemplary embodiments in conjunction
with the drawing, in which:
Figures lA - lC show schematic illustrations of basic
design embodiments of an internal
combustion engine according to the
invention,
Figures 2 - 7 show various applications of P/V graphs
(A) and T/V graphs (B) for machines
according to Figures lA - lC, and
30 Figure 8 shows a specific embodiment of the
invention, relating to the provision of
the cycle extension fluid.
In the embodiment according to Figure lA, one or
more combustion chambers 1 having cylinders 2 and a
corresponding number of pistons 3 are fed with supply
gas by a line 4 via inlet valves 5. The exhaust gases
produced from the combustion are dissipated via outlet
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valves 6, through an exhaust gas line 7. Fuel is
introduced to the combustion chamber 1 via a
carburettor 8, and the gas/fuel mixture in the
combustion chamber 1 is ignited by means of an ignition
apparatus 9. A cycle extension fluid, for example
water, steam or the like, is introduced to the
combustion chamber 1 via an injector 10. Furthermore,
fuel is fed into the combustion chamber 1 via secondary
injectors 11. The cycle extension fluid is supplied
from a fluid reservoir 12, for example via a mixing
chamber 13 in which fuel 14 and peroxide 15 can be
mixed with one another, with the aid of a fluid pump 16
and via a heat exchanger 17 which may optionally be
positioned in the exhaust gas line 7 to the injector
10. The cycle extension fluid may optionally be taken
from fluid collecting apparatus 18, positioned in the
exhaust gas line 7, instead of from the reservoir or
the supply apparatus 12. An oxygen enrichment
apparatus 19 or an oxygen storage tank may be
positioned in the supply gas line 4, via which
apparatus the supply gas can be enriched with oxygen.
The embodiment according to Figure lB differs from
that according to Figure lA essentially in that there
is no carburettor and in that a primary fuel injector
is provided instead of an ignition apparatus 9.
This embodiment relates to an internal combustion
engine with self-ignition.
Figure lC shows an embodiment of the invention
which represents a turbine internal combustion engine
in which supply gas is introduced into compressor
turbine stages 21, 22 via the line 4, which could
optionally be coupled to an intermediate cooler 23.
The combustion chambers are denoted by 24, and the
cylinders by 25. Fuel is introduced into the
combustion chambers 24 via fuel injectors 26. The
exhaust gases from the combustion chambers are emitted
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via expansion turbine stages 27, 28 to the exhaust gasline 29, and from there to a heat exchanger 30, which
is connected to a fluid collecting apparatus 32, which
collects CEF which can be recycled, and passes it to a
mixing chamber 33. Fuel 35 and peroxide 36 can be
mixed in the mixing chamber 33. Furthermore, a CEF
reservoir or a supply apparatus 37 is provided, via
which CEF is supplied to the mixing chamber 33. The
CEF is compressed by a fluid pump 34, is preheated via
heat exchangers 23 and 30, and is injected in a
distributed manner via injectors 31 into the combustion
chamber or chambers.
Exemplary embodiments 1 to 13 of different
internal combustion piston engines are explained in the
following text with reference to graphs which show
pressure/volume cycles and temperature/volume cycles.
Curve (1) uses solid lines to show in each case one
cycle of an internal combustion piston engine which is
designed in a known manner and operates in
stoichiometric conditions. Curve (2) and curve (3) use
dashed and then dotted lines to show a cycle of an
internal combustion piston engine according to the
invention, in normal operation and in over expansion
operation, and curve (4) uses dashed-dotted lines to
show a conventional, sub-stoichiometric operating cycle
of an internal combustion piston engine with stratified
charging of a known type.
Example 1:
Figure 2A shows the pressure/volume graph, and Figure
2B the temperature/volume graph of a known piston
engine with external ignition. Curve 1 applies to
operation in conventional stoichiometric conditions.
Curve 2 shows a cycle of the piston engine which has
been improved by injection of a cycle extension fluid
according to the invention, in which case this fluid is
injected in order to reduce the peak temperature which
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is reached during the combustion expansion cycle, and
nevertheless to achieve a correspondingly high pressure
in the cylinders. An equivalent or lower thermodynamic
efficiency, but a better mechanical efficiency, are
thus achieved, which leads to an equivalent or higher
efficiency, equivalent or higher engine power density,
and equivalent or longer engine life. The operating
conditions can be chosen such that either smaller, more
effective or longer-life engines are achieved.
Example 2:
The engine in Example 1 is operated in a (partial)
Atkinson cycle (overexpansion) in order to utilize the
higher cylinder pressure which is available after
conventional expansion. Cycle 1 is unchanged from
Example 1. Cycles 2+3 show operation of the
conventional piston engine with external ignition,
which is modified according to the invention to use the
Atkinson cycle. This leads to the cycle having a
higher or equivalent thermodynamic efficiency and a
higher or equivalent mechanical efficiency, which
results in an equivalent or higher engine efficiency,
equivalent or higher engine power density, and
equivalent or longer engine life. Once again, the
operating conditions can be chosen such that either
smaller, more efficient, or longer-life engines are
achieved.
Example 3:
A conventional piston engine with external ignition is
operated sub-stoichiometrically in stratified charging
conditions, improved by cycle extension fluid
injection, and optionally improved by conditional fuel
injection (Figure lA), in which case the cycle
extension fluid is injected in order to maintain or to
reduce the peak temperature which is reached during the
combustion/expansion cycle, and nevertheless to achieve
a correspondingly high pressure in the cylinders. The
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optional additional fuel injection is used to increase
the heat supplied and thus to increase the cylinder
pressure; both are limited by stoichiometric
conditions. In graphs 2A and 2B, the pressure/volume
cycles and temperature/volume cycles 4 apply to a
conventional piston engine with external ignition,
which is operated sub-stoichiometrically in stratified
charging conditions. The cycles 2 are modified
according to the invention and are limited by
stoichiometric conditions. This results in the cycle
having an equivalent or lower thermodynamic efficiency,
but a better mechanical efficiency, which leads to an
equivalent or higher engine efficiency, equivalent or
higher engine power density, and equivalent or longer
engine life. The operating conditions can be chosen
such that either smaller, more powerful or longer-life
engines are achieved.
Example 4:
The piston engine according to Example 3 is operated
using the (partial) Atkinson cycle (overexpansion) in
order to utilize the advantages of the higher cylinder
pressure available after expansion. The cycles 4
according to Figures 2A and 2B are based on a
conventional piston engine with external ignition,
which is operated sub-stoichiometrically in stratified
charging conditions. Cycles 2 and 3 result from a
modification of the invention using the Atkinson cycle,
in which case the cycle is limited by stoichiometric
conditions. This results in the cycle having higher or
equivalent thermodynamic efficiency and a better or
equivalent mechanical efficiency, equivalent or higher
engine efficiency, equivalent or higher engine power
density, and equivalent or longer engine life. The
operating conditions can once again be chosen such that
either smaller, more effective or longer-life engines
are achieved.
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Example 5:
A conventional piston engine with self-ignition is
operated sub-stoichiometrically, is enhanced by cycle
extension fluid injection and is optionally improved by
additional fuel injection according to Figure lB, in
which case cycle extension fluid is injected in order
to reduce the peak temperature occurring during the
combustion/expansion cycle and, nevertheless, to
achieve a correspondingly high pressure in the
cylinders. Additional fuel injection is optionally
carried out in order to increase the heat supplied and
thus the cylinder pressure; this is limited by
stoichiometric conditions. The graphs in Figures 3A
and 3B show the pressure/volume cycles and
temperature/volume cycles 4 of a conventional piston
engine with self-ignition, which is operated with
excess air. The cycles 1 in Figures 3A and 3B relate
to a piston engine with external ignition, which is
operated sub-stoichiometrically and in which the
operating temperature is excessively high. The cycles
2 result from an embodiment of the invention which is
limited by stoichiometric conditions. This leads to
the cycle having an equivalent or lower thermodynamic
efficiency but a better mechanical efficiency, which
results in an equivalent or higher engine power,
equivalent or higher engine power density, and
equivalent or longer engine life. The operating
conditions can be chosen such that either smaller, more
effective or longer-life engines are achieved.
Example 6:
The piston engine according to Example 5 is operated
using the (partial) Atkinson cycle (overexpansion) in
order to utilize the advantage of higher cylinder
pressure after conventional expansion. In the graphs
in Figures 3A and 3B, the cycles 4 are based on a
conventional piston engine with self-ignition, which is
operated sub-stoichiometrically. The cycles 1 relate
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to a conventional piston engine with self-ignition,
which is operated stoichiometrically, and which leads
to an excessively high operating temperature. The
cycles 2 and 3 relate to piston engines which are
modified according to the invention to use the Atkinson
cycle and are limited by stoichiometric conditions.
This results in the cycle having a higher or equivalent
thermodynamic efficiency and a better or equivalent
mechanical efficiency, which leads to an equivalent or
higher engine efficiency, equivalent or higher engine
power density, and equivalent or longer engine life.
The operating conditions can be chosen such that either
smaller, more efficient or longer-life engines are
achieved.
Example 7:
A conventional gas or fuel turbine or steam-augmented
gas or fuel turbine is always operated sub-
stoichiometrically, is augmented by injection of cycle
extension fluid and is assisted by additional fuel
injection at high pressure, in which case the cycle
extension fluid is injected in order to reduce the peak
temperature reached downstream of the combustion
chambers and to increase the fluid volume flowing into
the next combustion chambers. This process is
optionally repeated, and is finally limited by
stoichiometric conditions. Such a turbine, as is
illustrated in Figure lC is operated such that the
temperatures of the fluid reaching the expansion
turbine are reduced. Figures 4A and 4E relate to the
cycles 1 of a conventional gas or fuel turbine which is
operated sub-stoichiometrically, and the cycles 2 to a
conventional gas or fuel turbine which is operated
stoichiometrically and results in excessively high
operating temperatures. The cycles 3 relate to a
turbine which is modified according to the invention
and is limited by stoichiometric conditions. This
leads to the cycle having an equivalent or lower
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thermodynamic efficiency and an equivalent or better
mechanical efficiency, to an equivalent or higher
turbine efficiency, equivalent or higher turbine power
density and equivalent or longer turbine life. The
operating conditions can be chosen such that either
smaller, more effective or longer-life engines are
achieved.
Example 8:
All the Examples 1-7 can be operated with an operating
fluid enriched with oxygen, in order that the
stoichiometric point is shifted towards higher fuel
injection levels. This is combined with increased
cycle extension fluid injections, in order to keep the
combustion temperatures below the limits which are
important for long engine life. This results in the
cycle having a similar thermodynamic efficiency as well
as a better or equivalent mechanical efficiency, an
equivalent or higher engine efficiency, equivalent or
higher engine power density, and equivalent or longer
engine life. The operating conditions can be chosen
such that either smaller, more efficient or longer-life
engines are achieved.
Example 9:
This example represents a limiting case of the Example
8 based on one of the Examples 1-7, in which case pure
oxygen is used as the operating medium in conjunction
with repeated fuel injections and cycle extension fluid
injections (CEF injections), in order to keep the
combustion temperatures below the limits which are
critical for a long engine life. The graphs 5A and 5B
relate to the cycles 4 of a conventional piston engine
with external ignition, which is operated sub-
stoichiometrically in stratified charging conditions.The cycles 1 relate to a conventional piston engine
with external ignition, which is operated
stoichiometrically with pure oxygen and which reaches
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excessively high operating temperatures. The cycles 2
relate to a modification according to the invention, in
which operation is carried out with pure oxygen and is
limited by stoichiometric conditions. The cycles 2+3
represent operation which is modified according to the
invention and operates with pure oxygen using the
Atkinson cycle, in which case, once again, limiting
occurs as a result of stoichiometric conditions.
In Figures 6A and 6B, the cycles (4) relate to a
conventional piston engine with self-ignition, which is
operated sub-stoichiometrically. The cycles (1) relate
to a conventional piston engine with self-ignition,
which is operated stoichiometrically with pure oxygen,
which leads to an excessively high operating
temperature. The cycles (2) relate to an engine which
is modified according to the invention and which is
operated with pure oxygen, limited by stoichiometric
conditions. The cycles (2) + (3) relate to an engine
which has been modified according to the invention and
is operated with pure oxygen using the Atkinson cycle,
limited by stoichiometric conditions.
The graphs in Figures 7A and 7B show the cycles (1)
which are based on a conventional gas or fuel turbine
which is operated sub-stoichiometrically. The cycles
(2) relate to a conventional gas or fuel turbine, which
is operated stoichiometrically with pure oxygen, which
results in excessively high operating temperatures.
The cycles (3) are based on gas or fuel turbines which
are modified according to the invention and are
operated with pure oxygen, limited by stoichiometric
conditions.
This leads to the cycle having a similar thermodynamic
efficiency and a higher or equivalent mechanical
efficiency, which leads to an equivalent or higher
engine efficiency, equivalent or higher engine power
....
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density, and equivalent or longer engine life. The
operating conditions can be chosen such that either
smaller, more effective or longer-life engines are
achieved.
Example 10:
All the Examples 1-9 are operated with the addition of
small amounts of, for example 0.01% H2O2, O3, organic
peroxides or other oxidizing substances in the cycle
extension fluid, in order to clean the exhaust gases.
If water is added as the cycle extension fluid, small
amounts of H2O2 or O3 additives may be achieved simply
by on-line (through-flow) electrolysis of water.
Example 11:
All the abovementioned Examples 1-10 are operated with
a large amount of H202, O3, organic peroxides or other
oxidizing substances being added to the cycle extension
fluid, in order to increase the power density further,
in that a portion of the oxidizing substance is added
to the cycle.
Example 12:
All the Examples 1-11 described above are operated such
that the cycle extension fluid can also be mixed with
aqueous fuels or fuels which can be dispersed.
Ignition is carried out by a concentrated fuel charge,
and the diluted fuel then burns in an environment of
cycle extension fluid. This application is limited by
the situation in which all the fuel is supplied to a
cycle extension fluid base.
Example 13:
All the Examples 1-12 are provided with a recovery
system for cycle extension fluid in the exhaust gas
line. There are three reasons for such recovery.
Concentration of the cycle extension fluid is linked to
bonding of a major portion of materials in the form of
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particles and water-soluble impurities. A major
portion of this is destroyed in the combustion process
by feeding it back into the cycle, as a result of which
additional heat is obtained and the exhaust gases are
cleaned. A second reason is that the flow of the cycle
extension fluid can be up to 20 times greater than the
fuel flow. If one considers use in a car whose diesel
oil consumption is 3 l/100 km, the engine would consume
up to 60 l/100 km of cycle extension fluid. Even in
the case of water, which is available all the time and
is cheap, the water reservoir could be replaced by a
conventional water recovery unit, just for volume and
weight reasons. A third reason is the costs when
expensive cycle extension fluids are used.
Figure 8 shows a typical exemplary embodiment for
recovery of the CEF. This comprises a circulation pump
105, which causes the cycle extension fluid to
circulate through an air cooler 106, which is followed
by direct injection of the cycle extension fluid 107
into the exhaust gases 101 in a gas washer 102, in
which case direct contact condensation is achieved.
The condensed cycle extension fluid is then separated
in a settling tank and/or a cyclone 103. The cycle
extension fluid is fed back to the storage tank 104,
which is provided with an overflow 110 and an outlet
111. Exhaust gases 101 can optionally be precooled in
a heat exchanger 109, which once again heats the
exhaust gases 108 emitted from the cycle extension
fluid.
