Note: Descriptions are shown in the official language in which they were submitted.
GENERA~ DISCUSSION
Ihis invention refers to internal combustion en-
gines of any kind and especially to fuel injection engines
of the compression-ignition and of the spark-ignition types.
The main object of the invention is to minimize the energy
losses experienced with the usual internal combustion en-
gines.
Two major heat losses are encountered in the opera-
tion of the conventional engines: the first one derives
from the necessity to cool the metallic parts which come
into contact with, and contain the working substance while
it develops the thermodynamic process, the second one i8
due to the inevitable evacuation from the working space of
the combustion products while they still contain a substan-
tial portion of the heat of combustion. If we consider thatthe walls of the combustion chamber may be exposed to com-
bustion temperatures of 1500 to 2200C, and that the evac-
uated produots may enter the exhaust manifold with a tem-
perature of 400 to 800C, we realize that a considerable
waste of valuable energy may be caused by the heat losses.
Steps have been devised and occasionally put to
work to regain in some measure these losses; nevertheless
a distinction should be made regarding the scope and object
of such endeavors. lhose instances where the recovered en-
ergy is used for purposes independent from, and not affect-
ing the operation of the engines, should not be related to
the present invention. For example, the warm cooling fluid
or the hot exhaust gases may be fed to installations which
do not form a functional part of the internal combustion
engine. ~he recovered energy represents still a loss for
the engine, however useful the operation of said instal-
lations might be. In the section dealing with the prior
art, only those applications that are integrated in the
function of the engines and are devised to improve their
efficiency shall be taken into consideration.
Notwithstanding remarkable advancements in the
design of the engines, other disadvantages apart from the
mentioned heat losses still persist. ~or instance, limita-
tions are imposed to the compressiOn ratio because of pos-
sible knocking. It is evident that attaining higher tem-
perature levels of combustion, under higher pressures, and
without inducing knoc~ing, will result in improved thermo-
dynamic cycles. Increasing the compression ratio may be ac-
complished by supercharging or pre-compressing the combus-
tion air, or the air-fuel mixture, before they are intro-
duced into the engine's combustion space. This step has
been adopted only in limited cases for spark-ignition en-
gines with pistons. Of course, most compression-ignition en-
gines and all gas turbines must be equipped with compressing
apparatus for the air supply. It is, however, apparent that
providing internal combustion engines, in general, with pre-
compressing devices will improve their performance, on con-
dition that said devices be not wasteful energy-wise.
An inconvenience, inherent to the currently used
jacketed cooling systems, derives from the relatively cold
metallic surfaces enclosing the combustion process. There
results a quenching of the combustion in the layer adjacent
to the metallic surface, yielding products of incomplete com-
bustion. Dissociation of some nitric oxides, produced in the
hot zones is also prevented by the sudden cooling. These by-
products of the combustion are the pollutants currently be-
ing emitted by the engines. A remedy would consist in fea-
sibly increase the temper&ture of the walls confining the
process of combustion. Noteworthy, the ~anadian patent of
-- 2 --
1915, ~Jater Jacketing Process, 165954, to J.B.~eriam, claims
efficiently utilizing the fuel by maintaining the cooling
water at a temperature of about 135C while producing steam
under the pressure of 2.5 kg/cm2ga. A pressure of similar
magnitude, whereby the coolant may attain a similar temper-
ature has been adopted for the cooling systems of modern
engines; such pressurized systems are, however, not devised
as steam generat~rs, but are rather intended to prevent
boiling of the water inside the cooling jackets.
It cannot be maintained that the comparatively
small increase of the coolant's temperature, as related
here, would eliminate the production of pollutants. ~ven
putting into practice the system proposed in the Canadian
patent 157796 of 1914, to W.J.Still, Internal Combustion En-
gine, whereby circulating cooling water is caused to boil
under a pressure of about 15 kg/cm2ga, the temperature dif-
ference between the evolving combustion and the coolant
having the corresponding saturation temperature of about
1935, would not be significantly diminished, and conse-
quently the quenching of the working substance would not besubstantially reduced. It should be noted that a metallic
wall through which heat is being transferred will attain a
mean temperature nearer to that of the fluid presenting the
greater convection coefficient. In jacketed cooling systems
with circulating liquid coolants, mostly water, the walls
confining the combustion process will have a mean temper-
ature near to that of the coolant, the heat convection being
much more active from wall to said coolant.
PRIOR AR~
Many attempts have been devised to recuperate heat
that is usually wasted in the operation of internal combus-
tion engines. ~onsideration will be given here to specific
-- 3 --
endeavors which might be related to the present invention.
~ he ~anadian patent 157796 mentioned in the pre-
ceding section may be included in the prior art because it
represents an attempt to recover waste heat by generating
steam to be used in the engine. ~he saturated pressure
steam would be introduced into the engine's cylinder, under
the piston, thus transforming the engine into a hybrid ma-
chine, operating as an internal combustion engine above the
piston, and as a steam engine under the same piston.
In the Canadian patent 412278 of 1943, to C.K.New-
combe, Liquid Cooling Systems, vapor produced in the engine
jacket is compressed by means of an injector-type heat pump
and delivered with increased pressure and temperature to a
high pressure condenser (radiator). ~he high pressure con-
densate is returned to the cooling jacket through an expan-
sion valve. The high pressure steam to be used as motive
power in the heat pump is obtained from a by-pass stream of
the high pressure condensate which i9 circulated through a
jacket enclosing the exhaust manifold, or through a pipe
coiled around said manifold. A variant arrangement is des-
cribed, where usual cooling medium is circulated through
the engine jacket and is discharged through a heat-ex-
changer where it is cooled while heating and vaporizing a
highly volatile refrigerant.
Another invention having a similar object has
been patented in Canada in 1954 (Patent 505611, Engine Cool-
ing System Utilizing r1aste Heat, to ~.C.Harbert and W.~,
Corey). ~he cooling liquid is circulated through the engine
jacket whereby it is heated to substantially vaporizing
~0 te~peratures and is discharged into a steam separator. lhe
separated steam is used to drive a low pressure turbine
having a fan mounted on its output shaft. ~he fan produces
-- 4 --
an air current which activates the cooling effect of a
condenser wherein the exhaust steam from the turbine is
condensed. Remarkably, the inventors stress upon the ad-
vantages derived from maintaining the cooling fluid at
higher temperatures, omitting, however, to indicate the
magnitude of the "substantially vaporizing temperatures".
The Canadian patent 523692 of 1956, to ~.R.Hull,
is virtually an alternative to patent 505611. It presents
mainly an improvement to the vapor separator included in
the cooling circuit. ~he turbine, an essential feature in
the preceding patent, ha6 been abandoned. A solution to
the problem of removing the temporary hardness from the
make-up water i8 proposed: the salts precipi~ated in the
separator will be periodically blown out.
~he Oanadian patents 392846 of 1940, Steam Carbu-
retor, to ~h.Bibeau, and 700185 of 1964, Vapor Generating
Apparatus, to G.C.Berger, both having for object humidify-
ing the combustion air or the air-fuel intake to the en-
gine, comprise small vapor generating devices mounted on
-- 5 --
the engine's exhaust manifold. Apparently the steam supply
for the intended application is assumed to be very small,
accordingly the recovery of waste heat is minimal.
A nu~ber of inventions and adaptations have been
devised whereby liquid water is admixed, injected, or in-
troduced in some other way into the working substance or
into the components thereof, before, during, or after combus-
tion occurs. Some of these designs specify the added fluid
as a combustion modifying liquid ingredient such as water,
or a mixture of water with alcohol, etc. The admitted pur-
pose of the water injection is to control the strength of
fuel mixture in supercharged engines, or to control the in-
take pressure of the air-fuel mixture, or to prevent knock-
ing in supercharged engines. The Canadian patent 693772 of
1964, Internal Combustion Engine, to L.$.~arnes, describes
means for injecting water into the engine cylinder during
the power stroke. The water is converted into superheated
steam and supposedly contributes to pushing the piston.
Substantial gain in thermal efficiency is claimed
in the Canadian patent 901901 of 1972, ~ngine System And
$hermogenerator $herefor, to G.L.Ginter, describing a sys-
tem which combines internal combustion with external combus-
tion in a single engine. The working substance would be
supplied at nearly constant pressure and temperature. The
compression and the expansion strokes take place in sepa-
rate cylinders, the volumetric capacity of the expansion
cylinders being twice as large as that of the compression
cylinders. The doubling of the volume of the working sub-
stance is obtained by injecting water into the separately
provided combustion chamber, whereby the ideal rate of
water to be injected should equal, in weight, the combined
weight of the fuel and compressed air input. In terms of
-- 6 --
usual air to fuel ratios, this means that about 19 kg of
water would be injected for every kg of fuel consumed. To
minimize the heat dissipation into the ambient atmosphere,
the engine is completely enclosed in thermal insulation.
~or the record, it should be noted that the maxi-
mum rate of modifying liquid injected in turbo-jet engines,
consisting approximately of 75~ water and 25C~o alcohol, is
5 weight units of the liquid to one weight unit of fuel.
The techniques of supercharging the intake of in-
ternal combustion engines and, in general, of pre-compres-
sing the combustion air, which are at present in use, con-
sist of centrifugal compressors or of injector-type com-
pressors, the latter utilizing compressed air as motive
power. ~he centrifugal superchargers may be driven by the
engines, either directly or through appropriate gearing;
they may also be driven by gas turbines which use exhaust
gases from the engines as motive power. The compressed air
needed for the injector-type compressors must be furnished
by separate mechanically driven compressors. Injector-com-
pressors using steam as motive power have been proposedfor boosting the pressure of coolant vapors, as was men-
tioned in relation with Canadian patent 412278, but no such
steam injector-compressor has been used until now as super-
charger, or as intake air compressor, in combination with
internal combustion engines.
CO~C~USIO~S ~0 ~HE PRIOR AR~
~ he described attempts to recover the heat losses
by raising steam or vapor from the cooling liquid, and by
causing the produced vapor to perform useful work, shall be
evaluated with a view to the following two questions: first,
how large a portion of the heat that would otherwise be
wasted is being recuperated; second, in what measure is the
-- 7 --
engine's efficiency affected by putting to work the recov-
ered enrgy.
Recovering a more or less substantial portion of
the waste heat may be attained by means already known. An
5 average-to-good recuperation could be expected by imple-
menting the Canadian patents 157796, 165954, 412278, 505611,
523692, which take zdvantage of an active heat convection
from metal to coolant, and of possibly extended heat trans-
fer surfaces. Only poor recuperation might be achieved in
other cases, where the heat transfer surface is rather lim-
ited, or the water is stagnant, etc.
In the present state of the art, and with a view
to the above second question, the results obtained by uti-
lizing the recovered energy,through the vehicle of steam
15 generated from waste heat,are questionable. ~or instance,
in the application of the Canadian patents 412278 and 505611
an improvement in the specific function of the radiators or
condensers is achieved, resulting in a more intensive dis-
sipation into the atmosphere of the heat removed from the
thermodynamic process. ~o improvement in the engine's fuel
consumption is thereby intended or accomplished. ~o benefit
to the engine operation is derived from the generated steam
when implementing those other inventions where the steam is
used elsewhere. ~he same applies to the inventions where
the generated steam is condensed without performing work.
~ he parameters of the produced steam are important
for its possible utilization. In most patents relative to
steam generating cooling systems low pressures seem to be
preferred. ~he Canadian patent 157796, having for object
the already mentioned steam-internal combustion engine,
is an exception inasmuch as it specifies steam of about
15 kg/cm2ga.
-- 8 --
In all known vaporizers or generators using waste
heat from internal combustion engines, the steam, or vapor,
produced is in the saturated s~ate, it being separated from
the liauid phase either when it leaves the boiler, or in
distinct separators through which the liquid-vapor mixture
is circulated. ~he saturation temperature, associated with
the steam pressure, is significant because of its possible
effect in preventing cold metallic walls. As was shown in
the General Discussion, however, coolants at saturation
temperatures in the range of 193~ would not reduce substan-
tially the quenching of the working substance.
It will be sho~n now that the utilization of the
saturated steam, as devised and practised in the prior art
is uneconomical.
We shall consider in the first instance those sys-
tems where the steam is used as working substance in a
steam engine of the reciprocating or of the rotating type. -~
The steam engine shall, of course,form an integral part of
the internal combustion engine and shall contribute, as
such, to its efficient operation.
~ et us assume that in a waste heat recovery system
of a known type, about 1/3 (approximately 3000 kcal) of the
heating power of 1 kg fuel (rated at 9500 kcal/kg) is used
to generate steam at 15 kg/cm2ga. Ideally about 4.5 kg of
steam having an enthalpy of 662 kcal/kg might be produced.
Putting this fluid to work in a steam engine, from which
it would be exhausted under a pressure of at least 1.25 ata,
its quality would drop to about 0.92. ~aking into account
minimal thermal and mechanical losses, the equivalent of the
~ork regained could not exceed 50 kcal per kg steam used,
totaling about 225 kcal out of the 3000 kcal being recovered.
Should the stea~ be generated under a lower
_ g _
s~
pressure, the useful work to be gained would be even less.
In the second instance, we shall consider the pos-
sible effect regarding the performance of internal combus-
tion engines if saturated steam is admixed to the combustion
products in their working space.
An increase in the output of mechanical work was
expected as a consequence of the retarded combustion, when
injecting saturated steam into the working cylinders during
the power stroke. ~he expected increase of the produced
work is, however, not likely to occur.
~ et us assume that the following favorable condi-
tions prevail:
- h steam generator, recovering a sufficient portion
of the waste heat is provided, said generator being similar
to those known in the prior art but being capable to raise
steam having a pressure between 10 and 15 kg/cm2ga, which
would ha~e an enthalpy of 657 to 662 kcal/kg. Doubtless the
steam pressure has to be higher than the pressure of the
working substance at the time of the injection into the cyl-
inder (or working space);
- Steam is generated and injected at a rate of approx-
imately 4.5 kg per kg fuel consumed by the engine;
- ~he internal combustion engine is operated with a
minimum of excess air.
When it is introduced into the working space and
mixed with the products of the combustion, the steam attains
the state of one component in a mixture of several gaseous
components. Its pressure drops to the partial value corre-
sponding to the ~Iol ratio of H20 to the other components
present in the working space. It can be proved that at the
assumed rate of steam injection with an average fossil fuel,
burnt efficiently, the partial pressure of the (total) water
-- 10 --
vapors present will be equal to about 39~o of the pressure
of the mixture. ~ecause of the heat interchange with the
hot combustion products and its drop in pressure, the steam
becomes superheated. The superheat being achieved at the
expense of the combustion heat and the specific heat of the
steam being higher than that of the other gaseous components
present, a certain down toning and slowing of the combus-
tion will take place. Irrespective of the way the process
develops after the injection, the steam will continue to be
superheated until it is evacuated with the combustion pro-
ducts from the working space. It is convenient to use the
term "combined eYhaust gases" to denote the steam enriched
evacuated gases. Conditions and parameters of the gases
evacuated from internal combustion engines vary widely de-
pending on the type and mode of operation of the engines,on the back-pressure prevailing in the exhaust manifolds,
etc. ~ack-pressures of 1.3 to 1.7 kg/cm2abs may be reason-
ably assumed: the corresponding partial pressure of the
steam will range from 0.51 to 0.66 kg/cm2abs. Statistical
data from testing of various engines show values of ex-
haust temperatures ranging from 400 to over 800C, but even
if the temperature of the combined exhaust gases would drop
below 400C the steam in the mixture would still be super-
heated. Actually, under the assumed partial pressures, it
would be so at any temperature above 90C. ~he enthalpy of
superheated steam with the parameters of 0.51 to 0.66 kg/cm2
abs and, say, 300C is about 735 kcal/kg. It becomes evident
that in such circumstances additional combustion heat will
be wasted, namely at a rate of about 735 - 662 = 73 kcal
for every kg of saturated steam generated and fed into the
working space of the engine.
Consideration has been given to various systems,
-- 11 --
wherein liquid water is injected or sprayed, or introduced
in some other way into the working substance of internal
combustion engines. ~he purpose of admixing water to the
working substance may be to make the operation of the en-
gines more flexible. Prevention of detonation may also beattained. Whatever the advantages claimed, no gain in the
mechanical work produced is likely to result . ~he water
will vaporize and the vapor will be superheated, all of
this being obtained at the expense of the combustion heat.
~he superheated steam will participate to the further evo-
lution of the working substance, being evacuated from the
engine as a component of the combined exhaust gases. ~s
was shown above, the evacuated low pressure superheated
steam may have an enthalpy exceeding 700 kcal/kg, almost
all of which would be subtracted from the thermodynamic
process,to be dissipated into the surrounding atmosphere.
It is consequently evident that increasing the mass
of the working substance in the engine, by addition of sat-
urated steam or of liquid water, will not result in a gain
in the energy balance of the process.
Since the combustion products evacuated from the
working space may contain a substantial portion of the com-
bustion heat, adaptations of the exhaust system have been
made in order to possibly recuperate some of the heat. ~he
embodiment of the Canadian patent 157796 includes a heat-
exchanger equipped with a bank of tubes through which the
exhaust gases flow, giving up heat that generate~steam. In
other inventions only a part of the exhaust manifold is
adapted as a vapor generator. ~he saturated steam obtained
from the engine's jackets and the adapted exhaust system,
or from the latter alone, is eventually used in the opera-
tion of the engine. It is obvious, however, that for the
- 12 -
generated steam to be useful, at all, a minimum value of
the saturation pressure would be required. This sets a lim-
it to the lowest temperature at which the exhaust gases
should leave the vapor generator, in order that heat might
be transferred. The preceding analysis was based on the
desire to raise steam having a saturation pressure of 10 to
15 k ~cm2ga with saturation temperatures ranging from 183
to 193C, in which case the temperature of the exhaust
gases should not drop below 220 to 230C. Although it might
be argued that steam at a pressure of, say, 3 kg/cm2ga,
having a saturation temperature of 142C, could still be
usable, the exhaust gases could not practically be cooled
below about 170C. ~ut if this low pressure steam, having
an enthalpy of 652 kcal/kg is fed into the internal combus-
tion process and finds its way into the exhaust system, itwill terminate its supposed useful function as low pressure
superheated steam with increased enthalpy. At a partial
pressure of about 0.5 kg/cm2 abs and at a temperature of
about 170C (which would be required for the process to be
feasible) the steam enthalpy would amount to 671 kcal/kg,
contributing to increase the heat content of the combined
exhaust gases, instead of recovering some waste energy. In
the same way, if steam of higher pressures is generated,
higher temperatures of the exhaust gases would be required
to produce it, resulting in a still higher heat loss.
Finally, the result attained by using the exhaust
gases as motive power in a gas turbine, which would drive
a centrifugal supercharger, shall be considered. Turbo-
chargers are used to boost the intake pressure at a ratio of
1.5/1 to 3/1 or more. To make the system operative, the gases
shall enter the turbine at a measurably higher pressure than
the back-pressure maintained in the usual exhaust systems.
- 13 -
Reckoning with a reasonable efficiency of the turbine-
turbocompressor combination, a back-pressure of at least
4.5 kg/cm2abs at the exhaust valves of the engine would be
required, while the turbine outlet pressure could be kept
at 103 k~cm2abs. The increase of the back-pressure auto-
matically results in an increase of the temperature of the
combustion gases at the end of the expansion stroke. In
any case, the temperature of the exhaust gases fed to the
turbine might well be at a level of 600~. With a near-adi-
abatic expansion of this working substance, the exhaustgases will leave the turbine at a temperature of about 300C
which is well above the previously assumed exit temperature
of 170C.
In conclusion, whether evacuated directly or after
performing some useful service, as practised in the present
state of the art, the exhaust gases still have a relatively
high enthalpy.
In the once-through participation of the steam or
of the injected water, meaning by this that the generated
steam or the vaporized injected water is eliminated after
going once through the thermodynamic process, a big disad-
vantage has to be considered. Make-up wæter has to be sup-
plied at the set proportion to the consumed fuel. In the in-
ventions related to the vaporizing cooling fluid discussed
hereinbefore, the engine jackets form the essential elements
of the steam generators. It must be realized that procvring
water which is free from dissolved minerals would be quite
expersive, not to say prohibitive, especially when the re-
quired quantity is a multiple of the quantity of fuel con-
sumed. Mud and scale build-up is inevitable when co~monly
available fresh water is vaporized. ~he problem becomes
serious if deposits for~ in the intricate passes of the
- 14 -
cooling jackets of modern engines. Removing the coating
formed on the outside surface of the pipes arranged in a
bundle in a heat-exchanger may al~o be an almost Impossible
taskO Similar troubles may be experienced when liquid water
is injected or sprayed, or even introduced as an emulsion
with the fuel, to be vaporized in the combustion chambers,
in the cylinder6, or in the attached passages, leaving de-
posits that will obstruct the operation of the engines.
An attempt to deal with the problem has been made
in the Canadian patent 523692. ~his patent, however, does
not relate to a once-through utilization of the steam and
the quantity of make-up water iæ rather small. ~he solution
proposed provides for the fresh water to be fed into the
swirling current produced in the steam separator, where the
hardness forming minerals would precipitate. ~he precipitate
would be blown off periodically, presumably without being
entrained in the vaporization circuit.
Regarding the supercharging by the procedures used
in the present state of the art, it should be remarked that
these procedures consume useful energy, either by diverting
a part of the power from the crankshaft, or by converting
some other form of usable energy. It has been already shown
that driving a turbocharger by a gas turbine ut~lizing the
engine' 9 exhaust ga~es is relatively uneconomical. It is to
be noted also that increasing the engine's compression by
pre-compressing the charge without using a combustion modi-
fier might bring about knocking.
Æ ~RA~ D~S~RIP~ION OF ~HE INV~TIO~
In this disclosure steam with a pressure o~ 10 to
15 kg/cm2ga has been assumed as a desirable working medium,
to be produced by heat recuperated from the exhau~t gases,
~- thereby saving a great portion of the heat that would be
-15 -
otherwise rejected with said exhaust gases. After being dried
and ~uperheated to a temperature of about ~00C, which is to
be considered as an intermediate or partial superheat, the
working medium thu~ obtained is used in an injector - type
compres~ing apparatus to pre-compress the combustion air,
~he resulting air-steam mixture i9 forced to flow through
the jacketed cooling system of the engine. ~y circulating
through the engine's jacket, the steam is further superhea~d
together with the combustion air, the compressed mixture
being delivered to the engine with increaæed enthalpy, at
the rate required by the internal combustion process. While
being superheated, the air-steam mixture serves a~ a cool-
ant for the hot metallic parts of the engine, with the double
advantage of recuperating heat that would be dissipated with
usual cooling systems, and of maintaining the metallic walls
of the working space at conveniently higher temperatures.
~ he pressure steam is generated in two successive
steps, achieved in distinct devices arranged in countercur-
rent to the flow of the exhaust gases. In the first step
the feed water is heated from its storage temperature to a
temperature nearing, but appropriately below, its vaporiza-
tion temperature, while being pumped through the tubes of a
preheating heat-exchanger. ~he preheated water, maintained
at a pressure appropriately above the pre-selected working
pressure of the steam, is transferred to the second step
at a rate controlled 90 as to make up for the generated and
consumed steam.
The second step includes a vaporizing heat-exchan-
ger, through the tubes of which a fluid stream composed of
~0 recycling saturated water and of the preheated water from
the first step is kept in forced circulation whereby it is
_,
- 16 -
SS
sub~ected to heating and vaporization. ~he steam-water
mixture obtained is di6charged in a steam separator where
saturated steam is set free, whil~ the saturated water col-
lects as a reserve from which a circulating pump feeds the
continuous stream through the vaporizing heat-exchanger
incorporating on its way the preheated make-up water. ~he
saturated steam leaves the separator through suitable dry-
ing means and is condusted to an intermediate superheater
from where it emerges as partially superheated steam. ~he
intermediate superheater is combined with the engine's
exhaust manifold. In the application of this invention to
gas turbines, where a distinct exhaust manifold i9 miB9iIlg,
the intermediate superheater is formed around the turbines'
combustors. ~he partially superheated pressure steam shall
be used as motive power for a compressing apparatus oon-
sisting of an injector-compressor or, where a higher com-
pression i~ required, of at least two injector-compressors
mounted in series. Said compressing apparatus serves to
draw and supercharge or boost the required combustion air,
whereby the compressed air-steam mixture is forced to flow
through a one-way sequence of jac~eting compartments en-
closing the engine's working space, where it attains its
final temperature, and from where it is delivered through
suitable means to the combu~tion space of the engine.
A sufficient quantity of partially superheated
pressure steam shall be produced to achieve the required
compression. When being discharged through the steam noz-
zle (or nozzles) of the compressing apparatus, part of the
steam enthalpy is converted into kinetic energy. Enowingly
~0 in an in~ector-compres~or not all the capacity of the
steam jet is utilized for producing mechanical work.
; .~ However, the unused kinetic energy and the unconverted
- 17 -
enthalpy of the injected steam will not be wasted, because
the steam will mix thoroughly with the air in the diffuser
(diffusers) of the compressing apparatus and in the follow-
ing passages of the cooling jacket, whereby an interchange
of heat between the two fluids will occur.
In the reverse order, the devised recuperation of
heat is described as follows. The combustion taking place
in the working space of the engine yields high te~.perature
combustion products. In order to maintain the engine in
operating conditions, the metallic walls of the working
space must be adeouately cooled, whereby the hot products
of the combustion give part of their heat to the air-steam
mixture that flows through the cooling jac~et. ~he air-
steam mixture, serving as a cooling fluid, may be super-
heated to a pre-selected temperature in the range of 360
to 400~. ~o prevent the temperature of the metallic walls
rising above acceptable limits, means are provided to a-
chieve an active heat convection from metal to the air-
steam mixture, thus causing the metallic walls to maintain
a temperature close to that of the cooling fluid. ~hese
means consist of a succession of passages through which
said fluid is forced to flow at high speed, the surface of
the wall in contact with the fluid being provided with
fins which have the double function of increasing the heat
transfer surface and the Reynolds number of the flow.
It must be stressed upon that the primary function
of the flow of fluid in the jacketing system is to contin-
uously cool the engine. ~he superheating of the air-steam
mixture, which is essential to the successful recovery of
waste heat, actually represents a convenient secondary
function of the system.
~he combustion products flowing through the exhaust
- 18 -
~anifold, which is combined with the intermediate super-
heater, supply the heat required to superheat the saturated
steam to a pre-set intermediate temperature. Beaving the
intermediate superheater, the still hot exhaust gases flow
through the vaporizing heat-exchanger, outside the tubes
in which the described second step of the steam generating
is achieved. In order that heat might be transferred, the
exhaust gases leave this heat-exchanger with a suitably
higher temperature than the saturation temperature corre-
sponding to the pre-selected steam pressure. In continu-
ation, the exhaust gases are conducted to the preheating
heat-exchanger and flow outside the tubes wherein the
make-up water is preheated, whereby the temperature of the
gases drops to a final, low level. Oooling the exhaust
gases to 120C, or below, is quite feasible in this way.
The economic result of the invention may be illus-
trated by the following example.
~ et us assume that steam is generated with the de-
scribed procedure with a pressure of 15 k~cm2ga, to which
pressure corresponds a s~turation enthalpy of 662 kcal/kg,
and that by being partially superheated its temperature
rises to 300C, whereby its enthalpy increases to 725 kcal/
kg. In this state, the steam is discharged through the in-
jection nozzles of the compressing apparatus. As already
mentioned, said apparatus produces a compressed mixture of
combustion air and steam which is forced to flow through
the engine's cooling jackets and is delivered, after being
superheated, to the working space of the engine. A final
temperature of the superheated air-steam mixture of about
400O is considered as possible and advisable. Because of
the improved combustion conditions, it will be possible to
operate the engine with a minimum excess air. ~e shall
- 19 -
s
assume that 16 kg of (dry) air would suffice for the com-
plete combustion of one kg of conventional fossil fuel. In
the hypothesis that the combustion air is pre-compressed in
a ratio of 3/1, the energy demand for the compression can
5 reasonably be assumed to be about 17 kcal/kg air, adding up
to 272 kcal for the quantity of 16 kg air. From the enthal-
py ofthe partially superheated steam, approximately 63
kcal/kg is available, over its saturation enthalpy. If we
impose the condition that the steam should not condensate
in the diffuser of the compressing apparatus, about 4.5 kg
of partially superheated steam should be discharged through
the injectors. It will be assumed, accordingly, that the
steam entering the jacketing system admixed to the air will
have an enthalpy of no more than 662 kcal/kg.
~he partial pressure of the steam in the pre-com-
pressed air-steam mixture equals about 0.95 kg/cm2abs. ~he
steam enthalpy at this pressure and at the temperature of
400C is 783 kcal/kg, which means that by flowing through
the engine's jackets the steam will pick up about 121 kcal/
kg from the hot metallic walls. At the same time the com-
bustion air, which would be heated from, say, 20C to
400C would gain, at an average cp = 0.246 kcal/kg deg C,
about 93 .5 kca ~ kg.
It is assumed that adequate heat transfer areas and
25 fluid flow conditions are provided to achieve the devised
exchange of heat. Ideally, the heat quantities recovered
in the described system, when related to one weight ur.it of
fuel consumed in the engine (the calorific power of said
fuel being about 9500 kcal/kg) will be su~med up as follows.
Heat transferred in the engine's jackets:
- for superheating 4O5 kg steam 545 kcal
- for heating 16 kg air 1496 ll ~otal 2041 kcal
- 20 -
~Ieat transferred from the exhaust system:
- for preheating 4.5 kg make-up
water from 20C to 180C 720 kcal
- for producing sæturated steam
from the preheated water 2169 ~i Total 2889 ~:al
The recovered heat reintroduced in the thermodynamic pro-
cess would, accordingly, amount to 4930 kcal. Besides,
about 280 kcal would be recovered and converted irto the
useful work of pre-compressing the combustion air.
~ot all the heat recovered will represent a gain.
For example, after going through the process, the stea~
admixed to the com~ustion air will be evacuated at low pres-
sure but still in the superheated state. ~s was shown in
the examples discussed hereinbefore, which assumed steam
15 injected at similar rates, the partial pressure of the
total steam ~iOe. including the water vapor produced in the
combustion) that is evacuated from the engine, may be in
the range of 0.51 to 0.66 kg/cm2abs. At 0.66 kg/cm2abs and
at a temperature of 120C the steam will have an enthalpy
20 of 650 kcal/kg. The actual recuperation from the introduced
superheated steam will be equal to 783 - 650 = 133 kcal per
kg of steam, or 598 kcal per kg of fuel consumed. ~his
represents 6.3% of the heating value of the fuel, comparing
very favorably with the net loss experienced with all prior
25 systems utilizing saturated steam (or water). On the other
hand, introducing in the thermodynamic process the heated
combustion air will result in an important improvement of
the engine's efficiency. In this invention the two major
heat losses experienced with all known internal combustion
30 engines are concentrated in one single, substantially re-
duced, heat rejection. It can be demonstrated that, in the
assumed conditions, the heat content of the evacuated gases
will amount to about ~600 kcal/kg of the fuel consumed,
representing about 38~ of the fuel's heating value. In all
existing types of internal combustion engines the corres-
ponding heat 108S iS rated at 60% or more.
Since with the heat recovery system forming the ob-
ject of this invention there i8 no need to dissipate heat
until the exhaust gases are rejected, the exposed surface
of the metallic parts, that confine and handle the hot flu-
ids usefully employed in the process, is suitably insulated
against heat loss.
Other advantages are offered by this invention.
The metallic walls confining the engine's working
space will be maintained at higher temperatures than those
prevailing with customary cooling systems because of the
use as a coolant of a gaseous mixture being superheated.
A gain in energy is achieved in so far as les~ heat
is subtracted from the thermodynamic process.
The higher temperatureæ of the metallic walls in ~ - -
contact with the combustion process will also reduce the
emission of incomplete combustion products, as well as the
production of nitric oxides.
Using a gaseou~ fluid as a coolant, prevents the
build up of scale and obstructions inthe jacket system.
The increased content of water vapor of the working
substance, as a consequence of the ¢ombustion air being com-
pressed by means of steam injectors, will a¢t as a detons~ion
suppreæsor, making it possible to adopt higher compression
ratios. The combustion will, accordingly, take place at
higher pressures, resulting in more complete combustion re-
actions with a minimum of excess air.
The average specific heat of the combustion productswill increase because of their higher water vapor content.
- 22 -
~his will effect a lowering of the peak temperature and a
relative slowing of the combustion, e~tending the spread
over which heat i8 released at the highest pressure of the
cycle. ~he increased pressure-temperature parameteræ of
the supplied combustion air will contribute to maintain
the heat release at high potential.
Supplying the combustion air under pressure will
eliminate the intake suction work in the four-stroke cycle,
and the crankcase pumping in the two-stroke proces~.
~here is no special reason to set the rate of the
steam production at 4.5 kg per kg of fuel: an optimal rate
might be established by inveætigating all relevant condi-
tions. For in~tance, les~er pre-compression ratios than 3/1
may be sufficient for most reciprocating engines, but a
higher compression will be required in the case of gas tur-
bines. In that case, the heat for the intermediate superheat-
; ing of the ste&m could be supplied in ample quantity by the
turbines' combu~tors without need to have recourse to much
higher rates of steam in prq~rtion to the combu~tion air.
~he optimal rate of steam production shall match the
normal power output of the engine. With a variable power out-
put, variations in the production of steam will occur. An
adequate operation of the engine will be maintained by the
means of control described hereinafter. Ihese controlling
means have the purpose to adapt the system of air supply to
sustained changes in the engine output.
If the power output rises above the value set as nor-
mal, more recoverable heat will be available, and in con-
sequence of the increased heat supply, one of the following
alternatives is likely to occur: either the temperature of
the superheated air-steam mi~ture will tend to rise much
above the design value because the heat transferred from
- 23 -
the working space into the engine's cooling jackets exceeds
the amount required by the quantlty of mixture flowing
through said jackets; or the mixture's final temperature
drops substantially under its design value because the vol-
ume of the air-steam mixture being discharged by the com-
pressing apparatus exceeds the capability of the jacketing
system to heat it, the exceeding volume being the conse-
quence of a disproportionate increase of the steam produced
in the vaporizing circuit.
~ drop in the power output below the normal rate,
bringing about a decrease in the recoverable heat supply,
will have opposite but similar effects: either the tempera-
ture of the superheated air-steam mixture will fall much
below the design value because insufficient heat is trans-
ferred from the combustion-expansion process; or this tem-
perature will surpass the pre-set limit because of a dispro-
portionate decrease of the steam production in the vaporiz-
ing heat-exchanger, resulting in a relatively reduced air-
steam mixture being discharged through the engine's jackets.
The invention comprises a throttling valve mounted
in the duct leading the gases from the exhaust manifold to
the vaporizing heat-exchanger. Its function is to regulate
the pressure under which the gases are evacuated from the
working space at the end of the expansion phase. It is ob-
vious that,by regulating the back-pressure exerted on the
engine, this throttling device will control the temperature
(and the enthalpy) of the exhaust gases. ~he throttling
valve is actuated by a servomechanism taking the impulse
from a temperature sensor located in the transfer pipe of
~0 the superheated air-steam mixture. If the measured tempera-
ture of the mixture rises above a set limit, the throttle
reduces the free section of flow, causing the back-pressure
- 24 -
to rise. ~he enthalpy of the exhaust gases will increæse,
augmenting the heat svpply to the vaporizing heat-exchanger,
thus producing more steam. The throttling valve is adjusted
so that, in normal operating conditions, it will take an
intermediate position between the most restricted section
and the full opening of the gases'passage. Should the meas-
ured temperature of the air-steam mixture fall below the set
limit, the throttle will increase its opening, causing a
drop in the back-pressure and a decrease of the enthalpy of
the exhaust gases, thus reducing the production of steam.
~ he variations of the exhaust gases enthalpy, as de-
scribed above, may affect the heat supply to the make-up wa-
ter being preheated. ~ two-way damper, controlled by a ther-
mostat which measures the temperature of the preheated water,
is mounted in the gases' duct between the vaporizing heat-
exchænger and the preheating heat-exchanger. If the tempera-
ture of the water rises above a pre-set level, the thermo-
stat, acting through a transducer, causes the damper to turn
so as to divert part of the heating gases through a duct by-
passing the preheating heat-exchanger. If the heat supply is
insufficient to heat the water to the design level, no action
would be needed, since in any case the vaporizing exchanger
will supply the heat required to bring the circulating water
to the saturation temperature and to vaporize an adequate
amount of it.
~ he invention includes: automatic blow-off systems to
evacuate from the heat-exchangers the precipitated minerals
forming the hardness of the make-up water; a starting appa-
ratus comprising a cranking motor coupled with an auxiliary
~0 air compressor, the latter to supply motive power for the
injector-compressor d~ring the starting up period, and vari-
ous other accessories as will be described hereinafter.
- 25 -
DETAIIæD DESCRIPTION G~ THE Il~VE~IO~
A detailed description of this invention ~ill be pre-
sented in relation with the accompanying drawings which
illustrate some of its possible embodiments and in which:
Figure 1 is the flow diagram of an internal combus-
tion engine integrated with the heat recovering system;
Figure 2 is a fragmentary sectional view of the cyl-
inder block of a reciprocating engine, showing the system
of cooling jackets with the inlet nozzle for the air-steam
mixture, and the ram manifold for the distribution of the
; superheated intake;
Figure 3 is a lateral view of Fig. 2 , showing the
attached ram manifold, the exhaust manifold combined with
the intermediate steam superheater and the pre-compressing
apparatus;
Figure 4 is a sectional detail of a cylinder of a
two-stroke engine integrated with the heat recovery system;
Figure 5 is a diagrammatic sectional view of a gas
turbine integrated with the heat recovering system, includ-
ing an intermediate steam superheater formed around a com-
bustor, and a two-stage compressing apparatus;
Figure 6 is a detail cross-section taken along the
line II-II of Fig. 5 ;
Figure 7 is a detail cross-section taken along the
line III-III of Fig. 5 ;
Figure 8 is a sectional view across the cylinder
block and the cylinder head taken along the line I-l of
Figo 2 ;
Figure 9 is a sectional view of an exhaust manifold
combined with an intermediate steam superheater;
Figure 10 is a fragmentary view of the steam separa-
ting and water circulating and replenisning apparatus;
- 26 -
Figure 11 is a schematic representation of the
starting apparatus and of its hook up with the compressing
apparatus;
Figure 12 is a sectional view of the vaporizing
heat-exchanger;
~ igure 13 is a cross-sectional view taken along the
line IV-IV of Fig. 12 ;
~ igure 14 is a view of the preheating heat-exchanger;
~ igure 15 is a diagrammatic view of the make-up
water supply system.
In all figures, identical or similar components or
parts are designated by the same reference numerals.
It should be noted that the invention is by no means
restricted to the embodiments represented in the accompany-
ing drawings, it being applicable also in other ways con-
sistent with its stipulated priciples.
As shown in the flow diagram, Fig. 1 , feed water
from the storage tank 11 is pumped by the positive displace-
ment pump 12 through the heat-exchanger 1 where it is pre-
heated and from where it is conveyed to join the vaporizingcircuit, while being controlled by the flow regulating
valve 14 . Said regulating valve is linked with a liquid
level controller 25 attached to the steam separator 21 .
Water discharged by the pump 12 in excess of the make-up de-
mand, is returned to the storage tank 11 through the reliefvalve 13 ~ A circulating pump 22 , taking suction from the
reservoir of the steam separator 21 , maintains a continuous
flow of saturated water to which the controlled amount of
make-up water is added, the joint stream being forced to
flow through the heat-exchanger 2 , wherein steam is gener-
ated. h water-steam mixture flows from the outlet header of
heat-exchanger 2 through a transfer line which conducts it
- 27 -
s
to the stea~ separator. During the preheating and further-
more during the vaporization, minerals dissolved in the feed
water and forming its temporary hardness, precipitate and
are entrained into the outlet headers of both heat-ex-
changers, settling as a sludge at the bottom of said headers.Automatic blow-off devices 16 eliminate the collected sludge.
Practically dry steam leaves the separator 21 through
a vapor line equipped with a pressure regulating valve 26
and is conducted to the intermediate superheater 31 , from
where it is delivered as partially superheated stea~ to the
injector of the compressing apparatus, its flow being regu-
lated by the valve 34 . The combustion air is drawn through
suitable induction means 35 into the injector-compressor 33
thereby being mixed with the steam jet. ~y virtue of the
momentum of masses, the resulting air-steam mixture is dis-
charged through the diffuser whereby it is compressed. ~he
compressed mixture is forced to flow through the successive
sections of the system of jackets 4 , that encloses the en-
gine's working s?ace 3 . While serving as a coolant, the
the compressed air-steam mixture is superheated to its final
temperature, after which it is discharged into the chamber
36 of the ram manifold. The superheated mixture, which is
distributed to the engine through appropriate intake means,
is maintained in said chamber 76 under a pre-selected pres-
sure. To this effect, a pressure sensor actuates with theaid of a transducer 341 the above mentioned valve 34 control-
ling the supply of motive power to the compressing appara-
tus 33 . ~he reouired amount of fuel is suplied to the com-
bustion process by suitable means 37 . Suitable mechanisms
32 transmit the generated mechanical work.
~ leat is transferred during the combustion-expansion
process to the air-steam mixture being superheated. ~esides,
- 28 -
heat is given up by the combustion products, to the satura-
ted steam being partially superheated, at the end of said
process. In the flow diagram outlined in Fig. 1 , the inter-
mediate superheater is combined with the engine's exhaust
manifold; however, in aaapting the invention to gas tur-
bines which are not eauipped with a distinct exhaust mani-
fold, heat is supplied to the intermediate superheater at the
beginning of the combustion process, from the turbine's com-
bustors.
~he still hot combustion gases leaving the engine by
way of the exhaust tube 311 are conducted to the vaporizing
heat-exchanger 2 . ~he throttling device 23 , installed be-
tween the engine and the exchanger 2 , acts as an enthalpy
regulator of the exhaust gases, as was explained previouslyO
From heat-exchanger 2 , the gases are conveyed to the pre-
heating heat-exchanger 1 . A two-way damper 15 actuated by
a thermostat allows for part of the exhaust gases to be di-
verted directly to the evacuation pipe 19 , through a by-
pass duct.
Figures 2 , 3 , 4 and 8 exemplify the adaptation to
multicylinder engines of the system of jackets serving for
superheating the air-steam mixture. ~he mixture is guided
through a one-way path from the less hot to the hottest
regions of the engine, entering the cylinder jacket through
the inlet nozzle 41 , and leaving the jacketed cylinder
head through the outlet nozzle 48 . ~he illustrated system
is subdivided into three successive sections; however,the
number of sections anà their arrangement may be different,
in order to obtain best suited speeds of the flow of the
gaseous mixture and optimum heat convection. For example,
in the case of engine blocks having more than four cylin-
ders in line, it may be advisable to partition transversely
- 29 -
the jacketing 6ystem into several compartments, receiving
the gaseous mixture subdivided in parallel streams.
The surface of the metallic walls being swept by the
stream of gaseous mixture is provided with parallel fins 42
shaped to guide the flow, while transverse ridges 43 and 44
ensure the uniform distribution of the flow around the cyl-
inders and prevent stagnant pockets between adàacent cylinders.
~ he casting of a cylinder bank as exemplified in the
drawings, will require exact positioning of the elaborate
cores, and firm holding of the same during the pouring of
the molten metal. This i5 made possible by providing suit-
ably shaped and sized openings in the lateral walls. These
openings will also facilitate frittering and removing of the
cores after casting, a~ well as thorough cleaning of the
metalli~ surfaces. The openings are closed with covers 46
which were designed of the self-tightening type, and which
will be securily fastened to the structure of the lateral
walls. Sturdy posts 45 cast integral with said structure
serve to guide the flow of the gaseous mixture inside the
jackets and allow for studbolts to be in~talled, for join-
ing the cylinder head to the cylinder block.
The superheated air-steam mixture is conducted by
way of the transfer pipe 480 to the chamber 36 of the in-
take or ram manifold. Shown in ~ig. 3 are the possible lo-
cations of the fuel supply nozzle 371 and of the spark plug,or glow plug, 372 . ~he emplacement of these accessories is
also indicated in ~igures 4 and 8 .
~ igure 5 shows the diagram of a gas turbine ir,te-
grated with the heat recovery system. The turbine is fully
enclosed in a system of cooling jackets. ~or a convenient
assembling of the engine, its casing must be split along a
horizontal plane containing the shaft axis. Each half of
- 30 -
the casing shall consist, in turn, of two separate parts
joined together along a plane adjacent to the exhzust face
of the rotor. ~hen assembled, the system of jackets will
form two separate ringlike compartments, one of which will
encase the stator that collects the exhaust gases and forms
the first section of the superheating-cooling system; the
other one encasing the rotor and the stator that distributes
the combustion products and forms the second section of the
superheater. As shown in the detail ~igure 6 , a partition
plate 401 guides the compressed air-steam mixture, delivered
by the second stage of the compressing apparatus 330 , to
~low in one direction in the first ringlike section. After
completing the circuit, the air-steam mixture enters through
the opening 402 the second ringlike compartment. As shown in
Figure 7 , this compartment is also partitioned by a plate,
designated by the same numeral 401 , causing the mixture to
flow in an opposite direction, around the hotter portion of
the turbine. The superheated gaseous mixture is delivered
through the transfer pipe 480 to the combustor 481 where
the combustion process takes place. The combustion air is
drawn into the suction chamber of the compressor's first
stage 33 through the inàuction tube 35 . The diffuser of
this stage discharges into the suction chamber of the second
stage 330, the diffuser of which discharges directly into
the first ringlike section of the jacketing system.
The jacket 482 , around the combustor, forms the in-
termediate superheater ~iherein the saturated steam is par-
tially superheated, to be utilized as motive po~ler in both
stages of the compressing apparatus.
The numerals 34 , 311 , 371 , 372 designate elements
having the same functions as described in relation with the
Figures 2 , 3 , 4 and 8 . The hot metallic surfaces that are
- 31 -
in contact with the fluids being heated are, likewise, pro-
vided with parallel fins 42 , to guide and control the heat
transfer process.
Shown in the Figures 3 and 5 is the actuating sys-
tem of the flow regulating valve 34 . ~he actuating deviceof said valve is connected with the transducer 341 , con-
verting the relevant pressure variations into adjusting
movements of the valve stem. ~o be noted that, while in
Figure 3 the controlling pressure sensor measures the pre-
compression attained in the engine intake manifold, in Fig-
ure 5 said sensor measures the pressure reached at completed
combustion. The valve actuator is pro~ided with a dual con-
trol system, whereby a secondary transmitter 34~ , connected
with a control unit, may override the action of transducer
341 . ~he specific circumstance where transmitter 343 takes
action will be explained hereinafter.
Figure 9 illustrates the combination of the exhaust
manifold with the intermediate superheater 31 . ~he hot ex-
haust gases leaving the cylinder head via the ports 49 (Fig.
8) are conducted to the manifold through the passages 310 .
~he gases flow through the annular space formed around the
steam carrying, finned pipe 314 and are delivered by way of
the exhaust tube 311 to the following heat exchangers.
~eing subjected to a relatively low operating pres-
sure, the body of the manifold is~made of thinner metalplate and is providèd with at least two corrugations 313 to
compensate the strain due to the difference in thermal ex-
pansion between said body and the steam pipe 314. This pipe
is equipped with groups of longitudinal fins 315 arranged to
allow for the uniform distribution of the exhaust gases as
they enter the annular space through the single passages
310 ; but otherwise designed to achieve the required heat
- 32 -
5S
transfer for duly superheating the saturated steam which
flows through the pipe 314 0
Figure 10 is a diagram of the steam separating and
water circulating and replenishing apparatus. ~he water-
steam mi~ture being conducted from the vaporizing heat-
exchanger to the steam separator 21 in a continuous stream,
is discharged tangentially through the inlet nozzle 211 into
an annular space formed inside the separator. ~he centrifu-
gal force resulting from the swirl projects the water onto
the outer wall of the separator, forming a layer that flows
downwards. ~he steam being set free rises in the central,
bell shaped, compartment 212 with slowed down motion. A sys-
tem of baffles 213 suitably guides the steam through a tor-
tuous path, furthering the separation of entrained water
15 droplets. The practically dried saturated steam leaves the
separator by way of the pipe 260 . The pressure regulating
valve 26 maintains the pressure in the steam generating
system at a pre-set level, said valve being actuated through
the transducer 261 in a feedback system. A secondary trans-
20 ducer 263 connects the actuator of this valve with the above
mentioned control unit, to which it transmits the signals
of the sensor mounted on the pipe 260 . lhe separated water
collects in the enlarged section of the separator, which
forms a reservoir of the vaporization system.
A liquid level controller 25 , co~municating with the
separator through a liquid line 252 and a vapor line 253 ,
causes a float 251 to follow the variations of the level
occuring inside the separator. ~hrough the movements of the
outer forked arm 254, converted into driving forces by the
30 transducer 140 , the variations of the liquid level are con-
ducted to the actuator of the flow regulating valve 14 ,
thus apportioning the discharge of make-up water to the
- 33 -
~3L~5
amount of vaporized water leaving the separator. ~he circu-
lating pump 22 produces an uninterrupted flow of saturated
water through the pipe 221 , which flow is joined by the
preheated make-up water discharged through the converging
pipe 142 . A steam trap 215 evacuates automatically the
water, should the liquid level rise accidentally above the
open end of the pipe 216 . ~he evacuated water is led to
the feed water tank through the pipe 217 .
~he diagram in ~igure 11 represents the apparatu~
that facilitates the starting of the engine, while no steam
i8 yet available from the heat recovering system. Included
in the figure are: the compressing apparatus 33 to which
the ~tarting system is hooked up by means of the control
valve 53 , and the pressure control unit 5 governing the
starting procedure as well as the operation of the above
described valves 26 and 34 .
~ he starting apparatus comprises an electric motor
50 coupled with a drive pinion 51 and with an auxiliary air
compress~r 52 . When driven by the electric motor, the aux-
iliary compressor provides an adequate volume of compressedair to be used as motive power in the compressing apparatus
33 , whereby just enough combustion air is drawn and sup-
plied, pre-compressed, to the engine inthe same way as
described for the air-steam mixture, thus allowing for the
combustion process to take place. Meanwhile the control
valve 53 is kept open and the regulating valve 34 is kept
clo~ed. ~he drive pinion 51 will crank the engine until
the internal combustion process becomes operative, when said
pinion will disengage automatically. At this stage, the
electric motor will continue to run, maintaining the supply
-. of auxiliary compressed air. Except for the valve 34 being
kept closed, the steam generating system will be set into
~$~
operation automatically when the electric motor 50 is
started. When a pre-set minimum steam pressure has built
up in the system, the electric motor iB automatically
switched off, interrupting the supply of auxiliary compres-
sed air. Concomitantly, valve 34 opens and the steam beginsto flow through the injector-compressor, putting gradually
the engine on stream. All these operations will be gov-
erned by the said unit 5 , controlled by the pressure, or by
the absence of pressure, in the steam ~ystem, whereby the
electric motor 50 is startedthrough the transmitting line
345 , while the line 344 opens the valve 53 through its
actuator, and line 343 take~ control of the actuator of
valve 34 closing it, both valves 53 and 34 staying in their
so commanded pos-itions for as long as the electric motor
is running. To be noted that, as was mentioned when ex-
plaining Figure 10 , the control unit 5 receives signals
through the transducer 263 , over the actuator of valve 26 ,
from the pressure sensor of the steam separator, said sig-
nals de-activating the control unit when the steam pressure
has reached the pre-set minimal level.
~he ~igure 8 12 , 13 , 14 illustrate the heat exchang-
ing apparatus by means of which the feed water is preheated
and the Batur&ted Bteam iB generated.
~he ~aporizing heat-exchanger 2 shown in ~igures 12
and 13 consists of a bundle of straight tubes 205 enclosed
in an elongated shell. Strong tube sheets into which the
tubes are tightly expanded, are provided at both ends of the
shell, the tube sheets being integral with the headers 201
and 202 . At their outer ends the headers are equipped with
bolted covers 203 and 204 , allowing for inspection and
i cleaning of the tubes. ~he circulating stream composed of
saturated water from the steam separator and of the rela-
- 35 -
tively cooler preheated water is fed into the inlet header
201 , from where it runs through the tubes 205 . Enough
heat is transferred from the exhaust gases, flowing in
countercurrent outside the tubes, to restore the liquid en-
thalpy to saturation and then to generate the requiredamount of saturated steam. The water-steam mixture thus pro-
duced leaves the vaporizer through the outlet header 202 .
The preheating heat-exchanger 1 , shown in ~igure 14,
comprises similar elements to those of the heat-exchanger 2
namely: a bundle of tubes 105 enclosed in an elongated
shell, two tube sheets integral with headers 101 and 102 ,
equipped with bolted covers 103 and 104 , etc. The make-up
water is pur.ped into the inlet header 101 from where it
flows through the tubes 105 , it being preheated by the ex-
haust gæses flowing in the opposite direction outside thetubes. The preheated water leaves the heat-exchanger via
the outlet header 102 .
The size, number, length and array of the tubes in
each heat-exchanger shall be so selected as to achieve the
desired heat transfer from the heating gases to the heated
fluids. Speeds of the heated fluids of about 3 to 4 m/sec
are advisable in order to promote entrainment of the steam
bubbles in the vaporizing exchanger, and to avoid settle-
ment of precipitates in the tubes of both exchangers. As
was explained before, heating ~7ill bring about the precipi-
tation of dissolved minerals. Owing to the sudden slowing
down of the current when entering the enlarged section of
flow, in the outlet headers 102 respectively 202 , and to
the upwards change of direction of the stream, the particles
of precipitate separate and sink do~nwards, being guided
by a specially designed system of baffles 106 and 206 , at-
tached respectively to the covers 104 and 204 . The bottom
- 36 -
JI~,'$;~
of the outlet hea~ers is for~ed as a sump into which the
precipitates settle as a sludge. Drainage tubes 160 connect
the sludge sumps with the blow-o:Ef valves 16 .
While the headers 101 , 102 , 201 , 202 and the
tubes 105 , 205 are designed to withstand the full pressure
of the water preheating and vaporizing system, the shells
being subjected to a much lesser pressure are made of thin-
ner metal plate. On the other hand, since they are not cool-
ed by the heated fluids, the shells will attain a higher
temperature than the tube bundles. Said bundles, together
with the tube sheets and headers, form relatively rigid
structures. ~o relieve the stress which would result in the
thin plate from the difference in thermal expansion between
shells and tube bundles, the shells are provided with pre-
formed expansion corrugations 107 respectively 207. ~he
shell represented in ~igures 12 , 13 appears to have a
rectangular cross-section; however any other shape of cross-
section might be adopted, provided it accomodates suitably
the array of tubes as well as the other elements essential
to the performance of the heat-exchangers. Depending on the
overall length of the tube bundles, one ~ three baffle
plates 108 , respectively 208, are mounted inside the shells
with the purpose of forcing the heating gases to follow a
sinuous path through and across the bundles. ~he baffle
plates have oversize tube holes, providing for a partial
flow of the gases through them and, at the same time, per-
mitting the free expansion of the shell in relation to the
tube bundle.
As was described previously, the tube 311 (~igures 9 ,
3 and 5 )conveys the exhaust gases to the heat-exchanger 2
through the throttling device 23 , which performs the im-
portant function of controlling the enthalpy of the combus-
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tion products that leave the engine, in relation with the
attained final temperature of the air-steam miYture. ~he
schematic representation in ~igure 12 of the device 23,
shows a telescopic valve actuated by means of a trænsducer
231 . Said transducer is commanded by a ter.perature sensor
mounted on the transfer pipe 480, as shown in ~igures 2
and 5 . Other types of throttles, actuated by feedback sys-
tems, may be used to perform the described function. After
completing their run through the heat-exchanger 2 , the ex-
haust gases flow to the preheating heat-exchanger 1 by way
of the duct 17 . ~igure 14 shows that the duct 17 branches
off into the inlet passage to heat-exchanger 1 and into the
by-pass duct 18 . The by-pass joins the outlet passage of
the gases from the heat-exchanger, combining into an evacu-
ation pipe 19 . The two-way damper 15, mounted at the
junction of the inlet passage with the ducts 17 and 18, is
actuated by means of the transducer 152, commanded by the
thermostat 151 inserted into the outlet nozzle of the pre-
heater.
~igure 12 presents also the scheme of the blow-off
apparatus devised for the automatic evacuation of the sludge
collected in the sump of the outlet headers. ~he apparatus
is composed of the drainage tube 160 equipped with a con-
trol cievice 161, and of the blow-off valve 16 which is pro-
vided with a solenoid actuator 162 . The control device 161
consists of an electronic circuit known as an optical iso-
lator. The two main components of the isolator, namely a
light e~itter and a photocell, are mounted facing each other
on opposite sides of the drainage tube. As sludge seeps in
the liquid filled drain, gradually increasing its turbidity,
the intensity of the light beam falling on the photocell di-
minishes. The photocell, which is actually a light depending
-- ~8 --
~-3L~
resistor, is linked with the electric circuit of the sole-
noid 162 in such a way as to cause the valve 16 to open,
given a sufficient dimming of the light, and to close again
when the liquid has become acceptably clear. A calibrated
spring, integrated with the actuator, will adequately coun-
terbalance the solenoid action. ~he preheating heat-ex-
changer is equipped with an identical blow-off apparatus.
Figure 15 includes diagrammatic details of the feed-
water system. The positive displacement pump 12 that takes
suction from the storage tank 11 , discharges the make-up
water under appropriate pressure into the pi~ which
feeds the preheating heat-exchanger 1 . As already dis-
closed, the discharge through the preheater is controlled
by the flow regulating valve 14 . Depending on the steam
consumption, the flow might be more or less restricted,
causing pressure increases in the preheating circuit. ~he
pressure relief valve 13 maintains the pressure in the said
circuit within desired limits, in so far as it allows for
part of the stream to flow back into the tank 11 by way of
the pipe 123 . Should the pressure increase exceed the
range of control of the relief valve, a pressure sensor,
acting through a transducer 133 , will release a switch
that will stop the driving motor of pump 12 . ~he pump will
be automatically put back into operation when the pressure
drops to its normal value.
~ he invention includes a thermal insulating system
devised to feasibly reduce the heat dissipation into the
surrounding atmosphere. ~hermal insulation is applied over
the exposed surface of the metallic parts, or else encases
single devices, which confine or carry the hot substances
contributing usefully to the operation of the engine. ~he
insulating materials and components shall comply with the
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following requirements: efficient heat conservation, sta-
bility at the operating teDperature, and resistance to re-
peated dismantling and reassembling of the parts. Compliance
with the last requirement is achieved by the selection of
suitable insulation textures and adequzte design of the pro-
tective covering. Relative to the other two required proper-
ties (efficiency and stability) it is considered that the
three following grades, or classes, of insulation will suit-
ably correspond to the proposed application of the inven-
tion: high temperature insulation, good to about 1000C;medium-high temperature insulation, good to about 550C;
medium-low temperature insulation, good to about 350C.
I~umeral 60 in ~igures 2 , 3 , 5 designates the in-
sulation which covers the jacketing systems. It consists of
insulating blankets, good to 550C, held in place and pro-
tected by sheet metal coverings. The same type of insula-
tion, designated by numeral 63 , shall be used for the heat-
exchanger 1 , Fig. 14 ; while the insulation 64 , covering
the heat-exchanger 2 , ~ig. 12 , shall have blankets good
to 1000G Similar insulation but of lesser quality, i.e.
good to 350C, designated by nu~erals 61 and 62 , will be
provided for the steam separator 21 and the liquid level
controller 25 shown in Fig. 10 .
I~olded insulation, indicative 65 , of high tempera-
ture quality (to 1000C), provided with hard protectivecover, shall enclose the exhaust manifold 31 inclusive ex-
haust passages from the engine 310 and outlet duct 311 , 2S
well as combustor 481 with connecting tubes, ~ig. 3 , 5 , 9.
Similar molded insulation 66 but of nedium-high temperature
quality, shall enclose the distribution chamber 36 , the
engine's intake passages and the transfer pipe 480 , ~ig.2.
Single devices will be enclosed in metal boxes
- 40 -
padded with suitable insulating materials, said boY.es being
designed for easy disma~ing with a view to inspection and
maintenance. Such insulating components are designated by
the numerals 67 , 68 , 69 and insulate, respectively, the
the compressing apparatus 33 and 330 in ~ig. 3 and 5 , the
recycling pump 22 in Fig~ 10 , and the throttling device 23
in Fig. 12 . Similar insulating boxes, indicative 70 , will
enclose the various control and regulating valves.
I~ost piping, including duct 17 ~hich carries the ex-
haust gases away from heat-exchanger 2 , shall be provided
with insulation 71 , made of mineral wool of medium-low tem-
perature quality, wrapped in shock resistant covering. A
similar insulation, 72 , made of fibrous material good to
1000~, will be used for the tubes 311 and the inlet pas-
sages to heat-exchanger 2 (~igD ~ ,12 ),
Heat insulating pads 73 made of high temperature
material and having the upper side protected by a metallic
sheet, shall be installed on top of the cylinder heads, as
shown in ~igo 2 , 3 . ~he sealing gaskets 74 shall also
offer adequate insulating properties to break the heat con-
duction between the cylinder blocks and the underlying
casings, or metal bases.
As was disclosed in the foregoing description, vari-
ous controlling devices contribute to the operation of the
engines integrated with heat recovering apparatus. he
described regulating and relief valves, as wellas the actu-
ating mechanisms and transducers may be available as com-
mercial products or, eventually, they may be designed to
suit specific requirements but still conforming to kno~m
models. Included were, however, other accessories, which
although similar to devices already in use will require
basic transformations in order to perfor~ new functions,
- 41 -
consequently qualifying as innovations. Examples of such
innovations are the throttling device 23 (Fig. 12) and
the two-way da~per 15 (~igo 1~ he relief valve 13 com-
bined with a transducer 133 (Fig. 15 ) and the dual links
actuating the valves 26 and 34 (~igures 10 , 11) illus-
trate other innovative ideas. It should be noted that the
automatic blow-off device 16 , 161 , 162 , as represented
schematically in Fig. 12 , and eomplemented by the respec-
tive description, is to be considered a eharacteristic part
of the invention, although it has in its composition de-
vices used in kno~m applications.
~ ote: ~he term 'working space' used in the present
disclosure and in the following claims is understood to de-
fine the engine's confined space wherein the fuel combus-
tion and the subse~uent expansion of the combustion pro-
ducts take place.
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