CA1112055A - Heat recovering system for internal combustion engines - Google Patents

Abstract

ABSTRACT
More than 60 % of the heating value of the fuel con-sumed in the usual internal combustion engines is wasted past remedy. The present invention, which is applicable in combination with any kind of internal combustion engine, and especially with fuel injection engines of the compres-sion-ignition and of the spark-ignition types, is intended to reduce the heat losses and to improve the thermodynamic cycles by making practicable the increase of the compres-sion ratio. Besides, a reduction of the emission of pollu-tants is achieved.
The invention embodies various energy saving systems including: apparatus to generate superheated pressure steam, an injector-compressor apparatus utilizing the generated steam as motive power and serving to pre-compress the com-bustion air, a jacketed cooling system of the engine through which the compressed air-steam mixture delivered by the in-jector-compressor flows serving as a coolant, said mixture being thereby conveniently superheated and being rammed into the engine's combustion space by virtue of its pressure, and a feasibly complete thermal insulation system.
The invention offers the advantage of reducing the usual heat losses to the only heat being rejected with the cooled exhaust gases.

Description

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 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 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 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 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 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 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.

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 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, 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 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.

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 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 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 _, 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 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 ~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 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 ~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.

~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 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 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.

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;

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 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, 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 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 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 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 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 ~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-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 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-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 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 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, 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.

Claims (19)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In combination and functionally integrated with internal combustion engines, apparatus recovering heat that would otherwise be wasted, whereby liquid water, under pressure, is stepwise preheated, vaporized and par-tially superheated, in countercurrent with the general flow of the combustion products, the partially superheated pressure steam being used as motive power in a compressing apparatus performing the function of pre-compressing or supercharging the combustion air, whereby there results a compressed air-steam mixture which flows through a system of cooling jackets, wherein said air-steam mixture is uti-lized as a coolant for the engine while being superheated to a desired temperature, in which state it is supplied to the engine's working space wherein the combustion takes place, said heat recovering apparatus comprising means to supply make-up water at an appropriate pressure, a heat-ex-changer wherein the make-up water is suitably preheated, means to convey and discharge at a controlled rate the pre-heated water into a circulating stream of saturated water, a vaporizing heat-exchanger wherein enough heat is trans-ferred to the mixture of circulating saturated water with the relatively cooler preheated water to restore the satura-tion enthalpy of the liquid and to generate steam, whereby a saturated steam-water mixture leaves the heat-exchanger in a continuous stream, a steam separator having the func-tion of separating the two phases of the steam-water mixture whereby dry saturated steam leaves the separator through a vapor line while the saturated water collects in the bottom section from where a circulating pump takes suction, means to maintain a liquid volume within the separator by con-trolling the discharge of the preheated water into the vaporizing circuit, means to blow off as a sludge the miner-als forming the hardness of the make-up water, which precip-itate in the preheating and in the vaporizing heat-exchan-gers, an intermediate superheater consisting of a heating element combined with the engine's exhaust manifold or, in the case of gas turbines, combined with the turbines' combus-tors, said intermediate superheater serving to partially superheat the saturated steam, the resulting partially su-perheated steam being used as motive power in a compressing apparatus consisting of an injector-compressor or, if a higher compression is required, consisting of two injector-compressors mounted in series, said compressing apparatus serving to pre-compress or superchage the combustion air, a system of cooling jackets that encloses the engine's working space, consisting of a one-way sequence of jacket-ing compartments, through which the pre-compressed air-steam mixture delivered by the compressing apparatus flows serving as a coolant while being superheated, means to regulate the back-pressure of the exhaust gases thereby controlling their enthalpy and consequently the heat supply to the vaporizing heat-exchanger, means to control the supply of exhaust gases to the preheating heat-exchanger, apparatus to start the cold engine comprising an electric motor coupled with a cranking pinion and with an auxiliary air compressor supplying temporary motive power to the aforementioned com-pressing apparatus, and a complete thermal insulating system to minimize heat loss from the hot substances contributing to the operation of the engine.

2. In combination and functionally integrated with internal combustion engines, apparatus recovering heat that would otherwise be wasted, by means of which liquid water is preheated, vaporized and partially superheated, under high pressure, in distinct steps and through separate de-vices arranged in countercurrent with the general flow of the combustion products, whereby the partially superheated steam thus generated is used in an injector-type compressor to pre-compress the combustion air and to force the result-ing compressed air-steam mixture to flow through a system of cooling jackets, wherein said air-steam mixture serves as a coolant for the engine while being superheated, in which state it is supplied to the engine's combustion space, said heat recovering apparatus comprising : a water storage tank, a positive displacement pump which pumps water from said tank, a preheating heat-exchanger equipped with tubes in which the pumped water flows and is preheated by exhaust gases flowing in countercurrent outside the tubes, a flow regulating valve controlling the amount of preheated water delivered by the preheating system so as to make up for the generated steam, said make-up water being discharged through convergent piping into a stream of circulating saturated water, a by-pass loop provided with a relief valve, branched off the discharge pipe of the pump, allowing to maintain within set limits the water pressure in the preheating sys-tem, a thermostat operated damper controlling the heat sup-ply to the water being preheated by allowing for part of the exhaust gases to by-pass the heat-exchanger, a vapor-izing heat-exchanger equipped with tubes through which the mixture of circulating saturated water with the preheated make-up water is forced to flow while, from the exhaust gases flowing in countercurrent outside the tubes, enough heat is transferred to restore the saturation enthalpy of the liquid and to generate steam in the desired quantity, the resulting steam-water mixture being conducted to a steam separator into which said mixture is discharged in a swirl causing the liquid and vapor phases to separate, whereby the saturated steam, flowing through a central compartment and being dried therein by means of a system of baffles, leaves the separator through a vapor line, while the saturated water collects in the separator's bot-tom section, a throttling device located in the duct lead-ing the exhaust gases from the engine to the vaporizing heat-exchanger, having the function of regulating the back-pressure on said gases, thereby controlling their enthalpy and consequently the heat supply to said heat-exchanger, a pressure regulating valve mounted in the vapor line of the separator with the purpose of maintaining a constant pressure in the vaporizing system, a pump taking suction from the bottom section of the separator and discharging the aforementioned stream of saturated water that circulates through the vaporizing heat exchanger and back to the sepa-rator, a liquid level controller attached to the separator, actuating through a servo-mechanism the aforementioned flow regulating valve that discharges the preheated make-up wa-ter into the stream of saturated water flowing from the sep-arator, means provided at each of the aforementioned heat-exchangers to evacuate the minerals which precipitate in the tubes and accumulate as a sludge in the sumps of the outlet headers, said means comprising , for each heat-ex-changer, an optical isolator and a solenoid actuated blow-off valve, an intermediate steam superheater serving to su-perheat partially the steam delivered by the separator, con-sisting of a finned tube located inside the suitably de-signed exhaust manifold or, in the case of a gas turbine, an intermediate steam superheater consisting of a jacket enclosing the turbine's suitably designed combustor, a compressing apparatus consisting of an injector-compressor or, if a higher compression is required, a compressing ap-paratus consisting of two injector-compressors mounted in series, said compressing apparatus utilizing the partially superheated steam as motive power to pre-compress or to super-charge the combustion air, whereby the combustion air is dis-charged as a compressed air-steam mixture, a system of cool-ing jackets that encloses the engine's working space and forms a one-way sequence of compartments through which the compressed air-steam mixture delivered by the compressing apparatus is forced to flow serving as a coolant while being superheated to a pre-selected temperature, said air-steam mixture being guided from the less hot regions to the hot-test regions of the engine, a transfer pipe to conduct the compressed and superheated air-steam mixture to the intake -or ram - manifolds of reciprocating engines, or directly to the combustors of gas turbines, said transfer pipe being equipped with a temperature sensor actuating through a trans-ducer the aforementioned throttling device that controls the enthalpy of the exhaust gases, a flow regulating valve con-trolling the supply of steam utilized as motive power in the compressing apparatus, said regulating valve being governed by a pressure sensor mounted on the reciprocating engines' intake manifolds, or on the gas turbines' combustors, means to start the cold engine comprising an electric motor coupled with a cranking pinion and with an auxiliary air compressor, said compressor to supply temporary motive power to the en-gine's compressing apparatus, and a thermal insulating sys-tem covering or enclosing the metallic parts which confine or carry the hot substances usefully employed in the oper-ation of the engine.

3. In combination with internal combustion engines, apparatus recuperating heat according to claim 2, whereby steam having a pressure ranging from 10 to 15 kg/cm2ga is generated at a controlled rate ranging from 1.5 to 4.5 kg per 1 kg of fuel consumed in the engine, and whereby the generated steam is superheated to an intermediate temper-ature of about 300°C in order to be utilized as motive pow-er in an injector-type compressing apparatus that will pre-compress or supercharge the combustion air needed by the engine in a pre-selected ratio of up to 3 / 1 , the result-ing pre-compressed air-steam mixture being forced through a system of cooling jackets enclosing the engine's working space to serve as a cooling fluid, while being superheated to a temperature in the range of 360 to 400°C, the combus-tion air thus prepared and mixed with steam being fed to the engine.

4. Apparatus recuperating heat according to claim 3, wherein saturated steam is partially superheated while flow-ing through an intermediate superheater consisting of a finned tube located inside the engine's exhaust manifold or, in the case of a gas turbine, consisting of a cooling jacket enclosing the finned combustor of the turbine, the steam thus superheated being supplied as motive power to a com-pressing apparatus serving to pre-compress the required com-bustion air, said apparatus comprising an injector discharging a steam jet that draws through a suction chamber the combus-tion air and a diffuser that delivers the compressed air-steam mixture or, in the case of a gas turbine, said appara-tus comprising at least two injectors, each discharging a steam jet, and an equal number of diffusers arranged as successive stages of compression for the combustion air, the compressed air-steam mixture obtained by these means being forced to flow through a system of cooling jackets of the engine, wherein it is guided from the less hot regions to the hotter regions of the engine, whereby said mixture is superheated by heat being transferred from the metallic walls confining the engine's working space, and whereby the air-steam mixture serves as a cooling fluid for said metallic walls while it maintains their temperature within desired limits.

5. Apparatus according to claim 3, wherein the me-tallic walls confining the engine's working space are cooled by the compressed combustion air mixed with steam,while the compressed air mixed with steam is being superheated, whereby said walls are maintained at temperatures corresponding to the superheat thus achieved, in consequence of which quench-ing of the combustion within the working space and emission by the engine of products of incomplete combustion will be reduced, and whereby less heat from the internal combustion process is diverted into the cooling fluid because of the narrower temperature difference between the engine's work-ing substance and the confining walls.

6. Apparatus according to claim 3, wherein the com-pressed combustion air mixed with steam, serving as a cool-ant, flows through the engine's jacket, said jacket being partitioned into a system of successive compartments, where-by the surface of the hot metallic walls being swept by said coolant is provided with parallel fins projecting in-side the jacket and with transverse protuberances or ridges which guide the cooling fluid and prevent the forming of stagnant pockets, the number of the successive passes formed by the partitions and the fins and ridges being designed so as to obtain favorable conditions for the heat convection.

7. Apparatus according to claim 2, comprising an intermediate steam superheater consisting of a tube pro-vided with external longitudinal fins, located inside an elongated body made of thin metal plate, which body is connected with the engine's exhaust ports to form an ex-haust manifold and is provided with at least two corruga-tions to relieve the strain due to thermal expansion, the fins of said tube being arranged in groups to allow for a uniform distribution of the exhaust gases in the annular space around the tube t whereby the saturated steam flowing inside the finned tube in countercurrent to the exhaust gases is superheated to a temprature of about 300°C.

8. Apparatus according to claim 2, wherein heat from the exhaust gases is transferred to the make-up water being preheated and to the circulating water stream being heated and vaporized by separate means, each of said means being a heat-exchanger comprising a bundle of straight tubes enclosed in an elongated shell provided at both ends with a tube sheet into which the tubes are tightly ex-panded, and with two outer compartments attached to the tube sheets and forming the inlet and the outlet headers of the heat-exchanger, both headers being equipped with removable covers to allow for maintenance and cleaning of the tubes, the removable cover of the outlet header having a specially designed system of baffles attached to it, while the bottom of said header is formed as a sump to which a drainage tube is connected, said baffle system and sump serv-ing to facilitate the settlement and collection of sludge, the headers being designed to withstand a pressure of up to 20 kg/cm2ga, while the shell enclosing the tube bundle, being subjected by the exhaust gases to a pressure less than 2 kg/cm2ga, is made of thinner metal plate and is pro-vided with two expansion corrugations, said shell being equipped with appropriate inlet and outlet passages for the exhaust gases and, depending on its overall length, with one to three baffle plates mounted inside, to guide the flow of the exhaust gases through and across the tube bun-dle, said baffle plates having oversize tube holes provid-ing for a partial flow of the gases through them and per-mitting the free expansion of the shell in relation to the tube bundle, whereby size, length, and number of the tubes composing the bundle in each heat-exchanger are calculated to achieve the required heat transfer.

9. Apparatus according to claim 8, where dissolved minerals which form the hardness of the make-up water pre-cipitate in the tubes of the heat-exchangers during the preheating and furthermore during the heating and vaporiza-tion taking place therein, the precipitates being carried by the fluids,flowing at speeds of 3 to 4 m/sec, into the outlet headers where, due to change of direction and slow-ing of the speed, and being guided by a set of baffles, they separate and collect as a sludge in the sump of said headers, from where said sludge is evacuated through drainage tubes by means of automatic blow-off systems.

10. Apparatus according to claim 8, whereby each heat-exchanger is equipped with an automatic blow-off sys-tem comprising an electronic control device consisting of a light emitter and a photocell mounted on opposite sides of a drainage tube and facing each other thus forming an optical isolator, and a solenoid actuated blow-off valve, the electrical circuit of the solenoid valve being linked with the optical isolator so as to cause said valve to open when the turbidity of the fluid, due to the collected sludge, has reached a given concentration, and to close again when the fluid has become clear.

11. Apparatus according to claim 2, where a throt-tling device is mounted in the duct leading the exhaust gases from the exhaust system of the engine to the vaporiz-ing heat-exchanger, said device serving to regulate the back-pressure in the exhaust system, thereby controlling the pressure and the enthalpy of the combustion products being evacuated from the engine, and consequently regula-ting the heat supply to said heat-exchanger, said throt-tling device being actuated by means of a servo-mechanism comprising a temperature sensor located in the transfer pipe which conducts the superheated combustion air mixed with steam to the intake or ram manifold in the case of piston engines, respectively to the combustor of the turbine in the case of gas turbines, said servo-mechanism causing the heat supply for the vaporization to increase by closing the throttle when the temperature of the super-heated air-steam mixture exceeds a pre-set value, and con-versely causing the heat supply to be reduced by opening the throttle when said temperature drops below a pre-set limit.

12. Apparatus according to claim 2, where the heat-exchanger serving to preheat the make-up water is equipped with a two-way damper mounted at the junction of the exhaust gases duct with the inlet passage to the heat-exchanger and with a by-pass duct, said damper controlling the heat supply to said heat-exchanger by allowing for part of the exhaust gases to be diverted through the by-pass when heat is avail-able in excess of the demand, the damper being actuated by a transducer commanded by a thermostat located in the out-let nozzle of the heat-exchanger.

13. Apparatus according to claim 6, wherein the exterior walls of the compartments forming the system of cooling jackets are provided with suitable openings that will facilitate the exact positioning and the firm holding of the cores during the pouring of the molten metal, and also the removal of said cores after completed casting, the openings being closed, after being machined, by covers ade-quately made tight.

14. Apparatus according to claim 2, comprising a steam separator composed of an upper cylindrical body and of a lower enlarged body joined together by a widening section, enclosing in its upper section a bell shaped compartment forming an annular space into which the saturated steam-wa-ter flow,emerging from the vaporizing heat-exchanger, is discharged tangentially through a nozzle near the top of the separator whereby a swirl and a centrifugal force result that separates the water,projecting it onto the outer wall and building up a layer which flows downwards and collects in the larger bottom section, while the steam rises through the central bell shaped compartment wherein it is forced to fol-low a tortuous path formed by suitably designed baffles, thus furthering the separation of the water droplets that might be entrained, the dried saturated steam flowing out through a nozzle located on the top of the separator, whereby from the collected water in the lower section of the separa-tor a circulating pump draws a continuous stream of satura-ted water, forcing it to flow through the vaporizing heat-exchanger, a constant volume of water being maintained in the vaporizing system by means of a liquid level controller at-tached to, and communicating with the steam separator, and which controls through a flow regulating valve the quantity of preheated water to be supplied to the system.

15. Apparatus functionally combined with internal combustion engines according to claim 1, wherein partially superheated steam is used as motive power in compressing apparatus serving to pre-compress the combustion air, whereby part of the enthalpy of said steam, while being let off through nozzles producing jets, is converted into kinetic energy, and whereby the required combustion air is drawn by the suction of said steam jets and is discharged as a pre-compressed air-steam mixture through appropriate diffusers in one step or, if a higher compression is need-ed, in two successive steps, said air-steam mixture being forced to flow through a system of cooling jackets wherein it is superheated while serving as a cooling fluid for the engines, the pre-compressed air-steam mixture thus super-heated being supplied to the engines as combustion medi-um of high potential energy, the increased water vapor content of the working substance obtained being apt to prevent detonation in the combustion process, and the in-creased specific heat of the combustion products, due to the additional water vapor present, lowering the peak tempera-ture of the combustion, notwithstanding its higher poten-tial.

16. Apparatus according to claim 15, wherein the pre-compressed and superheated combustion air mixed with steam is conducted to a chamber, which in the case of recip-rocating engines forms the intake or ram manifold, while in the case of gas turbines forms the engine's combustor, whereby the supply of partially superheated steam utilized as motive power in the compressing apparatus that produces and moves the pre-compressed air-steam mixture, is con-trolled by a flow regulating valve actuated by a servo-mech-anism which is governed by a pressure sensor mounted on said chamber.

17. Apparatus according to claim 2, comprising a feed water system composed of a storage tank, a positive-displacement pump taking suction from said tank and dis-charging into the feed pipe of the preheating heat-ex-changer, a by- pass pipe between the pump discharge and the storage tank including a pressure relief valve which shall control the pressure generated in the preheating sys-tem by the positive-displacement pump, by establishing a relief flow through the by-pass pipe when the pressure ex-ceeds a pre-set value, as may occur when the supply of preheated water to the vaporizing circuit is temporarily reduced by the respective flow control valve, whereby if the increased pressure exceeds the range of control of the relief valve, a transducer governed by a pressure sensor mounted on said relief valve will switch off the driving motor of the positive-displacement pump for the duration of the excess pressure.

18. Apparatus according to claim 1, where means are provided to start the engine from a cold state, while no steam is yet available , all admission ways of the steam as motive power to the compressing apparatus being automat-ically closed, said means consisting of an electric start-ing motor coupled with a drive pinion, and with an auxil-iary air compressor which will deliver compressed air to be used as temporary motive power for the engine's compres-sing apparatus, the engine being cranked by the drive pin-ion until the combustion process becomes operative, when said pinion will automatically disengage, whereby however, the starting motor will continue to run thus maintaining the supply of compressed air until a pre-set steam pressure has built up in the steam generating system, when the start-ing motor will stop while steam will automatically start to flow through the compressing apparatus, putting gradually the engine on stream.

19. Apparatus according to claim 1, wherein there being no need to dissipate heat until the exhaust gases reach the outlet of the exhaust system, after running through the heat-exchangers, a feasibly complete thermal insulating system is provided which will minimize the heat loss into the surrounding atmosphere through the metallic walls and other parts confining or carrying the hot sub-stances contributing usefully to the operation of the en-gine, whereby the only major heat loss experienced with the internal combustion engine will be the reduced heat amount being rejected with the cooled exhaust gases.