Steam Engine Reaction Chamber, Fuel Composition Therefore, and Method of Making and Operating Same

The field of the present invention is Rankine cycle vapor pressure or steam engines obtaining their driving heat energy from a chemical reaction other than the usual combustion of fuel with oxygen from the air. Particularly, the theoretical possibility of utilizing the reaction energy of a reactive metal fuel such as Aluminum, Magnesium, or Lithium, and alloys or hydrides of these and similar reactants, with an "oxidizer" such as hydrogen peroxide, Freons, sulfur hexaflouride, water, and others, has been recognized for many years. However, the technical difficulties and conflicts standing between a theoretical construction of such a power system and a practical apparatus which is functional outside of the laboratory are legion.

By way of example, many of the fuel-reactant combinations proposed in the past require that the fuel be raised above ordinary ambient temperatures in order to permit reaction with the reactant. Such a heating requirement necessitates that some heating means, such as electrical heating coils or pyrotechnic chemicals be provided. In the former case, a significant start-up delay is incurred while a portion or all of the fuel is raised to reaction temperature. In the latter case, the pyrotechnic chemicals, which are or may be considered to be low velocity explosives, present the possibility of rupturing the reaction chamber and escape of highly reactive or toxic fuels. Such pyrotechnic heating chemicals also frequently produce a quantity of gaseous reaction products which must be contained within the reaction chamber, or else vented therefrom while preventing loss of fuel.

Another undesirable aspect of many previously proposed fuel-reactant systems is that intermediate reaction products or end reaction products are formed which on the one hand inhibit further progress of the reaction between the fuel and reactant, or on the other hand freeze at a temperature higher than the desired reaction chamber temperature. In the one case, complex structures and methods have been proposed to cure the shortcoming by removing the intermediate or final reaction product from the reaction chamber. Alternatively, only a portion of the fuel could be brought into contact with the reactant so that reaction products could not contaminate the remaining fuel. Again, complexity is increased.

The problem of the reaction intermediates or final products freezing at too high a temperature presents the difficulty that the reaction chamber may soon become filled with a "slush" of frozen reaction products in a slurry of molten fuel. Similarly, the high-freezing constituents present in the reaction chamber may form a "frost" or crust on the coolest surfaces present. These cool surfaces will ordinarily be heat transfer surfaces where it is desired to transfer heat from the chemical reaction for utilization in a steam or vapor pressure Rankine cycle engine. Such a crust on the heat transfer surfaces will ordinarily have a relatively high insulation value in comparison with the molten fuel. As a result, the crusted reaction products themselves progressively inhibit heat transfer from the reaction chamber to the engine.

A novel approach to the above-discussed problem is presented by the copending patent application Ser. No. 681,161 of Palmer Wood, having the same filing date and assignee as this application (hereinafter the Wood application). In the Wood application a fuel is reacted with water in the absence of oxygen to produce heat and hydrogen. The heat from this reaction is used to produce water steam. The hydrogen is burned with oxygen in a separate second reaction chamber to produce super heated steam. The steam from the first reaction chamber is used as a coolant and diluent in the second reaction chamber so that steam flowing from the second reaction chamber to a turbine, or other expander, has a metalurgically acceptable temperature. The disclosure of the Wood application is hereby incorporated herein by reference to the extent necessary for a complete understanding of the present invention.

A shortcoming of the invention of the Wood application discovered by the present inventors is that a hydrogen bearing reaction intermediate is formed which initially partially prevents the evolution of the hydrogen from the first reaction chamber. As the reaction progresses, the reaction intermediate further reacts to release the bound hydrogen. The result is that over the period of the reaction, the rate of hydrogen production is at first relatively low, reaches a stable plateau, and then raises above the plateau as the fuel supply is consumed.

A consequence of this nonuniform rate of hydrogen production is that the power output of the Rankine cycle steam engine is relatively low initially and cannot be increased until the hydrogen production rate of the chemical reaction chamber increases. Understandably, this sluggish initial power output of such a system is undesirable in almost every prospective applications. Additionally, the nonuniform rate of hydrogen production creates many difficulties in controlling the power output level of the Rankine cycle engine.

Conventional reaction chambers, fuel-reactant combinations, and methods of operating engines of the above-defined character are presented in U.S. patents noted hereinabove.

In view of the above discussion it is an object of the present invention to provide a reaction chamber fuel composition reactive with water to produce hydrogen at a substantially uniform rate during the life of the fuel supply. Another object of this invention is to provide such a reaction chamber fuel composition which is reactive with water at common ambient temperatures, and which does not require preheating or pyrotechnic chemicals, for example, to be used in starting the reaction.

Another object of the present invention is to provide a reaction chamber structure for use with the inventive present fuel composition, and other fuel compositions of a similar nature.

Still another object of the present invention is to provide a method of making a reaction chamber according to the present invention.

Yet another object of the present invention is to provide a method of operating a reaction chamber according to the present invention.

The present invention according to one aspect provides a two-part fuel composition including a first or main fuel part of magnesium and aluminum in a molar ratio of 1:2, respectively. The second or starter fuel part is composed of lithium hydride, magnesium, and aluminum in equal molar ratio. On a weight basis, the starting fuel composition and main fuel composition are presented at a ratio of about 1:4.

In a reaction chamber according to the present invention, the above-outlined fuel is present in the form of prealloyed powders produced, for example, from condensed vaporized or atomized metal. The reaction chamber structure provides in addition to heat transfer means, a means for introducing water into the chamber for reaction with the fuel.

According to one aspect of the invention, the means for introducing water comprises a manifold with foraminous distribution tubes depending in the fuel. The distribution tubes are immediately surrounded by a comparatively thin layer of the starting fuel part. The main fuel part is received within the reaction chamber around the distribution tubes and layer of starting fuel part.

According to another aspect of the invention, the main fuel part is disposed in a lower portion of the reaction chamber. In an upper portion of the reaction chamber is disposed an appropriate quantity of the starting fuel part. The reaction chamber includes a water inlet nozzle disposed in an upper part of the reaction chamber above both the starting and main fuel parts. Preferrably, the water nozzle is separated from the fuel during operation of the reaction chamber and engine.

In accord with yet another aspect of the invention, a method of operating a reaction chamber of the descibed character includes reacting water with a hydride of a reacting fuel element to form a hydroxide of the fuel element which hydroxide is further reactive with a first mixture of fuel elements being rather less reactive than the hydride of the first fuel element. The heat liberated from the above described reaction is employed to raise the temperature of the less reactive fuel elements to a level where they are vigorously reactive with the present hydroxide and with water.

Still another aspect of the present invention involves the method of making a reaction chamber according to the invention and including the steps of providing means for introducing water into the reaction chamber, disposing a selected quantity of the first starting fuel part in proximity with said water introducing means to be first contacted by water introduced therethrough, and filling the remainder of the reaction chamber, or a selected portion thereof, with the second main fuel part.

The advantages offered by the present invention include the absence of any need or requirement to provide fuel preheating before the reaction chamber is operational. Further, the introduction of simple water is all that is required to initiate operation of the reaction chamber to produce both heat and a supply of hydrogen. This latter feature is of particular advantage when the invention is used in connection with a water bourne vehicle. Understandably, a quantity of the available water may be used in the Rankine cycle steam engine, eliminating entirely the need to store water aboard the vehicle for such use.

Further to the above, the rate of heat and hydrogen, production may be moderated during the life of the available fuel supply by controlling the rate of water supply to the reaction chamber so that the Rankine cycle engine may be throttled. Additionally, the rate of hydrogen production during the use of the fuel supply is substantially uniform in proportion to moderation of the reaction rate with the rate of water supply. The reaction intermediates and final reaction products do not seriously interfere with heat transfer out of the reaction chamber.

Still further, the applicants have discovered that the present invention virtually eliminates anticipated difficulties with separating the evolved hydrogen from the reaction products and fuel. Such separation is essential to prevent fuel and reaction products being carried into and damaging the steam expander of the Rankine cycle engine. Surprisingly, the fuel composition and reaction chamber of the present invention allows a very simple filter structure to be interposed between the fuel and the hydrogen outlet from the reaction chamber. An unexpected phenomenon described herein below results in a simple filter accomplishing almost perfect filtering of the evolved hydrogen

FIG. 1 schematically depicts a reaction chamber according to the present invention, and having a two-part fuel composition disposed therein;

FIG. 2 schematically depicts an alternative embodiment of a reaction chamber according to the invention; and

FIG. 3 graphically depicts and compares the rates of hydrogen production of reactions according to the Wood application, and in accordance with the present invention.

With reference to FIG. 1, a preferred embodiment of the inventive reaction chamber 10 is depicted. The reaction chamber 10 includes a vessel 12 defining a reaction water inlet 14 and a hydrogen outlet 16. Additionally, the vessel 12 includes structure 18 for transfering heat from the interior of vessel 12 to a Rankine cycle or other heat engine (not illustrated). The heat transfer structure is depicted as a boiler tube 20 passing into the vessel 12 at 22 to define a water inlet, and passing out of the vessel at 24 to define a steam outlet.

Within the vessel 12, the reaction water inlet 14 communicates with a manifold 26 having a plurality of foraminous water distribution tubes 28 depending therefrom. Also disposed within the vessel 12 in surrounding relation with the inlet 14 is a hydrogen filter structure generally referenced with the numeral 30. The hydrogen filter 30 preferrably includes a lower perforate plate 32, and a pair of felt-metal pads 34,36 disposed above the plate 32.

Also disposed within the vessel 12 in surrounding relation with the perforate distribution tubes 28 is a selected quantity of a first or starting fuel part 38. The starting fuel 38 is disposed within the reaction chamber 10 somewhat in the form of a coating upon or around the tubes 28. Similarly, around the starting fuel 38 is disposed a certain quantity of a second or main fuel part 40. The main fuel 40 fills substantially all of the remaining volume of the vessel 12 and is in surrounding relation or otherwise in heat transfer relation with the structure 18.

One example of a fuel composition for use within reaction chamber 10 is composed of starting fuel part 38 having equal molal components of lithium hydride, magnesium, and aluminum. This starting fuel composition is employed with a main fuel part 40 of aluminum and magnesium in a molar ratio of 2:1. Preferably, the main fuel part 40 and starting fuel part 38 are present in a ratio of about 4:1, on a weight basis.

Turning now to FIG. 2, an alternative embodiment of the invention is depicted wherein reference numerals previously used and with a prime added designate similar elements. The reaction chamber 10' includes a vessel 12' with reaction water inlet 14', hydrogen outlet 16', heat transfer structure 18', and filter structure 30'. However, the main fuel part 40' is simply disposed in the lower portion of the vessel 12', with a layer of the starting fuel part 38' disposed on the main fuel part in an upper portion of the vessel 12'. A distance above the upper surface of the starting fuel part 38' is disposed an inlet nozzle 26' at the lower end of the inlet 14'. The nozzle 26' is arranged to project water received via inlet 14, downwardly upon and into the fuel 38',40' as a single penetrating stream, plurality of such streams, or penetrating mist. Importantly, the nozzle 26' is spaced sufficiently away from the fuel 38',40' that even allowing for thermal expansion of the reactants, nozzle 26' is not contacted by the molten fuel.

Having observed the structure of the two preferred embodiments of the invention, attention may now be directed to their operation. With respect to FIG. 1, when it is desired to start operation of the Rankine cycle heat engine (not shown) water is supplied to inlet 14 at a determined rate. The supplied water is distributed by manifold 26 to distribution tubes 28. The perforate distribution tubes 28 carry the supplied water into immediate contact with substantially all of the starting fuel part 38. Such is the case because, as pointed out above, the starting fuel part 38 is disposed in surrounding relation with the tubes 28 as a relatively thin layer or coating. The supplied water reacts with the starting fuel part to produce Lithium hydroxide and heat. Lithium hydroxide further reacts with the other constituents of the starting fuel part and with the main fuel part to produce hydrogen gas and additional heat. The initial heat production from the starting fuel part 38', serves both to increase the temperature and to increase the propensity to react with water of the remaining fuel. In very short order, the entire mass of fuel is raised to a sufficiently high temperature that the fuel is molten and readily reacts with water.

FIG. 3 graphically depicts the time rate of hydrogen production from a reaction chamber according to the invention with the passage of time from the moment of first water injection into the reaction chamber, Viewing FIG. 3, line A represents, for comparison only, the rate of hydrogen production from a reaction chamber according to the Wood application. As line A represents, a reaction chamber according to the Wood application initially produces hydrogen at a relatively low rate which increases more slowly than desired (portion A.sub.1,). Following the initially slow start, the reaction chamber reaches a plateau (portion A.sub.2) of relatively stable hydrogen production rate. Finally, as the fuel mass nears exhaustion, the reaction chamber according to the Wood application produces hydrogen at an increased rate (portion A.sub.3), leading to a drop off at exhaustion of the service life of the reaction chamber.

In contrast, line B on FIG. 3 depicts the rate of hydrogen production from a reaction chamber according to the present invention. As line B shows, after an initial starting surge, the rate of hydrogen production is substantially uniform throughout the service life of the reaction chamber. It will be understood, of course, that FIG. 3 is representative for comparison purposes only. In fact, the actual rate of hydrogen production from a particular reaction chamber is variable dependent on many factors including the relative size of the chamber and the controlled rate of reaction water introduction thereto.

With respect to the reaction chamber of FIG. 2, it will be noted that inlet 14', and nozzle 26' direct the water supplied thereto downwardly from above onto and into the fuel 38', 40'. Of course, the upper layer of starting fuel part 38' is first contacted by the introduced reaction water, much in the same fashion as the reaction chamber of FIG. 1. However, the nozzle 26' is at all times spaced apart from and above the zone of reaction which is formed where the reaction water reacts with the fuel parts 38' and 40'. Because the nozzle 26' is not immersed in the molten fuel 38',40', there is virtually no chance of the nozzle 26' becomming plugged with fuel or reaction products. Further, because the nozzle 26' is substantially free of heat transfer from the molten fuel 38',40', high-temperature materials of construction for the nozzle are not necessary, and the nozzle may be made of relatively common, inexpensive materials.

Surprisingly, an actual test of a reaction chamber similar to that of FIG. 2 has shown that the bath of molten fuel does not, as previously assumed, require agitation from direct immersed reactant injection. In other words, the reaction is sufficiently vigorous that the stirring, mixing influence of a jet or stream of water injected from a nozzle immersed in the bath is unnecessary. Simply spraying the water upon the fuel will allow the reaction chamber to run to completion of the reaction with acceptably high utilization of the fuel mass. Specifically, the Applicant's tests have shown a 95% or greater fuel utilization may be expected from a reaction chamber according to FIG. 2. The reaction chamber of FIG. 1, it is beleived, would provide a somewhat higher percentage of fuel utilization.

With both of the reaction chambers shown in FIGS. 1 and 2, the evolved hydrogen is filtered by filter structures 30 and provided via outlet 16 for utilization in the Rankine cycle engine (not shown). The fuel mixtures of the present invention are believed to offer a supprising and unexpected advantage by simplifying the required filter structure. The conflicting requirements for the filter structure 30 are that it be open to passage of hydrogen while being sufficiently closed to both fuel and reaction products that the latter are not allowed to pass downstream with the hydrogen via outlet 16. Further, the filter dare not clog. Surprisingly, the present fuel mixtures have been found to deposit reaction products on the filter 30 to a extent resulting in a self-regulating filter mechanism. An actual test of a reaction chamber 10' according to FIG. 2 employed a perforate plate 32 having apertures of 0.125" size, and comprising 60% open area of the total plate area. The felt metal pads 34, 36 were of 0.006" filament size with 95.mu." pore size having 60% theoretical density. During operation of the reaction chamber virtually perfect filtering of the evolved hydrogen resulted. The internal pressure of the reaction chamber was within acceptable limits, indicating that the filter 30 was not clogged or overly restrictive to passage of Hydrogen. Neither was there indication of excessive openness or porosity of the filter. Astonishingly, where the reaction chamber was disassembled for visual inspection, the filter 30, and particularly pad 34, gave the appearnce of being clogged with reaction products. The filter was not in fact clogged with respect to passage of evolved hydrogen, however, as the acceptably low internal pressure of the reaction chamber during operation indicated.

Examination of the start up fuel reaction products of a test run indicated two product phases. The primary product phase was LiAlO.sub.2. The smaller secondary reaction product phase was MgAL.sub.2 O.sub.4 +LiAL.sub.5 O.sub.5. The percentages of pure fuel metals remaining were Li less than 1%, Mg less than 1%, and AL less than 1%. LiOH and MgO were both present in trace amounts.

In view of all of the above, it is seen the present invention provides novel fuel compositions for use in a reaction of the type described. Two preferred embodiments of the reaction chamber itself are presented along with methods of operating and making the reaction chambers. The invention also provides a substantially uniform rate of hydrogen evolution and allows the use of reactant injection nozzles which are optionally either immersed in or spaced above the molten bath of reactive fuel. Finally, it is seen that a significant and unexpected advantage results from the present invention in that filtering of the evolved hydrogen becomes self regulating.

The starting and main fuel part reactions with water are believed to be as follows:

While the present invention has been depicted and described with reference to multiple preferred embodiments thereof, such reference does not imply a limitation upon the invention, and none is to be inferred. The invention is intended to be limited only by the scope and spirit of the appended claims, and range of equivalents thereto, which also provide a definition and disclosure of the invention.