Closed Cycle Engine System

Abstract

Disclosed is an engine, preferably of the diesel type, operating in a closed cycle system in which there is generated a mixture of gaseous oxygen and water vapor for its "breathing." The generation of this mixture uses the engine exhaust products, which comprises mainly, carbon dioxide, oxygen and water vapor. This synthetic "air" combusts with the diesel fuel to drive, for instance, an electrical generator. The system incorporates units connected to the engine exhaust which employ the carbon dioxide to produce new oxygen, condense the water vapor and recycle the unused oxygen, and a further provision for control of the oxygen production.

Description

BACKGROUND OF THE INVENTION

The diesel engine is widely respected as the most practical source of power for most terrestrial surface applications such as trucks, rail and marine transportation. Further application of this engine to undersea, underground and contaminated environments is highly desirable since it is low in cost, excellent in performance and reliability and available in a wide variety of power levels.

Until very recently, attempts extensive in expense, frequency and time have not resulted in the development of a simple, efficient and practical way to operate the diesel in an enclosed system. The best that was known to the art is a system for submarine engines which returns the exhaust gases to the input while it adds oxygen from stored tanks; the induction working fluid thus is oxygenated carbon dioxide. The exhaust is cooled, thereby condensing out the water vapor from the combustion and, to obtain a constant operating pressure and material balance in the loop, the excess oxygen, water and carbon dioxide are pumped out of the vessel against the sea pressure.

What is considered an appreciable advance in this art is divulged in a copending application for patent Ser. No. 851,586, filed on Aug. 20, 1969, now U.S. Pat. No. 3,658,043. As described therein, the diesel engine exhaust passes to a cooler-condenser in which the water vapor is condensed and the oxygen and carbon dioxide mixture is conveyed to a unit wherein the carbon dioxide is absorbed by a potassium hydroxide solution to generate the bicarbonate and new oxygen. The oxygen, supplemented as necessary, is humidified by a lung which uses the condensed water and is then returned to the engine input.

The arrangement of this system was based upon certain observations made during extensive tests of diesel engines:

1. combustion gas analysis data indicate that "lean" (4 to 6 oxygen to fuel ratio) operation evolves only oxygen, carbon dioxide and, in the case of air-breathing operation, the inert constituent nitrogen;

2. an engine will operate efficiently on water vapor-oxygen mixtures as a substitute for air;

3. in proper proportions, the water vapor will serve the same purpose as the nitrogen with regard to limiting combustion temperature;

4. under the above operation, the exhaust comprises mainly steam, which may be condensed to allow isolation of other exhaust constituents;

5. the psychrometric properties of the water vapor-oxygen mixture may be used to maintain automatically the oxygen to-fuel ratio within limits for producing an exhaust compatible with closing the cycle.

BRIEF SUMMARY OF THE INVENTION

The present invention is submitted as a further advance in the art directed to achieving further compactness, light weight and simplified operation; it is based on the realization that the alkali metal superoxides, such as sodium or potassium superoxide, NaO.sub.2 or KO.sub.2, have the ability to liberate oxygen as well as to absorb carbon dioxide, in a ratio very close to the oxygen-combusted to carbon dioxide-emitted ratio of the diesel engine. The invention uses this concept in providing a bed of KO.sub.2 solid granules in a thin walled canister having openings at its ends for gas throughflow. Cooled engine exhaust, after condensation of most of its water content, flows through the canister and chemical reaction therein produces potassium carbonate (K.sub.2 CO.sub.3) in granular form and gaseous oxygen in a continuous basis. It has been found that, when allowed to operate at relatively high temperatures (e.g.q 120.degree. F to 150.degree. F), the KO.sub.2 bed remains firm and dry, pressure drop in the system is very low, in the steady state, little oxygen needs to be added to the loop, and both pressure regulation and oxygen-concentration regulation are feasible (and therefore incorporated).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of the system of Ser. No. 851,586;

FIG. 2 is a diagram of the system of the present invention; and

FIG. 3 is a graph showing the operation of the by-pass regulation circuit of the system of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 comprises a simplified diagram of the aforementioned closed cycle engine, which briefly, consists, in its preferred embodiment, of diesel engine 10 supplied with fuel from tank 12 and "air" from lung 14. Engine 10 drives through gearbox 15, electrical generator 16 or some other power converter and pumps 18 and 19, and exhausts into heat sink 20. The input to engine 10 is thus the active ingredient of the fuel, chemically idealized as CH.sub.2, and moisturized oxygen from lung 14, which react in accordance with:

CH.sub.2 + 3/2 (O.sub.2) .fwdarw. CO.sub.2 + H.sub.2 O.

The exhaust of engine 10 is thus made up mainly of carbon dioxide, water and unused oxygen and trace materials; the water is condensed by sink 20 into tank 22 from which it enters pump 17 and lung 14 and the carbon dioxide-oxygen mixture enters absorption tank 24 by way of outlets in pipe 26 where it is sprayed by a caustic solution, preferably potassium hydroxide solution, issuing from spray head 28. Chemical reaction in tank 24 may be represented by:

2 KOH + CO.sub.2 .fwdarw. K.sub.2 CO.sub.3 + H.sub.2 O

and thus the entering oxygen merely passes through tank 24 to re-enter lung 14, together with an auxiliary supply from tank 30. The excess KOH solution is also circulated by pump 19 to head 28.

In effect, FIG. 1 shows the following circuits:

1. engine circuit, including fuel tank 12, engine 10, heat sink 20 and oxygen supplies, tanks 24 and 30;

2. water circuit, including heat sink 20, tank 22, pump 17 and lung 14;

3. KOH circuit, including tank 24, pump 19 and spray head 28.

In operation, lung 14 takes in oxygen, passes it through a water spray for humidification, and passes it on to the intake of engine 10. The water spray in lung 14 is provided by circulation of coolant water between lung 14 and engine 10 by pump 17. The partial evaporation of the water which takes place in lung 14 to humidify the oxygen, also cools the circulating water and hence engine 10 by evaporation.

Engine exhaust is piped to heat sink 20 where the water vapor is condensed by cooling. The condensed water is drained into tank 22 which in turn supplies make-up water to the water circuit. The exhaust gas enters absorption tank 24 where the carbon dioxide is absorbed, forming potassium carbonate solution. The remaining gas (unused oxygen) passes out where it is then piped back to lung 14 for re-circulation.

In the foregoing system, it is the function of the caustic spray to absorb, by chemical action, the engine exhaust carbon dioxide so that the system might operate in a "closed" mode, and it is the function of lung 14 to humidify the oxygen so that combustion in engine 10 may occur at a reduced temperature acceptable to engine 10, namely, about 2,500.degree. to 3,000.degree. F; also, in this system, the input oxygen needed to supplement the recirculated oxygen is supplied by an external source, here, tank 30.

FIG. 2 presents a closed cycle engine system characterized by considerable departure from that of FIG. 1.

Here, as before, fuel tank 42 supplies fuel to engine 40, which operates generator 46 through gearbox 45, and engine exhaust is cooled by heat sink 50, coolant in the jacket of which is circulated by pump 48, also driven by engine 40 through gearbox 45. Condensate water from the exhaust is collected in tank 52 for disposal and the carbon dioxide-oxygen mixture flows partly to canister 54, which contains a bed of potassium super-oxide, KO.sub.2 and partly to the intake of engine 40.

It has been found that a metallic superoxide such as KO.sub.2, in this type of system, is capable of performing the two functions of absorbing the carbon dioxide and generating oxygen ideally as follows:

4KO.sub.2 + 2CO.sub.2 .fwdarw. 2K.sub.2 CO.sub.3 + 3O.sub.2

and, further, that the oxygen generation and CO.sub.2 absorption, under most conditions of operation, are closely matched to the oxygen intake and CO.sub.2 release of engine 40. As a consequence, under ordinary circumstances, it has been found unnecessary to supply to engine 40 any additional external oxygen or other breathing component; accordingly, the humidified oxygen output of canister 54 is fed as shown, directly into engine 40.

With regard to canister 54, granules of solid KO.sub.2 are packed in wire mesh container 56, and it is provided with a conduit entrance opening near its bottom and a conduit exit at its top so that the exhaust gas may enter and generated oxygen may be emitted. The reaction results in a K.sub.2 CO.sub.3 product also in a granule form which remains in container 56 and, periodically, is replaced by a container of fresh KO.sub.2.

Experience with the above system has shown that it is feasible to control the rate of oxygen generation, especially by varying the exhaust flow through canister 54, at practically no pressure loss in the system, particularly under high temperature operation.

Accordingly, bypass valve 58, installed at the output of heat sink 50 operates to shunt the exhaust around canister 54 and back into engine 40 in response to control from pressure sensor 60; thus, when sensor 60 recognizes an oxygen pressure level beyond a prescribed level, it operates to open valve 58 so that exhaust directed to canister 54 is reduced. As a result, no "lung" is required in this preferred embodiment since valve 58 operates to provide inherently for a dilution of the oxygen concentration of the gas flowing to the intake of engine 40.

It should be obvious to those skilled in this art that, alternatively, valve 58 may be operated according to oxygen concentration, if so desired, by substituting for control by sensor 60, control through one of the known oxygen analyzers available on the market.

However, regardless of which method of oxygen generation is employed, it will be found that the system behavior in this respect will, in a general way, accord with FIG. 3. This graph depicts the operation of valve 58 with regard to response to oxygen pressures variation, shown as the ordinate and the effect thereof, shown as the ratio of vapor by-passed around canister 54 to that admitted to canister 54, along the abscissa. Point 62 on the curve represents a condition of oxygen overproduction which causes substantial opening of valve 58 (bypassing canister 54) whereas point 64 on the curve represents a condition of "choking" which causes valve 58 to close, thereby admitting all the exhaust from heat sink 50 to canister 54.

In the further development of this invention, it has been discovered that a mode of operation is possible for which control of the generation of oxygen is not required, i.e., it eliminates the need for valve 58 despite the fact that any of the known methods of supplying external oxygen (the KOH-CO.sub.2 reaction of FIG. 1, the KO.sub.2 -CO.sub.2 reaction of FIG. 2, a liquid oxygen supply, etc., or any combination of these may be used.

This operating mode is based on the precharging of the system with a mixture of gases: oxygen, water vapor and an inert gas such as argon, and operating it as a completely closed system in which the oxygen supply is controlled by sensor 60 to admit fresh oxygen only where pressure or analysis indicates that it is lacking. The precharge mixture constituency and ratio may be selected to suit specific conditions of environment and the requirements of adequate dilution of the oxygen in the combustion reaction and suppression of reaction of the oxygen with lubricants.

Claims

What is claimed is:

1. Apparatus for supplying breathing fluid to an engine having an intake comprising:

means to cool the engine exhaust, to condense water vapor therefrom, and to dispose of the resulting liquid;

means to react with the carbon dioxide in the exhaust from said cooling means to generate oxygen; and

means to supply said generated oxygen to said engine.

2. Apparatus according to claim 1 and further including

means to selectively combine the exhaust from said cooling means and said generated oxygen from said reactor; and

means to supply the output of said combining means to the intake of said engine.

3. The apparatus of claim 1 wherein said cooler includes

a pump operated by the engine and adapted to have coolant circulated thereto.

4. The apparatus of claim 1 wherein said reactor includes

a supply of superoxide and

means to stream the exhaust through said supply.

5. The apparatus of claim 4 wherein said superoxide supply comprises

a bed of potassium superoxide pellets and

a mesh basket for containing said bed.

6. The apparatus of claim 5 wherein said bed and the exhaust combine in accordance with the equation

4 KO.sub.2 + 2 CO.sub.2 .fwdarw. 2 K.sub.2 CO.sub.3 + 3O.sub.2 .

7. The apparatus of claim 2 wherein said combining means comprises

a conduit forming a stream of exhaust gases bypassing said reactor to said engine intake.

8. The apparatus of claim 2 and

a sensor to determine appropriate generation of input in the engine intake and

means responsive to said sensor to adjust the operation of said reactor.

9. The apparatus of claim 2 wherein said sensor is installed in said supply means.

10. The apparatus of claim 2 wherein said sensor is pressure-responsive.

11. The apparatus of claim 2 wherein said sensor is oxygen-quantity responsive.

12. The apparatus of claim 2 wherein said adjust means comprises a valve.

13. The apparatus of claim 2 wherein said valve is installed between said cooler and said reactor such that said reactor may be bypassed by the engine exhaust.

14. The apparatus of claim 2 wherein said adjust means controls said reactor for continuous although variable oxygen generation.

15. The apparatus of claim 1 wherein

said engine and said means are connected in a circuit closed to ambient influence.