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Title:
METHOD AND ARRANGEMENT FOR CONVERSION OF CHEMICAL ENERGY FROM AQUEOUS, LIQUID, ADN-BASED MONOPROPELLANTS INTO MECHANICAL ENERGY
Document Type and Number:
WIPO Patent Application WO/2013/048315
Kind Code:
A2
Abstract:
The present invention generally relates to a method of converting chemical energy from aqueous,liquid, ADN-based monopropellantsinto mechanical energy and a corresponding arrangement comprising a reactor for combustion of aqueous,liquid,ADN-based monopropellants and a mechanical-energy converting device, and to a vehicle, vessel, missile, secondary power plant, EPU, APU and the like comprising such arrangement.

Inventors:
ANFLO KJELL (SE)
THORMAEHLEN PETER (SE)
Application Number:
PCT/SE2012/051017
Publication Date:
April 04, 2013
Filing Date:
September 26, 2012
Export Citation:
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Assignee:
ECAPS AKTIEBOLAG (SE)
Domestic Patent References:
WO2000050363A12000-08-31
WO2002096832A12002-12-05
WO2002095207A12002-11-28
Foreign References:
SE528301C22006-10-17
SE2012050589W2012-06-01
Attorney, Agent or Firm:
BRANN AB (S- Stockholm, SE)
Download PDF:
Claims:
Claims

1. Method of converting chemical energy from an aqueous, liquid, ADN based monopropellant into mechanical energy comprising the following steps:

A. injecting a liquid, aqueous, ADN based monopropellant into a reactor for combustion of the monopropellant,

B. combusting the monopropellant so as to generate gases at elevated pressure and temperature,

C. directing the gases obtained in step B into a mechanical-energy converting device, converting energy carried by the flow of hot gases into mechanical energy,

characterized in additionally comprising step D, wherein an additive fluid as a coolant is injected into the reactor, and/or into the hot gases resulting from step B, and further characterized in that, in step C, also the additional gas generated from step D is directed into the mechanical-energy converting device.

2. The method of claim 1 , further comprising a step E, wherein mainly water contained in the gases obtained in step B is being condensed on the downstream side of the mechanical-energy converting device.

3. The method of claim 2, wherein a condensable additive fluid is used in step D, and wherein the condensable additive fluid is being condensed on the downstream side of the mechanical-energy converting device.

4. The method of claim 2 or 3, further comprising a step F wherein remaining gases after step E, or a portion thereof, are compressed, and preferably led to and stored in a pressurized tank.

5. The method of any one of the previous claims, wherein the additive fluid is liquid water.

6. The method of any one of the previous claims, wherein the outside of the reactor is being cooled using cooling means.

7. An arrangement for converting chemical energy from a liquid, ADN- based monopropellant into mechanical energy, comprising:

a reactor (20) for combustion of an aqueous, liquid, ADN-based monopropellant; and,

a mechanical-energy converting device (30) operatively connected to the reactor, so as to be able to receive gases generated in the reactor, and to convert energy carried by the hot gases into mechanical energy,

characterized in comprising means (25) for injection of an additive fluid into the reactor and / or into the resulting hot gases obtained from the combustion before entering the mechanical-energy converting device. 8. The arrangement of claim 7, wherein the mechanical-energy converting device is selected from the group consisting of a gas turbine, a steam turbine, a gas piston engine, and a steam piston engine.

9. The arrangement of claim 7 or 8, further comprising a condenser (40) downstream of the mechanical-energy converting device.

10. The arrangement of claim 9, further comprising a compressor (50) downstream of the condenser. 1 1. The arrangement of any one of claims 7- 10, further comprising a tank (80) for compressed gas obtained from the compressor, and / or comprising a tank (70) for condensed liquid obtained from the condenser.

12. The arrangement of any one of claims 9- 1 1 , wherein the arrange - ment comprises means for passing the liquid obtained from the condenser into the reactor and /or into the hot gases.

13. The arrangement of claim 10 or 1 1 , wherein the arrangement comprises means for passing the compressed gas from the condenser into the reactor and /or into the hot gases.

14. The arrangement of any one of claims 7- 13, further comprising cooling means for cooling the exterior of the reactor (20).

15. A vehicle, vessel, torpedo or missile comprising the arrangement of any one of claims 7- 14.

16. An emergency power unit (EPU), an assistant or secondary power plant or power unit, an auxiliary power supply, or auxiliary power unit (APU) comprising the inventive arrangement of any one of claims 7- 14.

Description:
METHOD AND ARRANGEMENT FOR CONVERSION OF CHEMICAL ENERGY FROM AQUEOUS, LIQUID, ADN-BASED MONOPROPELLANTS INTO MECHANICAL ENERGY Technical field

The present invention generally relates to the combustion of liquid, ammonium dinitramide (ADN) based, water-containing monopropellants for generation of gases at elevated pressures and temperatures for driving a gas/ steam turbine, a gas/ steam piston engine, or similar device, wherein an additive fluid is used as a coolant. More specifically the invention relates to a method of generating gases wherein a liquid ADN based monopropellant is combusted in a reactor and wherein additionally an additive fluid is injected into the reactor and/or into the resulting hot gases. The present invention also relates to an arrangement com- prising a reactor for combustion of a liquid, aqueous, ADN based monopropellant, and an energy-converting device, converting the flow of combustion gases into mechanical energy, which arrangement may be used as an integrated system in a vehicle, a vessel, a torpedo, or a missile, and a secondary power plant. Background art

In the prior art, ADN-based, aqueous, liquid monopropellants are known. Such monopropellants have been disclosed primarily for space applications, i.e. as propellants for thrusters, e.g. in WO 00/50363, WO 02/096832, and SE

528 301 , with the aim of generating hot gases and a high impulse.

In a preferred embodiment the propellant of WO 00/50363 is based on ADN, and also comprises water. According to WO 00/50363, the amount of water in the monopropellant should be kept as low as possible in order to maximize the specific impulse of the propellant.

In addition to rocket propulsion, WO 00/50363 also briefly mentions that the gases generated from combustion of the monopropellants disclosed therein are suitable for driving a turbine, vane or piston motor, inflating air bags, or for other vessel or vehicle propulsion.

WO 02/095207 discloses a reactor for the decomposition of ADN based liquid monopropellants (such as those described in WO 00/50363, and more preferably for such monopropellants to which a base has been added as a combustion stabilizing agent, such as the monopropellants described in WO 02/096832), into hot, combustible gases for combustion in a combustion chamber, and more particularly a rocket engine or thruster comprising such reactor and a combus- tion chamber. According to WO 02/095207, the reactor disclosed therein could also be used for generating hot gases at high pressure for driving a turbine, vane motor, or piston motor.

SE 528 301 teaches a liquid, ADN-based monopropellant comprising a solution of ADN in a mixture of water and formamide. The liquid monopropellants disclosed therein are said to be suitable for generating hot gases and use in various engines for air-independent propulsion, e.g. underwater and space applications.

The object of the invention is to provide a method and arrangement for conver- sion of energy from an aqueous, liquid, ADN-based monopropellant into mechanical energy. The conversion should preferably be as efficient as possible.

For a method and arrangement as alluded to in the prior art, this object has been solved by means of the characterizing features of the independent claims, according to which an additive fluid is used, to reduce the temperature of the combustion gases before entering into the energy converting device.

Summary of invention The present inventors have found that in order to be able to convert energy from an aqueous, liquid, ADN based monopropellant, such as described in WO 00/50363, WO 02/095207, and WO 02/096832 into mechanical energy using a reactor for combustion of such monopropellant as e.g. disclosed in WO 02/095207, the temperature of the combustion gases must be markedly reduced before entering into the energy converting device, as otherwise virtually any energy converting device would be damaged. According to the invention, an additive fluid (liquid and / or gaseous) is added for cooling the gases before entering the mechanical-energy converting device. By enhancing the resulting gas flow, the addition of the inventive coolant will also improve the efficacy of the intended energy conversion.

In order to further improve the efficiency of the conversion, a condenser may be used downstream the mechanical-energy converting device to condensate mainly water from the gases.

The steam content of the gases can be increased by using water as the coolant. The inventive use of water as a coolant corresponds to a new inventive use of liquid, aqueous, ADN-based monopropellants, namely the use of such mono- propellants for generating steam.

Steam is a very useful working medium for conversion of heat energy into mechanical energy.

In one aspect the invention relates to a method of converting chemical energy from an aqueous, liquid, ADN based monopropellant into mechanical energy, comprising the following steps:

A injecting a liquid, aqueous, ADN based monopropellant into a reactor for combustion of the monopropellant;

B combusting the monopropellant in the reactor so as to generate gases at elevated pressure and temperature;

C passing the gases obtained in step B into a device converting energy carried by the flow of hot gases into mechanical energy;

which method additionally comprises a step D, wherein an additive fluid as a coolant is injected into the reactor, and / or into the hot gases resulting from step B, and, in which method, in step C, also the additional gas gener- ated from step D is being passed to the mechanical-energy converting device.

In another aspect the invention relates to an arrangement for converting chemical energy from a liquid, aqueous, ADN-based monopropellant into mechanical energy, comprising a reactor 20 for combustion of an aqueous, liquid, ADN- based monopropellant, and a mechanical-energy converting device 30 operative - ly connected to the reactor, so as to be able to receive gases generated in the reactor, and to convert energy carried by the flow of hot gases into mechanical energy, wherein the arrangement additionally comprises means 25 for injection of an additive fluid into the reactor and / or into the resulting hot gases obtained from the combustion before entering the mechanical-energy converting device.

In a preferred embodiment of the invention the reactor disclosed in WO

02/095207 is used for combusting the propellant. The modified reactor as disclosed in Swedish patent application No. SE 1250474-2 exhibiting a heat bed having catalytic activity, or the reactor as disclosed in Swedish patent application No. SE 1200286- 1 exhibiting an inner reactor housing may also be used. Preferably, the catalyst retainer in the reactor is separate from the reactor housing or the inner reactor housing, respectively, and for example rests on an inner circumferential flange within the reactor housing, or the inner reactor housing, respectively.

The inventive arrangement could e.g. be used for propulsion, such as for the propulsion of a vehicle, vessel, torpedo, or missile, or for generating electric power, such as in an emergency power unit (EPU) , assistant or secondary power plant or power unit, or auxiliary power supply, or auxiliary power unit (APU) or the like, e.g. on an oil platform, an industrial plant, an airport, a ship, e.g. a submarine, an aircraft or other vessel or vehicle.

In a further aspect the invention consequently relates to a vehicle, vessel, torpedo or missile comprising the inventive arrangement. In yet an aspect the invention relates to an emergency power unit (EPU) , an assistant or secondary power plant or power unit, auxiliary power supply, or auxiliary power unit (APU) comprising the inventive arrangement. Such units can e.g. be used on aircrafts.

The high energy content, the low toxicity, the storability, and the stability of the monopropellant, which is used according to the present invention for generating mechanical energy, will obviously be of major advantage in any power generating applications, such as auxiliary power generation, e.g. in an APU or EPU.

For improved efficacy, a condenser is preferably provided downstream the mechanical-energy converting device to condense mainly steam contained in the gases downstream of the mechanical-energy converting device. Furthermore, the water condensate can be recycled as an additive fluid of the invention and be injected into the reactor and/or into the hot combustion gases, as described above. In combination with a condenser, a compressor can be utilized to recycle non-condensable combustion gases, e.g. for pressurization of propellant tanks, or for confining such gases to separate storage. The system can thus be made so as to not emit any gases during operation, which may be of benefit for use in e.g. underwater vehicles.

By virtue of the present invention a "green", safe, propulsion, or generation of electric power can be achieved. The propellant used is also safe and easy to handle.

This is in contrast to e.g. an emergency power unit (EPU) , or auxiliary power unit (APU) using hydrazine, such as used in the art on some aircrafts, and similar EPU or APU units using hydrogen peroxide as an oxidizer, which will all require rigorous safety arrangements and extreme careful handling due to the hazard and/or toxicity of the propellant used.

In the case of a missile, the liquid, ADN based monopropellant could be used both for generating thrust, i.e. for propulsion and attitude control according to the prior art, and, by virtue of the present invention, also for generating electric energy required for any motorized steering, or for any electric on-board equipment, such as by beans of an APU. Thereby, unified propulsion can be accomplished, and merely one propellant could be used.

In the present disclosure, the terms "mechanical-energy converting device", and "energy converting device" are used interchangeably to denote any device which can be used for obtaining mechanical energy, such as rotational energy, from the flow of hot gases resulting from the combustion of the monopropellant, in- eluding expanded or gasified coolant. Such devices are e.g. a gas or steam turbine, a gas or steam piston engine, or any similar mechanical device.

The hot gases obtained from the combustion will invariably contain steam as one of their gaseous components. In the prior art thruster applications, water in the propellant and steam in the resulting hot gases have merely posed an obstacle, especially when it comes to the demanding and extreme requirements on a suitable catalyst, and in reducing the impulse. In the prior art thruster applications steam is merely one of several gaseous species generating impulse. Moreover, in order to maximize the impulse the water content of the monopropellant should be kept low. According to the invention, on the other hand, the gaseous steam constitutes a special, and very useful component of the hot gases, in that it can readily be condensed. This is in contrast to the prior art thruster applications, wherein any condensation of the gases must be avoided, as it would counteract the intended propulsion by reducing the impulse. In preferred em- bodiments of the inventive method the gaseous steam is being condensed. When terms such as steam turbine and steam piston engine are being used herein, specific use of the steam constituent, and thus associated condensation thereof, at least to some degree, is implied. For example, as used herein, a steam turbine will take advantage not only of the all gaseous components of the hot gases just like a gas turbine, but also additional advantage of the steam component contained in the gases, by providing for some extent of condensation thereof. The term "additive fluid" is used herein to denote a gaseous or liquid component, which is injected into the reactor and / or hot gases to reduce the temperature of the overall gas flow being entered into the energy converting device.

The term "LMP" is used herein to denote liquid monopropellant. Brief description of the attached drawing Fig. 1 is a schematic view over a preferred embodiment of the arrangement of the invention, wherein 10 is a pressurized monopropellant tank, 20 is a reactor (as described in WO 02/095207), 25 means for injection of additive fluid, 30 a mechanical-energy converting device, 40 a condenser, 50 a compressor, 70 is a tank for an additive fluid of the invention, 80 is a tank for pressurized gas ob- tained from the compressor. In the figure, the portion within the broken line corresponds to the most generic embodiment of the invention.

Detailed description of the invention The present inventors have found that, for the driving of a mechanical device, such as a turbine, as briefly suggested in WO 02/095207, using a reactor as disclosed therein, the high temperature of the combustion gases, i.e. typically about 1700- 1800°C, obtained when combusting a prior art liquid, aqueous, ADN-based monopropellant, such as disclosed in WO 00/50363, WO

02/095207, and WO 02/096832, will make the suggested driving of e.g. a turbine not feasible. When exposed to such high temperatures virtually any known mechanical-energy converting device will be damaged or even destroyed. The energy conversion as suggested in WO 02/095207 using the reactor disclosed therein is therefore not practically feasible.

The present inventors have found that in order to make such conversion feasible, the high temperature of the combustion gases must be reduced. At the same time the high temperature could be used for enhancing the gas flow enter- ing into a mechanical-energy converting device. Accordingly, by injection of an additive fluid into the reactor and /or into the hot gases, the temperature of the overall gases entering into said device will be reduced, and the intended conversion will be enhanced by expansion of the added additive fluid, and also by evaporation, when a liquid additive fluid is being used.

According to the invention, the hot gases are cooled to a temperature within the working range of the specific mechanical-energy converting device used. Typically, the temperature of the gases entering the mechanical-energy converting device will be in the range of from about 500°C to about 1200°C, depending on the temperature resistance of the mechanical-energy converting device and the materials used. Obviously, the temperature of the gases may be cooled to a lower temperature if desired for certain applications.

The present inventors have also found that, in contrast to the prior art space applications of the reactor, in the present application, a reactor of the prior art will typically have to be provided with a radiation shield, thermal insulation or means for cooling the reactor body, such as a cooling jacket, in order to protect the surroundings from heat radiation from the reactor.

The cooling requirements according to the invention open for new possibilities of making the intended energy conversion more efficient. For example, a condenser can be used to further improve the energy conversion, and/ or water can be used as the inventive additive fluid.

The invention disclosed herein, which is based on using an aqueous, liquid, ADN based monopropellant for driving a mechanical-energy converting device, is fundamentally different to the prior art space applications of such monopropel- lants.

For example, the before-mentioned prior art, i.e. WO 00/50363, WO

02/096832, and WO 02/095207, only describe space applications. For such applications a high specific impulse is fundamental. For this reason the content of water in the propellant should be minimized according to the teachings of the prior art applications. According to the present invention, on the other hand, maximising the specific impulse is not relevant. Instead, for driving a mechani- cal-energy converting device of the present invention, optimising the temperature, volume and pressure of the gases formed, so as to make the conversion into mechanical energy feasible, and also efficient is of primary importance.

Accordingly, as opposed to the prior art space applications, according to the present invention, water can be added to improve the efficacy.

According to the invention, in order to increase the efficacy, a condenser is preferably provided to increase the overall system performance. Obviously, in any prior art space applications any condensation of combustion gases would be very undesirable, as this would severely decrease the impulse.

According to the present invention, which, in contrast to the prior art, will not be carried out with the reactor exposed to space, cooling of the reactor, including heat recovery systems, will typically be required.

According to the invention a gas or liquid is injected as an additive fluid into the reactor and / or into the hot gases formed from the combustion in order to reduce the temperature of the gases entering the mechanical-energy converting device. Suitable additive fluids are e.g. water, nitrogen, and carbon dioxide. Other fluids are also conceivable. Obviously, the net of any reactions, including the heat of evaporation, when a liquid additive fluid is being used, of the specific additive fluid occurring upon injection must be endothermic.

In its most generic embodiment, which is depicted within the broken line in Fig- ure 1 , the inventive arrangement will comprise a reactor 20, a mechanical- energy converting device 30, and means 25 for injecting an additive fluid into the reactor, and / or into the hot gases exiting the reactor before entering into the mechanical-energy converting device. Suitable reactors have already been described in WO 02/095207, SE 1250474-2 and SE 1200286- 1 and will not be described in further detail herein. When injected into the reactor, the additive fluid is preferably injected at a location in the reactor downstream of the heat bed, and more preferably downstream of the catalyst bed.

In a preferred embodiment, the inventive arrangement also comprises a conden- ser 40 for condensing steam contained in the hot gases.

The additive fluid may be contained in a separate tank 70, which may be included in the inventive arrangement. In a preferred embodiment, wherein a condenser 40 is used, condensed additive fluid is recirculated back from the condenser to injection means 25, e.g. via tank 70.

In yet a preferred embodiment, wherein a condenser 40 is used, the inventive arrangement further includes a compressor 50 for compressing gas exiting the condenser 40. A portion of the compressed gas can for example be led to mono- propellant tank 10 for pressurizing the tank, while the remaining gas is led to and stored in a separate tank 80. Alternatively, as shown in the Figure, gas for pressurizing monopropellant tank 10 may be taken from tank 80. The com- pressed gas obtained from compressor 50 could also be used as an additive fluid and be injected into the reactor and/or hot gases (not shown). This possibility may e.g. be useful in applications wherein the system is required to have zero emissions, or wherein the power generating system has to be sealed off from the surroundings.

Accordingly, the inventive arrangement, if desired, can be made to have zero emissions to the surroundings. Radiation shielding, thermal insulation, and external cooling of the reactor

The monopropellant will generate an extremely high temperature upon combustion thereof, so that parts of the reactor typically will be incandescent. In the prior art space applications, i.e. as a part of a rocket engine or thruster, the external surface of the reactor will be able to radiate heat into the space. In the present applications, however, which are predominantly terrestrial, such as land based or marine, the exterior of the reactor may have to be radiation shielded, thermally insulated or even cooled off, depending upon the specific application.

A radiation shield may be used to reduce heat radiation from the reactor to protect temperature sensitive and/ or proximate parts. Thermal insulation may also be used for same purpose. Suitable means for thermal insulation and radiation shielding are known in the art and can be used herein.

A suitable means for cooling is e.g. a jacket surrounding the reactor, in which jacket a cooling medium is being circulated. A suitable cooling medium is e.g. water. The cooling agent may be circulated to a heat exchanger, such as a radia- tor.

In one embodiment the cooling agent is also used as an additive fluid. In such embodiment the cooling agent encirculating the reactor body may be injected through nozzles or orifices in the reactor body, or preferably through nozzles or orifices downstream of the reactor. The cooling jacket could also extend downstream of the reactor so that the combustion gases exiting the reactor will pass through the downstream portion of the jacket. In such embodiment the inner wall of the jacket facing the combustion gases may be provided with orifices of or nozzles through which the cooling agent may be injected into the hot gases as an additive fluid. The condenser

In order to further improve the efficacy of the intended energy conversion in the inventive arrangement, steam is condensed in the arrangement downstream of the mechanical-energy converting device. This will significantly lower the pressure on the downstream side in the arrangement, thus maximizing the energy output from the mechanical-energy converting device. As already pointed out above, the water obtained from condensing steam can e.g. be led back to a storage tank for water 70, or be injected again into the reactor and/ or into the hot gases generated, e.g. via tank 70. Accordingly, in a preferred embodiment a condenser is included in the inventive arrangement. For obvious reasons, there is no need for a condenser to reduce the downstream pressure if the mechanical-energy converting device is operated in space or at very high altitude. The aqueous, liquid, ADN based monopropellant

Especially preferred monopropellants for use in the present invention are composed of ADN, methanol, water and ammonia. Suitable monopropellants have been disclosed in e.g. WO 00/50363, WO 02/096832, and

PCT/SE2012/050589 (not published).

Example 1

With reference to the Figure, a preferred embodiment of the inventive arrange - ment will be described in this example.

With reference to Fig. 1 , an aqueous, liquid, ADN-based monopropellant is fed from tank 10 and injected into reactor 20, wherein the monopropellant is combusted. Reactor 20 is provided with cooling means (not shown). The hot gases generated in the reactor 20 are directed to the mechanical-energy converting device 30, which converts the energy carried by the flow of hot gases into mechanical energy. Before entering energy converting device 30, however, the hot gases exiting reactor 20 are cooled by means of addition of an additive fluid into the flow of hot gases, which fluid can be gaseous and/or liquid, via injection means 25. The gases exiting energy converting device 30 are conveyed to a condenser 40, wherein water from the monopropellant and its combustion, and any other condensable gases formed from the additive fluid or from the combustion, are condensed into liquid. The liquid obtained from condenser 40 is directed into storage tank 70, e.g. by means of a pump (not shown), and is thereafter, via injection means 25, injected as an additive fluid into the hot gases exiting the reactor 20, which gases thereafter enters energy-converting device 30. The gases leaving the condenser 40, or a portion thereof, are compressed in compressor 50 and, a portion thereof is thereafter directed to the monopropellant tank 10 for pressurizing same, and the remaining portion is led to a storage tank 80. Possibly, the compressed gases can also be used as an additive fluid (not shown).