METHOD FOR THE PROPULSION OF AN UNDERWATER TORPEDO

Abstract: The motor (2) of the torpedo is supplied in a steady state with steam generated by the combustion of a fuel in an oxygen atmosphere in the absence of nitrogen. During a start-up phase the motor is supplied with steam generated by heating water. The water is heated in a container (12) until it reaches its saturation pressure, whereupon the container is opened by pyrotechnic means so that the vapour pressure can drive out the water for the purpose of its evaporation.

Description: Method for the propulsion of an under.water torpedo The present invention relates to a method for the pro¬ pulsion of an underwater torpedo in which the motor of the torpedo is supplied in a steady state with steam ge¬ nerated by the combustion of a fuel in an oxygen atmos¬ phere in the absence of nitrogen. Thermally powered underwater torpedos have propulsion mechanism consisting of a motor element with a piston engine or turbine and a steam generation element. The steam generation element contains a combustion chamber inside which a fuel is burned in order to give off heat. The oxygen for the combustion process is commonly taken from air, which is carried in an air container. The vo¬ lume of the air container has always accounted for a significant proportion of the total volume and weight of the torpedo. A switch has been made to other oxygen carriers in the form of oxides in order to permit a larger supply of oxygen to be carried. Pure oxygen in liquid form is also- encountered. The combustion of the fuel in the combustion chamber in the presence of air produces exhaust gases consisting mainly of nitrogen. The exhaust gases from the engine are generally released into the water behind the propellers of the torpedo. As nitrogen gas is not soluble in water, it rises to the surface and leaves a wake of bubbles be¬ hind the torpedo. This wake of bubbles is easily observed from a surface vessel of aeroplane. Apart from the fact that this will enable the target to change course and avoid the torpedo, the location of the vessel which fired the torpedo is also revealed. Especially in the case of submarines, there is a wish to avoid the position of the torpedo being disclosed. If the combustion of the fuel in the combustion chamber takes place in pure oxygen or in an oxygen atmosphere in the absence of nitrogen, the exhaust gases produced by the propulsion mechanism will be condensable or soluble in water, and the torpedo will leave no trace of its path on the surface. If, for example, hydrogen peroxide H2O2 is used as the oxygen carrier, the exhaust gases will consist primarily of water vapour and carbon dioxide CO2, which condense and dissolve respectively in the water, causing no trace to appear behind the. torpedo. If the oxygen is supplied in the form of an oxide, then- it must be released and converted into the gaseous form, for example by being passed over a catalyzer. If liquid oxygen is used, vaporization will occur as a result of heating. A common feature of all these processes is their instabi¬ lity during the start-up phase, before steady state running has been achieved. Liquid oxygen or hydrogen peroxide in the form of droplets can enter the motor ele¬ ment, where it is vaporized of broken down, and the pure oxygen can come into contact with fuel or lubricatng oil, resulting in explosion-like self-ignition phenomena. Explosions of an order of magnitude which may put at risk the safety of the firing vessel can occur. In order to avoid the risk of explosions in the motor element, the combustion process in the combustion chamber may be initiated with air, and once stable combustion and a high temperature have been achieved, a gradual change¬ over may be made to the other form of oxygen supply. Once a high temperature has been reached in the combustion chamber, any droplets present there will be vaporized if oxygen in liquid form is used. If hydrogen peroxide is used, this will be broken down at temperatures above 625 C into oxygen gas and water vapour. The use of air during the start-up phase means, however, that the torpedo will not run without leaving a trace for the duration of air operation, byt that nitrogen will rise to the surface and will reveal the point of firing. The object of the present invention is, therefore, to propose a method of the type described by way of intro¬ duction in which said risk of explosions has been essen¬ tially eliminated. This object is achieved by supplying the motor of the torpedo during a staft-up phase with steam generated by heating water. The invention is described below in greater detail with reference to the accompanying drawing, which illustrates a system for the best mode implementation of the method in accordance with the invention. Figure 1 represents schematically a section of a torpedo showing the relative positions of the torpedo motor, the permanent combusion chamber and a starting means for the generation of said water vapour. Figure 2 shows on an enlarged scale a longitudinal section through the starting means in accor¬ dance with Figure 1. Figures a and 3b show on an even more enlarged scale a section through the starting means in its inactive and active positions respectively. Figure 1 represents schematically a cut-away section of a torpedo 1. A torpedo motor 2 is so arranged as to be supplied in its steady state with steam from a conventio¬ nal combustion chamber 3 ' via a steam pipe 4. The combus- tion chamber 3 is so arranged via a transfer device 5, which is controlled by a valve 5a via a line 5b, as to be supplied with fuel via a pipe 6a, with water via a pipe 6b, and with an oxidizing agent via a pipe 6c. The com¬ bustion chamber itself is of conventional execution, for which reason it is not considered necessary to describe it here. The motor 2 is also connected, via steam pipe 7, to a starting means 8, which is described in greater detail - below. Between the motor 2 and the starting means 8 is present a space 9 containing control apparatus. Since this does not constitute part of the invention, it is not described here an any greater detail. The reference designation 10 is used to denote a fan for the circula¬ tion of hot air through the space 9 to the motor 2. The starting means 8 is shown in greater detail in Fi¬ gures 2, 3a and 3b. It consists (see Figure 2) essential¬ ly of a heat exchanger 11 and a water container 12. The heat exchanger 11 is shown here to consist of an outer pipe 13 and an inner pipe 14 wound together in the form of a spiral. The space 15 between the pipes 13 and 1 forms an enclosed space which is filled with a salt. This salt must possess a high heat content in its molten state, and may be lithium hydride or a fluoride, for example. The salt is heated* to a temperature above its melting point by means of a resistance element 16, which is positioned between the coils in the outer- pipe 13 wound Into the form of a spiral. The resistance element 16 is connected via lines 17 and 18 with a power source situated outside the torpedo and its tube. Thermoelements 19 are inserted in the walls of the pipe 13 and are connected via a line 20 with a regulator (not described here in any greater detail) situated outside the torpedo and its tube, which regulates the power supply to the resistance element 16. The resistance element 16 is electrically isolated from the outer pipe 13 by means of fire-clay insulators 21, threaded over the resistance element 16. The insulators 21 are so executed as to exhibit the greatest possible area of contact with the pipe 13. The inner pipe 14, which is surrounded by the molten salt, may be provided with flanges 22 for the purpose if increasing the surface area available for the transfer of heat. Through the pipe 14 passes steam which is generated at a constricting plate 23 in the presence of heat and is then fed to the motor 2, the steam pipe 7 of which is connected at a flange 24. The water 25 which is to be vaporized is stored in said container 12, this is filled with water up to a certain level 26, so as to leave an air space 27 above it. Around the container 12 is fitted a resistance element 28 for heating purposes. The resistance element 28 is connected via lines 29' to a power source situated outside the tor- pedo and its tube. A thermoelement 30 is connected via a line 3 with a re¬ gulator (not described here in any greater detail) situa- ted outside the torpedo and its tube. The regulator con- trols the power supply to the resistance element 28, so that the temperature of the water is maintained within certain pre-set limits. The container 12 is fitted with two stub connections 32 and 33, which are joined together by means of a pipe 34- The pipe 34 has two flanges 35 and 36, which are attached to the stub connections 32 and 33 respectively by means of welded joints 37 and 38 (see Figure 3a in particular). The reason for using welded joints is to provide fully tight connections on those occasions when the container 12 is heated and the pressure inside it rises. The lower flange 36 has a machined groove 36a intended to provide a shearing zone 36b. The pipe 34 has one or more ridges 39, the purpose of which is to absorb by elastic deformation the variation in length which occurs as the container 12 is heated. The ridge 39 is also intended to provide a deformation zone ' 39a, as shown in Figure 3b. Through the pipe 34 there passes a piston rod 40, having at its lower end a flange 41 , which is connected to the flange 36 by means of a welded or soldered joint 42. The upper end of the piston rod 40 exhibits a piston 43 which forms a chamber 44 between itself and the flange 35. To the chamber runs a pipe 45 leading from a powder cart¬ ridge 46 (see Figure 2). The powder cartridge 46 is pro¬ vided with a powder charge 47 containing one or more fuse heads 48 which are connected via a line 49 to a firing arrangement (not described here in any greater detail) in the torpedo. When the torpedo is fired the powder charge 47 is ignated and the powder gases are led via the pipe 45 to the cham¬ ber 44 beneath the piston 43- The piston 43 is forced up- wards by the pressure of the powder gases, and the force is transferred via the piston rod 40 to the lower flange 36. This will then rupture in the shearing zone 36b, and the ridge 39 will be deformed until it adopts the appea¬ rance 39a shown in Figure 3b. Once the ridge 39 has been deformed, the piston 43 and the piston rod 40 will move upwards, causing a gap 50 (see Figure 3b) to form at the rupture surface of the shearing zone 36b. Free passage is thus provided for the water 25 from the container 12 to the pipe 14 in the heat exchanger 11. The container 12 is filled with water through a non-return valve 1 • Water continues to be admitted until the pre-set level 26 is reached. The non-return valve 51 is sealed by means of a cover 52 and welded or soldered joint 53- When the water 25 is heated by the element 27 and is caused to vaporize, the pressure inside the container 12 will rise until its saturation pressure at ambient tempe¬ rature is reached. After firing, the water 25 is forced by the vapour pres¬ sure present inside the container 12 out via the gap 50 and the constriction plate 23 into the pipe 14, and the water is transformed into saturated steam. As it passes through the pipe 14 the steam is superheated by heat transfer through the wall of the pipe 14 from the heated salt which surrounds same in the space 15. The method of allowing the pressure inside the container 12 to drive ' out the water 25 for vaporization produces a higher energy content for the steam at the beginning of the starting procedure. This is an advantage because, when the motor 2 is cold, a proportion of the energy of the steam will be utilized for heating. During the later part of the starting procedure a gradual change-over is made to the generation of steam inside the combustion chamber 3. The change-over is effected by means of the transfer de- vice 5; see Figure 1. The change-over is initiated by the valve 5a, shown here only in schematic form, this is con¬ trolled by the flow of water along the torpedo. As the flow of water reaches a certain speed, indicating that the torpedo has safely left its firing tube and has achieved a certain forward speed, the valve 5a will open. In connection with this oil is so arranged as to flow under pressure in the line 5b as far as the transfer de¬ vice 5, in so doing slowly causing three valves (not shown) which are operated mechanically in relation to each other to be opened, said valves allowing fuel to flow via the pipes 6a and 6b to ' the combustion chamber 3- 8 When oxygen and fuel meet inside the combustion chamber 3, the result is spontaneous ignition. The temperature increases, and the water which is being injected simul¬ taneously via the pipe 6b is vaporized, causing a build-up in pressure. The steam is fed into the motor 2 via the pipe 4- Since the pipes 4 and 7 are connected to each other, the flow of water In the pipe 7 from the con¬ tainer 12 will cease once the pressure inside the combus¬ tion chamber 3 is as great as the pressure inside the container 12, at which point the starting phase is termi¬ nated. The remaining water inside the container 12 will remain at the same pressure as exists inside the combus¬ tion chamber 3 as the torpedo continues to operate. The temperature of the water will fall only insignificantly, as will that of the salt in the heat exchanger. Heat will radiate outwards into the surroundings* from around the heat exchanger 11. In order to reduce the heat losses, the heat exchanger is enclosed by'an insulating casing 54, 55, 56 and 57. The container 12 is also en¬ closed by a thermally insulating casing 58 as indicated in Figure 2. In spite of the insulation 54-58, some heat will still radiate outwards into the gap 59 between the insulation 56 and 58. This heat is led away by means of air circula¬ ted through the gap 59 by the fan 10 in accordance with Figure 1. The circulating hot air is passed, in the manner already described, towards the motor 2 via the control room 9 for the purpose of their heating. The starting of the torpedo will, in fact, be faciliated at low external temperatures if the motor and its auxiliary equipment have been heated beforehand.

Claims: Claims 1. Method for the propulsion of an underwater torpedo in which the motor (2) of the torpedo is supplied in a steady state with steam generated by means of the combustion of a fuel in an oxygen atmosphere in the absence of nitrogen, c h a r a c t e r i s e d in that the motor of the torpedo is supplied during a start-up phase with steam generated by heating water. 2. Method in accordance with Claim 1, c h a r a c t e ¬ r i s e d in that the water (25) is heated in a contai¬ ner (12) so that the pressure inside the container rises to the saturation pressure at ambient temperature, and so that the water inside the container is driven out by means of the aforementioned saturation pressure for the purpose of its evaporation. 3. Method in accordance with Claim 2, c h a r a c t e - r ϊ s e d in that the water vapour driven out of the container (12) is super-heated before being supplied to the motor (2) of the torpedo. 4. Method in accordance with any of the Claims 1-3, c h a r a c t e r i s e d in that the heating of the water is achieved by electrical means. 5. Method in accordance with any of the Claims 2-4, c h a r a c t e r i s e d in that an opening (50) is made in said container (12) by pyrotechnic means so as to permit said driving out of the water from the container to take place. 6. Method in accordance with any of the foregoing Claims, c h a r a c t e r i s e d in that the transi¬ tion from the start-up phas p to the steady is made once the torpedo has reached a certain speed.

Inventors: HALLQVIST ERNST, LJUNGLOEF BERTIL, HALLQVIST, ERNST, LJUNGLOEF, BERTIL
Applicants: AFFARSVERKET FFV, AFFAERSVERKET FFV
Application year: 1985
Main classification: F42B19
IPC codes: F42B19