WO1998019907A1 - Dual propeller propulsion system for a water craft - Google Patents

Abstract

Dual propeller propulsion system for water crafts having two propellers (3, 4) fitted in the same axis outside the ends of an underwater housing (2) configured as a gondola so as to facilitate flow, said housing being placed under the hull of the water craft having a driving mechanism lodged in the underwater housing for both propellers (3, 4) to which the energy coming out for both propellers (3, 4) to which the energy coming out of the hull of the water craft is guided by means of a housing shank (18), one of the ends of which is mounted on the hull (24) of the water craft while the other is mounted in the underwater housing (2). Said propulsion system is characterized in that the underwater housing (2) forms part of a control device (20) by means of which the water jet coming out with increased energy from the front propeller (3) in the direction of travel of the water craft is guided with minimal energy loss and optimal irrotational flow to the back propeller (4) placed in the other end of the underwater housing in the direction of travel of the water craft. Both propellers (3, 4) are driven by the driving mechanism placed in the underwater housing in the same direction of rotation and are configured in the area of the respective water jet cross section in such a way that the differing flow energy entering both propellers (3, 4) is optimally used.

Description

 DOUBLE PROPELLER DRIVE FOR WATER VEHICLES

The invention relates to a water jet drive with a prime mover and a double propeller which is driven by the prime mover.

Such drives are known in a design such that the actual drive machine, in particular a diesel engine, is arranged inside the ship's hull and a transmission as a further part of the drive machine is located in a nacelle below the ship's hull, from the shafts connected to the transmission at opposite ends are led out, which are connected at their outer ends with a propeller rotation test. Such a solution is described in DE 44 30 738 AI, the essential feature being a guide device arranged between the two propellers, which eliminates the swirl in the water after leaving the propeller in the direction of travel, so that this water causes the rear propeller with higher energy in the direction of travel, but just as swirl-free as the front propeller. Generic drives are also known in the training that the entire drive is in the aforementioned gondola. (In this solution, an electric motor for the propellers at both ends of the nacelle is the prime mover, to which the electrical energy is supplied by a power generation system which is housed in the ship's hull. Such a solution is described in EP 0 590 867 AI.

When driving the first-mentioned design, a shaft is generated between the drive motor inside the ship's hull and its gearbox in the nacelle. see lines between the power generation system inside the hull and the electric motor in the nacelle surrounded by a cladding tube. If the cladding tube is assigned to the ship's hull at its upper end rotatable about its longitudinal axis and carries the nacelle at its lower end in a rotationally fixed manner, then a servomotor can be assigned to it, which forcibly rotates the cladding tube with the gondola and the propellers assigned to it about the longitudinal axis of the cladding tube is capable of changing the outflow direction of the rear propeller into the open water and a rudder double propeller system is available. In addition, in the first-mentioned embodiment, the cladding tube is formed as part of the guide grill.

Before this and further prior art, which, however, brings no further aspects with regard to the present invention, it is the object of the present invention to optimize a ship propulsion system with a double propeller in such a way that an efficiency which is optimal according to the current state of knowledge is achieved, the structural and Manufacturing effort is not significantly higher than that associated with the prior art.

The solution to this problem according to the invention consists in the combination of individual, appropriately selected individual problem solutions, not only for summation, but for potentiating the individual advantages to an overall concept that is optimal in its entirety.

Accordingly, the ship propulsion system according to the invention is a water jet propulsion system with two propellers at the ends of a propeller led out of a gondola outside the ship's hull, a propulsion system arranged in the gondola Energy is supplied from the ship's hull through a cladding tube, one end of which is assigned to the ship's hull, the other end of which is assigned to the gondola, the cladding tube being part of a guide apparatus through which the propeller in the direction of travel of the watercraft at one end of the shaft and gondola arranged propeller with enriched flow energy leaving water jet swirl-free, in order to supply the water jet leaving the front propeller with high energy but little swirl to the rear propeller in the direction of travel of the watercraft, for which purpose both propellers are driven by the drive in the nacelle in the same direction of rotation and in the area of the jet cross section in are essentially the same.

In a further embodiment, the two propellers also have essentially the same diameter, the front propeller in the direction of travel of the watercraft in the entire diameter range and the rear propeller in the diameter range in the direction of travel of the watercraft, the diameter determined by the jet contraction when leaving the front propeller both different Blade configuration, the front propeller in the direction of travel of the watercraft and the rear propeller in the direction of travel of the watercraft in an annular area lying radially outside the diameter range determined by the jet contraction have the same blade configuration.

These and further features of the invention result from the following description of several exemplary embodiments of the invention, the exemplary embodiments of the invention shown in the drawing and finally from the claims.

Show in the drawing

Fig. 1 shows a first embodiment of a water jet drive according to the invention, each with a propeller at the ends of a gondola-like, aerodynamically designed underwater housing, which is arranged by means of a housing shaft or foot on the underside of a ship below this ship and receives an electric motor on its shaft or the ends of which are each arranged a propeller;

FIG. 2 shows a second exemplary embodiment in a further embodiment which is expedient compared to FIG. 1;

Fig. 3 shows a third embodiment, in which an angular drive is arranged in the underwater housing, in which drive energy is supplied via a shaft line accommodated in a cladding tube or housing shaft from an inboard drive motor, which is not shown but a conventional internal combustion engine, an electric motor or the like.

Fig. 4 to

6 in representations corresponding to the previous one, yet another embodiment in three variants and with an electric motor in the underwater housing, to which energy is supplied inboard by a power generator via cables which are guided through the housing shaft, and FIG. 7 shows a double propeller design which is particularly expedient and which is a double propeller arrangement as is particularly the subject of the invention and can be used in all of the above-mentioned embodiments.

Description of the embodiment according to FIG. 1

The drive essentially consists of an electric motor 1 ^{"• '} in a housing 2 ^{* •"} outside, in particular below the hull and two propellers, 3 ^* - ^' , 4 ^* '^" , which are driven by the electric motor 1 ^{' • *} . The two propellers will generally be structurally different, even though they have tip circles 5 ^"•" with the same diameter and a similar wing geometry. They have the same direction of rotation and the same speed and, for example, the flow is in the same direction according to arrow A.

The electric motor 1 ^* - ^" is arranged watertight in the underwater housing 2 ^'•" . The output shaft is made of it on both sides! ^{'•' led} out and laterally rotatably mounted in one of two bearings 8 ^{"• *} , 9 ^{" • "of} the housing 2 ^{" • "} on the side of the motor. Seals 10, 11 ^' - ^" on the side of the bearing 8 ^" serve the seal ^{• *} , 9 ^" - ^* between shaft 7 ^'•" and front housing walls 2a ^* - ^" , 2b ^" * ^' in connection with the design of the end faces as parts of labyrinth seals. Outside the housing 2 ^'•' are on the shaft! ^' • ^' Flanged stub 12 ^* - ^' , 13 ^' - ^" , one of each of the two propellers 3 ^" - ^' , 4 ^' • ^" non-rotatable. At the front, connect to the housing 2 ^'•' hub caps 14 ^" - ^" , 15 ^" * ^* , whereby a continuous, streamlined outer contour with head 14 ^" - ^' in the area of the front propeller 3 ^* - ^' , middle part in the shape of the housing 2 ^{'• "} and end part 15 ^* - ^* in the area of the rear propeller 4 ^"" . The end walls 14a ^* * ^" , 15a ^{"•" of} the hub caps 14 ^' - ^' , 15 ^" '^" facing the housing 2 ^* - ^' . are second parts of the labyrinth seals 16 ^" - ^" , 17 ^* - ^" the first parts of which are the end faces 2a ^" - ^" , 2b ^" - ^" already mentioned. The housing 2 ^" - ^' is held on the hull with a foot 18 ^' - ^* , which is hollow, the outer contour of which is part of the guide device 19 ^" - ^" between the propellers 3 ^* - ^" , 4 ^' - ^" , which has further blades associated with the housing 2 ^' - ^' , one of which is the base 18 ^' - ^* diametrically opposite vane 20 ^{' "is} referred to a total of the blades of the diffuser 19th ^{*' -"} gleichmä ig about the longitudinal axis of the shaft 7 ^{"• *} distributed fixed to the housing ^{2" is} assigned ^{• ".}

Overall, the propellers 3 ^"■" , 4 ^" - ^{" are designed} so that the initial working level of the second propeller 4 ^{"•" is} approximately the final working level of the first propeller 3 ^" - ^" and in conjunction with the guide device 19 ^* - ^" the initial twist of the first propeller 3 ^" - ^' as well as the input twist of the second propeller 4 ^* - ^{* are} purposefully influenced in such a way that little energy losses occur when the liquid passes from the first to the second propeller.

The energy supply to the electric motor takes place through lines 21 ^* - ^" , which are guided in the foot 18 ^* - ^* and in the housing 2 ^" - ^" to the motor, which is why the interior of the foot 18 ^* - ^" and the housing 2 ^" - ^" with each other Connect. In order to be able to use the drive not only to generate a thrust in the longitudinal direction of the ship (longitudinal axis of the drive shaft), but also to steer the ship, the entire drive must be appropriately assigned to the ship and an appropriate swivel mechanism known per se around the vertical longitudinal axis 22 ^* - ^' pivotable in the middle between the two propellers, optionally pivotable by 360 ° all around, the axis 22 ^' - ^{"being directed} perpendicular to the axis of rotation of the shaft axis 23 ^'#" .

Description of the embodiment according to FIG. 2

The drive essentially consists of an electric motor l ^"" in a housing 2 ^{* "} outside, in particular below the hull and two propellers 3 ^"' , 4 ^"" which are driven by the electric motor l ^{' *} . The two propellers will generally be structurally different, although they have tip circles 5 ^{* "} with the same diameter and may have a similar wing geometry. They have the same direction of rotation and the same speed and are flowed in in the same direction, for example, according to the arrow A ^"" .

The electric motor 1 ^'" is arranged in the underwater housing 2 ^{* * in a} watertight manner. The output shaft 7 ^{""is led} out of it on both sides and is rotatably supported in one of two bearings 8 ^"' , 9 ^{* "of} the housing 2 ^" in the side of the motor . The seal is provided by seals 10 ^″ , 11 ^{′ ″} on the side of the bearings 8 ^″ , 9 ^{″ ″} between shaft 7 ^″ and the front housing walls 2a ^{* ′} , 2b ^{″ ”} in connection with the formation of the end faces as parts of labyrinth seals. half of the housing 2 ^{* '} are flanged to the shaft 7 ^'" stub shaft 12 ^'" , 13 ^'" , each of which carries one of the two propellers 3 ^"' , 4 ^{* "in a} rotationally fixed manner. End caps connect to the housing 2 ^"" 14 ^'* , 15 ^*' , with a continuous, streamlined outer contour with head 14 ^'* in the area of the front propeller 3 ^{* "} , middle section in the shape of the housing 2 ^** and end section 15 ^*' in the area of the rear propeller 4 ^{* '} is formed. The housing 2 ^** facing end walls 14a ^{* ",} 15a ^{* 'of} the hub caps ^{14"", 15"'} are second parts of the labyrinth seals 16 ^'', 17 ^{* ',} the first parts of the already mentioned end surfaces ^{2a' *,} 2b ^{* "} are. The housing 2 ^{* "} is held on the ship's hull with a foot 18 ^'" which is hollow, the outer contour of which is part of the guide apparatus 19 ^"" between the propellers 3 ^'" , 4 ^'" , the other being assigned to the housing 2 ^*' Has blades, of which a blade diametrically opposite the base 18 ^'" is designated 20 ^** . Overall, the blades of the guide apparatus 19 ^{* * are} uniformly assigned to the housing 2 ^"" distributed uniformly around the longitudinal axis of the shaft 7 ^*" .

Overall, the propellers 3 ^"' , 4 ^{*' are designed} such that the initial working level of the second propeller 4 ^""is approximately the final working level of the first propeller 3 ^*" and, in conjunction with the guide device 19 ^{* ',} the initial twist of the first propeller 3 ^{* "} as well as the input twist of the second propeller 4 ^{* * are} purposefully influenced in such a way that at most small energy losses occur when the liquid passes from the first to the second propeller.

The energy supply to the electric motor takes place through lines 21 ^{* '} , which are in the base 18 ^'' and in the housing 2 ^{* *} to the motor are introduced, which is why the interiors of the foot 18 ^"' and the housing 2 ^"' are connected.

In order to be able to use the drive not only to generate a thrust in the longitudinal direction of the ship (longitudinal axis of the drive shaft), but also to steer the ship, the entire drive must be appropriately assigned to the ship and an appropriate swivel mechanism known per se around the vertical longitudinal axis 22 ^{* "can be} pivoted in the middle between the two propellers, possibly pivoting 360 ° all around; axis 22 ^{""is directed} perpendicular to the axis of rotation of the longitudinal axis 23 ^{* '} .

The motor 1 ^{* '} is designed as a permanent synchronous motor and is therefore an electrical machine with a very high power density. The technology of such an engine makes it possible to design the housing 2 ^** between the two propellers to be hydrosdynamic in such a way that very high efficiency is achieved.

With this technology it is possible that the foot 18 ^{* 'can be designed} as a shaft, that it too has an optimal hydrodynamic design.

The shaft 18 ^"" is formed in its lower area close to the housing 2 ^'" so that together with a second, diametrically opposite guide fin 20 ^{*" it forms} a pair of guide fins and thus a guide apparatus, so that an optimal inflow of water to the seen in the flow direction A ^{* *} second propeller 4 ^{* "is} possible. The guide fins end in the diameter circles 5 ^{*" of} the two propellers 3 ^{* "} , 4 ^*" . By combining the permanent synchronous motor with high power density on a small diameter with the optimal guide device (pair of guide fins or guide device 20 ^{* "} ) and the two propellers 3 ^** , 4 ^{* '} , a drive system is achieved that is characterized by an extreme Improved effectiveness both electrically and hydrodynamically.

The design of the motor 1 ^** as a permanent synchronous motor makes it possible to reduce the diameter of the housing 2 ^{* '} by up to 20% compared to other motors known per se. The advantages are obvious: only smaller masses and more favorable flow conditions or lower flow resistance should be mentioned.

Another embodiment according to the invention relates to the rotor bearing of the permanent motor, which also includes the propeller shaft bearing. In order to reduce or eliminate the displacements and deformations as well as the dynamic loads from the propellers, the rotor, ie the drive shaft 7 ^{"" is connected} to the propeller shafts 12 ^"" , 13 ^"" via diaphragm couplings 23 ^"" , 24 ^"" . This allows a minimal air gap between the stator and rotor, which means a significant, additional improvement in efficiency.

Description of the exemplary embodiment according to FIG. 3.

3 shows a ship drive designed as a rudder double propeller with a drive machine arranged in the ship's hull with a vertical drive shaft 1 ^' and drive propellers outside the ship's hull. In a conventional manner and therefore not shown in FIG. 3, a drive machine comprising a motor and gear acts on the upper end of the vertical drive shaft 1 ^{* in} order to set the drive shaft 1 ^* in rotation about its longitudinal axis 2 ^″ at a variable speed. The lower end the input shaft 3 ^"of an angular drive 3 ^* , 4 ^{* is} associated with the drive shaft 1 ^" , which is operatively connected to the output bevel gear 4 ^'of the angular gear 3 ^" , 4 ^* . The output bevel gear 4 ^' rotatably supports a horizontal output shaft 5 ^" which extends in both directions and at the free ends of which a propeller 6 ^* , 7 ^' is arranged. The propellers will generally be structurally different, although tip circles 14 ^{" have the} same Diameter and similar wing geometries may be possible. Due to the common assignment to the output shaft 5 ^{", they have the} same direction of rotation and the same speed and, for example, the flow is in the same direction according to arrow A ^* .

The angular gear 3 ^" , 4 ^' is surrounded by a housing 9 ^' in which the output shaft 5 ^{* is} rotatably mounted by means of two bearings 10 ^' , 11 ^" . This housing 9 ^* is carried by a housing tube 9a ^" which concentrically surrounds the vertical drive axis 1 ^' and can be pivoted about its longitudinal axis for the rowing function.

The underwater part of the drive system can be arranged within a nozzle 12 ^* .

The front propeller 6 ^* generates a residual or re-spin in its outflow, which represents lost energy. The downstream, co-rotating propeller l ^' is with the outflow of the front propeller. Without a guide device between the two propellers 6 ^" , 7 ^* , the above-mentioned unfavorable outflow would lead to increased cavitation and increased energy losses.

In order to counteract this loss of energy, a guide device 8 ^'is provided between the two propellers 6 ^* , 7 ^' , with which the re-spin of the front propeller 6 ^'is directed. In the process, lost energy is recovered by generating a propulsive force in the flow around the guide device. Furthermore, a pre-twist is generated for the downstream propeller 7 ^" so that it can implement a higher energy gradient. Taking this criterion into account, the second propeller 7 ^'will preferably have a structural design that differs from the first propeller 6 ^" .

The guide device 8 ^'is shown in FIG. 3 consists of two vanes ^8a' and 8b ^', said one vane ^8a' through which the vertical drive shaft 1 surrounding casing tube ^"is formed. The second vane ^8b" 9a ^* is located 9b at the bottom ^" of the housing 9 ^" surrounding the horizontal output shaft 5 ^* , ie offset by 180 ° from the first guide vane. Both guide blades 6 ^" , 7 ^" form a structural unit with the overall housing 9 ^" , 9a ^' .

Description of the embodiments according to FIGS. 4 to 6.

The drive essentially consists of an electric motor 1 in a housing 2 outside, in particular below of the hull and two propellers 3, 4, which are driven by the electric motor 1. The two propellers will generally be structurally different, although they have tip circles 5 with the same diameter and may have a similar wing geometry. They have the same direction of rotation and the same speed and, for example, flow in the same direction according to arrow A (FIG. 1).

The electric motor 1 is arranged watertight in the underwater housing 2. The output shaft 7 is guided out of it on both sides and is rotatably supported in the side of the motor in one of two bearings 8, 9 of the housing 2. The seal is provided by seals 10, 11 on the side of bearings 8, 9 between shaft 7 and end housing walls 2a, 2b in connection with the formation of the end faces as parts of labyrinth seals. Outside the housing 2, shaft ends 12, 13 are flanged to the shaft 7, each of which carries one of the two propellers 3, 4 in a rotationally fixed manner. Hub caps 14, 15 connect to the end of the housing, a continuous, flow-favorable outer contour with head 14 being formed in the region of the front propeller 3, middle part in the form of the housing 2 and end part 15 in the region of the rear propeller 4. The end walls 14a, 15a of the hub caps 14, 15 facing the housing 2 are second parts of the labyrinth seals 16, 17, the first parts of which are the end surfaces 2a, 2b already mentioned. The housing 2 is held on the ship's hull with a foot 18 which is hollow, the outer contour of which is part of the guide apparatus 19 between the propellers 3, 4 and which has further blades associated with the housing 2, one of which has a blade diametrically opposite the foot 18 is designated by 20. Overall are the blades of the diffuser 19 uniformly distributed around the longitudinal axis of the shaft 7 and assigned to the housing 2.

Overall, the propellers 3, 4 are designed in such a way that the initial working level of the second propeller 4 is approximately the final working level of the first propeller 3 and, in conjunction with the guide device 19, the output swirl of the first propeller 3 as well as the input swirl of the second propeller 4 are purposefully influenced that at most small energy losses occur when the liquid passes from the first to the second propeller.

The energy supply to the electric motor takes place through lines 21 which are brought to the motor in the foot 18 and in the housing 2, which is why the interiors of the foot 18 and the housing 2 are connected to one another.

In order to be able to use the drive not only to generate a thrust in the longitudinal direction of the ship (longitudinal axis of the drive shaft), but also to steer the ship, the entire drive must be appropriately assigned to the ship and an appropriate swivel mechanism known per se about the vertical longitudinal axis 22 in the middle between the two propellers can be pivoted, possibly pivoted 360 ° all around, the axis 22 being directed perpendicular to the axis of rotation of the shaft axis 23.

A particularly expedient embodiment of the drive according to the invention will now be described with reference to FIGS. 2 and 3. The electric motor 1 is a permanently excited synchronous motor with the permanent magnet rotor 25 and the stator laminated core 26. Such motors are known per se, which is why the electric motor designed as a permanently excited synchronous motor does not have to be described in detail either.

The use of such a motor in the nacelle-shaped housing 2, which is arranged below the ship's outer skin 24 below the water surface, for driving the two propellers 3, 4 rotating in the same direction and conveying in the same direction A has various application-specific advantages, in particular with regard to the electrical efficiency the machine and it eliminates the need for forced cooling equipment. In addition, a small construction volume is made possible, which in turn makes a resistance-optimal shape of the underwater housing possible, in particular a housing with a small maximum diameter is possible.

Such a permanently excited synchronous motor 1 is now arranged in a further embodiment in the nacelle-like housing 2 such that the continuous propeller shaft 12, 13 and the rotor 25 have a common bearing with the two bearings 8, 9. Specifically, this is done in such a way that the permanent rotor 25 is seated on a support tube 27 which it concentrically surrounds and which, near its two ends, is assigned to the propeller shaft 12, 13 in a rotationally fixed manner via one of two annular membrane couplings 28, 29, with both shaft ends the diaphragm coupling 28 or 29 and the associated bearing 8 or 9 are close together. The fact that the propeller shaft and the electric motor tube have a common bearing means that the drive unit is minimized in components and the reliability is increased. By using close to the the respective radial coupling located in the radial bearing, a very exact centering of the rotor within the stator, which is largely independent of the propeller shaft deflection, is achieved. This has considerable advantages with regard to the dynamic behavior of the rotor within the machine (e.g. structure-borne noise is minimized).

Also as a result of the design of the electric motor as a permanently excited synchronous motor 1 (FIGS. 2, 3), an integration of the underwater housing shaft 18 (referred to as “foot” in connection with FIG. 1) in the drive is possible in a particularly expedient manner. This housing shaft can be made very slim, which considerably reduces the flow resistance of the system. This slender underwater housing shaft 18 is profiled in cross section in such a way that in connection with a lateral pair of guide fins (not shown) offset by 90 ° and the counter fin 20 offset by 180 °, an additional jet swirl of the propeller outflow of the front propeller 3 is achieved, which The improvement in efficiency means that the concept on which the drive is based should bring the two propellers that are essentially the same and rotate in the same direction (speed and direction of rotation).

A parking brake for holding the propeller shaft 12, 13 and thus the assembly, the parts of which are the propeller shaft, is arranged within the underwater pod 2 and is identified by 33.

2, 3 results in a significant simplification of the underwater assembly effort. Rudder propellers that can be assembled / disassembled on a floating ship are offered by various rudder propeller manufacturers. The corresponding assembly effort is still considerable. The present invention, in particular in the embodiment according to FIGS. 2, 3, enables a greatly simplified underwater assembly / disassembly at the separation point of the underwater housing shaft support cone. The underwater housing shaft is also identified in FIG. 3 by the reference symbol 18, its upper end lies in the plane 24 of the ship's outer skin and is connected to the supporting cone 30. At the upper end, the support cone is mounted in a control bearing 31 in the support structure of a ship. This control bearing 31 has an inner ring 31a with an inner ring gear 31b and this inner bearing ring 31a is firmly assigned to the outer circumference of the support cone 30. The outer ring 31c interacts with the inner ring via the rolling elements and it is firmly integrated into the supporting structure of the ship. The pinion (not shown) of a drive (not shown) engages in the inner ring gear of the inner ring of the control bearing, so that the entire drive can be rotated through 360 ° about the longitudinal axis 22 to control the ship.

The detachable connection between housing shaft 18 and support cone 30 is symbolized by a flange connection 32.

All embodiments have the combination of features of claim 1 in common that it is a water jet propulsion system for watercraft, in particular ships, which has a prime mover and two propellers driven by it, which at the two ends of a gondola-like, streamlined underwater housing outside are arranged in this water housing and are driven by a drive means which is located within the underwater housing and acts on the drive shaft common to the two propellers, the first propeller significantly increasing the flow energy of the fluid and this fluid having a high energy content after eliminating the unavoidable re-swirl in a guide device is fed to the second propeller, which differs in its blades from the first propeller in that the relatively low flow energy is optimally increased in the first propeller, while the relatively high flow energy is increased again in the second propeller; In a special embodiment described below with reference to FIG. 2, the second propeller has a central part which differs from the first propeller in the manner described and a peripheral part which in this respect is identical to the first propeller and in the same way as the first propeller is blown.

Description of the embodiment according to FIG. 7.

The front propeller 3 in the inflow direction A has optimal blading for increasing the energy of the fluid. The propeller 4 at the rear in the inflow direction A has the same blading in a peripheral area. This peripheral area surrounds a central area in which the blading deviates from that of the front propeller 3, as has been described several times above, ie it increases the energy increased in the first propeller again from this energy level after that of the first propeller 3 leaving fluid swirled in the diffuser 19 and the energy loss caused by the swirl was compensated. The core and peripheral areas are separated from one another by the contraction surface 100, ie the lateral surface which surrounds the flowing fluid after it has left the first propeller 3 and which circumscribes a cross section which is significantly smaller than the inflow cross section. In the peripheral area, the second propeller is consequently flowed by the fluid B in the same way as the first propeller by the fluid, which is indicated by the arrows A.

Claims

claims 1. water jet drive for watercraft with two axially arranged propellers (3, 4) outside the ends of a gondola-like, streamlined underwater housing (2) under the hull of the watercraft with a drive means for the two propellers (3, 4) arranged in the underwater housing, the energy from the hull of the watercraft is supplied through a housing shaft (18), one end of which is assigned to the watercraft hull (24) and the other end to the underwater housing (2), characterized in that the underwater housing (2) is part of a Guide device (20), through which the water jet leaving the front propeller (3) with increased energy in the direction of travel of the watercraft with minimized energy loss and optimized swirl is fed to the rear propeller (4) in the direction of travel of the watercraft at the other end of the underwater housing, both of which Propeller (3,4) from the drive with tel in the underwater housing are driven in the same direction of rotation and are formed in the area of the respective beam cross-section so that the different flow energy at the inlet of both propellers (3, 4) is optimally utilized. 2nd Water jet drive according to claim 1, characterized in that the propeller (4) at the rear in the direction of travel of the watercraft has a cross-sectional area which is smaller by the amount of the contraction of the jet than the propeller (3) at the front in the direction of travel of the watercraft with the different inflow energy in the inlet areas of both Propeller (3,4) differently designed blading of both propellers. Water jet drive according to claim 2, characterized in that the smaller cross-sectional area corresponding to the jet contraction of the propeller (4) at the rear in the direction of travel of the watercraft is the total cross-sectional area of this propeller, ie both propellers (3, 4) have different diameters. Water jet drive according to claim 2, characterized in that both propellers (3, 4) have essentially the same diameter, the rear propeller (4) in the direction of travel of the watercraft having different blading in the core area than in the edge area, the core area also having the cross section of the water jet leaving the front propeller (3) contracted in the direction of travel of the watercraft, the rear propeller (4) in this area, like the front propeller (3), having a blading that is optimally adapted to the inflow energy, so that the blading of both Differentiate propellers, and finally the edge area of the second propeller (4) radially following the core area is flowed freely like the first propeller and its blading corresponds to the blading of the first propeller (3). Water jet propulsion according to claim 3 or 4 in the respective back-reference to claims 1 and 2, characterized in that the pitch of the blades of the blading of the propeller (4) in the direction of travel of the watercraft in the area corresponding to the jet contraction is 1.04 to 1 , 52 times the pitch of the blades of the blades of the front propeller (3) in the direction of travel of the watercraft. 6. Water jet drive according to claim 4, characterized in that the same blades of both propellers (3,4) in the entire cross-sectional area of the front propeller in the direction of travel of the watercraft (3) and in the annular outer region of the rear propeller (4) in the direction of travel of the watercraft Spread of +/- Allows 5%. 7. Water jet drive according to claim 5, characterized in that the different blading of the two propellers (3, 4) is achieved not only by different pitch of the blades but also by different blade curvature, the range of different blade pitch mentioned in claim 5 being 0.9-1, 6 lies. 8. Water jet drive according to claim 7, characterized in that the different blading of the two propellers (3, 4) is achieved instead by different blade pitch by correspondingly different blade curvature. 9. Water jet drive according to one of claims 1 to 8, characterized in that the diffuser comprises parts of the underwater housing (2). 10. Water jet drive according to claim 9, characterized in that the diffuser comprises parts of the underwater housing (2) and the housing shaft (18) is designed so that it does not affect the effect of the parts that it affects the effect of the part of the underwater housing (2) comprehensive leaves. 11. Water jet drive according to one of claims 1, 9 and 10, characterized in that the guide apparatus is essentially formed by guide vanes (20). 12. Water jet drive according to claim 11, characterized in that the guide vanes (20) have a curvature length ratio in the range from 0.0 to 0.2 and an employment in the range from -7 ° to + 7 °. 13. Water jet drive according to claim 11 or 12, characterized in that the guide apparatus has two ratio-symmetrical guide vanes arranged around the common axis of rotation of the propellers (3, 4). 14. Water jet drive according to one of claims 1 to 12, characterized in that the drive means in the underwater housing (2) a gear (4 ', 5') with two output shaft parts for the two propellers (3, 4) on the underwater housing ends and mechanical force introduction ( 2 ') from a motor in the hull of the watercraft, preferably an internal combustion engine or a hydraulic motor, by means of a connecting shaft guided through the housing shaft. 15. Water jet drive according to one of claims 1 to 13, characterized in that the drive means in the underwater housing (2) is an electric motor with two shaft parts (13, 14) of the output shaft for the two propellers (3, 4) at the underwater housing ends and supply of energy from a power generator in the hull of the watercraft via lines which are passed through the housing shaft (18). 16. Water jet drive according to one of claims 1 to 13, characterized in that the drive means in the underwater housing (2) is a hydraulic motor with two output shaft parts (12, 13) for the two propellers (3, 4) at the ends of the underwater housing and energy supply from one of the energy of the hydraulic engine operating means increasing device in the hull of the watercraft by tubular guide means which are passed through the housing shaft. 17. Water jet drive according to claim 15, characterized in that the heat dissipation from the motor (1) via the wall of the underwater housing (2) takes place with the heat-generating parts of the motor (1) are connected in a heat-conducting manner. 18. Water jet drive according to one of claims 1 to 16, characterized in that the front propeller (3) in the direction of travel of the watercraft is encased by an acceleration nozzle, the cross section of which decreases from the inlet to the propeller plane. 19. Water jet drive according to one of claims 1 to 16, characterized in that each propeller (3,4) is encased by a delay nozzle, the cross section of which increases from the respective nozzle inlet to the propeller plane of the first propeller (3). 20. Water jet drive according to one of claims 1 to 19, characterized by the connection of the vertical housing shaft (18) on the hull of the watercraft so that it is rotatable with its underwater housing at its lower end about its longitudinal axis. 21. Water jet drive according to claim 20, characterized in that the rotatability of the housing shaft (18) about its longitudinal axis by means of a servomotor is possible through 360 °. 22. Water jet drive according to claim 15, characterized in that the attachment of each propeller (3,4) on the shaft (7) or each partial shaft (12,17) is enclosed by a hub (14,15) and the outer contour of Underwater housing (2) and hubs (14, 15) result in a streamlined flow profile, whose nose (14) identifies the propeller (3) in this area as the front propeller in the direction of flow (A), while the tail (15) of the flow profile Propeller (4) identifies in this area as the rear propeller in the direction of flow. 23. Water jet drive according to claim 15 and / or 22, characterized in that the electric motor (1) is a permanently excited synchronous motor. 24. Water jet drive according to claim 23, characterized in that the rotor (25) of the motor (1) is concentric within the stator (26). 25. Water jet drive according to claim 24, characterized in that the rotor (25) via membrane couplings (28, 29) with that of the concentrically guided through the rotor at both ends for receiving the propeller (3, 4) from the rotor (25) led out propeller shaft (7 or 12,13) is rotatably connected. 26. Water jet drive according to claim 25, characterized in that a bearing (8,9) is arranged outside the rotor (25) immediately next to each of the membrane couplings (28, 29) and that with these bearings the assembly of rotor (25). and propeller shaft (12, 13) is mounted in the underwater housing (2) of the watercraft drive. 28. Water jet drive according to one of claims 22 to 28, characterized in that the rotor (25) via a rotor support tube (27) is coupled to the propeller shaft (12, 13). 29. Water jet drive according to one of claims 22 to 28, characterized in that the underwater housing (2) via the housing shaft (18) with a supporting cone (30) around a perpendicular to the propeller shaft (12, 13), the longitudinal axis (23) of the Propeller shaft intersecting pivot axis (22) can be pivoted continuously through 360 °. 30. Water jet drive according to claim 29, characterized in that the housing shaft (18) and support cone (30) in the plane of the ship's outer skin (24) are detachably connected to one another (flange connection). 31. Water jet drive according to one of claims 29 and 30, characterized in that the smaller cross section faces the housing shaft (18) and the support cone in the region of the larger, upper cross section around the vertical, the longitudinal axis (23) of the propeller shaft (12, 13) ) cutting axis (22) is pivotally mounted in the watercraft (bearing 31). 32. Water jet drive according to one of claims 22 to 31, characterized in that the housing shaft (18) is designed as one of several identical guide vanes (18, 20) of the guide apparatus (19) between the two propellers (3, 4), which are equally spaced are distributed over the circumference of the housing (2). 33. Water jet drive according to one of claims 1 to 16, characterized in that the front propeller (3) in the direction of travel of the watercraft is encased by a delay nozzle, the cross section of which widens from the inlet to the propeller plane. 34. Water jet drive according to one of claims 1 to 16, characterized in that each propeller is encased by an acceleration nozzle, the cross section of which decreases from the inlet to the propeller plane or is surrounded by a deceleration nozzle, the cross section of which increases from the inlet to the propeller plane. 35. Water jet drive according to one of claims 1 to 16, characterized in that both propellers are surrounded by a common nozzle, which is an acceleration nozzle by reducing its cross-section from the nozzle inlet to the propeller plane of the first propeller or is a deceleration nozzle by itself their cross section enlarged from the nozzle inlet to the propeller plane of the first propeller.