The invention relates to shipbuilding, namely: to propulsion units of various purpose vessels.

A gas-and-hydraulic propulsion unit according to patent RU 2285636 C2 is known in the prior art that comprises a shaped water intake channel with inlet and outlet diffusion openings, gas feed conduit, cylindrical insert in the channel located after an inlet diffuser, as well as air feeding and acceleration device (accelerator) located in the gas feed conduit casing that includes at least two tapered nozzles with sealed connection between each other, and each nozzle is coaxially inserted into another one in the direction of air flow forming a cavity or cavities between the nozzles. Additionally, at least one of said cavities is fitted with air ionization means that ensure air ionization in the cavity and movement thereof in the accelerator, with ambient air ejection from the inlet opening. As a result of ionization, molecules of air (nitrogen and oxygen) are partially collapsed emitting a huge amount of heat and kinetic energy. The disadvantages of this design are low efficiency, poor environmental friendliness, and design complexity, and air ionization results in heat emission which increases energy consumption and reduces the propulsion unit efficiency, and the design itself can be used for low displacement vessels only.

Thus, the problem to be solved during development of the propulsion unit claimed covers further improvement of devices of this kind; however, the technical result achieved upon resolution of the problem includes improvement of the propulsion unit performance with simultaneous simplification of its design.

To achieve this result, a watercraft propulsion unit is provided which comprises a turbine-driven air compressor, an air duct the inlet of which is connected with said compressor, water intake channel the inlet of which is designed to ensure intake of outside water in the channel, and flow stilling chamber with outlet nozzle; accordingly, outlets of air duct and water intake are connected with the inner cavity of the stilling chamber designed as a combination of three directly interconnected areas A, B and C, where area A is the first one in the direction of (air/outside water) flow and has the shape of an expansion cone with inlet opening having a cross-section area SI and outlet opening having a cross-section area S2; area B has the shape of a tapered cone with inlet opening having a cross-section area S2 and outlet opening having a cross-section area S3; area C is a nozzle and has the shape of an expansion cone with inlet opening having a cross-section area S3 and outlet opening, whereas the air duct outlet is located in area C of the stilling chamber.

Area A inlet opening in the embodiments of the propulsion unit may be interconnected with the water intake channel outlet; air duct outlet may be located coaxially with the inner cavity of the stilling chamber or be mounted on a wall or walls of this chamber; the propulsion unit may additionally comprise the turbine-driven compressor driving and control means including the turbine-driven compressor driving means designed as a motor.

Possibility to achieve said result is conditioned by the combination of air intake duct location on one hand, and the shape of the stilling chamber inner cavity on the other.

Thus, location of the air intake duct outlet allows for feeding of air flow virtually on the edge of the water flow stilling chamber which practically eliminates the possibility of formation of water backflow areas, and water feeding is ensured by formation of low-pressure area near the nozzle. In turn, empirically obtained shape of the stilling chamber inner cavity comprising the combination of narrowing and expanding areas allows for generation of a laminar flow without vortexes and changes in liquid discharge condition (laminar condition implies smooth flow of liquid). In this case, jet or flow inner layers are not intermixed, contrary to turbulent flow that is represented by an immense amount of multidirectional vortexes with continuous mixing of liquid or gas. All above- mentioned points allow for provision of uniformity and stability of water flow in all speed rates of the propulsion unit which, in aggregate, makes it possible to minimize or practically eliminate occurrence of adverse effects of different nature, such as air locks, "backflow" areas, etc., essentially increasing the propulsion unit performance under any operating conditions.

Additionally, absence of the propulsion unit parts contacting with water provides for a number of additional advantages, namely: low wear and tear of operating mechanisms, relative inexpensiveness and design simplicity, low energy consumption (in case of use of a motor), possibility to perform maintenance without vessel dry docking (maintainability), and safety for sea fauna.

The essence of the solution claimed is explained using the following graphical data:

Fig. 1 - structural schematic diagram of the propulsion unit;

Fig. 2 - schematic diagram of the air stilling chamber;

Fig. 3 - options of sections l-l according to Figure 2;

Fig. 4 - layout diagram of damper in the air duct;

Fig. 5 - example of parameter calculation for the air stilling chamber;

Fig. 6 - schematic diagrams of air flow feed to the stilling chamber;

Fig. 7 - location (depth) of the water flow stilling chamber in relation to the outside water level;

Figs. 8, 9 - schematic variants of the propulsion unit location in a vessel.

With reference to Fig. 1, the device claimed generally consists of a turbine- driven air compressor (5) that, by means of engine (6), control system (7) and power supplies (8) (for example, electric ones) feeds air flow to a water stilling chamber (1) through an air duct (4). At the same time, outside water is fed to said water flow stilling chamber (1) through water intake channel (3) where it is mixed with said air flow and is discharged through a nozzle (2), thus forming a gas-air mixture jet (reactive thrust) in the direction opposite to the direction of vessel movement. Feeding of outside water in chamber (1) at the initial time point before a vessel starts moving (i.e., when the compressor is deactivated) is based on the location of the channel inlet opening (3) below the water level which results in natural (gravity flow) of water into chamber (1) at the initial time point. Then, when the compressor is activated and the vessel starts moving, oncoming flow of water enters chamber (1) through the channel inlet opening (3) enabling the operating cycle of the propulsion unit.

The above-mentioned structural design makes it possible to ensure higher position of the nozzle outlet opening in relation to water level which, in turn, allows for decreasing air pressure in the air duct and decreasing the compressor power maintaining the same performance, and the vessel speed will then depend on the velocity and amount of air flow only.

Schematic diagram of water flow stilling chamber (1) that is the main structural element of the propulsion unit claimed is illustrated in Fig. 2. It should be noted that the water flow stilling chamber in said propulsion unit is not an active chamber of the propulsion unit as such, but is specifically the air and water flow stilling chamber. The chamber is designed as a combination of three directly interconnected areas A, B and C. Area A is the first one in the direction of water flow and has the shape of an expansion cone with the length LI and inlet opening having a cross-section area SI and outlet opening having a cross-section area S2. Area B has the shape of a tapered cone with the length L2 and inlet opening having a cross-section area S2 and outlet opening having a cross-section area S3. Area C is essentially a nozzle 2 and has the shape of an expansion cone with the length L3 and inlet opening having a cross-section area S3 and outlet opening having a cross-section area S4. From a practical perspective, it would be feasible to make transition points (coupling lines) between the areas smooth to minimize the operating medium stalling. Optionally, the stilling chamber may also comprise additional areas (one and more) taking the first positions in the direction of flow with the inlet opening of area A.

Fig. 3 schematically illustrates the variants of cross-section types for water flow stilling chamber (1) and air duct (4) that may be either round - Fig. 3a, rectangular - Fig. 3b, or have any other shape.

Reverse movement of a vessel fitted with the propulsion unit of the design claimed is ensured by redirection of air flow by closing air duct (4) using a reverse damper (9) - Fig. 4. In normal mode, damper (9) is retracted and practically is a part of air duct (4), thus making no obstacles for air flow; see Fig. 4 A. In case of reverse movement of a vessel, dampener (9) closes air duct (4), thus redirecting the air flow in the opposite direction; see Fig. 4 B.

In a possible practical embodiment, the initial parameter for determination of cross-section areas S1 -S4 (Fig. 5 A, B) may be the cross-section area of the outlet opening of air duct (4) S5. Based on this parameter, other cross-section areas shall be determined by multiplication of S5 by empirically obtained crosssection factor Ks, for example: for section SI, the factor Ksl=2.7, then S1=S5 x Ksl ±10%; for section S2, the factor Ks2=3.7, then S2=S5 x Ks2 ±10%; for section S3, the factor Ks3=2.0, then S3=S5 x Ks3 ±10%; for section S4, the factor Ks4=3.5, then S4=S5 x Ks4 ±10%;

Similarly, the initial parameter for determination of linear dimensions L1 -L3 of water flow stabilization chamber (1) may be represented by the diameter (height) of the outlet opening of air duct (4) D5 (Fig. 5 C) where numeric values L1 -L3 shall be determined empirically by means of factor K which shall also be obtained empirically, for example: for dimension LI, the factor KL1=4, then Ll=(D5-D5/4) x KL ±10%; for dimension L2, the factor KL2=7.5, then L2=(D5-D5/4) x KL2 ±10%; for dimension L3, the factor KL3=3.8, then L3=(D5-D5/4) x KL3 ±10%.

Fig. 6 illustrates practically possible structural options of air flow feeding patterns to water stilling chamber (1):

- air flow feeding to the center of stilling chamber - Fig. 6 A;

- air flow feeding to the periphery of stilling chamber - Fig. 6 B.

With reference to Fig. 7 B, the optimum position of the propulsion unit in terms of maximization of the positive effect achieved is the position where the top edge of the outlet opening of air duct (4) is located at the water level. In turn, when water level is assumed as "0", the top edge of the outlet opening of air duct (4) may be located both above this level within the range of "0" up to approximately D5/3 - Fig. 7 A, and below the water level within the range of "0" up to D5 -Fig. 7 C.

The propulsion unit claimed may be used both as an outboard motor - Fig. 8 and be installed on the vessel aft, and as a motor built in the vessel hull - Fig. 9 and be installed both on the aft and/or in the central part, and/or in the bow of a vessel. The number of propulsion units, regardless of the installation pattern, may vary (one or more), and the embodiment according to Fig. 9 also provides for consecutive installation. However, the essential point in all installation cases is that the inlet opening of the water intake channel shall be positioned below the outside water level (see above).

Thus, the invention allows for significant simplification of the design of known direct flow gas-and-hydraulic propulsion units, reduction of structural dimensions, improvement of service life due to absence of rotary parts in the water intake channel along its entire length, and predetermination of possibility to make similar propulsion units with different power, for various purposes, and without significant financial and construction expenditures.