WO2019244181A1

WO2019244181A1 - Gliding hull with motor gas insufflation in water

Info

Publication number: WO2019244181A1
Application number: PCT/IT2019/000051
Authority: WO
Inventors: Eugenio GUGLIELMINO; Filippo CUCINOTTA; Felice SFRAVARA
Original assignee: Universita' Degli Studi Di Messina
Priority date: 2018-06-20
Filing date: 2019-06-18
Publication date: 2019-12-26
Also published as: IT201800006486A1

Abstract

A gliding hull with motor gas insufflation in water is described, comprising a main motors apparatus (1), an outlet duct of the exhaust gases (2), a cooling apparatus of the exhaust gases (3), a safety valve (4), a compensation box (5), a plurality of nozzles (6) and a portion of surface of the hull in contact with the exhaust gases (7). A controller (10) with two PID control rings in cascade is connected to the cooling apparatus of the exhaust gases (3) and to the compensation box (5). The controller (10) is adapted to determine a control signal applied to the shock absorber (51) to check a pressure (P5) downstream of the compensation box (5).

Description

GLIDING HULL WITH MOTOR GAS INSUFFLATION IN WATER

The present invention refers to a gliding hull with motor gas insufflation in water.

.In general, the present invention refers to hydrodynamic or hydrostatic features of hulls or of hydrofoils .

In particular, the present invention refers to means for changing the intrinsic hydrodynamic features of hulls, reducing the surface friction by using gas bubbles or layers of gas, using exhaust gases from motors.

The problem of reducing the resistance to advancement of boats, crafts and ships has always been studied and searched to reduce costs and environmental impacts.

From the studies of Froude on, the resistance to advancement has been traditionally divided into a wave component and a viscous component.

The wave component is mainly responsible for phenomena due to pressures present near the air/water interface, responsible for generating the wave field.

The viscous component, instead, is responsible for phenomena related to medium viscosity, namely phenomena which are typical of a non-ideal and viscous fluid.

Such phenomena are essentially the fluid friction and the depth pressure ones, such as vortexes, separation of the limit layer, etc.

Also due to the support of experimental, statistical and numerical techniques, an accurate design of shapes allows optimizing the behaviour of the boat with respect to the wave component and the viscous component. However, the current level of knowledge allows a rather small reduction of consumptions with respect to the standards.

Due to this, the search is more and more moving away from a classical approach. In fact, a typology of hulls, known as Air Cavity Ships, ACS, or Air Cushion Vehicles, ACV, theoretically developed in the ' 60s but still currently very scarcely used, has even recently found numerous applications, mostly as experimental prototypes.

Air Cavity Ships has a cavity on their bottom suitable to house air, in order to exploit its viscosity, much smaller than that of water, and consequently reduce the viscous resistance component .

Air Cavity Ships, divided into dislocating hulls and gliding hulls, are essentially grouped into two big categories: air cushion hulls, wherein the conveyed air assume the appearance of a layer, more or less thick and more or less stable, under the hull; and micro-bubble hulls, wherein a fine mixture of water and air is pumped on the bottom and on the bulwarks .

In both categories, air is generally produced by fans or compressors which convey, through a system of channels and nozzles, the flow of air or of the fine mixture of water and air under the hull .

A further category, in a limited number of cases, deals with hulls wherein the conveyance of atmospheric air occurs by exploiting channels which transform the dynamic pressure due to the advancement speed of the means.

What has so far stopped the diffusion of this type of means, in addition to the reduced number of scientific experiences and publications aimed to orient the designer in its design choices, is the business risk involved in choosing counter- productive technical solutions, due to high plant costs and due to the reduction of on-board spaces.

In fact, a plant with air cavity ships is generally composed of a fan or compressor, having big sizes and weight, equipped with its own electric or hydraulic motor, which can be connected with difficulty to the drive shaft of the boat.

The cost of such type of plant reduces the economic return of its consumptions. Moreover, also the energy cost to keep the fan or compressor operating, subtracts resources to the global energy balance .

Summarizing, the main technologic problems which have stopped the diffusion of traditional ACS means are: weight and sizes of fan and of compressor; need of a motor to supply the fan or the compressor; plant costs, operating costs in working the fan or the compressor and indirect costs following the increase of on-board weights; difficulty in surely and reliably quantifying the global savings.

The prior art is given by DE-A1-100 53 453 dealing with the application through nozzles of a thin layer of gas between hull and surrounding water in the submersed part of the hull. The nozzles are designed in order to absorb air from water under-pressure. At a higher depth, the gas is pressed under the tank by a compressor. A guide in the front part of the hull adjust the ship movements and expels a mix of gas and water to form the gas film, allowing to reduce friction under the hull. Several distributed guides are placed along the submersed part of the hull for bigger ships. It is possible to use combustion gases from the actuation to form the gas film as required. In a first solution, the air film is transported through auto-jets in the submarine area of a boat with a scarcely deep draft. In a second solution, for a boat or hull of a ship with deeper draft, air of the film adhering to the hull is compressed by means of a compressor. For a water motion with reduced draft, such as motored boats, the air cushion for the film which reduces friction is formed through discharge nozzles which generate, through the water flow, a partial vacuum. With the increase of speed, the air film adhering to the surface of the boat hull is increased, so that the friction resistance decreases. For ships with deeper draft, such as cargos, gas or air is pressed against the hull with the help of a compressor, so that the relatively costly outlet nozzles can be replaced by simple exit openings.

Moreover, the prior art is given by US-A-5 207 379 dealing with controller with two PID control rings in cascade for controlling the fans, of the type with a heating coil, a fan and a gate for entering external air in a room in which the fan is located. The controller uses the detected ambient temperature and a set point of the ambient temperature to generate a set point for the temperature of air discharged by the fan and uses the set point of the discharge temperature and the detected discharge temperature to check the position of the shock absorber and the operation of the heating serpentines of the fan.

Ά problem regarding a gliding hull with motor gas insufflation in water deals with the control of the pressure value and of the temperature of exhaust gases.

For such purpose, solutions must be used such as: a cooling apparatus of exhaust gases, in order to reduce the damages of the hull parts in contact with hot gases; a safety valve to prevent gases from reaching excessive overpressures, as safeguard of the efficiencies of main motors; a compensation box to even the gas pressures, in order to reduce the inlet peaks deriving from the thermodynamic cycles of the main motors, and even the downstream pressures of the outlet duct of the exhaust gases; a plurality of nozzles shaped as to guarantee a correct flow-rate of the exhaust gases and avoid critical pressures near the compensation box.

In spite of the use of a cooling apparatus for exhaust gases, a safety valve, a compensation box and suitably shaped nozzles, the solution of this problem must employ an automatic control model with feedback in order to guarantee an efficient operation .

The starting point is given by US-A-5 207 379 dealing with a control composed of a pair of PID control rings in cascade.

Object of the present invention is solving the above prior art problems, by providing a gliding hull with motor gas insufflation in water equipped with a control apparatus with feedback in order to intervene on thermodynamic variables responsible for the operation of the thermodynamic cycle of motors and for keeping the structural features of the materials composing the hull.

A further object is providing a gliding hull with motor gas insufflation in water whose cooling apparatuses for exhaust gases, safety valve, compensation box and nozzles, have reduced overall sizes to a minimum, by exploiting the operation with feedbac to reduce the excursion of the above apparatuses .

The above and other objects and advantages of the invention, as will result from the following description, are obtained with a gliding hull with motor gas insufflation in water as claimed in claim 1. Preferred embodiments and non-trivial variations of the present invention are the subject matter of the dependent claims.

It is intended that all enclosed claims are an integral part of the present description.

It will be immediately obvious that numerous variations and modifications (for example related to shape, sizes, arrangements and parts with equivalent functionality) can be made to what is described, without departing from the scope of the invention as appears from the enclosed claims.

The advantages of the present invention, in addition to those typical of ACS hulls with respect to traditional ones, namely the reduction of consumptions and the improvement of means performances, are: simplifying the ventilation plant and consequently saving the construction and managing costs; reducing or removing compression energy costs; reducing weights and sizes on-board the compression plant.

The invention deals with a method for reducing the viscous resistance of high-speed hulls based on conveying exhaust gases of motors under the hull.

The invention can be used on new hulls or by transforming existing hulls.

The invention can be applied on quick hulls, such as gliding hulls, semi-gliding hulls, hulls with surface effect, or hydrofoils, by exploiting the low pressures generated at high speeds.

The hull can be suitably shaped to house the gas or can have specific geometries.

The exhaust gases, before being sent in water, can be treated with systems such as a cooling one, a pressure compensating one or a pressure increasing one, and can be mixed with air or other gases dr nebulized liquids in order to increase flow-rate or efficiency.

The present invention will be better described by some preferred embodiments thereof, provided as a non-limiting example, with reference to the enclosed drawings, in which:

Figure 1 shows a schematic view along a longitudinal direction of the distribution of the fluid-dynamic pressure of an embodiment of the gliding hull with motor gas insufflation in water according to the present invention;

Figure 2 shows a schematic view of the important apparatuses of an embodiment of the gliding hull with motor gas insufflation in water according to the present invention;

Figure 3 shows a schematic view of the cross section of an embodiment of the gliding hull with motor gas insufflation in water according to the present invention; and

Figure 4 shows a schematic view of the control of the operation of an embodiment of the gliding hull with motor gas insufflation in water according to the present invention.

With reference to the Figures, it is possible to note that a gliding hull with motor gas insufflation in water comprises a main motors apparatus 1, at least one outlet duct of the exhaust gases 2, a cooling apparatus of the exhaust gases 3 to reduce the damages of those hull parts in contact with hot gases, a safety valve 4 to prevent gases from reaching excessive overpressures as safeguard of the efficiencies of the main motors 1, a compensation box 5 to even the gas pressures in order to reduce the inlet peaks deriving from the thermodynamic cycles of the main motors 1, and even the downstream pressures of the outlet duct of the exhaust gases 2, a plurality of nozzles 6 shaped as to guarantee a correct flow-rate of the exhaust gases and avoid critical pressures near the compensation box 5, a portion of surface of the hull in contact with the exhaust gases 7.

Advantageously, a controller 10 with two PID control rings in cascade is connected to the cooling apparatus of the exhaust gases 3 and to the compensation box 5.

The controller 10 is adapted to use the detected temperature Tr5 and a set temperature value Ti5, in a point downstream of the compensation box 5, to generate a set temperature value of the exhaust gases Ti2, in a point along the outlet duct of the exhaust gases 2.

Moreover, the controller 10 is adapted to use the set temperature value of the exhaust gases Ti2 and the detected temperature of the exhaust gases Tr2, m the point along the outlet duct of the exhaust gases 2, to check the position of a shock absorber 51 of the compensation box 5.

The controller 10 operates during following cycles to determine the difference between the set temperature value and the measured temperature DELTA T5 = Ti5-Tr5, of the point downstream of the compensation box 5.

Moreover, the controller 10 is adapted to provide a regulation point of the temperature value, of the point along the outlet duct of the exhaust gases 2, depending on the temperature difference DELTA T5 = Ti5-Tr5, of the point downstream of the compensation box 5.

The controller 10 is also adapted to determine a control signal applied to the shock absorber 51 to check a pressure P5 downstream of the compensation box 5.

The set temperature value Ti5 depends on the value of a control signal D51 applied to the shock absorber 51, to check the pressure P5 downstream of the compensation box 5.

The shock absorber 51 of the compensation box 5 is actuated through an actuator.

The invention of a gliding hull with motor gas insufflation in water derives from ACS hulls, trying to overcome the majority of known critical points with the innovative idea of exploiting exhaust gases of motors instead of compressed atmospheric air.

The gliding hull with insufflation system of exhaust gases of motors on the bottom is particularly useful for applications on gliding hulls since, by exploiting the natural depression occurring abaft of the pressure peak, exhaust gases can be directly sent, without further compression, according to a principle similar to the natural ventilation exploited by multistep or redan hulls.

In Figure 1, it is possible to note the typical behaviour of pressures on the bottom of gliding hulls, on whose distribution there is ample scientific literature. Downstream of the pressure peak, in the minima points, there is the best placement of the nozzles. At high speeds, the occurring depression tends to naturally recall the exhaust gases without the need of further compressions .

In this way, more economic plants can be obtained, not needing a dedicated compressor which subtracts power for operation, with smaller overall sizes and without additional maintenance costs. The gliding hull of the present invention does not imply further increases for the environment in terms of emissions. The exhaust gases are anyway sent in water in several applications, or in air in other ones.

The invention can also be used on surface effect ships, wherein the relevance of the dynamic component of the pressure allows obtaining points with relative negative pressure.

In the hull made according to the present invention, instead of air, exhaust gases coming from motors are used, recovering thereby the enthalpy and kinetic contents in terms of flow-rate and pressure, otherwise dispersed. In this way, something already present on-board is exploited, without a further cost apart from the one for adjusting plants and ducts.

Once gone out of the propulsion plant, the gas can be cooled with water sprays, as normally occurs, and can be send to a pressure-stabilizing chamber and from there, through the nozzles, on the bottom.

To increase the efficiencies, it is possible to shape the bottom in order to optimally convey the exhaust gases. Moreover, it is possible to increase flow-rate or pressure, if necessary, with a compressor downstream or with a restrictor to obtain a contrary effect.

Figure 2 shows an operating diagram through the following apparatuses: main motors; outlet duct of the exhaust gases; optional cooling of exhaust gases. The exhaust gases can be cooled with a spray of soft water or sea water. The cooling reduces the damages of the hull and of the box in contact with hot gases; there is also a safety valve, calibrated at a limit operating pressure, to prevent gases from reaching excessive overpressures, which could reduce the efficiencies of main motors; compensation box, cofferdam, namely a box whose purpose is evening the gas pressures in order to reduce the inlet peaks deriving from the thermodynamic cycles of the main motors, and evening the pressures on the various nozzles. The geometry of the nozzles can be of various nature, with the purpose of essentially guaranteeing the correct flow-rate of the outlet gases, avoiding to take the compensation box at pressures which can affect the efficiency of the motors; an area aerated by gases, namely the area reached by the exhaust gases.

Figure 3 shows a transverse view of the hull of the present invention.

Claims

1. Gliding hull with motor gas insufflation in water, comprising a main motors apparatus (1), at least one outlet duct of the exhaust gases

(2) , a cooling apparatus of the exhaust gases

(3) to reduce damages of hull parts in contact with hot gases, a safety valve (4) to prevent the gases from reaching excessive overpressures as safeguard of the efficiencies of the main motors (1), a compensation box (5) to even the gas pressures in order to reduce the inlet peaks deriving from the thermodynamic cycles of the main motors (1) and even the downstream pressures of the outlet duct of the exhaust gases (2), a plurality of nozzles (6) shaped as to guarantee a correct flow-rate of the exhaust gases and avoid critical pressures near the compensation box (5), a portion of surface of the hull in contact with the exhaust gases (7), characterized in that it comprises a controller (10) with two PID control rings in cascade connected to the cooling apparatus of the exhaust gases (3) and to the compensation box (5), said controller (10) adapted to use the detected temperature (Tr5) and a set temperature value (Ti5) , in a point downstream of the compensation box (5), to generate a set temperature value of the exhaust gases (Ti2), in a point along the outlet duct of the exhaust gases (2), and use the set temperature value of the exhaust gases (Ti2) and the detected temperature of the exhaust gases (Tr2), in the point along the outlet duct of the exhaust gases (2) , to check the position of a shock absorber (51) of the compensation box (5), said controller (10) operating during following cycles to determine the difference between the set temperature value and the measured temperature (DELTA T5 = Ti5-Tr5) of the point downstream of the compensation box (5), and provide a regulation point of the temperature value, of the point along the outlet duct of the exhaust gases (2), depending on said temperature difference (DELTA T5 = Ti5-Tr5) , of the point downstream of the compensation box (5) , said controller (10) adapted to determine a control signal applied to said shock absorber (51) to check a pressure (P5) downstream of the compensation box (5),

2. Gliding hull with motor gas insufflation in water according to the previous claim, characterized in that said set temperature value (Ti5) depends on a value of a control signal (D51) applied to said shock absorber (51) to check the pressure (P5) downstream of the compensation box (5).

3. Gliding hull with motor gas insufflation in water according to claim 1 or 2, characterized in that said shock absorber (51) of the compensation box (5) is actuated through an actuator .