Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63H—MARINE PROPULSION OR STEERING
  • B63H1/00—Propulsive elements directly acting on water
  • B63H1/02—Propulsive elements directly acting on water of rotary type
  • B63H1/12—Propulsive elements directly acting on water of rotary type with rotation axis substantially in propulsive direction
  • B63H1/14—Propellers
  • B63H1/18—Propellers with means for diminishing cavitation, e.g. supercavitation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63H—MARINE PROPULSION OR STEERING
  • B63H21/00—Use of propulsion power plant or units on vessels
  • B63H21/22—Use of propulsion power plant or units on vessels the propulsion power units being controlled from exterior of engine room, e.g. from navigation bridge; Arrangements of order telegraphs
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63H—MARINE PROPULSION OR STEERING
  • B63H3/00—Propeller-blade pitch changing

Definitions

• a method of operating a ship's propeller the present invention relates to a method for Operator Op ben ⁇ a ship's propeller.
• Cavitation is generally understood to mean the formation of cavities in a liquid. In the case of hydrodynamic cavitation see this cavitation is caused by a flow-induced change in the static pressure in the liquid ⁇ speed.
• the object of the present invention to provide an improved method for operating a ship's propeller.
• the object is achieved by a method according to claim 1 and an apparatus according to claim 4.
• the inventive method for operating a ship propeller ⁇ comprising the steps of: detecting an induced gas cavitation and / or Pseudokavitation noise in a solid state by a sensor; Transmitting egg nes measurement signal of the sensor by a non-contact Studentstra ⁇ transmission method from the sensor to a signal processing unit, that an evaluation unit; and generating control ⁇ command for changing the speed of the propeller by a drive motor and / or for changing the Blattan- pitch angle of the ship propeller by a servomotor.
• the control commands are generated by the signal processing ⁇ unit, in response to the received measurement signal.
• the inventive device for operating a ship propeller ⁇ comprises a sensor unit, a Signalübertra ⁇ supply unit and a signal processing unit.
• the sensor is able to detect a noise caused by gas cavitation and / or pseudo cavitation on a solid body.
• the signal transmission unit is for contactless
• the signal processing unit is for generating control commands to a drive motor for changing the propeller speed and / or to a servomotor for changing the blade pitch angle of
• Suitable ship propeller wherein the control commands are generated in depen ⁇ dependence on the received measurement signal.
• the present invention utilizes the fact that in the hydrodynamic cavitation usually three different types are observed cavitation: on the one hand as “hard cavitation” or “cold boiling” designated Dampfka ⁇ vitation, on the other hand, the “soft under the term Kavita ⁇ tion "summarized types of gas cavitation and pseu- docavitation, see, for example, Sauer, Jürgen: Transient cavitating currents - A new model, based on Front Capturing (VoF) and Bladder Dynamics, Dissertation, Faculty of Mechanical Engineering, University of Düsseldorf (TH), 2000,
• Gas cavitation is based on another phenomenon: as the static pressure of the fluid decreases, so does the solubility of a gas dissolved in the fluid, eg of air. In the transition from dissolved gas by diffusion in the undissolved state, small gas-filled cavities form in the liquid. When Gaskavita ⁇ tion therefore a dependent of the saturation pressure Ausdif ⁇ fusion of dissolved in the liquid gases occurs.
• pseudo-cavitation which - as the prefix "pseudo" indicates - is not really a "formation" of cavities in a liquid
• the pseudo-cavitation thus does not designate "formation” of cavities, but rather a “widening" of gas bubbles of the gases undissolved in the liquid as a result of a pressure reduction. Only with completely degassed and cleaned liquids, the cavities fill exclusively with steam.
• cavitation usually occurs as a combination of gas, pseudo and vapor cavitation.
• the gas and the steam cavitation occur in a mixed form.
• bubbles at the so-called cavitation nuclei grow through gas cavitation and pseudo-cavitation up to a critical radius, with the attainment of which and the associated drop below the vapor pressure curve then steam cavitation sets in.
• gas cavitation is a very slow process compared to steam cavitation and pseudo cavitation.
• gas cavitation re-solution of the Gasbla ⁇ sen in areas of higher pressure does not take place abruptly.
• the gas cavitation usually does not lead to WerkstoffSchä ⁇ ending; the gas bubbles even act as a kind of damper counteracts the high frequency blows of vapor cavitation, see Vortmann, Claas: Studies on Thermodyna ⁇ dynamics of the phase transition in the numerical calculation kavi- animal Nozzles currents; Dissertation, Faculty of Mechanical Engineering, University of Düsseldorf (TH), 2001,
• pseudo-cavitation usually does not cause any damage to a ship propeller, since the gas-filled cavities merely grow and shrink, but do not implode. Also in terms of noise, the steam cavitation differs significantly from the gas and pseudo cavitation. While the pressure surges in steam cavitation lead to a relatively strong development of noise, the characteristic cavitation noise, the two other types of cavitation, the gas and the pseudo-cavitation, produce only a relatively quiet noise.
• Vapor cavitation and gas / Pseudokavitation differ in the following point: vapor cavitation occurs only when the static pressure exceeds the boiling point in the direction of the FLÜS ⁇ sigen phase to the gaseous phase. Gas and Pseudokavitation, and thus their "noise" on the other hand occurs, in principle, always on when the pressure in the water changes, however, the boiling point and the gas solubility mitein ⁇ other are coupled. In the preliminary stage of vapor cavitation, the gas solubility decreases, so the dissolved gas is mixed ent ⁇ . the gas solubility is so greatly reduced shortly before reaching the boiling point, that a strong Bla uses sen Struktur, and thus a detectable noise. so the Entmischungslui leads to noise detek- to be advantage.
• the invention thus makes it possible to detect an imminent, ie immediately imminent onset of steam cavitation.
• countermeasures can be taken in good time and the unfavorable side effects of steam cavitation avoided.
• the measurement of the evoked by the gas and / or Pseudoka ⁇ levitation noise is not carried out by an acoustic or pressure measurement in the surrounding of the ship's propeller liquid phase, but by a tapping acoustic signals to a solid state such as the propeller itself, to a propeller shaft or on a the ship hull ship ⁇ skin in question, that is on a fixed body in the vicinity of the liquid phase.
• the noise caused by the gas and / or pseudo cavitation is written on a acoustic conductor acting solid, such as the drive shaft, acoustically measured; Gas and / or pseudo-cavitation are caused by a rotation of the ship's propeller in the liquid phase.
• a watercraft eg has a submarine
• the invention offers the possibility of the speed of the vessel, ie the speed of the ship's propeller to optimum avoiding vapor cavitation and consequent cavitation mieren.
• the solid body of the ship propeller and / or serving for driving the propeller propeller shaft and / or a ship's skin are provided.
• the contactless transmission method uses electromagnetic waves, preferably radio waves or optical waves.
• the sensor unit can be arranged on a vessel, into ⁇ particular to the ship's propeller and / or serving at a power for turning the propeller drive shaft and / or egg ⁇ nem hull of the watercraft.
• a sensor is provided which is suitable for detecting an induced gas cavitation and / or Pseudokavitation noise in the liquid, is transmitted upon detection of said noise a measurement signal from the sensor to a signal ⁇ processing unit, and generates the Signalverar ⁇ beitungsech triggered by an input of Messsig ⁇ Nals, data relating to the change of at least one operation ⁇ size of the ship propeller.
• said detection is used as an indicator of a change in the static pressure in the liquid.
• the said detection is used to determine a range of values within which a content of a dissolved gas in the liquid.
• overpressure thrust
• stroke negative pressure
• the term "propeller” includes all propellers that are used to drive a water ⁇ vehicle, such as a ship or a submarine. In the case of the operation of a ship's propeller noise of the gas and Pseudokavitation serves as an indication that the static pressure of the liquid in the region of the Pro ⁇ Pellers changes. in particular, a reduction of the static pressure is of importance since it can mean an upcoming insertion of vapor cavitation.
• the noise is detected and thus determined that the static pressure in the liquid, in particular in the water carrying the vessel is reduced, can reduce the speed of the propeller and / or the angle of attack of at least one when operating a ship propeller as a possible counter ⁇ measure
• Propeller blades of the shipper ⁇ pellers are changed to the pressure on the back lift and thus not reach the area of steam cavitation.
• Other measures to increase the pressure on the back of the propeller blades are blowing in water or opening ducts penetrating the propeller blades, through which water can flow from the overpressure to the vacuum side.
• a sensor which can detect the said noise on a propeller shaft, which serves to drive the ship's propeller.
• the propeller shaft is mechanically fixed to the propeller to enable it to rotate.
• the sensor preferably contacts the propeller shaft. It is also possible lent that at least a part of the sensor on the shaft buildin ⁇ is Untitled.
• a sensor when using the method in the operation of a ship's propeller, a sensor is provided, which can detect said noise on a ship's hull.
• the hull forms the outer shell of the vessel, which will be ⁇ moved by using the ship's propeller.
• the sensor preferably contacted the ship's hull ⁇ . It is also possible that at least part of the sensor is attached to the hull.
• a sensor when using the method in the operation of a ship's propeller, a sensor is provided which can detect the said noise on the ship's propeller.
• the sensor preferably contacted the Propel ⁇ ler. It is also possible that at least a part of the sensor is attached to the propeller, eg on a propeller blade.
• the sensor unit is arranged on a watercraft, in particular on a propeller and / or on a propeller driving shaft and / or on a hull of the watercraft. Since cavitation formation is dependent not only on the static pressure p in the liquid and the temperature T of the liquid but also on n, ie on the number or concentration of dissolved gases in the liquid, the content or saturation state of liquids can be determined with this method derived Geloes ⁇ th gases.
• the propeller provokes gas cavitation and / or pseudo cavitation and the resulting noise in the fluid.
• the speed of rotation of the propeller is preferably increased slowly until the point is reached at which the typical noise can then be detected.
• this application comprises the further steps of: performing a calibration where different values to the content of the dissolved gas in the liquid in each case a corresponding boundary ⁇ speed is determined; and storing the corres ⁇ exploding pairs of values of gas content and speed limit for a subsequent step of said deriving.
• the limit velocity at which the gas and / or Pseudokavitation and caused thereby noise up occurs so the range of values can be derived from the stored value pairs, in which the Content of dissolved gas is. It is possible that in this application, the propeller is operated at intervals or continuously operated at this limit speed after reaching the limit speed. It is possible to operate the propeller continuously at a limit revolution speed; If the gas content exceeds a critical limit, gas and / or pseudo-cavitation and the characteristic noise occur.
• Fig. 1 is a phase diagram of water; 2 a ship propeller;
• FIG. 3 shows a signal processing chain; and FIG. 4 shows a control circuit.
• the static pressure p in the liquid is lowered, for example as a result of egg ⁇ ner rotation of a ship's propeller.
• the static pressure p decreases to the point where it reaches the boiling point curve SPK at the second state point P2
• steam cavitation starts even with a further drop in the pressure p, for example, up to the third state point P3, persists.
• Fig. 2 shows a plan view of a ship's propeller 1 comprising a propeller 2 and a plurality of attached thereto Propel ⁇ ler hypothesis. 3
• the propeller 1 with the Propellerblät ⁇ tern 3 is brought in the operation of the propeller 1 in the water 5 by a shaft 4 for rotation.
• the shaft 4 protrudes through a sealed with a seal 10 against ingress of water 5 opening in a ship's skin 8 into the interior 9 of a ship's hull, where it can be rotated by a drive motor in rotation.
• Each movement of the leaves 3 in the water 5 causes changes in the static pressure in the water 5.
• these pressure changes only become so great at a certain speed that steam cavitation occurs.
• occur even with small changes in pressure in the water 5 cavitation onsarten the gas and the pseudo cavitation, through which with gas, especially air, filled bubbles 6 in the water 5 he testify ⁇ .
• Vibrations About the fixed connection of the propeller 1 with the shaft 4, these vibrations are also detectable by a vibration sensor 11 c, which is in contact with the shaft 4.
• FIG. 3 shows a signal processing chain consisting of a sensor 11, a signal processing unit 12 and a control unit 13.
• the sensor 11 is one of the sensors IIa, IIb and 11c shown in FIG. If the sensor 11 detects a noise caused by the gas bubbles and pseudo-cavitation associated air bubbles 6, he sends a corresponding measurement signal 14 to the signal processing ⁇ unit 12. It is possible that the sensor 11 is only a measurement signal 14 to the signal processing unit 12 transmits when the sound pressure level of the noise a predetermined
• Threshold exceeds.
• the sensor 11 generates independent of the sound pressure level of the noise measurement ⁇ signals 14 that it sends to the signal processing unit 12th
• an evaluation or filtering of the measurement signals 14 can be carried out by the signal processing unit 12.
• the signal transmission from the sensor 11 to the signal processing unit 12 preferably takes place via a cable, for example via a conducting wire, since a wireless transmission by means of electromagnetic waves in the water may be subject to a relatively high attenuation due to absorption.
• the Sensor is arranged on the rotating propeller, the electrical connection can be maintained by means arranged for example in the propeller hub sliding contacts.
• the signal processing unit receives a measurement signal 14 12 that corresponds to a noise level with a minimum sound pressure, it generates data 15 which relate to a ⁇ nde ⁇ tion of the static pressure in the liquid.
• the data 15 may be in the form of a flag variable which simply indicates whether noise has been detected.
• the data 15 may include information about a sound level, a waveform, a frequency, and other characteristics of the noise.
• the data 15 may also include output data for output on an output device, eg, a screen or a speaker, to inform a user of the detected noise.
• the data 15 generated by the signal processing unit 12 contain input data for a ne control unit 13, which according to the input data, for example in a motor driving the shaft 4, a speed reduction or in a the propeller blades 3 controlling actuator a change in an angle of the Pro ⁇ pellertrust 3 causes.
• Those measures aim at a displayed by the noise reduction of the pressure in the water stati ⁇ rule 5 to stop or reverse, so that insertion of the vapor cavitation is avoided.
• FIG. 4 shows a control circuit for operating a ship's propeller.
• a sound pressure or vibration is measured by a sensor for detecting a noise in the water caused by gas cavitation and / or pseudo-cavitation.
• the sensor 11 may be one of the sensors IIa, IIb and 11c shown in FIG.
• box 31 it is checked whether the sensor has detected an evoked by Gaskavitati ⁇ on and / or Pseudokavitation noise in the water.
• An assignment of a measured noise to a gas cavitation and / or pseudo-cavitation can, for example, be based on characteristic properties of the measured value, such as frequencies, amplitudes, oscillation form, etc. In this way, a noise caused by gas cavitation and / or pseudo-cavitation can be distinguished from other noises.
• test result in box 31 that the sensor has detected an evoked by gas cavitation and / or noise in the water Pseudokavitation Y is put ⁇ asks in box 32 whether this noise exceeds a predetermined threshold, for example, using a sound level or a
• a control signal 35 is generated, for example a command to be sent to a motor for reducing a rotational speed of the propeller or a command to be sent to an actuating device for reducing an angle of attack of the propeller blades.
• a control signal 35 is generated, for example a command to be sent to a motor for reducing a rotational speed of the propeller or a command to be sent to an actuating device for reducing an angle of attack of the propeller blades.
• a control signal 37 is generated in field 33, for example a command to increase the speed of the propeller or a command to be transmitted to the actuating device Command to increase the angle of attack of the propeller blades. Since the low volume of the noise indicates that there is still no danger of getting into the area of steam cavitation, these measures can further increase the thrust of the propeller and thus further increase the static pressure be lowered. In parallel, the loop 38 returns to the field 30 so that a new measurement can take place.
• test in box 31 shows that the sensor has detected no noise in the water caused by gas cavitation and / or pseudo-cavitation, then it is possible to proceed directly to box 33.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• Ocean & Marine Engineering (AREA)
• Remote Sensing (AREA)
• Radar, Positioning & Navigation (AREA)
• Aviation & Aerospace Engineering (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)
• Exhaust Silencers (AREA)
• Measuring Fluid Pressure (AREA)
• Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
• Toys (AREA)
• Arrangements For Transmission Of Measured Signals (AREA)

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