54 results about "Propeller noise" patented technology

The invention discloses a method for forecasting the noise value of a propeller noise value in uneven inflow. The method for forecasting the noise value of the propeller in the uneven inflow comprises the steps that firstly, a CFD computation grid is divided, steady iterative computation is conducted so that the water flowing performance parameter and the water speed of an inflow opening can be worked out and the accuracy of a model is verified; secondly, CFD unsteady computation is conducted, the period state of blade cavitation and the blade cavitation area change of the propeller are recoded; thirdly, through CFD flow field data, acoustic boundary element value computation is conducted, and load noise of the propeller is worked out; finally, the noise of the propeller is worked out through the blade cavitation monopole radiation noise of the propeller and the load noise of the propeller.

A propeller is provided including a hub and a first blade group and a second blade group. The first blade group includes at least one first propeller blade and the second blade group includes at least one second propeller blade. The at least one first propeller blade and the at least one second propeller blade are mounted to and equidistantly spaced about the hub. The at least one first propeller blade of the first blade group has at least one geometric characteristic different from the at least one propeller blade of the second blade group. The different blade groups will generate different noise signatures over a wider range of frequencies allowing for the design of low noise propeller systems.

An undersea vehicle having both low emitted noise and low reflectivity is provided. The undersea vehicle has a hollow cylindrical hull with all components, sensors, electronics, motors, and other internal components with the exception of the propellers, located within the shell of the cylindrical hull. The hollow center of the hull provides a duct and propeller configuration with the shaping of the inlet tube designed to reduce forward noise transmissions, such as reflected active sonar signals and emitted noise. The internal duct gradually constricts to a throat section and thereafter diverges to an output section where dual counter-rotating propellers are located. The result is that most of the internal turbulent flow and the propeller noise is located behind the throat and is thereby reflected in the aft direction. Steering of the vehicle is accomplished by canting the leading edge intake section and the duct exhaust section.

The invention discloses a self-noise test system and level test method for a ship sonar platform and belongs to the field of underwater noise control engineering. According to the invention, three signal source generators are controlled through a computer to generate excitation signals, and so the three signal source generators generate simulated hydrodynamic noise, simulated mechanical noise andsimulated propeller noise. Then data is collected and analyzed through a signal acquisition and recording end. A sonar platform self-noise test under a single noise resource effect can be carried out,a platform self-noise test under the effects of multiple noise resources at the same time can be implemented, test data in a whole wide frequency band can be obtained at a time, tests in different frequency bands are avoided, the work efficiency is improved, and the self-noise characteristics of a sonar chamber under various working conditions are more realistically simulated, and the establishment of a self-noise test system for the ship sonar platform is achieved.

The invention relates to a direct sound production test device of a large-proportion propeller model, and belongs to the technical field of underwater vehicle propeller noise control. The device comprises two-way tensioning drag equipment, a water-surface unpowered ship, data acquisition equipment, a power cable, control and data processing equipment, a hydrophone array, the propeller model, a main shaft system, a non-watertight shell, a watertight shell, a sensor, a supporting part, a rigid connecting part and a motor. Water-surface unpowered chip parameters, main shaft system parameters, motor parameters and two-way tensioning drag equipment parameters are determined according to the needed maximum thrust, dimension, weight, power and rotating speed of the propeller model; when the propeller model is not installed, the noise of a system is tested; a clutch is disconnected, and the no-load noise of the motor is tested; the test device is rectified according to the test result till test demands are met. The test device is good in test result repeatability, short in test period and low in cost.

This disclosure is related with propeller noise and cavitation abatement in applications like propulsion, ventilation, pumping or turbine systems on liquid or gas fluids working like a propellers, pumps, fans or turbines, by novel techniques that allows a stronger propellers and improves laminar flow and allow a smooth acceleration or deceleration of the liquid or gas by means of a propeller that consist on a rotating cylindrical block with one or more tunnels around it axis, said cylindrical block also may have flow separators structures at both input and output that helps to keep laminar flow of the fluid or gas with it surrounding media, having This rotating cylindrical block tunnels with either circular or irregular oval section that accelerates fluid or gas by means of both combined centrifugal and axial movement.

Enriching and balancing the acoustic spectrum radiated by a propeller by introducing a differential pitch angle on certain blades of the propeller. Modifying the acoustic spectrum makes it possible to render the propeller noise more pleasant to the human ear.

The invention puts forward a calculation method for electric aircraft propeller noise. The method comprises the following steps that: according to the structure parameter of an electric aircraft propeller, establishing a three-dimensional geometric model of the propeller; adopting a finite element method to carry out mesh generation on the flow field area of the three-dimensional geometric model of the propeller to obtain a propeller flow field subjected to the mesh generation; adopting a large eddy simulation calculation model to carry out unsteady pressure pulsation solving on the circulation area of the propeller flow field subjected to the mesh generation to obtain the transient pressure distribution of a paddle surface; and adopting an acoustic boundary element method to carry out acoustic field simulation on an acoustic mesh model to obtain the radiation noise distribution of the propeller. The method comprehensively considers each influence factor of noise, and therefore, a calculation result is accurate and reliable. The method can be used for aerodynamic noise frequency domain analysis and the like, and a theoretical basis and technical guidance are provided for effectively lowering the propeller noise.

While keeping a propeller located in a negative direction of a y-axis turning, transmission of acoustic waves from vibrating elements of a transducer unit is interrupted. Reference signals “A” and “B” which are receiving beam signals having principal acoustic axes oriented in a propeller direction are generated from received signals obtained by “A” and “B” group vibrating elements, respectively. Next, adjustment factors used for removing propeller noise from received signals obtained by vibrating elements on positive and negative sides of an x-axis are calculated by performing arithmetic operation on time-series data on the received signals obtained by the positive and negative sides vibrating elements and on time-series data on the reference signals “A” and “B”, respectively. When performing underwater sounding operation by transmitting acoustic waves, a product of the reference signal “A” or “B” and the adjustment factor is subtracted from the received signal obtained by each of the positive and negative sides vibrating elements, respectively.

Enriching and balancing the acoustic spectrum radiated by a propeller by introducing a differential pitch angle on certain blades of the propeller. Modifying the acoustic spectrum makes it possible to render the propeller noise more pleasant to the human ear.

The invention provides an acoustic anti-icing panel structure for controlling noise in a cabin of a turbo-propeller plane. The acoustic anti-icing panel structure comprises an anti-icing panel and an acoustic material inner core attached onto the anti-icing panel, wherein the periphery of the anti-icing panel is in arc connection with a pneumatic sealing edge; the other side of the pneumatic sealing edge is in the arc connection with a body installation edge; and an arc-shaped opening matched with a raised plane body structure is also formed in the bottom of the anti-icing panel. The acoustic anti-icing panel structure has the characteristics of low pneumatic sound and high sound reduction index, and the sound insulation performance of the wall panel structure can be effectively improved, so that the influence of the propeller noise on a sound field in the cabin of the plane is reduced, and the cabin comfort level of the turbo-propeller plane is improved.

The invention belongs to the technical field of aviation acoustics, and particularly relates to a propeller-driven aircraft cabin noise control design method. The method starts from an aircraft designprocess, propeller noise and aircraft aerodynamic noise are predicted, a noise index in the cabin is demonstrated and preliminary design is carried out; a propeller noise wind tunnel test and an airplane aerodynamic noise wind tunnel test are then carried out, a detailed prediction model is established, simulation calculation is carried out on distribution of propeller noise and aircraft aerodynamic noise along an aircraft body, and on the basis, an aircraft cabin noise detailed model is established, evaluation and optimization design are carried out on a detailed design scheme, ground and flight noise test is carried out on an actual aircraft, the detailed design scheme is further optimized, propeller aircraft cabin noise control design is completed, and the driving and riding comfort ofan aircraft cabin is improved.

The invention discloses an acoustic baffle composite structure for underwater detection equipment. The acoustic baffle composite structure comprises an acoustic baffle body, the acoustic baffle body comprises a cavity steel plate, a damping layer and a sound absorption layer, the cavity steel plate is of a main body supporting structure, the sound absorption layer and the damping layer are both pasted to the two sides of the cavity steel plate through mucilage glue, the cavity steel plate is formed by overlapping cavity steel plate units through flanges, each cavity steel plate unit is formedby welding a vertical face, a flange face and a bottom plate, a cavity is formed in each cavity steel plate unit, the damping layer is made of polyurethane underwater acoustic damping materials, and the sound absorption layer is of a wedge structure. According to the acoustic baffle composite structure for the underwater detection equipment in the invention, the cavity steel plate is adopted as asound insulation structure, propeller noise, mechanical noise and hull vibration radiation sound from the stern are reflected through an impedance mismatch effect, the reflection sound insulation effect is achieved, the influence of the noise on the underwater detection equipment is reduced, and therefore the detection performance of the equipment is improved.

The invention discloses a water surface target avoiding method based on three-dimensional sparse array sound source orientation recognition. The method is realized by arranging a three-dimensional sparse hydrophone array on an underwater vehicle, and the method comprises the following steps of acquiring propeller noise from a water surface target received by the three-dimensional sparse hydrophonearray, and estimating the position of the water surface target; calculating the movement speed of the water surface target according to the position change of the water surface target at fixed time intervals; judging whether the water surface target approaches the underwater vehicle or not according to the distance between the underwater vehicle and the water surface target and the motion speed of the water surface target, and if the water surface target approaches the underwater vehicle, re-planning a traveling route of the underwater vehicle so as to avoid the water surface target, otherwise, keeping the original route of the underwater vehicle to advance. The water surface target avoiding method can timely and flexibly avoid the water surface target under the condition of ensuring thenavigation safety of the underwater vehicle.

The invention discloses an unmanned plane automatic stealth system. According to the invention, a propeller wing system is coated with a sound-absorbing coating used for reducing propeller noise, andthe noise of an unmanned plane propeller is reduced; an air inlet of the power system is provided with a radar shielding net made of a conductive material, the outer surface of an unmanned plane bodyis coated with a wave-absorbing coating made of X fiber as a wave-absorbing paint, and the stealth of the unmanned plane is realized through cooperation; a heat dissipation layer is disposed on an airintake duct and a jet pipe; the heat dissipation layer forms a cavity with the air intake duct and the jet pipe, and the cavity is filled with a high polymeric compound having a large cold capacity to absorb the heat radiated by a turbine jet-propelled engine during operation. The automatic stealth system has simple structure and low manufacturing cost. Under the condition of not changing the structure of the original unmanned plane, the stealth and performance optimization of the unmanned plane can be realized, and the system has great promotion significance to a large number of the unmannedplanes that have been used at present.

The invention discloses a carbon fiber acoustic baffle applied to underwater detection equipment. The carbon fiber acoustic baffle applied to the underwater detection equipment includes a baffle body,a damping layer and a sound absorbing layer; the damping layer is closely adhered to one side of the baffle body, and the sound absorbing layer is closely adhered to the other side of the baffle body; the baffle body 1 adopts a structural form in which a shell wraps a carbon fiber honeycomb core material, and the carbon fiber honeycomb core material and the shell are both a carbon fiber reinforced resin composite structure; the shell and the carbon fiber honeycomb core material are bonded by resin; and the carbon fiber honeycomb core material forms cavities with the inside of the shell. According to the invention, the structural form in which the shell wraps the carbon fiber honeycomb core material is adopted; the carbon fiber honeycomb core material and the shell form a large number of independent and closed cavities as the sound insulation structure; and the propeller noise, mechanical noise and hull vibration sound radiation from the stern are blocked by using the impedance mismatch effect; therefore, the impact of such noise on the underwater detection equipment is reduced, and the detection performance of the equipment is improved.

The invention discloses a novel ducted propeller device and an achieving method thereof. The device comprises a hollow cylindrical motor stator; a plurality of coils are evenly wound on the outer wall of the motor stator, and the inner wall of the motor stator is fixedly connected with an outer ring of each bearing; the motor rotor is composed of two mutually-nested cylindrical structures and an annular structure, the cylindrical structure inside the motor rotor penetrates through the center of each bearing and is connected with an inner ring of each bearing, the cylindrical structure outside the motor rotor is arranged on the outer face of the motor stator in a sleeving mode, and the inner wall of the cylindrical structure outside the motor rotor is inlaid with a magnetic sheet; the motor stator, the motor rotor and the bearings are each of a symmetrical structure, and the symmetry axes of the motor stator, the motor rotor and the bearing are overlapped; the motor stator is connected with a motor driving control module through a guide line, and blade tips at the two ends of a propeller are fixedly connected with the inner wall of the cylindrical structure inside the motor rotor; and the motor driving control module galvanizes the coils on the motor stator through the guide line, the coils generate a magnetic yield and drive the motor rotor to rotate, and the motor rotor drives the propeller to rotate. The novel ducted propeller device and the achieving method thereof contribute to improve efficiency of the propeller, noise of the propeller is reduced, the diameter of a motor is reduced, and the applicability of the motor is improved.

The present invention relates to an asymmetric wake generating vortex generator for reducing propeller noise and vibration, configured such that, by controlling a flow that is introduced into a propeller installed on a ship so as to reduce cavitation that occurs on a wing surface of the propeller of the ship, the noise and vibration of the propeller can be reduced. Conventional wing-shaped added materials or flow control fins have the following problems: a wing-shaped structure is attached to the surface of a hull in front of a propeller and, in order to control a flow introduced into the propeller, is made to have an angle of attack with regard to the introduced flow; therefore, the same is configured to control the velocity of flow and the direction of flow, resulting from a fluid force, and thus can exhibit an effect only when the same is a large structure; furthermore, when the same is attached to the surface of the hull in front of the propeller so as to change the velocity in the tangential direction, the resulting pre-swirl effect improves the efficiency of the propeller, while the increased cavitation increases noise and vibration of the propeller. In order to resolve the above problems, the present invention provides an asymmetric wake generating vortex generator for reducing propeller noise and vibration, configured such that the angle of attack, which is introduced to a wing surface, is reduced through a change in velocity in the axial direction resulting from generation of an asymmetric vortex, thereby generating an asymmetric wake distribution that makes the flow on a first or second quadrant of a propeller surface, on which the largest degree of cavitation occurs, particularly fast, and thereby minimizing generation of cavitation noise.

While keeping a propeller located in a negative direction of a y-axis turning, transmission of acoustic waves from vibrating elements of a transducer unit is interrupted. Reference signals “A” and “B” which are receiving beam signals having principal acoustic axes oriented in a propeller direction are generated from received signals obtained by “A” and “B” group vibrating elements, respectively. Next, adjustment factors used for removing propeller noise from received signals obtained by vibrating elements on positive and negative sides of an x-axis are calculated by performing arithmetic operation on time-series data on the received signals obtained by the positive and negative sides vibrating elements and on time-series data on the reference signals “A” and “B”, respectively. When performing underwater sounding operation by transmitting acoustic waves, a product of the reference signal “A” or “B” and the adjustment factor is subtracted from the received signal obtained by each of the positive and negative sides vibrating elements, respectively.

The application relates to systems and methods for reducing the propeller noise. Disclosed is an aerial vehicle having a reduced noise signature. The aerial vehicle may be a vertical take-off and landing (VTOL) aerial vehicle. The aerial vehicle comprises an airframe and a plurality of rotors operatively coupled with one or more motors. The plurality of rotors may comprise a first, second, third,and fourth rotor. Each of the first, second, third, and fourth rotors may be arranged in a single plane and oriented to direct thrust downward relative to the airframe. In certain aspects, at least two of the plurality of rotors employ a different geometry to generate a targeted noise signature.

The invention discloses an acoustic real-time detection method for ocean internal waves based on line spectrum identification. A propeller with a set rotating speed is used as a sound source, a standard hydrophone 8301 is used for passive acquisition of propeller noise, and real-time detection of ocean internal waves can be realized based on a propeller line spectrum identification algorithm and in combination with physical features of ocean acoustic. The method comprises the steps of: transmitting propeller noise to a standard hydrophone fixed to seabed through the propeller with the set rotating speed, obtaining an envelope value by performing band-pass and low-pass filtering on acquired signals, extracting a demon spectrum to complete the line spectrum identification; comparing with theset propeller rotating speed, tracking continuously, performing secondary identification when abnormal jumping is discovered, and detecting and alarming in real-time. The steps of the method are simple, the propeller is taken as a sound source, cost is low; the method is suitable for any water area, and has a wide application value.

The invention provides a gravity type propeller noise measuring device. The device comprises a high-level water tank, an experimental water tank and a reservoir which are connected in sequence througha water pipe, a long-shaft dynamometer, a propeller and a hydrophone are mounted in the experimental water tank, the hydrophone is connected with a computer, the reservoir is divided into two parts,one part is an open part, the other part is a closed part, a partition plate is arranged between the two parts, an air bag is arranged in the closed part, the open part is connected with the experiment water tank and is provided with a first valve on a communication water pipe, and the closed part is connected with the high-level water tank and is provided with a second valve on the communicationwater pipe. According to the gravity type propeller noise measuring device provided by the invention, by grading utilization of the reservoir, a noise measuring experiment is separated from circulating water, and collected rainwater is utilized to carry out the experiment, thereby reducing the operation of a motor during water circulation, reducing the influence of background noise on the experiment, and enabling an experiment result to be more authentic and more reliable.

The invention discloses a sound source system for simulating underwater propeller noise. The sound source system can simulate hydrodynamic noise of an underwater propeller and cavitation noise of theunderwater propeller, achieves the simulation of the propeller noise in a low-speed dragging state, and achieves a purpose of simulating the real working process of a ship propeller. The sound sourcesystem comprises a control unit, a high-pressure gas station, a valve control unit and a noise simulation device; the control unit is used for controlling opening and closing of electric control valves in the high-pressure gas station and the noise simulation device; the high-pressure air station is used for providing enough high-pressure air for system work; the valve control unit is used for stabilizing the pressure and flow of high-pressure gas generated by the high-pressure gas station and conveying the high-pressure gas to the noise simulation device; the noise simulation device is dragged to work underwater and is used for simulating hydrodynamic noise and cavitation noise of an underwater propeller.

The invention discloses a multi-scale simulation analysis method for propeller noise. The method comprises performing dimension analysis, progressive analysis, statistical analysis and correlation analysis on the noise to obtain a noise expression; performing Fourier transform on the noise expression and rewriting the noise expression in combination with a Green function; performing physical modeling of the propeller noise based on the rewritten noise expression and a physical process of the propeller noise to obtain a modeling model; dividing each single blade of the propeller into n parts along the axial direction or the radial direction, wherein n is initially 1; analyzing each parameter in the modeling model corresponding to each part, and calculating a far-field noise spectrum function of each part; calculating a far-field noise spectrum function of a single blade; and calculating an error value between the far-field noise spectrum function of the single blade and the far-field noise spectrum function obtained by a test, if the error value is greater than a set value, re-dividing the blade area for calculation, and otherwise, taking the modeling division process as the propeller noise simulation analysis method of the blade configuration and the blade number of the blades.

The invention discloses a sound insulating device for a four-rotor aircraft. The sound insulating device for the four-rotor aircraft mainly comprises a connecting arm part and a sound insulating coverpart. The sound insulating device for the four-rotor aircraft can absorb and reflect propeller noises generated by rotors. The connecting arm is a light high-strength structure made of an aluminium product or a plastic product. 1 / 4 of the spherical sound insulating cover is fixed by one end of the connecting arm. The sound insulating cover is formed by three layers of materials which are glass wool, damping paint and aluminium plate in sequence from inside to outside; and by selecting appropriate sound absorbing materials, the noise absorbing capacity of the sound insulating cover can be improved. As the sound insulating cover has certain distances from the rotors, the noise is reduced on the premise of reducing interference to rotor flow fields.

The invention relates to the technical field of ship noise forecasting methods, and concretely relates to a ship propeller noise forecasting method considering fluid-structure interaction. The noise forecasting method is characterized by comprising the following steps: 1, establishing a propeller model and a ship appearance model according to a ship body design drawing, a profile drawing and a propeller profile value table; 2, combining the propeller model and the ship body shape model, and performing non-fluid-structure interaction transient flow field calculation; 3, performing mesh generation, material attribute endowing and boundary condition setting on the ship body structure model; 4, calculating a fluid-structure interaction transient structure of the ship body and the propeller; and 5, considering the noise forecasting under the fluid-structure interaction condition. The noise forecasting method is adopted to achieve the advantages of being simple, small in noise forecasting error, high in noise forecasting effect and the like.

The invention discloses a propeller cavitation degree identification method based on pulse frequency characteristic mode identification. The method comprises the following steps: (1) acquiring a propeller noise signal; (2) importing the noise signal into a program, and calculating by using a rapid cyclic stationary characteristic function to obtain a cyclic density spectrum; (3) normalizing to obtain a cyclic coherence spectrum, and then further integrating and averaging to construct an enhanced envelope spectrum under logarithmic coordinates; (4) judging the characteristic frequency accordingto the obtained enhanced envelope spectrum, selecting integral multiples of the corresponding time period, and carrying out improved time domain averaging on the source data; (5) performing ensembleempirical mode decomposition to obtain a corresponding intrinsic mode function; (6) detecting and counting the pulse frequency of the intrinsic mode function by adopting a constant false alarm rate; and (7) taking the pulse frequency as a characteristic matrix, and performing BP neural network training identification to obtain judgment of a cavitation state. By utilizing the method, the statistical characteristics of the propeller in different cavitation states can be shown, and the estimation of the obtained state is more accurate.