54 results about "Propeller noise" patented technology

A system and method for reducing the noise penalty of a pusher propeller, allowing an aircraft to retain its advantages for UAV configurations, while allowing acoustic performance similar to that of a tractor propeller by reducing, or eliminating, propeller noise emissions. The system and method provide an airfoil-shaped flight surface with (i) a scoop configured to route boundary layer air and associated wake from said flight surface, and (ii) a suction device configured to provide a suction pressure, wherein the scoop routes boundary layer air from the flight surface to the suction device via an opening in the flight surface.

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.

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.

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 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.

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 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 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.