Two neural networks are used to control adaptively a vibration and noise-producing plant. The first neural network, the emulator, models the complex, nonlinear output of the plant with respect to certain controls and stimuli applied to the plant. The second neural network, the controller, calculates a control signal which affects the vibration and noise producing characteristics of the plant. By using the emulator model to calculate the nonlinear plant gradient, the controller matrix coefficients can be adapted by backpropagation of the plant gradient to produce a control signal which results in the minimum vibration and noise possible, given the current operating characteristics of the plant.

Neural net controller for noise and vibration reduction

This disclosure describes a new type of flow meter. A housing defines a passage wherein fluid flows through a plurality of capillaries. The flow in these capillaries is laminar even if the fluid in the passage upstream of the capillaries is in turbulent flow. There are pressure taps across the meter wherein the pressure drop thereacross is linear with respect to the flow through the meter.

Capillary flow meter

One aspect relates to a hybrid propulsive technique, comprising providing at least some first thrust associated with a flow of a working fluid through at least a portion of an at least one axial flow jet engine. The hybrid propulsive technique includes extracting energy at least partially in the form of electrical power from the working fluid, and converting at least a portion of the electrical power to torque. The hybrid propulsive technique fiuther includes rotating an at least one substantially axial-flow independently rotatable compressor rotor at least partially responsive to the converting the at least a portion of the electrical power to torque.

Hybrid propulsive engine including at least one independently rotatable compressor rotor

Hand calculation procedures for predicting aerodynamic noise from propellers, rotors, and lift fans

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A review of aerodynamic noise from propellers, rotors, and lift fans

One aspect relates to a hybrid propulsive technique comprising providing at least some first thrust associated with a flow of a working fluid through at least a portion of an at least one axial flow jet engine. The hybrid propulsive technique comprises extracting energy from the working fluid that is at least partially converted into electrical power, and converting at least a portion of the electrical power to torque. The hybrid propulsive technique further comprises rotating an at least one independently rotatable propeller/fan of at least one rotatable propeller/fan assembly at least partially responsive to the converting the at least a portion of the electrical power to torque, wherein the rotating of the at least one independently rotatable propeller/fan of the at least one rotatable propeller/fan assembly is arranged to produce at least some second thrust.

Hybrid propulsive engine including at least one independently rotatable propeller/fan

An "adaptive synchrophaser" is disclosed for modifying the phase angle relationship between aircraft propellers to reduce cabin noise and/or vibration. Rather than use a constant pre-selected angle for a specific passenger cabin configuration during a particular flight mode (e.g., during liftoff or cruise), the synchrophaser periodically monitors actual operating conditions and modifies the phase angle accordingly. In the preferred embodiment, a plurality of transducers (microphones) are installed at several cabin locations to sample noise periodically. The signals are then transmitted via a signal conditioner, a multiplexer and an analog-to-digital converter to a signal processor. The processor calculates the maximum acoustic noise at each microphone location for all possible phase angles. It then identifies the optimum phase angle that resulted in the lowest maximum noise anywhere in the cabin, and signals a synchrophaser to set that angle. This process not only reduces noise based on actual on-going conditions, but also balances the cabin noise so that there are not any "hot" seats with high noise levels.

Adaptive synchrophaser for reducing aircraft cabin noise and vibration

The rotation of N-bladed propellers of a multi-engine aircraft is controlled by phase angle synchronizer 30 such that a predetermined phase angle offset φ3 is maintained between the blades of a first propeller 10 and the blades of a second propeller 20, at which offset cabin noise is reduced to a minimum and cabin vibration to a near minimum. The controller 40 determines the optimum phase angle offset φ3 to be that phase angle of the set of N periodic phase angles: φ1+K(360/N), where K ranges in integer steps from 0 to N-1, each characteristic of minimum cabin noise generation, beginning with the minimum first phase angle, φ1, lying between 0 and 360/N degrees, which is closest to the second phase angle, φ2, characteristic of minimum cabin vibration.

Method for reducing aircraft cabin noise and vibration

The fuselage (cabin) (15) of a propeller (45) driven aircraft (10) is isolated from vibration associated with the wake (46) of the propeller by vibration isolators (50, 55 and 110) in the wing and tail surfaces of the aircraft.

Cabin noise suppression in propeller driven aircraft

Noise is reduced on an aircraft engine of the type having aft mounted propeller blades 10 which pass through exhaust gas streams 20 expelled from circumferentially spaced nozzles 14. The nozzles 14 are rotated, or the exhaust flow deflected, such that the high velocity exhaust streams 20a expelled from the nozzles 14 are directed away from their normal axial direction to impact the blades 10 at the same relative angle of attack 36a as the relative angle of attack 34 of the low velocity ambient air stream 22 thereby reducing fluctuations in blade lift and the associated noise.

Bernard Magliozzi

Papers

Adaptive synchrophaser for reducing aircraft cabin noise and vibration

Method for reducing aircraft cabin noise and vibration

Cabin noise suppression in propeller driven aircraft

Engine exhaust/blade interaction noise suppression

Laminar volume flow meter and construction thereof