Powered Resonance Tube Actuators Research Articles

Jet Impingement Tone Suppression Using Powered Resonance Tubes

This work is an experimental study of high subsonic jet impingement tone suppression. We begin by documenting the characteristics of the impingement tone for various Mach numbers and standoff (nozzle exit to ground plate) distances. The results revealed frequency staging and the presence of two types of impingement tones. A novel feature of our work is the use of four miniature high-frequency actuators known as powered resonance tubes that were located circumferentially around the main jet nozzle. The powered resonance tubes were capable of producing high amplitude acoustic excitation over a range of frequencies, up to 17.5 kHz. Our target excitation frequency range was about 3-5 times that of the natural flow instability. Using high-frequency excitation, tonal suppression levels as high as 20 dB and broadband suppression levels as high as 5-10 dB were obtained. The mass addition rate from the powered resonance tubes was of the order of 2% of the mass flow rate from the main jet. Mass flow reductions could be obtained under conditions when the powered resonance tube resonated strongly. Our results suggest that appropriately designed miniature powered resonance tube actuators have potential for use in flow control applications.

Development of high bandwidth powered resonance tube actuators with feedback control

A high bandwidth powered resonance tube (PRT) actuator potentially useful for noise and flow control applications was developed. High bandwidth allows use of the same actuator at various locations on an aircraft and over a range of flight speeds. The actuator selected for bandwidth enhancement was the PRT actuator, which is an adaptation of the Hartmann whistle. The device is capable of producing high-frequency and high-amplitude pressure and velocity perturbations for active flow control applications. Our detailed experiments aimed at understanding the PRT phenomenon are complemented by an improved analytical model and direct numerical simulations. We provide a detailed characterization of the unsteady pressures in the nearfield of the actuator using phase averaged pressure measurements. The measurements revealed that propagating fluctuations at 9 kHz were biased towards the upstream direction (relative to the supply jet). A complementary computational study validated by our experiments was useful in simulating the details in the region between the supply jet and the resonance tube where it was difficult to gather experimental data. High bandwidth was obtained by varying the depth of the resonance tube that determines the frequency produced by the device. Our actuator could produce frequencies ranging from 1600 to 15,000 Hz at amplitudes as high as 160 dB near the source. The frequency variation with depth is predicted well by the quarter wavelength formula for deep tubes but the formula becomes increasingly inaccurate as the tube depth is decreased. An improved analytical model was developed, in which the compliance and mass of the fluid in the integration slot is incorporated into the prediction of resonance frequencies of the system. Finally a feedback controller that varied both the resonance tube depth and spacing to converge on a desired frequency was developed and demonstrated. We are optimistic that numerous potential applications exist for such high bandwidth high dynamic range actuators.

Development of a high bandwidth Hartmann–Whistle type actuator

There is current interest in using Hartmann–Whistle type powered resonance tube actuators for aeroacoustic control. Previous experiments (Raman et al. (2000, 2001) AIAA 2000-1930; Stanek et al. (2000) AIAA 2000-1905) have shown that such actuators with no moving parts are very effective in the suppression of flow impingement and cavity noise. However, fixed geometry actuators can only produce effective actuation over a small range of frequencies. Our idea is to use a variable depth powered resonance tube actuator where the depth of the resonance tube and the distance between the supply jet and the resonance tube can be controlled actively during the experiment. The experimental setup consists of a 1/4′′ diameter jet facing the open end of the resonance tube that is closed at the other end. The tube depth is changed by a computer controlled piston fitted inside the tube. Microphone and pressure sensors located at various locations in the vicinity of actuation were used to measure the frequency and amplitude of the fluctuations produced by this device. Due to the high amplitudes of pressure within the resonance tube the linear eigenfrequencies do not predict the measured frequencies. [Work supported by AFOSR.]

Linear arrays of powered resonance tube actuators for aeroacoustic control

Experiments were conducted to characterize the performance of a linear array of powered resonance tube actuators developed jointly by Boeing and IIT. The actuator is an adaptation of the Hartmann whistle and devices of this type have been shown to be effective in suppressing flow generated acoustic tones that commonly occur in aircraft applications, such as impingement tones and cavity resonances (Raman et al., AIAA Paper 2000-1930; Stanek et al., AIAA Paper 2000-1905). The goal of this characterization is to provide a database that can be used to compare the performance of these actuators with other actuator designs (such as piezoelectric actuators) and to optimize the design of these actuators. Optimization involves modifying the geometric parameters of the actuator in order to get the maximum acoustic control with minimum input mass flow rate. In order to accomplish these tasks, detailed measurements of the fluctuating velocity and pressure were made at numerous locations in the flowfield at the actuator exit. Results indicate that the actuation could produce frequencies ranging from 4352 to 11<th>070 Hz (for the 1/2 inch depth tube chosen). Amplitudes were as high as 156 dB in the vicinity of actuation. [Work supported by Boeing/DARPA.]