Development of Synthetic Jet Actuator Hardware for the Green Regional Aircraft Low Noise Configuration

Project Information

VELOCIRAPTOR

Grant agreement ID: 255797

Closed project

Start date 15 February 2010

End date 14 April 2011

Funded under

• Specific Programme "Cooperation": Joint Technology Initiatives

Total cost € 145 682,40

EU contribution € 109 261,00

Coordinated by

THE UNIVERSITY OF MANCHESTER
United Kingdom

Final Report Summary - VELOCIRAPTOR (Development of Synthetic Jet Actuator Hardware for the Green Regional Aircraft Low Noise Configuration)

Executive Summary:

Synthetic Jet Actuators (SJAs) have been routinely used for wind tunnel applications for around the last ten years. These actuators are typically Helmholtz resonator devices based on an actuated membrane, cavity and orifice. With the membrane natural frequency matched with cavity/orifice Helmholtz frequency to improve maximum jet velocity from the device. The orifice axis may be normal or inclined relative to the local wetted surface (skin) depending on the type of flow control actuation input required (single vortex or counter rotating vortex pair). The membranes are typically based on using a polycrystalline piezoelectric (PZT) patch applied to a metallic disc. These discs are commercially available components typically used for buzzers or low quality speakers. The typical operating frequency of the devices is around 2kHz consistent with audio applications. The currently achievable maximum velocity is around 150m/s with a power conversion efficiency of around 10%. Device mechanical/electrical reliability is an issue and health monitoring on arrays of devices is typically not available.

The University of Manchester (UNIMAN) and Aircraft Research Association (ARA) have delivered a single, linear spanwise array of 30 synthetic jet actuators with integrated health monitoring.

The VELOCIRAPTOR project has advanced the state of the art in SJA technology by

1. Producing a sealant-free array with reduced number of parts

Manufacture of the module using stereolithography rapid prototyping technique has been achieved which, relative to the AVERT array, has enabled:

• the ability to include more complex geometry
• 33% reduction in part count per SJA
• 75% reduction in leadtime

2. Increasing power density of the SJA array

To meet the application requirements proposed by CIRA (placement of module at the 20% chord point of the inboard main flap element of a three element wing), a skewed opposite SJA configuration was utilised consisting of an array of overlapping SJAs. Relative to the AVERT array, the module reduces usable depth requirements by 50% while maintaining comparable performance in terms of peak jet exit velocity, i.e. ~90ms-1 at f = 2.7kHz.

3. Providing real-time actuator health monitoring

Distributed sensors in the array (in the form of small microphones housed in each SJA) demonstrate real-time monitoring via a 2-colour LED, the output of which is dependent on a pre-set threshold. The system provides a more rapid and continuous method of actuator health monitoring, as opposed to the previous practice of measuring actuator performance via hot-wire anemometry, which can be done only infrequently. The health monitoring system is expected to form a fundamental requirement towards the future certification of in-flight active flow control systems.

Project Context and Objectives:

The VELOCIRAPTOR module provides an array of 30 synthetic jet actuators in a single spanwise linear array. The module is designed to allow placement at the 20% chord point of the inboard main flap element of the three element wing. The module will require modification to match the contour of the wetted surface to the eventual application. This strategy was chosen as the confirmed final geometry was unavailable at the time of design completion. The module is manufactured using the stereolithography (SLA) rapid prototyping technique. This had several advantages when compared to conventional machining techniques including: Cost, Leadtime, Part count reduction and ability to include complex geometry. The latter was particularly important in this application in allowing the array to meet the packaging requirements while retaining an adequate spacing between individual actuators. Following consideration of design concepts based on previous practice, a new design concept was created which incorporated previously optimised cavity geometry.

The module incorporates thirty individual synthetic jet actuators (SJAs). The housing of each is integrally manufactured in one piece with the top plate and uses a commercial-off-the-shelf (COTS) brass/piezoceramic (PZT) diaphragm. Each actuator includes a simple monitoring system using a COTS microphone, allowing assessment of threshold performance during operation. Peak velocity around 90ms-1 at 200V peak-to-peak has been demonstrated.

Project Results:

1. Reduced part count, reduced maintenance, increased reliability actuator array design
2. Increased power density of array using existing piezo diaphragm technology to reduce installed volume requirements
3. Real time monitoring of actuator health using a simple acoustic measurement system with visual feedback of actuator health

Potential Impact:

This work addresses the high implementation costs of active flow control arrays through a range of engineering techniques and demonstrates significant improvement on the state of the art can be obtained with relatively simple engineering improvements in design, operation and monitoring

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