Performance Characteristics of the SparkJet Flow Control Actuator

OBJECTIVE Practical application of active flow control is dependent upon the development of robust actuators that are reliable, low cost, and responsive, and that consume little power. Under AFOSR sponsorship, The Johns Hopkins University Applied Physics Laboratory continues development of a promising device for highspeed flow control called the SparkJet actuator. This actuator, which produces a synthetic jet with high exhaust velocities, holds the promise of manipulating supersonic flows without active mechanical components. Combined computational and experimental techniques are being applied to investigate the operating characteristics of a cavity SparkJet device. Previous experimental and numerical parametric studies of the current (second-generation) design characterized the performance attributes of the device as a function of orifice size, chamber volume, and energy deposited. This paper discusses the flow characteristics of the SparkJet’s discharge and cooling stages after a single energy deposition pulse when discharging into a fullydeveloped supersonic boundary layer. Results from the numerical simulation indicate that the device has the potential to penetrate a Mach 3 crossflow when operating in a single-pulse mode (i.e. before establishing a synthetic jet). Effective manipulation of a flow field can lead to a number of significant benefits to aerospace vehicle systems, including enhanced performance, maneuverability, payload, and range, as well as lowered overall cost. These macro benefits are directly achievable through the application of flow-control technology to impact fluid phenomena such as transition, turbulence, and flow separation on the micro-scale. 2, 3, 4, 5, 6 Under AFOSR sponsorship, The Johns Hopkins University Applied Physics Laboratory (JHU/APL) is investigating a system for high-speed flow control called the SparkJet. The SparkJet, which produces a synthetic jet with high exhaust velocities, holds the promise of manipulating high-speed flows without moving structures. Analyses and demonstrations performed to date indicate that the SparkJet concept has the potential of generating exhaust streams that can penetrate supersonic (as well as subsonic) boundary layers without the need for active mechanical components. Computational and experimental techniques being used to quantify the performance characteristics of the pulsating flow from a cavity SparkJet are discussed herein. The highlight of the discussion centers on a numerical demonstration of a SparkJet * Senior Aerospace Engineer, AIAA Associate Fellow † Senior Mechanical Engineer, AIAA Member ‡ Assistant Supervisor, Aeronautical Sciences and Technology Group, AIAA Member Copyright ©2004 by the American Institute of Aeronautics and Astronautics, Inc. Under the copyright claimed herein, the U.S. Government has a royalty-free license to exercise all rights for Governmental purposes. All other rights are reserved by the copyright owner. 1 American Institute of Aeronautics and Astronautics 2nd AIAA Flow Control Conference 28 June 1 July 2004, Portland, Oregon AIAA 2004-2131 Copyright © 2004 by the American Institute of Aeronautics and Astronautics, Inc. Under the copyright claimed herein, the U.S. Government has a royalty-free license to exercise all rights for Governmental purposes. All other rights are reserved by the copy-right owner. device firing into a supersonic crossflow and penetrating the boundary layer in single-pulse operation. Future work will focus on (1) further analysis of the SparkJet operating cycle, (2) characterization of multiple-pulse operation and scaling laws, and (3) final actuator design and experimental demonstration of supersonic flow penetration.