Chemical Impulse Actuation for Aerodynamic Flow Control
Abstract
Recent advances in active flow control (AFC) demonstrated remarkable enhancements in the aerodynamic performance of flight platforms in a broad range of external and internal applications by mitigation of separation and regulation of the aerodynamic loads. Much of this work has been based on momentum-based fluidic actuation engendered by steady or time-dependent surface air jets. However, despite their demonstrable control effectiveness, platform integration of momentum-based AFC systems has been hampered by the need for high air flow rates and actuation power as well as the weight, volume, manufacturing complexity, and cost of the AFC hardware.Earlier flow control investigations revealed that, in addition to steady and unsteady jet actuation, shear flows over external and internal aerodynamic surfaces are also susceptible to transitory, impulsive actuation effected on time scales that are significantly shorter than the convective time scale. This AFC actuation is effected by brief, anharmonic high-impulse actuation and exploits the disparity between the onset and relaxation time scales of the embedding flow response. Since impulsive actuation is not easily realizable by conventional hardware, several investigations have demonstrated the AFC utility of chemically-based actuation by exploiting stored chemical energy to produce controllable high-impulse jets using combustion of gaseous fuel and air within a small-scale chamber which does not rely on actuation power from other flight systems. While combustion-powered actuation was successfully demonstrated for mitigation of flow separation over static and moving aerodynamic surfaces and yielded substantial reductions in air flow and hardware weight and volume compared to conventional AFC actuation, it still requires a separate air source and associated plumbing. However, the inherent advantages of chemical actuation for forming high-impulse control jets can be greatly extended by using solid or gel propellants whose energy densities are about three orders of magnitude higher than gaseous reactants and therefore obviate the need for the supply infrastructure of the gaseous constituents. Chemical actuation using these reactive compounds is the subject of the proposed collaborative 4-year research program between Georgia Tech and Virginia Tech that will focus on the development of novel variants of chemically-based impulsive AFC actuation using advanced solid or gel propellants. In the proposed approach, high-impulse actuation jets will be formed by ignition of flowable propellant mixtures in refillable, individually addressable reaction chambers. The use of flowable propellant actuators can lead to radical simplification of AFC systems that will facilitate their integration on a range of flight platforms. In the proposed program, Virginia Tech will focus on the development of propellant chemistry, reaction initiation, and scaling for multiple cycles of robust, safe operation. Georgia Tech will focus on the flow physics of impulse actuation jet arrays and their interactions with the cross flow over flat and curved surfaces in a small-scale wind tunnel (upto M = 0.7) with specific emphasis on the dynamic characteristics of separation reattachment during repetitive actuation. Georgia Tech and VPI will collaborate closely and iteratively on tuning and optimizing the performance of the actuator arrays. The proposedeffort will culminate in a larger scale wind tunnel test to demonstrate the efficacy of chemical impulse actuation for controlling the aerodynamic performance of a flight platform model to be determined in consultation with ONR. It is anticipated that the proposed program will help the development of new Navy and DoD aerodynamic platforms that are enabled by advanced integrated AFC systems that fit within the platform#s power, volume, and weight constraints. Approved for Public Release.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 15, 2023
- Source ID
- N000142312430
Entities
People
- Ari Glezer
Organizations
- Georgia Tech Research Corporation
- Office of Naval Research
- United States Navy