Active Flow Control in an Inlet Offset Diffuser for Tactical Aircraft
Abstract
Advanced sea-based tactical aircraft require well-integrated aerodynamic and propulsion systems for aerodynamic performance, survivability, and small spot factor. Such a design requires an aggressively offset inlet diffuser with a relatively short length. Without any aerodynamic treatment, such an inlet would suffer from flow separation and robust secondary vortices generating strongdynamic distortion at the aerodynamic interface plane (AIP). Dynamic distortion significantly degrades the propulsion performance and adversely affects the compressor stability and high-cycle fatigue life expectancy. To mitigate these problems, significant research and development efforts have gone into exploring the use of various flow control techniques over the past 15 years. Passivemeans (e.g. micro vanes), active means (e.g. micro-jets), and hybrid methods have been explored. Such control devices are typically designed and optimized for cruise conditions; however, they must also perform well in off-design conditions: at different flight Mach number or at angle of attack during maneuvers or wind gust. Therefore, the desired control technique must be robust, effectiveunder both design and off-design conditions, and economical in the use of onboard resources. We are proposing an alternative active control approach, which uses plasma actuators to target flow instabilities. The power consumption is very small as proposed technique is based on excitation of flow instabilities and the actuators provide only small amplitude perturbations at desired frequenciesand modes. This also results in a small heat signature which completely dissipates within the diffuser. Additionally, the excitation frequency and spatial modes can be changed electronically (i.e. rapidly) to make it effective in both design and off-design conditions. We propose to use a class of plasma actuators called Localized Arc Filament Plasma Actuators (LAFPAs) that we have developed and successfully used to control high-speed and high Reynolds number jets and cavity flows in otheraerospace applications. We already have the infrastructure and facility, but a modular offset diffuser model will be designed and used in the proposed project. The model to be used is an advanced design recommended by NAVAIR with a diameter at the AIP of 12.7 cm and a variable inlet throat Mach number (Mt) up to 0.8. The diagnostics will include surface pressure and stagnation pressure map at AIP, surface oil flow visualization, and detailed PIV measurements.The objective of the proposed research is three-fold. First, to design and build a modular model of an advanced inlet with offset diffuser and variable Mach number at the inlet throat of up to 0.8 and distribute the actuators on the azimuthal segment of the cross-section where flow separates and the secondary vortices originate. The design will also include accommodation for pitch and yaw, though these variables will not be explored in this phase of the proposed research. Second, to explore the effects of the excitation frequency and spatial mode with detailed surface and flow diagnostics to better understand the flow physics and the effect of control on the separation, pressure recovery, and dynamic distortion. Based on our previous work with LAFPAs in high-speed flows, both excitation frequency and spatial modes, especially their combination will play a significant role in controlling the global characteristics of the flow. Third, to use the information obtained to optimize the actuators??? frequency and spatial mode for the best performance.The focus of the proposed work is on aggressively offset diffuser flows, understanding their physics and controlling their performance. Therefore, it has direct relevance to sea-based advanced tactical aircraft and to the Navy. The PI has extensive working relation with the NAVAIR researchers and will conduct the research in close consultation with them and ONR to maximize the relevancy of thework.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 10, 2018
- Source ID
- N000141812389
Entities
People
- Mohammad Samimy
Organizations
- Office of Naval Research
- Ohio State University
- United States Navy