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Technologies for the Suppression of Combustion Instability or Screech
Navy SBIR 2013.1 - Topic N131-002 NAVAIR - Ms. Donna Moore - [email protected] Opens: December 17, 2012 - Closes: January 16, 2013 N131-002 TITLE: Technologies for the Suppression of Combustion Instability or Screech TECHNOLOGY AREAS: Air Platform ACQUISITION PROGRAM: JSF-Prop RESTRICTION ON PERFORMANCE BY FOREIGN CITIZENS (i.e., those holding non-U.S. Passports): This topic is "ITAR Restricted". The information and materials provided pursuant to or resulting from this topic are restricted under the International Traffic in Arms Regulations (ITAR), 22 CFR Parts 120 - 130, which control the export of defense-related material and services, including the export of sensitive technical data. Foreign Citizens may perform work under an award resulting from this topic only if they hold the "Permanent Resident Card", or are designated as "Protected Individuals" as defined by 8 U.S.C. 1324b(a)(3). If a proposal for this topic contains participation by a foreign citizen who is not in one of the above two categories, the proposal will be rejected. OBJECTIVE: Develop innovative technologies for the suppression of combustion instabilities (screech) for thrust augmentors in high-performance gas turbine engines. DESCRIPTION: Combustion instability, or screech, occurs in many combustion systems. Combustion instability is due to the complex physical coupling of the acoustic resonances in the combustion chamber with fluctuations in the heat release of the combustion process. In modern gas turbine afterburners, instability or screech modes typically occur in the range of frequencies from hundreds to thousands of hertz. Coupling can produce large pressure fluctuations that can be severe enough to damage engine hardware. Three stream engines and the integration of the augmentor, exhaust ducts, and nozzle for next generation gas turbines will increase the desired range of operability for the augmentor and further challenge the ability to manage instabilities. Historically, screech has been mitigated by two very different approaches; adding damping and altering the coupling or driving. In the case of damping, liners and resonators have been fashioned to absorb acoustic energy. By their nature, acoustic or screech liners are most effective on modes with frequencies greater than 1 kHz. These liners are a cost effective way to reduce instabilities above 1 kHz and improve durability. Resonators are can be tuned to suppress much lower frequency modes, less than 1 kHz. To absorb acoustic energy at these frequencies, the resonators are physically large, introducing a weight impact. Resonators provide excellent suppression of combustion instability in ground-based gas turbine systems, where weight is not a significant factor. In aero systems, current resonator technology has a significant system weight penalty. Integration of screech liners or resonators with multi-stream engines also presents significant integration challenges for future systems. Altering the coupling or driving for screech involves changing the aerodynamics or at least the fuel delivery to change the spatial or temporal characteristics of the heat release. This is often accomplished empirically since reliable analytical tools do not exist for this complex process. If such changes are needed late in the engine development program, this can be very costly to implement and difficult to retrofit. Another method of altering the heat release is to implement an active control system which will modulate the fuel or air sources depending on the operating condition and instability presence to alter the heat release. One of the main active control approaches is high bandwidth active control using the fuel, whereby fuel is modulated at the frequency of the instability using an actuator valve. The phase of the modulation is varied actively until sufficient heat release is out of phase with the instability which results in suppression of the instability. Active control methods have demonstrated excellent control of combustion instability in ground-based gas turbine systems, where weight and actuator power consumption are not significant factors. Development of actuators with sufficient driving capability is still an open research area. Combustion in the augmentor is governed by many unsteady physical processes. Desired are new screech suppression technologies that target the physical processes in the afterburner. New technologies may not be limited to just damping or active control. These new technologies should be developed such that they could easily be implemented in current gas turbine augmentors with little weight or cost consequence. New technologies should also address exhaust integration issues for next generation systems. Close collaboration with an original equipment manufacturer (OEM) of high-performance afterburners is highly recommended to ensure successful transition of technology concepts at the end of Phase II and in Phase III. PHASE I: Identify an innovative concept for suppression of combustion instabilities. Develop and demonstrate the feasibility of the concept in a laboratory environment. Identify the experimental methodology to evaluate the influence of the technology on the magnitude and bandwidth of the instabilities observed in modern augmentors and address the feasibility for full-scale implementation. PHASE II: Further develop the proposed concept and conduct extensive experimental evaluation of the technologies identified in Phase I. Assess the ability of the candidate technology to reduce the magnitude and bandwidth of screech instabilities that occur in modern augmentors. Perform a prototype demonstration of the suppression concept to TRL of 4. PHASE III: Demonstrate a fully functional screech suppression system on a relevant rig/engine platform if available or if the opportunity exists through TRL 5 or beyond. Address the primary risks for transitioning the approach to appropriate platforms. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The technology has the true potential for dual-use applications by suppressing combustion instabilities in both military and civil gas turbine engines because the methodology should be applicable to mainburner combustion instabilities. In a Military environment, light-weight, and low-cost technologies can be transitioned to military gas turbine OEMs for incorporation into existing and future augmentor design systems. REFERENCES: 2. Yu, K.H., & Wilson, K.J. (2002). Scale-Up Experiments on Liquid-Fueled Active Combustion Control. Journal of Propulsion & Power, Vol. 18 (1), pp. 53-60 3. Yu, K.H., Parr, T.P., Wilson, K.J., Schadow, K.C., & Gutmark, E.J. (1996). Active Control of Liquid-Fueled Combustion Using Periodic Vortex-Droplet Interaction. Twenty-Sixth Symposium (International) on Combustion/Proceedings of the Combustion Institute, Vol. 26 (2), pp. 2843-2850. KEYWORDS: Combustion instability, screech, active combustion control, active flow control, active instability suppression, augmentor instability
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