You are invited to hear
William A. Sirignano
Henry Samueli Endowed Chair in Engineering
Professor of Mechanical and Aerospace Engineering
University of California, Irvine
"Liquid-Propellant Rocket Combustion Instability: A Physics-based Multi-fidelity Approach"
11 a.m., Monday, June 11
About the talk:
Three physical models of liquid-propellant rocket engines are applied for the nonlinear acoustical oscillations that couple with the combustion process, injector-port flow, and choked-nozzle flow. Two of the models also consider coupling of the vortex dynamics with the combustion and acoustics. The work addresses both spontaneous and triggered instabilities. The partial differential equations are solved by various means in different cases: RANS for flame zones and Eulerian wave propagation are used in the simplest model; hybrid LES with RANS for wall boundary layers is used elsewhere; and a two-time-variable perturbation expansion is also used. The use of a flamelet model to replace chemical-kinetic analysis allows a huge savings in computational cost especially when coupled with the hybrid LES-RANS method. A stochastic analysis yields the probability for triggering of an instability to occur. The new destabilizing mechanism of engine acceleration or vibration is discovered. It is found that the same mechanisms that can trigger the growth of an instability may be used in a designed fashion to arrest the growth of an instability. The importance of the vortex dynamics resulting from propellant injection and its coupling with the nonlinear acoustics is clearly seen.
The work was collaborative with Dr. Pavel Popov, Dr. Tuan Nguyen, Dr. Juntao Xiong, Jeremy Krieg, Hugh Morgan, Professor Feng Liu, and Professor Athanasios Sideris.
Dr. Mitat Birkan of AFOSR is thanked for the sponsorship.
About the speaker:
Dr. Sirignano is interested in combustion theory and computational methods, fluid dynamics, multiphase flows, and propulsion and power. He holds a Bachelor's degree in Aeronautial Engineering from Rensselar Polytechnic Institute and a M.A. and Ph.D from Princeton University.
His current research activities address the problems of the vaporization and burning of liquid fuels in very small volumes, turbulence-droplet interactions, distortion and breakup of thin liquid streams, flame spread across liquid fuel pools, and a study of combustion in high speed flows. The applications of the research include miniaturization of combustors, spray technologies, fire safety, and a new high-performance technology for combustion in the turbine stages of a gas-turbine engine.
Dr. Sirignano leads the Combustion, Fluid Dynamics and Propulsion Group and is the director of the Spray and Droplet Science and Technology Center at UCI.