ACOUSTIC CHARACTERIZATION OF A MODEL GAS TURBINE COMBUSTOR

Open Access
Author:
Lee, Jackson B
Area of Honors:
Interdisciplinary in Engineering Science and Mechanical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Jacqueline Antonia O'Connor, Thesis Supervisor
  • Lucas Jay Passmore, Honors Advisor
  • Alexander S Rattner, Faculty Reader
  • Jacqueline Antonia O'Connor, Honors Advisor
  • Judith Todd Copley, Faculty Reader
Keywords:
  • Comsol
  • Acoustic Instabillities
  • Acoustic Modes
  • Gas-Turbine Combustor
  • Eigenmode
  • Eigenfrequency
  • Combustion Instability
  • Fourier Transform
Abstract:
Regulations in the aerospace and power generation industries continue to place increasingly stringent limitations on the amount of pollutants a gas turbine combustion system can emit. This is often achieved by lean fuel-air mixture systems that operate at much lower flame temperatures. Lower flame temperatures push these systems to the limit of instabilities that destroy hardware and decrease the lifetime of these systems. These instabilities are the result of a feedback cycle between acoustic pressure oscillations, perturbations in the flow and mixture of reactants, and consequent oscillations in heat release. Although each component of this feedback loop has been studied, acoustic pressure oscillations are highly dependent on the geometry of each combustor configuration. This inherent challenge is further driven by the fact that these studies must often be conducted experimentally after all components of the system have been assembled. Developing techniques capable of evaluating acoustic characteristics of a system early in the design of the system will help lower cost of development while improving detection and prevention of instabilities. This study assesses inherent acoustic characteristics of a model gas turbine combustion system experimentally and through simulation. Resonant frequencies of the physical system are presented and impedances of boundary conditions at the nozzle exit are calculated. These boundary conditions serve as necessary inputs to numerical modeling methods that replicate experimental studies conducted prior. Comparison between experimental results and modeling results show that modeling techniques can be effective in analyzing a system at preliminary stages of the design process.