An Experimental Study of Flame Response in a Technically-premixed Multi-nozzle Gas Turbine Combustor

Open Access
Author:
Borsuk, Alex James
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 25, 2014
Committee Members:
  • Domenic Adam Santavicca, Thesis Advisor
Keywords:
  • combustion
  • dynamics
  • instability
  • gas
  • turbine
Abstract:
The response of flames to velocity perturbations is studied experimentally in a multi-nozzle lean-premixed (LPM) gas turbine combustor experiment, representative of a realistic gas turbine combustor. Under fully-premixed fueling conditions, the system is subject to velocity perturbations only, while under technically-premixed conditions, both velocity and equivalence ratio fluctuations are present. The flame transfer function is used to quantify the response of CH* chemiluminescence intensity fluctuations to velocity perturbations. Literature is cited that shows chemiluminescence emissions indicate heat release rate in fully-premixed, but not technically premixed flames. Under technically-premixed conditions, chemiluminescence measurements are used as inputs to a model to predict the flame transfer function. Results indicate that the fueling strategy, whether fully-premixed (FPM) or technically-premixed (TPM), has a significant effect on flame response. It is shown that the presence of equivalence ratio fluctuations in technically-premixed flames can act to increase or decrease the flame transfer function gain, compared to the fully-premixed case, depending on operating condition and forcing frequency. This behavior is attributed to the interaction of flame response mechanisms. The effect of forcing amplitude on fully- and technically-premixed flame response was also studied. Nonlinear behavior and saturation of the heat release rate was observed at several forcing frequencies as amplitude was increased. Explanations were developed for the observed TPM flame response behavior, based on the interaction of flame response mechanisms due to fluctuations of velocity and equivalence ratio.