Modeling, control, and optimization of fuel/air mixing in a lean premixed swirl combustors using fuel staging to reduce pressure pulsations and NOx emissions
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Beschreibung
This work deals with the fuel/air mixing process in a lean premixed gas turbine combustor and how it can be modeled, controlled and optimized to reduce pressure pulsations and \nox~emissions. The methodology used to derive models is primarily based on cold flow measurements conducted in a water test rig. The standard fuel injection of the swirl-inducing burner is completed with two additional fuel injection stages. Through adjustment of the fuel distribution, stabilization of the combustion chamber can be achieved, with \nox~emissions comparable to the ones produced by standard fuel injection. Measurements of the mean turbulent and coherent flow fields as well as passive scalar mixing properties confirm the similarity of water test rig and combustion chamber. Furthermore, velocity and chemiluminescence measurements with combustion show that the flame has a weak influence on the mean and coherent flow properties just upstream of its stabilization location when it is not anchored inside the burner, validating the cold flow modeling approach. The fuel/air mixing quality at the burner outlet is measured in the water test rig for numerous operating conditions at different axial locations and the flame position recorded in the combustion chamber is used to predict the real mixing quality at the flame. The information gained is then implemented using an experimental fit to more accurately predict the \nox~emissions of the burner over a wide operating range. A method is then developed to record and model the temporal response of the burner to fuel/air fluctuations. The so-called measured mixing transfer function confirms that variation of the fuel distribution in the burner strongly influences the convective time delays and partly explains the stabilizing effect of switching the fuel distribution. Using the recorded flame shape recorded by a camera, an estimation of the response of the flame to fuel/air fluctuations is obtained. Comparison with the directly measured flame transfer function shows that a satisfying estimation of the response of the flame to fuel/air fluctuations can be obtained with the new method. An extremum seeking controller (ESC) is implemented on the fuel distribution for the purpose of reduced pressure pulsations and \nox~emissions. The chemiluminescence signal is used as a surrogate of the \nox~emissions to increase the controller speed. The ESC is then able to track the best injection configuration when the operating conditions are varied as well as avoid local minimum when the cold flow model is taken into account. Passive and active fuel injection methods are then tested to improve the mixing quality at the burner outlet. The investigations show that high frequency fuel injection pulsations can improve the mixing quality recorded at the burner outlet. A fluidic injector array is then developed and implemented at the inlet of the burner. For this configuration, the mixing quality is only weakly influenced by the fluidic injector. However, tested in a generic configuration, these fluidic actuators improved the mixing quality by up to 50\% over a wide range of operating conditions, confirming thus the effectivity of such devices.
Autor*in
Arnaud Lacarelle
Themen in »Modeling, control, and optimization of fuel/air mixing in a lean premixed swirl combustors using fuel staging to reduce pressure pulsations and NOx emissions«
Drallbrenner[DNB] Emissionen Gasturbine[DNB] Gemischbildung[DNB] Mageres Gemisch Mischung Prozessmodell[DNB] Prozessoptimierung[DNB] Stickstoffoxidemission[DNB] Strömungskontrolle Thermoakustik Turbulente Verbrennung[DNB] Verbrennung Verbrennungsgeräusch[DNB]