Effects of acoustic oscillations on flame dynamics of homogeneous propellants in rocket motors

1995 ◽  
Vol 11 (4) ◽  
pp. 640-650 ◽  
Author(s):  
Tae-Seong Roh ◽  
I-Shih Tseng ◽  
Vigor Yang
Keyword(s):  
Acoustic Oscillations ◽  
Rocket Motors ◽  
Flame Dynamics

Nonlinear Flame Transfer Function Characteristics in a Swirl-Stabilized Combustor

2006 ◽  
Vol 129 (4) ◽  
pp. 954-961 ◽  
Author(s):  
Benjamin D. Bellows ◽  
Mohan K. Bobba ◽  
Jerry M. Seitzman ◽  
Tim Lieuwen
Keyword(s):  
Nonlinear Response ◽  
Amplitude Dependence ◽  
Acoustic Excitation ◽  
Acoustic Oscillations ◽  
Flame Dynamics ◽  
Large Velocity ◽  
Planar Laser ◽  
Flame Response ◽  
Test Points ◽  
Unsteady Flame

An understanding of the amplitude dependence of the flame response to acoustic excitation is required in order to predict and/or correlate combustion instability amplitudes. This paper describes an experimental investigation of the nonlinear response of a lean, premixed flame to imposed acoustic oscillations. Detailed measurements of the amplitude dependence of the flame response were obtained at approximately 100 test points, corresponding to different flow rates and forcing frequencies. It is observed that the nonlinear flame response can exhibit a variety of behaviors, both in the shape of the response curve and the forcing amplitude at which nonlinearity is first observed. The phase between the flow oscillation and heat release is also seen to have substantial amplitude dependence. The nonlinear flame dynamics appear to be governed by different mechanisms in different frequency and flowrate regimes. These mechanisms were investigated using phase-locked, two- dimensional OH Planar laser-induced fluorescence imaging. From these images, two mechanisms, vortex rollup and unsteady flame liftoff, are identified as important in the saturation of the flame’s response to large velocity oscillations. Both mechanisms appear to reduce the flame’s area and thus its response at these high levels of driving.

scholarly journals Flame Edge Dynamics and Interaction in a Multi-Nozzle Can Combustor With Fuel Staging

2019 ◽  
Author(s):  
Daniel Doleiden ◽  
Wyatt Culler ◽  
Ankit Tyagi ◽  
Stephen Peluso ◽  
Jacqueline O’Connor
Keyword(s):  
Vortex Shedding ◽  
High Speed ◽  
Pollutant Emissions ◽  
Destructive Interference ◽  
Combustion Instabilities ◽  
Acoustic Oscillations ◽  
Oscillation Phase ◽  
Phase Cancellation ◽  
Flame Dynamics ◽  
Fuel Staging

Abstract The characterization and mitigation of thermoacoustic combustion instabilities in gas turbine engines is necessary to reduce pollutant emissions, premature wear, and component failure associated with unstable flames. Fuel staging, a technique in which the fuel flow to a multi-nozzle combustor is unevenly distributed between the nozzles, has been shown to mitigate the intensity of self-excited combustion instabilities in multiple nozzle combustors. In our previous work, we hypothesized that staging suppresses instability through a phase-cancellation effect in which the heat release rate from the staged nozzle oscillates out of phase with that of the other nozzles, leading to destructive interference that suppresses the instability. This previous theory, however, was based on chemiluminescence imaging, which is a line-of-sight integrated technique. In this work, we use high-speed laser-induced fluorescence to further investigate instability suppression in two staging configurations: center-nozzle and outer-nozzle staging. An edge-tracking algorithm is used to compute local flame edge displacement as a function of time, allowing instability-driven edge oscillation phase coherence and other instantaneous flame dynamics to be spectrally and spatially resolved. Analysis of flame edge oscillations shows the presence of convecting coherent fluctuations of the flame edge caused by periodic vortex shedding. When the system is unstable, these two flame edges oscillate together as a result of high-intensity longitudinal-mode acoustic oscillations in the combustor that drive periodic vortex shedding at each of the nozzle exits. In the stable cases, however, the phase between the oscillations of the center and outer flame edges is greater than 90 degrees (∼114 degrees), suggesting that the phase-cancellation hypothesis may be valid. This analysis allows a better understanding of the instantaneous flame dynamics behind flame edge oscillation phase offset and fuel staging-based instability suppression.

Nonlinear Flame Transfer Function Characteristics in a Swirl-Stabilized Combustor

2006 ◽  
Author(s):  
Benjamin D. Bellows ◽  
Mohan K. Bobba ◽  
Jerry M. Seitzman ◽  
Tim Lieuwen
Keyword(s):  
Nonlinear Response ◽  
Amplitude Dependence ◽  
Acoustic Excitation ◽  
Acoustic Oscillations ◽  
Flow Oscillation ◽  
Flame Dynamics ◽  
Large Velocity ◽  
Flame Response ◽  
Test Points ◽  
Unsteady Flame

An understanding of the amplitude dependence of the flame response to acoustic excitation is required in order to predict and/or correlate combustion instability amplitudes. This paper describes an experimental investigation of the nonlinear response of a lean, premixed flame to imposed acoustic oscillations. Detailed measurements of the amplitude dependence of the flame response were obtained at approximately 100 test points, corresponding to different flow rates and forcing frequencies. It is observed that the nonlinear flame response can exhibit a variety of behaviors, both in the shape of the response curve and the forcing amplitude at which nonlinearity is first observed. The phase between the flow oscillation and heat release is also seen to have substantial amplitude dependence. The nonlinear flame dynamics appear to be governed by different mechanisms in different frequency and flowrate regimes. These mechanisms were investigated using phase-locked, two-dimensional OH PLIF imaging. From these images, two mechanisms, vortex rollup and unsteady flame liftoff, are identified as important in the saturation of the flame’s response to large velocity oscillations. Both mechanisms appear to reduce the flame’s area and thus its response at these high levels of driving.

scholarly journals Flame Edge Dynamics and Interaction in a Multinozzle Can Combustor With Fuel Staging

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Daniel Doleiden ◽  
Wyatt Culler ◽  
Ankit Tyagi ◽  
Stephen Peluso ◽  
Jacqueline O'Connor
Keyword(s):  
Vortex Shedding ◽  
High Speed ◽  
Pollutant Emissions ◽  
Destructive Interference ◽  
Combustion Instabilities ◽  
Acoustic Oscillations ◽  
Previous Theory ◽  
Oscillation Phase ◽  
Flame Dynamics ◽  
Fuel Staging

The characterization and mitigation of thermoacoustic combustion instabilities in gas turbine engines are necessary to reduce pollutant emissions, premature wear, and component failure associated with unstable flames. Fuel staging, a technique in which the fuel flow to a multinozzle combustor is unevenly distributed between the nozzles, has been shown to mitigate the intensity of self-excited combustion instabilities in multiple nozzle combustors. In our previous work, we hypothesized that staging suppresses instability through a phase-cancelation effect in which the heat release rate from the staged nozzle oscillates out of phase with that of the other nozzles, leading to destructive interference that suppresses the instability. This previous theory, however, was based on chemiluminescence imaging, which is a line-of-sight integrated technique. In this work, we use high-speed laser-induced fluorescence to further investigate instability suppression in two staging configurations: center-nozzle and outer-nozzle staging. An edge-tracking algorithm is used to compute local flame edge displacement as a function of time, allowing instability-driven edge oscillation phase coherence and other instantaneous flame dynamics to be spectrally and spatially resolved. Analysis of flame edge oscillations shows the presence of convecting coherent fluctuations of the flame edge caused by periodic vortex shedding. When the system is unstable, these two flame edges oscillate together as a result of high-intensity longitudinal-mode acoustic oscillations in the combustor that drive periodic vortex shedding at each of the nozzle exits. In the stable cases, however, the phase between the oscillations of the center and outer flame edges is greater than 90 deg (∼114 deg), suggesting that the phase-cancelation hypothesis may be valid. This analysis allows a better understanding of the instantaneous flame dynamics behind flame edge oscillation phase offset and fuel staging-based instability suppression.

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