Laser-based investigations in gas turbine model combustors

Abstract

Dynamic processes in gas turbine (GT) combustors play a key role in flame stabilization and extinction, combustion instabilities and pollutant formation, and present a challenge for experimental as well as numerical investigations. These phenomena were investigated in two gas turbine model combustors for premixed and partially premixed CH 4 /air swirl flames at atmospheric pressure. Optical access through large quartz windows enabled the application of laser Raman scattering, planar laser-induced fluorescence (PLIF) of OH, particle image velocimetry (PIV) at repetition rates up to 10 kHz and the simultaneous application of OH PLIF and PIV at a repetition rate of 5 kHz. Effects of unmixedness and reaction progress in lean premixed GT flames were revealed and quantified by Raman scattering. In a thermoacoustically unstable flame, the cyclic variation in mixture fraction and its role for the feedback mechanism of the instability are addressed. In a partially premixed, oscillating swirl flame, the cyclic variations of the heat release and the flow field were characterized by chemiluminescence imaging and PIV, respectively. Using phase-correlated Raman scattering measurements, significant phase-dependent variations of the mixture fraction and fuel distributions were revealed. The flame structures and the shape of the reaction zones were visualized by planar imaging of OH distribution. The simultaneous OH PLIF/PIV high-speed measurements revealed the time history of the flow field-flame interaction and demonstrated the development of a local flame extinction event. Further, the influence of a precessing vortex core on the flame topology and its dynamics is discussed.

5 kHz thermometry in a swirl-stabilized gas turbine model combustor using chirped probe pulse femtosecond CARS. Part 1: Temporally resolved swirl-flame thermometry

“…11 , plots J, K, and L, were also seen in the flow-field and OH gradient results presented by Meier et al . [44] . For this operating condition in the post flame region, heights 40 mm and above shown in Fig.…”

“…11 . Previously, simultaneous OH PLIF and PIV measurements were performed at 5 kHz by Meier et al in this flame [44] . The reference contains figures and a discussion of the flow field and phase-correlated flame structure as determined by experiment.…”

“…11 , plots A, B, C, and F, the effects of the thermoacoustic pulsations are clearly evident. A strong longitudinal thermo-acoustic pulsation is known to occur at a frequency of 308 Hz for this flame [34,44] . Spectra from Flame B did not exhibit interference from scattered pump beam, as illustrated by the low theoretical fit error values for temperature measurements at ( x = 0 mm, y = 60 mm) shown in Fig.…”

“…The DLR GTMC used in this work has been the subject of numerous previous studies in which the geometry is described in detail [34,[40][41][42][43][44] , only a brief overview is provided here. A schematic diagram of the burner is shown in Fig.…”

Simultaneous 5 kHz OH-PLIF/PIV for the study of turbulent combustion at engine conditions

“…Simultaneous integration of these systems has supported concurrent scalar and velocity field measurements at kHz interrogation frequencies in laboratory-scale flames. These efforts have yielded a greater understanding of dynamic turbulent flame behavior through tracking the temporal evolution of transient phenomena such as local extinction, auto-ignition, and turbulence-chemistry interactions [13][14][15][16][17][18][19][20].…”