Simultaneous Flame, Spray, and Flow Imaging in a High Pressure Swirl Combustor

H.  Ek; I.  Chterev; N.  Rock; H. Ozogul; B. Emerson; T. Lieuwen; N. Jiang; S. Roy; J. Gord

This paper presents measurements of the simultaneous flame position and flow velocity in a high pressure, liquid fueled combustor. Liquid fuels injected in swirling flows are commonly used in gas turbines, but data collection and analysis pose a challenge in the two-phase, reacting flow field, particularly when operating at high pressure. Measurements in a liquid fueled, swirl combustor were performed using simultaneous, high speed stereo-PIV, OH-PLIF and fuel-PLIF. The OH and fuel fluorescence were separated, and regions of liquid fuel, OH and liquid fuel+OH were identified during data reduction. The measurements were taken at elevated pressures to visualize the gaseous and liquid flow field, heat release region and fuel spray distribution. This paper extends work in a prior paper by analyzing the sensitivity of the physical locations of these regimes to the processing approach. Introduction Increased knowledge of the highly dynamic, reacting flow fields encountered in gas turbine combus-tors is important to the understanding of operational limits and emissions, and how improvements in one area affect the other. High speed (kHz), spatially resolved imaging techniques, such as particle image ve-locimetry (PIV) and planar laser-induced fluorescence (PLIF), contribute to the understanding of the dynamic combustion environment. The morphology of unsteady , three dimensional swirling flows is better understood thanks to high speed PIV measurements [1], [2], while high speed PLIF measurements, primarily using OH, have enabled understanding of the flame location [3-6]. This paper extends work on this topic described in Chterev et al. [12], and the rest of this section and the following summarize several key points described there. There are a number of challenges associated with simultaneous OH-PLIF and fuel-PLIF measurements in high pressure, liquid-fueled, swirling com-bustors. OH-PLIF measurements suffer from [7-10]: (1) reduction of fluorescence yield due to increased collisional quenching (mitigated somewhat by increase in number density); (2) collisional broadening and overlap of the excitation lines; (3) fluorescence trapping due to increased optical density at high pressures ; (4) laser energy absorption by liquid fuel and higher elevated gas concentrations; (5) interference from liquid fuel and unburnt hydrocarbon fluores-cence resulting from fuel decomposition [11]. Our prior study [12] obtained simultaneous high speed ste-reoscopic PIV (sPIV), OH-PLIF and fuel-PLIF measurements in a high pressure, liquid-fueled, swirling combustor. One of the challenges addressed was the difficulty of distinguishing fuel containing regions from OH containing regions using fluorescence measurements when burning complex fuels. A specialized detection method, utilizing both temporal and spectral filtering techniques, was demonstrated. In addition, a post-processing scheme using intensity histograms was developed to provide final separation of the signals. The objective of this paper is to further consider the sensitivity of the results to the thresholds used in the separation technique.

Simultaneous Flame, Spray, and Flow Imaging in a High Pressure Swirl Combustor

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