Trupti Kathrotia

An Experimental and Modeling Study of Laminar Flame Speeds of Alternative Aviation Fuels

The present work reports on measurements of burning velocities of synthetic fuel air mixtures exploiting the cone-angle method, as part of the EU project ALFA-BIRD. The GtL (Gas-to-Liquid)-air mixtures — (i) 100% GtL and (ii) GtL+20% hexanol, respectively — were studied at atmospheric pressure, with values of the equivalence ratio φ ranging between φ ∼ 1.0 and φ ∼ 1.3, at preheat temperatures To = 423 K (GtL+20% hexanol) as well as To = 473 K (for 100% GtL and GtL+20% hexanol). A comparison between experimentally obtained burning velocities and predicted values of laminar flame speed is presented, too. In general, good agreement was found between predicted and measured data for the range of conditions considered in the present study. The predictive capability of the detailed reaction model consisting of 3479 reactions involving 490 species will be discussed focusing on the laminar flame speed and the combustion of the components (n-decane, iso-octane, and 1-hexanol) of the surrogate used.Copyright

Investigation of differences in lean blowout of liquid single-component fuels in a gas turbine model combustor

An atmospheric, single-jet combustor with rectangular confinement was previously developed based on the FLOX concept. In this study, premixed, preheated H2-air and CH4-air turbulent jet flames were stabilized in this combustor. Self-sustained jet oscillation was observed in both non-reacting and reacting cases. A 3-D and periodic jet flapping is identified via proper orthogonal decomposition (POD) of various 2-D views of the flow field, measured by particle imaging velocimetry (PIV). The frequency of the oscillations and couplings between different Eigenmodes are determined based on results from PIV at 5 kHz repetition rate. The influence of jet flapping on combustion stability is examined in detail using simultaneous PIV/OH chemiluminescence imaging and PIV/planar laserinduced fluorescence of OH radicals (OH PLIF) at 5 kHz repetition rate. The up/down and expand/contract motions of the lateral recirculation zone (LRZ) due to jet flapping is found to modify the flame shape and flame lift-off height. Such variations are traced to the transformation of low-speed regions in the junction of the back flow and the jet. These regions contain counter flows and vortices with relatively long flow residence time and can therefore enhance the mixing between recirculated hot burned gas and fresh fuel-air mixtures. In some cases, the jet flapping is also found to cause temporary local extinction of the flame, due to reduced entrainment of burned gas. However, the flame is able to recover as the jet flaps away from combustor chamber and reopens the back flow channel.