Experimental Study on Stabilization of Lifted Swirl Flames in a Model GT Combustor

Abstract

This study reports on experimental investigations on isothermal and reacting swirled nonpremixed flows under varying pressure conditions. In this configuration, a central high speed fuel jet was surrounded by a heated swirling air flow. For the reacting case natural gas served as fuel whereas for isothermal conditions fuel was replaced by a mixture of helium and air to achieve Reynoldssimilarity. The optically accessible combustor allowed for application of laser diagnostics. Here we report on Laser Doppler Anemometry and planar laser-induced fluorescence (PLIF) experiments used to characterize the flow field and visualize selected scalars, respectively. Acetone served as a fluorescence marker for mixture fraction investigations. The hydroxyl radical was used to provide general features of the reaction zone such as flame shape and mean stabilization. To expose the influence of pressure on the flame structure three different operating points were investigated varying the combustor pressure between 2 and 6 bar while the inflow bulk velocities remained the same. Striking features of the present configuration are a detached flame, multiple recirculation zones, and complex coherent flow structures.

Study of Flow and Mixing in a Generic GT Combustor Using LES

“…This configuration, which features a single real industrial fuel injector nozzle operated at near-realistic aero-engine conditions, is investigated in house by means of advanced laser-based measuring techniques. These measurements already reported in Janus et al [13,14] have revealed the presence of a PVC for both isothermal and reacting conditions in this model combustor. Measurements by Midgley et al [22] on the same swirler nozzle in a water rig have also shown the existence of a PVC and will also be used as a reference for the present study.…”

“…The generic combustor considered resembles a segment of a gas turbine combustion chamber which has been studied in house by Janus et al [13,14] by means of laser Doppler velocimetry (LDV) velocity measurements and tracer-and OH-planar induced fluorescence (PLIF) for isothermal and reacting conditions, respectively. The nozzle is based on a generic design by TURBOMECA and consists of a central round jet of natural gas surrounded by swirled, preheated combustion air.…”

Large Eddy Simulations of gaseous flames in gas turbine combustion chambers

“…The PVC is known to be weakly dependent of Re and its frequency f can be expressed in terms of a Strouhal number, fDe/U 0 where De stands for the swirler exit diameter [228]. Evaluations of the LES issued PVC's [239,240] and their Strouhal numbers for the cold flow configuration of Fig. 5(a) [238,254,255], results are very satisfactory (cf.…”

“…The latter relies on tabulated chemistry and a conserved scalar [144] approach while the former uses a reduced two-step mechanism [261] coupled to the Dynamic Thickened Flame model [262]. The main outcome is a weak but observable difference in exit swirler axial velocity and RMS profiles, [240,253,263]. Certain LES results confirm the presence of a PVC in cold flow conditions and observe its presence or disappearance in reacting flows.…”

“…Such a comparison has recently been produced within the context of the TIMECOP AE European project 1 involving major European aeronautical engine manufacturers. This specific study follows the MOLECULES European project 2 where the same injector was studied but operated with gaseous methane [240,241]. For the case discussed here, pure gaseous kerosene is injected separately from the swirled air stream CERFACS's code is third order in time and space, explicit and fully compressible.…”