Olaf Diers

Investigation of Two Advanced Cooling Mixing Concepts for a Rich Quench Lean Combustor

To support the development of a rich quench lean pilot zone for a staged aeroengine combustor, two rectangular rich quench lean (RQL) combustor sectors have been investigated under atmospheric conditions. Two advanced cooling mixing concepts, effusion and impingement cooling, with one and two rows of secondary air inlet holes in the mixing zone, have been measured using intrusive and noninstrusive measurement techniques. The results elucidate the interrelations between the cooling concepts and the respective mixing and emissions performances. The measurements were accompanied by numerical calculations supporting the interpretations of the measured data. Drawbacks were observed for the near stoichiometric conditions of the effusion cooling concept near the wall, however, the quench zone design with two rows of staggered holes performs well. On the contrary, the impingement cooling system shows good results for the homogeneity of the primary zone, but since less quench air is available with impingement cooling, optimum mixing is more difficult to achieve.

Investigation of Combustion Oscillations in a Lean Gas Turbine Model Combustor

This contribution is a continuation of ASME-GT2006-90300. While still working at atmospheric pressure, the range of operating conditions was extended to more realistic reduced mass flows to reproduce the engine pressure loss and air preheat up to 700K. The thermoacoustic behaviour of the burner was mapped over that operating range. Two different types of oscillations were observed for flames anchored at the nozzle or lifted from it. Both exhibited a frequency dependence on the Strouhal number for constant reduced mass flows. For a selected operating point with the lifted flame at a preheat temperature of 600K and a reduced mass flow of 0.3kg K0.5/(s bar), the thermoacoustic behaviour of the burner was characterised by phase locked Particle Image Velocimetry as well as phase locked OH- and OH-T- LIF measurements and correlated to the acoustic pressure signal obtained by microphones. The combined data showed pulsating combustion being supported through periodic reignition of the main flame zone by a recirculating volume of hot, OH-rich gas, the cycle time being connected to the observed frequency. The characterization of the preheated operating point was completed with a heat balance investigation quantifying the non-adiabatic combustion conditions of the uncooled combustor.

Characterization of a Real Size Retrofittable Catalytic Combustion System

This contribution describes the investigation of an engine-scale catalytic hybrid burner. The burner has been investigated under atmospheric conditions with preheated air and natural gas fuel in two operating points, with and without the catalytic reactor. By using the catalyst, an extension of the operating range to leaner stoichiometries has been demonstrated. Exhaust gas analysis performed directly downstream of the burner as well as in the burner far-field showed a NOx reduction potential of more than 20% when employing the catalyst. For the operation with the catalytic reactor, the flame stabilization process and dependency of NOx formation on the piloting gas ratio is described with results of OH chemiluminescence measurements. Radial temperature profiles taken with Coherent Anti Stokes Raman Scattering (CARS) suggest a reaction delay directly downstream of the catalytic section of the burner. Calculations with a perfectly stirred reactor model help to obtain a better understanding of the kinetics of the hot gases leaving the catalyst section.Copyright