Revision as of 09:59, 11 February 2013

Particle-laden swirling flow

Application Challenge AC3-12 © copyright ERCOFTAC 2013

Introduction

The special features of swirling flows are utilised in combustion systems in order to provide flame stabilisation and good mixing between fuel and oxidiser. This is achieved by the central recirculation bubble developing in front of the burner exit. Swirl burners are usually operated with liquid (spray) or pulverised fuels.

In order to obtain a better understanding of the particle behaviour in such a complex swirling flow, detailed experiments were conducted on particle-laden swirling flow emanating into a pipe expansion (Sommerfeld and Qiu 1991). The gas-particle mixture was injected centrally without swirl together with a co-flowing swirling annular gas jet yielding a swirl number of about 0.5. Downstream of the inlet simultaneous measurements of gas and particle velocities (all three components) were conducted by phase-Doppler anemometry, which also provided local particle size distributions and the stream-wise particle mass flux. Two cases with different injection flow rates, but roughly identical swirl number were considered. Both cases showed a closed central recirculation region. Inlet conditions are available from highly resolved profiles 3 mm downstream of the edge of the inflow tubes. Since the particle mass loading is rather small two-way coupling effects are of minor importance. Numerical computations performed with the finite-volume code FASTEST in connection with the k-? turbulence model showed reasonable good agreement with the measurements (Sommerfeld and Qiu 1993). The particle phase was simulated by Lagrangian tracking also yielding a quite good agreement with measured velocity profiles, the particle mass flux and the number mean particle diameter.