The lean combustion process is one of the most promising methods for reducing NOx emissions of jet engines. Since the risk of flash back is major for premixed concepts a diffusion flame concept is applied. In order to realize the lean condition in this concept the percentage of air flowing through the injection system and combustor dome has to be drastically increased. This leads to nozzles with a high effective area and to high volume flux in the primary zone of the combustor chamber. Such an injection system demands a particular focus towards flame stability at low load. Hence, it is essential to gain information on characteristics such as vortex breakdown, turbulent mixing and coherent structures (e.g. PVC) of the flow by means of numerical simulations. In the paper it is reported on the flow characteristics of the PERM injection system, which equips the AVIO annular combustor designed and developed within NEWAC, an integrated project co-funded by the European Commission. For this injections system RANS and LES simulations have been performed to investigate the isothermal flow field. The results are compared to detailed field measurements of velocity components and Reynolds stresses.Copyright © 2011 by ASME