This work presents an experimental and numerical study of a pulsed detonation combustion chamber. It consists of a pipe obstructed by one convergent-divergent nozzle, filled with a stoichiometric mixture of hydrogen and oxygen-enriched air. The proposed geometry is analysed with regard to its influence on the outset of detonation and its suitability for pulse detonation engines (PDEs). The study reveals the essential aspects for detonation initiation. The results of one of the configurations indicate a deterministic and reliable deflagration-to-detonation transition (DDT) with a short run-up distance, crucial for technical applications. The simulation reproduces the measurements in great detail and the origin of detonation is unequivocally identified. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.