The effects of the diaphragm shape and boundary layer near walls on auto-ignition induced by high-pressure hydrogen release in a real size tube are numerically studied using the Navier-Stokes equations with multi-component gases. The numerical results show that there is a grid dependency that provides the optimal grid system via a comparison the theoretical boundary layer thickness. The validity of the present numerical system is confirmed by comparing the numerical and experimental precursor shock wave velocities. The initial diaphragm shape affects the hydrogen release flow structure and its auto-ignition mechanism. Two different auto-ignition styles are observed from the numerical results: one occurs near the boundary layer owing to the induction time effect and Kelvin-Helmholtz instability and another may occur near the center axis owing to the Rayleigh-Taylor instability. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.