A real-size calculation is performed for high-pressure hydrogen release in a tube using the axisymmetric Navier Stokes equations with the full hydrogen chemistry. A Harten Yee-type total variation diminishing scheme and point-implicit method are used to integrate the governing equations. The calculated real-size results show that the leading shock wave velocity is similar to that calculated using a smaller tube. The mixing process and ignition behavior of high-pressure hydrogen are explained in detail; the velocity shear layer and Kelvin Helmholtz instability are the main causes of mixing of hydrogen with air and ignition in the high-temperature region behind the leading shock wave.