This paper describes a CFD model of the blast wave and fireball dynamics after high-pressure hydrogen tank rupture in a fire in the open atmosphere. Experiments on rupture in a fire of tanks with nominal working pressure 35 MPa and 70 MPa are used to validate the model and get insights into underlying physical phenomena. Parametric studies are performed to understand the effect of different physical sub-models, numerical methods and other model parameters, e.g. instantaneous or inertial tank opening, on the convergence of simulations and closer reproduction of experiments. The model reproduces experiments well using different turbulence (RNG, Smagorinski-Lilly) and combustion (EDC, FRC) sub-models. It is demonstrated that hydrogen combustion at the contact surface between heated by starting shock air and cooled by expansion hydrogen at the initial stage of the process affects the blast wave strength, i.e. the peak pressure of the leading front and the blast wave impulse. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.