Evaluation of Engineering Models for Vented Lean Hydrogen Deflagrations

Hydrogen gas produced from the renewable energy source can be the prefect future energy carrier. It will not only reduce the demands for depleting hydrocarbons fuels but will also help in reducing the greenhouse gas emissions. The 20-ft ISO standard containers are widely considered for building self-contained portable fuel cell based power generation units. Safety analysis of these installations is essential to prevent any future catastrophic accidents. The present paper evaluates existing engineering models to predict vented explosion peak overpressures in case of an accident release of hydrogen in these container. Such predictions are required in the design of venting panels, which are commonly used to prevent damage to enclosures by reducing overpressure of combusting gases.
Although various engineering models and empirical correlations have been developed, a number of which have been included in engineering standards and guidelines [4-7]. These correlations, however, often have conflicting recommendations [3]. None of the engineering models in the public domain have been validated with vented hydrogen tests data in realistic configurations, such as ISO shipping containers, used in hydrogen energy applications. Evaluating/improving these engineering models with the aid of full scale experimental data and computational fluid dynamics (CFD) based numerical modelling is a main objective of the HySEA project supported by the Fuel Cells and Hydrogen 2 Joint Undertaking (FCH 2 JU) under the Horizon 2020 Framework Program for Research and Innovation.
The present study aims to assess capabilities of existing engineering models for vented deflagrations of lean hydrogen-air mixtures. As hydrogen has much higher flame speeds than hydrocarbon fuels like methane and propane, it is not possible to use models derived for hydrocarbons directly with hydrogen flames. The leaner flames of hydrogen are also susceptible to instabilities like Darius-Landau instability, Rayleigh-Taylor instability, which are often overlooked in the derivation of engineering models.