On the explosion characteristics for central and end-wall ignition in hydrogen-air mixtures: A comparative study

To demonstrate the influence of different ignition positions on the explosion characteristics of H-2-Air mixtures, a series of experiments at central and end-wall ignition under turbulent and quiescent conditions are carried out in a constant volume spherical container. Three explosion characteristics including explosion time tau(e), maximum explosion pressure rise rate (dp/dt)(max), and maximum explosion pressure p(max) are measured and derived from the explosion overpressure curve. The experimental results demonstrate that the explosion hazard with the central ignition is generally stronger than that with the end-wall ignition under quiescent conditions. At lower initial pressure, the difference between two ignition cases is greater. The results show that for central ignition, the energy loss is small, and the explosion behavior is similar to the ideal constant volume explosion. While for end-wall ignition, the interaction between supersonic blast wave and cooling rough wall consumes a large amount of explosive energy. Under turbulent conditions, the increase of the jet pressure p(jet) and the jet time T-jet leads to the increase of turbulence intensity and duration, which enhances the explosion hazard of central ignition, but restrains the explosion process of end-wall ignition. The difference between the two ignition locations increases with the increase of p(jet) and T-jet. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

The experimental results demonstrate that central ignition is generally more hazardous than end-wall ignition, especially under quiescent conditions and lower initial pressure. Central ignition results in small energy loss and behaves similarly to an ideal constant volume explosion, while end-wall ignition consumes a large amount of explosive energy. Under turbulent conditions, the increase in jet pressure and jet time intensifies the explosion hazard of central ignition but restricts the explosion process of end-wall ignition.