Initial flame propagation characteristics of the hydrogen spherical premixed flame

Hydrogen energy is considered as one of the most recognized future energy systems by most of countries. Much hydrogen related technologies have been developed such as H2 engine. However, safety issue could be specially taken care since leaked hydrogen could disperse quickly into the enclosed environment and lead to the possible explosion. The spherical flame propagation is a basic process for explosion. Initial spherical flame characteristics is important due toits effect on the ignition in the hydrogen explosion hazard. Thus, numerical research on the initial flame propagation characteristics of the hydrogen spherical premixed flame at various initial temperature and radius are investigated. Results show that the initial flame temperature and radius will affect the self-sustained hydrogen flame characteristics. For smaller initial radius and temperature, H, OH radicals and HRR increase greatly to a maximum value and then decrease to almost zero in a short time. However, HRR is still very low and the initial flame kernel could not propagate without external energy. When the initial flame temperature or radius increase, the reaction rate becomes to be stronger and H, OH radicals and HRR all increase with the time. Both of the flame kernel could be selfsustained. With the increase of the initial temperature, the heat release increases. There is a critical initial temperature for various initial radius. For smaller initial radius of 0.2 mm, the critical initial temperature is around 3075 K for equivalence ratio of 1.0. With the increase of the initial radius, the critical initial temperature will decrease but change little after the initial radius of 0.8 mm. The critical initial temperature is around 1500 K. Theoretical analysis shows that initial temperature, laminar flame speed, reaction heat release and thermal diffusivity are the most important parameters which affect the initial flame kernel development. Larger laminar flame speed, reaction heat release and smaller thermal conductivity could be favor of the flame kernel development.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Hydrogen energy is considered a promising energy source for the future, but safety issues must be addressed. This study numerically investigated the initial flame propagation characteristics of hydrogen spherical premixed flame at various initial temperature and radius. The results showed that the initial flame temperature and radius significantly influenced the self-sustained flame characteristics.