Computational Fluid Dynamics Model for Analysis of the Turbulent Limits of Hydrogen Combustion

Abstract

This paper presents a novel numerical approach for assessing the turbulent limits of hydrogen combustion. In the framework of this approach, the premixed combustion is studied numerically in the externally generated turbulent field with defined parameters. Two-dimensional calculations are carried out for hydrogen–air mixtures of different compositions, and all the possible modes of near-limit combustion are reproduced. Among these modes are: combustion in the form of spatially separated individual kernels and combustion in the form of kernels with subsequent quenching. The critical conditions between the mentioned two modes correspond to the turbulent limits of hydrogen combustion, which are necessary for the evaluation of the hazardous risks related to hydrogen explosions.

On the Critical Condition for Flame Acceleration in Hydrogen-Based Mixtures

“…Note that the obtained critical mixture composition containing ∼11 % hydrogen in air is close to the limit at which the mechanism of flame propagation is changed from the deflagration mode to a significantly different one defined mainly by the diffusion of hydrogen into the reaction zone [ 34 ]. Such combustion modes are also affected by the gas dynamics (as it is clearly demonstrated in our previous works, e.g., in [ 10 ]), but there is a certain flame speed limit that can be achieved, and one should not expect further flame acceleration after that speed limit is achieved.…”

“…On the other hand, a local increase in the flame front area defines the increase in the heat losses from the stretched part of the flame front, which could even lead to local flame quenching in the case of less reactive mixtures. In particular, that mechanism is responsible for the quenching of both laminar [ 11 ] and turbulent [ 33 , 34 ] flames. As a result, when flame stretching occurs due to the flame’s interaction with the boundary layer, competition between those two mechanisms arises in the flame stretching region.…”

On the Features of Numerical Simulation of Hydrogen Self-Ignition under High-Pressure Release

“…Conventional detailed mathematical models include both gas dynamics and chemical kinetics that allow numerical simulation of all the peculiarities of explosion development [1]. At the same time, among the variety of numerical techniques, one should choose the most appropriate one to resolve all the necessary features of the particular mode of gas explosion [2][3][4].…”