Study on the Thermal Ignition of Gasoline-air Mixture in Underground Oil Depots based on Experiment and Numerical Simulation

The study on the special phenomenon,occurrence process and control mechanism of gasoline-air mixture thermal ignition in underground oil depots is of important academic and applied value for enriching scientific theories of explosion safety,developing protective technology against fire and decreasing the number of fire accidents.In this paper,the research on thermal ignition process of gasoline-air mixture in model underground oil depots tunnel has been carried out by using experiment and numerical simulation methods.The calculation result has been demonstrated by the experiment data.The five stages of thermal ignition course,which are slow oxidation stage,rapid oxidation stage,fire stage,flameout stage and quench stage,have been firstly defined and accurately descried.According to the magnitude order of concentration,the species have been divided into six categories,which lay the foundation for explosion-proof design based on the role of different species.The influence of space scale on thermal ignition in small-scale space has been found,and the mechanism for not easy to fire is that the wall reflection causes the reflux of fluids and changes the distribution of heat and mass,so that the progress of chemical reactions in the whole space are also changed.The novel mathematical model on the basis of unification chemical kinetics and thermodynamics established in this paper provides supplementary means for the analysis of process and mechanism of thermal ignition.

Theory and Applications of Ignition with Variable Activation Energy

The determination of critical conditions for thermal ignition of combustible materials has been traditionally studied by the use of one overall reaction with bounded parameter values for the activation energy and other chemical constants, Significant errors can occur in the values of the threshold parameters for ignition when there are two (or more) simultaneous reactions present with distinct values of the chemical constants. Recent work with simultaneous parallel reactions showed the thresholds for ignition could be lowered in this case. In this paper, motivated by experimental results for forest litter and coal, it is shown that for sequential reactions (different values of parameters in different temperature ranges) that the threshold conditions are changed (safer for lower ambient temperatures and less safe for higher ambient temperatures). The mathematical analysis is summarised and a detailed analysis is given for the forest litter and crushed coal applications. The experimental results show that variable activation energy does occur and that this extension of the classical Frank-Kamenetskii theory is needed. Here the analysis is confined to the slab geometry only but the ideas developed can easily be extended to more general systems, including those involving mass transport, consumption, and phase changes.