Sheng Qi

Effects of concentration, temperature, humidity, and nitrogen inert dilution on the gasoline vapor explosion

This study aims at providing basic information for the explosion-protecting technology in the gasoline storage and transportation process. Experiments were conducted to investigate the explosion parameters under different gasoline vapor concentrations (0.92-2.40%), temperatures (283-343K), relative humidities (35-98%), and oxygen concentrations (12.66-20.32%) in a 20L spherical vessel. Results show that both the maximum overpressure and the rate of pressure rise are quadratic functions of initial gasoline vapor concentration. At constant initial concentration, the maximum overpressure and the rate of pressure rise decrease linearly with the increase of temperature or humidity. When using nitrogen as the dilution, the maximum overpressure and rate of pressure rise respectively show a negative exponential and a linearly relationship with the oxygen concentration. The introduced nitrogen also narrowed the explosive limits. The fuel inertization point is 12.65%. A nonlinear regression formula with 4 variables was obtained, which can be used to quantitatively predict the maximum overpressure at various initial conditions. These results are useful for predicting the explosion pressures of gasoline-air mixtures at various conditions when direct measurements are difficult to achieve.

Large eddy simulation and experimental study on vented gasoline-air mixture explosions in a semi-confined obstructed pipe

In this work, LES simulation coupled with a TFC sub-grid combustion model has been performed in a semi-confined pipe (L/D=10, V=10L) in the presence of four hollow-square obstacles (BR=49.8%) with circular hollow cross-section, in order to study the premixed gasoline-air mixture explosions. The comparisons between simulated results and experimental results have been conducted. It was found that the simulated results were in good agreement with experimental data in terms of flame structures, flame locations and overpressure time histories. Moreover, the interaction between flame propagation process and obstacles, overpressure dynamics were analyzed. In addition, the effects of initial gasoline vapor concentration (lean (ϕ=1.3%), stoichiometric (ϕ=1.7%) and rich (ϕ=2.1%)), and the number of obstacles (from 1 to 4) were also investigated by experiments. Some of the experimental results have been compared with the literature data. It is found that the explosion parameters of gasoline-air mixtures (e.g. the maximum overpressure peaks, average overpressure growth rates, etc.) are different from some other fuels such as hydrogen, methane and LPG, etc.

Study on Gasoline-Air Mixture Deflagration Flame with Different Equivalence Ratios in a Closed Vessel

ABSTRACT An experimental investigation was carried out on the influence of equivalence ratio on gasoline-air mixture deflagration in a closed vessel. High-speed flame images, flame illuminance, illumination duration, overpressure and reaction produces were recorded for equivalence ratios ranging between the flammable limits. Efforts were made to explore the potential relationships between the visual character presented on the flame images and the deflagration parameters, e.g., the equivalence ratio, the flame duration, and the maximum overpressure. Results show that the gasoline-air mixture presents a smooth spherical flame with lean fuel, a spherical cellular flame with rich fuel, and a curled flocculent flame with very rich fuel. The three flame patterns could be quantitatively identified by calculating the edge pixel amounts and the average b* value (in a Lab color space) of the flame images. The maximum flame illuminance, illumination duration, reaction products, rate of pressure rise, and maximum pressure showed a discriminating value and variation trend versus equivalence ratio under different flame patterns. The rich flame could be considered as the most dangerous flame regime among the three because of its fastest pressure rising speed and highest maximum overpressure. The result is of value to the fundamental research as well as the video-based flame detecting technology.

Experimental Study on the Explosion of Gasoline-air Mixture in Reduced-scale Storage Tank

Fire and explosion accidents often occur in storage tanks leading to great economic loss and serious casualties during the working, operation and maintenance. This paper established a reduced-scale storage tank experimental system, and then the explosion characteristics of gasoline-air mixture in storage tank were studied. The experimental results show that several parameters (such as concentration of gasoline-air mixture, initial temperature of gasoline-air mixture, initial O2 and N2 contained in the storage tank) have very important influence on the gasoline-air mixture explosion and its explosion products. The upper and lower explosion limits of gasoline-air mixture are about 0.86% and 4.3% HC respectively according to the experimental results, and the critical explosion concentration is about 2.5% HC. The explosion of gasoline-air mixture under different initial temperatures in the concentration of 2.5% was carried out to find out that the biggest explosion overpressure is at the initial temperature of 308 K. The concentrations of explosion products namely CO and CO2 are closely related to the initial concentration of gasoline-air mixture, and the critical initial concentration of gasoline-air mixture to determine the higher and lower concentrations of CO and CO2 in explosion products is around 2.5% HC. Meanwhile, the ignition of gasoline-air mixture under various concentrations of premixed N2 and O2 in the storage tank was carried out, and the results show that the ignition of gasoline-air mixture with the concentration of 2.0% HC is impossible when the concentration of O2 is below 18.80%.