基于微积分的LPG和CNG喷射火模型建立和三维数值模拟

由液体和气体泄漏引发的喷射火灾事故屡见不鲜,而现有的喷射火模型却有诸多缺陷。将喷射火形状近似为圆锥,鉴于液体和气体的泄漏速度随压强和温度均有变化、点源离地面会有一定高度、风速对火焰倾角也有影响、圆锥喷射中心线上每个点源对目标的热辐射均不同等实际情况,新建液体和气体扩展半径的计算方法,引入风速对火焰高度和火焰偏角的作用,比较AGA法和Thornton模型,发现AGA法更加符合实际,再利用微积分原理建立三维点源喷射火模型,展示火焰形状对目标的影响,从而得出热辐射的最终危险性。最后以LPG和CNG储罐喷射火事故为例进行对比验证,首次模拟出喷射火的形状,更清晰准确地展示了目标入射热辐射通量随目标点位置的变化和危险范围,可为火焰阵面处的消防安全决策提供参考。

3-D numerical simulation model for jet fire spray of LPG and CNG and its establishment based on the calculus

Tew reports have been seen on the basic theory of the jet fire models.Some models might be inaccurate because they fail to take into full account the effects of leakage situation,wind speed and flame shape in the thermal radiation.To make up for the inadequacy in this way,we have managed to treat the shape of the jet fire as a focus,intending to give full detailed report on the study of the jet fire thermal radiation model by taking into account all the realistic restrictions,such as the leakage rate of the liquid and gas fuels at different pressures and temperatures,the height from the point source to the ground,the wind speed effects on the flame angle,the different thermal radiations on the target resulting from each point source of the jet fire cone centralized and so on.Thus,by introducing the wind effects on the flame height and angle,we have developed a brand new method for calculating the liquid and gas expansion and extension rates.And,then,a synthetic comparison made between the AGA model and Thornton model has enabled us to find that the AGA model sounds more reasonable and realistic.What is more,we have established a 3-D jet fire model based on the calculus principles.And,in turn,the above said model has displayed its due impact of the flame shape on the target,whereas the model has gained its thermal radiation flux of the jet fire on the target point.Finally,the jet fire model of LPG and CNG tanks has been verified by the Matlab program.Besides,we have also simulated the shape of the jet fire under the different wind conditions,which accurately proves that the incident's thermal radiation flux tends to change with the different target positions and the wind speeds,as well as the thermal radiation hazardous areas of the jet fire.In addition,the jet fire radiation model can reflect the precise calculation of the thermal radiation flux of the close-in target,signifying that the model can be of great practical implication both for prediction of the accident consequences and the safety decisions on the flame front.