长直水平管道中铝粉/空气混合物爆炸试验研究

Test on the explosion probability of the aluminum powder and air mixture in the largescaled tube

在长为32.4 m,内径为0.199 m的大型长直水平管道中对铝粉/空气两相流的爆炸过程进行了试验研究。试验初始压力为0.14MPa,初始温度为20℃,水平布置17个传感器对试验数据进行测量记录。采用40 J电火花进行点火,对铝粉/空气混合物燃烧转爆轰过程(DDT)进行分析,并对不同质量浓度时混合物的燃爆情况进行比较。结果表明:铝粉质量浓度为184g/m~时,铝粉/空气混合物未被引燃;铝粉质量浓度为230 g/m^3时,水平管道末端刚好进入爆轰阶段,此质量浓度为该条件下燃烧转爆轰的最低临界质量浓度;质量浓度为276g/m^3、367 g/m^3、459g/m^3、505g/m^3、551g/m^3、643 g/m^3时,均能在此水平管道内完成爆燃向爆轰的转变,并且能够自持。铝粉/空气混合物爆轰的最优质量浓度为551 g/m^3。对质量浓度为505 g/m^3时的铝粉/空气混合物的燃烧转爆轰过程进行分析,进入爆轰阶段后,多相燃料空气混合物爆轰超压和速度曲线呈现随距离传播不断振荡,但均值稳定的典型特征,其爆轰波胞格尺寸λ约为0.486 m。

Motivated by the recent interest in the mechanism of the deflagration to the detonated transition （DDT）, we have come to mind to investigate the probability of the accidents of explosion caused by the aluminum powder and air mixture that would like to happen in an experimental system, a large-scale tube 32.4 m long with its inner diameter of 0.199 m. in addition, the mixture is expected to get ig- nited by 40 J initial energy, with a initial pressure of 0.14 MPa and a initial temperature of 20 ℃. Besides, 17 transducers should be set a- long the round tube for recording the explosion. The processes of DDT in the two-phase flow in the experimental tube can be analyzed by comparing the different concentrations of mixtures. To make the ex-periment as successful as possible, we have worked out the optimal concentration of mixture in the experimental tube and the critical con- centration of DDTI We have also found that the aluminum/air mixture cannot be ignited at the concentration of 184 g/m3, but, at the end of the tube, the deflagration transition is 1/kely to get completed when the aluminum/air mixture is as the concentration of 230 g/m3 and then leads to detonation because it is the minimal critical concentra- tion under the given condition. Thus, the aluminum/air mixture can complete the overall DDT process when the concentration reaches 276 g/m3, 367 g/m3, 459 g/m3, 505 g/m3, 551 g/m3 and 643 g,/m3, with the 551 g/m3 being the optimal one. In spite of this,： we have paid special attention to the analysis of the concentration of 505 g/m3. Though the curves of overpressure and velocity appear oscillat- ed but the pressure on the average tums to be steady, which indicates the typical characteristic of multi-fuel-air mixtures detonation. Out research also proves that the cellular size λ of the mixture of the 505 g/m3 concentration is 0.486 m.