The desensitization degree of emulsion explosives （EE） was calculated with the peak pressure of explosion shock waves tested in water. To an explosive, the less the desensitization degree, the better the compression...The desensitization degree of emulsion explosives （EE） was calculated with the peak pressure of explosion shock waves tested in water. To an explosive, the less the desensitization degree, the better the compression resistance, so the compression resistance of an explosive can be compared and analyzed quantificationally with the desensitization degree. The influence of an emulsifier on the pressure desensitization of EE was studied, including the content and category of emulsifiers. Three kinds of emulsifiers （Span-80, compound emulsifier, and T-152） were used in the tests. The experimental results show that both the content and category of emulsifiers make a great effect on the pressure desensitization of EE. The desensitization degree of EE reduces with the emulsifier content being increased, but there is an optimal content of an emulsifier for the compression resistance of EE. While the content of Span-80 reaches 4wt%, the desensitization degree of EE becomes a minimal value, and augments somewhat if the emulsifier content is increased more. That is to say, the compression resistance of EE becomes the highest while the content of Span-80 is 4wt%, and the compression resistance will decline if the content of Span-80 is increased more. The compression resistance of the explosive emulsified by compound emulsifier is the highest among all the explosives, when the content of the whole components and manufacturing engineering are kept invariable.展开更多
The object of the research are explosive properties of the pyrotechnic composite consist of fine grade magnesium-aluminium powder(PAM)and highly dispersed polytetrafluorethylene(PTFE).The composite reveals high resist...The object of the research are explosive properties of the pyrotechnic composite consist of fine grade magnesium-aluminium powder(PAM)and highly dispersed polytetrafluorethylene(PTFE).The composite reveals high resistance to all mechanical and thermal impulses and is extremely sensitive to hot sparks and open fire.The burning rate of the composition changes from 1 cm·s-1 to 100 m·s-1 along with decreasing its density.Charges of the composition with density below 1 g·cm-3 burn so violently,that the phenomena is similar to explosion.Charges with density above 1.1 g·cm-3 burn relatively rapidly and stably.The main part of the paper concerns the pressure impulses in the air generated during high-rate burning of the composition of bulk density.The nature of the generated pressure impulse is not that of a typical shock wave.A rise of pressure over the distance from the point of explosion to the maximum value lasts 50-100 milliseconds,while for shock waves this factor is less than a microsecond for equivalent charges.The methods of initiation of the composition influence the shape and parameters of the pressure impulse.The explanation of the nature of great changes of the composition burning rate has been proposed.The effect described in the paper was used for evaluation of explosive pressure resistance of industrial doors and windows.展开更多
An experimental investigation was conducted to identify the characteristics of crack growth in high performance concrete (HPC) subjected to fire, including two parts of work, i.e. crack growth resistance determination...An experimental investigation was conducted to identify the characteristics of crack growth in high performance concrete (HPC) subjected to fire, including two parts of work, i.e. crack growth resistance determinations and cracking observations, using concrete of three strength grades 40 MPa, 70 MPa, and 110 MPa. The crack growth resistance curves (R-curves ) of HPC subjected to high temperatures were determined using notched three-point bend beam specimens of 100 mm×100 mm×300mm. The R-curve (crack growth resistance curve) flattening shows that the crack growth resistance has been significantly reduced by elevated temperature. Concrete with a higher strength grade has a steeper R-curve, with a higher fracture toughness but a shorter critical crack growth. The shorter critical crack growth means that concrete of a higher strength grade has a more brittle behavior. The concrete cracking observations reveal that the consequences of rapid heating are quite different from those of slow heating. For slow heating at a rate of 0.5℃/min, HPC suffered no obvious cracking below 600℃ even if it had a high moisture content. Explosive spalling is an extreme case of the internal cracking driven mainly by vapor pressure. All these results confirmed the vapor pressure mechanism for spading behavior which should be more significant for denser concrete. The crack growth ranges obtained from the R-curve determination results are in good agreement with those measured in the concrete cracking observations.展开更多
为保证煤粉燃料在粉仓内的安全、可靠存储并解决煤粉工业锅炉系统粉仓设计不完善问题,需提高泄压防爆装置设计的可行性。采用泄压面积计算及仓体抗爆安全设计,并结合实例对用于动力煤煤粉燃料的储仓防爆安全设计提出具体要求和建议,以...为保证煤粉燃料在粉仓内的安全、可靠存储并解决煤粉工业锅炉系统粉仓设计不完善问题,需提高泄压防爆装置设计的可行性。采用泄压面积计算及仓体抗爆安全设计,并结合实例对用于动力煤煤粉燃料的储仓防爆安全设计提出具体要求和建议,以达到规范化及标准化之目的。参照国内外相关规范并分析研究煤粉储仓的防爆设计方法可知,其关键之处为泄压防爆面积设计计算,若当1000 m 3煤粉储仓的仓体设计耐压强度为0.2 MPa时,计算所需的泄压面积为4.56 m 2,远小于非耐压仓体所需的泄压面积108.6 m 2。研究表明,实时填充CO 2或N 2的惰化保护仓以及设计耐压强度大于最大爆炸压力时全抗爆仓的安全性最高,但其存在实施困难与经济性差的问题,工程实践中宜采用耐压泄爆仓设计以保证设备安全,推荐仓体设计的耐压强度为(0.2~0.4)MPa;根据GB 12476《可燃性粉尘环境用电气设备》中对可燃性粉尘环境防爆区域划分及释放源的定义,对煤粉储仓的防爆区域划分提出了相应建议。展开更多
基金This work was financially supported by the National Natural Science Foundation of China (No.50574004).
文摘The desensitization degree of emulsion explosives （EE） was calculated with the peak pressure of explosion shock waves tested in water. To an explosive, the less the desensitization degree, the better the compression resistance, so the compression resistance of an explosive can be compared and analyzed quantificationally with the desensitization degree. The influence of an emulsifier on the pressure desensitization of EE was studied, including the content and category of emulsifiers. Three kinds of emulsifiers （Span-80, compound emulsifier, and T-152） were used in the tests. The experimental results show that both the content and category of emulsifiers make a great effect on the pressure desensitization of EE. The desensitization degree of EE reduces with the emulsifier content being increased, but there is an optimal content of an emulsifier for the compression resistance of EE. While the content of Span-80 reaches 4wt%, the desensitization degree of EE becomes a minimal value, and augments somewhat if the emulsifier content is increased more. That is to say, the compression resistance of EE becomes the highest while the content of Span-80 is 4wt%, and the compression resistance will decline if the content of Span-80 is increased more. The compression resistance of the explosive emulsified by compound emulsifier is the highest among all the explosives, when the content of the whole components and manufacturing engineering are kept invariable.
文摘The object of the research are explosive properties of the pyrotechnic composite consist of fine grade magnesium-aluminium powder(PAM)and highly dispersed polytetrafluorethylene(PTFE).The composite reveals high resistance to all mechanical and thermal impulses and is extremely sensitive to hot sparks and open fire.The burning rate of the composition changes from 1 cm·s-1 to 100 m·s-1 along with decreasing its density.Charges of the composition with density below 1 g·cm-3 burn so violently,that the phenomena is similar to explosion.Charges with density above 1.1 g·cm-3 burn relatively rapidly and stably.The main part of the paper concerns the pressure impulses in the air generated during high-rate burning of the composition of bulk density.The nature of the generated pressure impulse is not that of a typical shock wave.A rise of pressure over the distance from the point of explosion to the maximum value lasts 50-100 milliseconds,while for shock waves this factor is less than a microsecond for equivalent charges.The methods of initiation of the composition influence the shape and parameters of the pressure impulse.The explanation of the nature of great changes of the composition burning rate has been proposed.The effect described in the paper was used for evaluation of explosive pressure resistance of industrial doors and windows.
基金The authors gratefully acknowledge the financial support of both the National Natural Science Foundation of China(project No.50108001)the Pandeng Foundation Project of Beijing Jiao Tong University.
文摘An experimental investigation was conducted to identify the characteristics of crack growth in high performance concrete (HPC) subjected to fire, including two parts of work, i.e. crack growth resistance determinations and cracking observations, using concrete of three strength grades 40 MPa, 70 MPa, and 110 MPa. The crack growth resistance curves (R-curves ) of HPC subjected to high temperatures were determined using notched three-point bend beam specimens of 100 mm×100 mm×300mm. The R-curve (crack growth resistance curve) flattening shows that the crack growth resistance has been significantly reduced by elevated temperature. Concrete with a higher strength grade has a steeper R-curve, with a higher fracture toughness but a shorter critical crack growth. The shorter critical crack growth means that concrete of a higher strength grade has a more brittle behavior. The concrete cracking observations reveal that the consequences of rapid heating are quite different from those of slow heating. For slow heating at a rate of 0.5℃/min, HPC suffered no obvious cracking below 600℃ even if it had a high moisture content. Explosive spalling is an extreme case of the internal cracking driven mainly by vapor pressure. All these results confirmed the vapor pressure mechanism for spading behavior which should be more significant for denser concrete. The crack growth ranges obtained from the R-curve determination results are in good agreement with those measured in the concrete cracking observations.
文摘为保证煤粉燃料在粉仓内的安全、可靠存储并解决煤粉工业锅炉系统粉仓设计不完善问题,需提高泄压防爆装置设计的可行性。采用泄压面积计算及仓体抗爆安全设计,并结合实例对用于动力煤煤粉燃料的储仓防爆安全设计提出具体要求和建议,以达到规范化及标准化之目的。参照国内外相关规范并分析研究煤粉储仓的防爆设计方法可知,其关键之处为泄压防爆面积设计计算,若当1000 m 3煤粉储仓的仓体设计耐压强度为0.2 MPa时,计算所需的泄压面积为4.56 m 2,远小于非耐压仓体所需的泄压面积108.6 m 2。研究表明,实时填充CO 2或N 2的惰化保护仓以及设计耐压强度大于最大爆炸压力时全抗爆仓的安全性最高,但其存在实施困难与经济性差的问题,工程实践中宜采用耐压泄爆仓设计以保证设备安全,推荐仓体设计的耐压强度为(0.2~0.4)MPa;根据GB 12476《可燃性粉尘环境用电气设备》中对可燃性粉尘环境防爆区域划分及释放源的定义,对煤粉储仓的防爆区域划分提出了相应建议。
