<p>&nbsp; &nbsp; &nbsp; &nbsp;氢气管道造价昂贵，不管是人力、财力都价格不菲，因此一些国家设法将天然气管道进行改造后用于氢气运输。但氢气与天然气各自化学属性不同，其危害性也不同，需要从基础研究层面揭示氢气与天然气爆炸危害的差异，从而为氢能源的安全高效利用提供理论基础。本文基于实验对比研究了氢气或天然气在不同气体浓度、点火源位置条件下的爆炸火焰传播特性，并利用光谱仪监测和分析氢气与天然气瞬态爆炸传播火焰中的OH&bull;自由基辐射特性，为氢能源的安全高效利用及防护提出防爆抗爆建议、安全利用可行性方法以及OH&bull;自由基靶向抑爆剂的发展方向，主要结论如下：</p> <p>&nbsp; &nbsp; &nbsp; &nbsp;点火源位于密闭管道底部时，氢气爆炸火焰不易形成完全轴对称Tulip形火焰，且在同一气体浓度条件下，氢气爆炸传播火焰形态形成多种典型火焰峰面的时间更短；在本实验装置中氢气测得有明显火焰亮度的浓度是13%，天然气测得有明显火焰亮度的浓度是6%。因此在实际应用中应该在存在泄漏风险的装有氢气的管道或压力容器附近安装更适用于氢气浓度侦测和燃烧或爆炸火焰监测装置。</p> <p>&nbsp; &nbsp; &nbsp; &nbsp;在实测7%~14%气体浓度范围内，天然气爆炸压力峰值较氢气爆炸压力峰值大，且下部热电偶测得的火焰温度峰值均比上部热电偶测得的火焰温度峰值高，并从Chemkin量子化学计算角度进一步得到了验证。当气体浓度大于13%时，氢气爆炸比天然气爆炸的火焰温度峰值高，当气体浓度小于和等于13%时，则天然气比氢气爆炸的火焰温度峰值高。当在13%、14%气体浓度时，氢气火焰传播速度达到峰值时间比天然气的提前了18.60、30.01 ms。由此可知在7%~14%气体浓度范围的氢气没有天然气爆炸威力大，但装运氢气的管道或压力容器会有氢脆现象，因此要充分结合当量比为1的氢气爆炸威力来考虑和设计增强管道或压力容器的耐压强度和屈服极限，尤其是不选用有过明显压力变化的管道。</p> <p>&nbsp; &nbsp; &nbsp; &nbsp;当点火源位于密闭管道中部时，无论氢气还是天然气，爆炸火焰向管道上部传播形成多种典型火焰锋面的时间比向下传播形成相同类型火焰锋面的时间早。在7%~14%各气体浓度下，无论是氢气还是天然气爆炸，点火源位于管道中部均比位于管道底部时的爆炸压力峰值大，这说明在点火源位于管道中部时产生的爆炸威力较大。在实际作业中点火源出现位置是不确定的，故而在实际生产中要充分考虑到因点火位置引起的压力、温度等参数的增大，依此对承装氢气介质的管道或压力容器的耐压极限进行设计，且泄爆口应尽量设置在靠近点火区域附近。</p> <p>&nbsp; &nbsp; &nbsp; &nbsp;氢气或天然气爆炸火焰中的OH&bull;自由基光谱信号出现时间都是在火焰到达光纤位置之前的5~15 ms内，自由基相对辐射强度达到最大值总是在恰好过光纤位置处，且下部光纤测到的相对光谱强度较上部光纤小。在13%~17%气体浓度范围时，对比氢气与天然气火焰中OH&bull;自由基辐射特性发现，同一浓度的氢气爆炸火焰比天然气爆炸火焰中OH&bull;相对光谱强度值小。不论点火源位于管道底部还是中部，氢气爆炸的光谱出现时间t₁，峰值时间t₂以及消失时间t₃均比天然气早，且光谱存在时间t₄比天然气短。对爆炸压力、火焰温度与光谱强度进行耦合分析发现，氢气或天然气OH&bull;自由基达到相对光谱强度峰值对应的时间均早于爆炸压力、火焰温度达到峰值的时间，且氢气OH&bull;自由基相对光谱强度峰值达到时间比天然气提前50~100 ms。因而在抑制氢气爆炸时，需要选择极易与OH&bull;自由基反应的抑爆剂或根据氢气OH&bull;自由基辐射特性的变化规律研制新型抑爆剂，亟待研发针对氢气爆炸火焰需选择灵敏性更高、适应性更强的光学传感设备。</p>

<p>&nbsp; &nbsp; &nbsp; Hydrogen pipelines are expensive, both human and financial, so some countries have tried to transform natural gas pipelines for hydrogen transportation. However, the chemical properties of hydrogen and natural gas are different, and their hazards are also different. It is necessary to reveal the differences in the explosion hazards of hydrogen and natural gas from the level of basic research, so as to provide a theoretical basis for the safe and efficient utilization of hydrogen energy. In this paper, based on the experimental comparison, the explosion flame propagation characteristics of hydrogen or natural gas under different gas concentration and ignition source location conditions were studied, and the OH&bull; radical radiation characteristics in the transient explosion propagation flame of hydrogen and natural gas were monitored and analyzed by spectrometer. The main conclusions are as follows:</p> <p>&nbsp; &nbsp; &nbsp; (1) When the ignition source is located at the bottom of the closed pipeline, compared with natural gas, the hydrogen explosion flame is not easy to form a completely axisymmetric Tulip-shaped flame, and under the same gas concentration conditions, the hydrogen explosion propagating flame forms form a variety of typical flame peaks. The time is shorter; in this experimental device, the concentration of hydrogen with obvious flame brightness is 13%, and the concentration of natural gas with obvious flame brightness is 6%. Therefore, in practical applications, a device that is more suitable for hydrogen concentration detection and combustion or explosion flame monitoring should be installed near the pipeline or pressure vessel containing hydrogen where there is a risk of leakage.</p> <p>&nbsp; &nbsp; &nbsp; (2) Within the measured gas concentration range of 7%~14%, the peak value of the explosion pressure of natural gas is larger than that of hydrogen, and the lower thermal power The peak flame temperature of hydrogen or natural gas measured by the couple is higher than the peak temperature of the flame measured by the upper thermocouple, which is further verified from the perspective of Chemkin quantum chemical calculation. When the gas concentration is greater than 13%, the peak flame temperature of hydrogen explosion is higher than that of natural gas explosion. When the gas concentration is less than or equal to 13%, the peak flame temperature of natural gas explosion is higher than that of hydrogen explosion. When the gas concentration is 13% and 14%, the peak time of hydrogen flame propagation speed is 18.60 and 30.01 ms earlier than that of natural gas. It can be seen from this that hydrogen in the gas concentration range of 7%~14% is not as powerful as natural gas, but the pipeline or pressure vessel that transports hydrogen will have hydrogen embrittlement. Therefore, the explosion power of hydrogen with an equivalence ratio of 1 should be fully considered and designed. Strengthen the compressive strength and yield limit of pipelines or pressure vessels; especially do not use pipelines with obvious pressure changes.</p> <p>&nbsp; &nbsp; &nbsp; (3) When the ignition source is located in the middle of a closed pipeline, regardless of hydrogen or natural gas, the gas explosion flame will propagate to both ends of the pipeline, and the time for the explosion flame to propagate to the upper part of the pipeline to form various typical flame fronts is earlier than the time for the downward propagation to form the same type of flame front. Under each gas concentration of 7%~14%, whether it is hydrogen or natural gas explosion, the peak explosion pressure when the ignition source is located in the middle of the pipeline is larger than that when the ignition source is located at the bottom of the pipeline, which indicates that the explosion power generated when the ignition source is located in the middle of the pipeline is greater. In actual operation, the location of the ignition source is uncertain, so in actual production, the increase in pressure, temperature and other parameters caused by the ignition location should be fully considered. The pressure limit should be designed, and the explosion vent should be set as close to the ignition area as possible. Comparing the increase in the peak explosion pressure of the middle ignition and the bottom ignition, the maximum change of the hydrogen explosion pressure peak is 54.84%, and the minimum is 8.01%, but the maximum explosion pressure of natural gas is only 10.74%, and the minimum is 0. In addition, compared with the ignition at the bottom of the pipeline, the peak flame temperature of the hydrogen explosion in the middle of the pipeline is higher, while the flame temperature of the natural gas explosion is less affected by the change of the ignition source position. Therefore, when transforming a natural gas pipeline or pressure vessel into hydrogen use, while increasing the pressure resistance limit of the pipeline, it is necessary to comprehensively investigate the location that is prone to ignition source hazards, and install a hydrogen flame monitoring and alarm device. Important factors to consider are response time, monitoring distance, coverage, sensitivity, and installation location.</p> <p>&nbsp; &nbsp; &nbsp; (4) The spectral signals of OH&bull; radicals in hydrogen or natural gas explosion flames are all within 5~15 ms before the flame reaches the position of the fiber, and the relative radiation intensity of the radicals reaches the maximum value at the position just passing the fiber. And the relative spectral intensity measured by the lower fiber is smaller than that of the upper fiber. In the range of 13%~17% gas concentration, comparing the radiation characteristics of OH&bull; radicals in hydrogen and natural gas flames, it is found that the relative spectral intensity value of OH&bull; in the hydrogen explosion flame with the same concentration is smaller than that in the natural gas explosion flame. Regardless of whether the ignition source is located at the bottom or the middle of the pipeline, the spectral appearance time t₁, peak time t₂ and disappearance time t₃ of hydrogen explosion are earlier than those of natural gas, and the spectral existence time t₄ is shorter than that of natural gas. The coupling analysis of explosion pressure, flame temperature and spectral intensity shows that the time corresponding to the peak relative spectral intensity of hydrogen or natural gas OH&bull; radicals is earlier than that of explosion pressure and flame temperature, and the relative spectral intensity of hydrogen OH&bull; radicals is earlier than that of explosion pressure and flame temperature. The intensity peak reached time 50~100 ms earlier than that of natural gas. Therefore, when suppressing hydrogen explosion, it is necessary to select an anti-detonation agent that can easily react with OH&bull; free radicals or develop a new type of detonation inhibitor according to the change law of the radiation characteristics of hydrogen OH&bull; free radicals.</p>