Large vapor cloud explosions (VCEs) and deflagration to detonation transition (DDT) events are of considerable interest to the petroleum refining and chemical processing industries. A detonation results in a very high flame speed and can significantly increase explosion energy and decrease standoff distance, increasing the blast load. Potential mitigation options to limit VCE severity include multiple simultaneous ignition sources to limit flame travel distance, suppressants to limit flame speed, and controlling the congested volume geometry to limit the flame travel distance. Another approach is minimizing the flame travel distance to free vent. Some VCE blast load prediction methods consider flame travel distance within a congested volume, but not the distance to free vent (D_FV). Decreasing the D_FV limits flame acceleration and decreases the potential for a DDT. High fuel reactivities and elevated congestion/confinement levels require smaller distances to free vent. This paper describes a test program to demonstrate this mitigation option using near-stoichiometric ethylene-air mixtures in an elongated test rig configured with a medium level of congestion to determine the free vent distance required to prevent a DDT. Test program results, associated Flame Acceleration Simulator predictions, and potential areas for future research are included.

中文翻译：

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设计爆燃

大型蒸气云爆炸 (VCE) 和爆燃到爆轰转变 (DDT) 事件对石油精炼和化学加工行业具有相当大的兴趣。爆炸会导致非常高的火焰速度，并可以显着增加爆炸能量并减少间隔距离，从而增加爆炸载荷。限制 VCE 严重性的潜在缓解选项包括多个同时点火源以限制火焰传播距离、抑制剂限制火焰速度以及控制拥挤的体积几何形状以限制火焰传播距离。另一种方法是最小化火焰传播到自由通风口的距离。一些 VCE 爆炸载荷预测方法考虑了拥挤体积内的火焰传播距离，但不考虑到自由通风口的距离 (D _FV )。减少 D_FV限制了火焰加速并降低了 DDT 的可能性。高燃料反应性和升高的拥堵/限制水平需要更短的距离来释放排气孔。本文介绍了一个测试程序，该测试程序使用接近化学计量的乙烯-空气混合物在配置有中等拥堵水平的细长测试台中演示此缓解选项，以确定防止 DDT 所需的自由通风距离。包括测试程序结果、相关的火焰加速模拟器预测以及未来研究的潜在领域。