Hydrogen Safety: Pressure Peaking Phenomena-ignited releases

The Pressure Peaking Phenomena (PPP) is the effect of introducing a light gas into a vented volume of denser gas. This will result in a nonequilibrium pressure as the light gas pushes the dense gas out at the vent. Large scale experiments have been performed to produce relevant evidence. The results were used to validate an analytical model. Pressure and temperature were measured inside a constant volume, while the mass flow and vent area were varied. The analytical model was based on the conservation of mass and energy. The results showed that increasing the mass flow rate, the peak pressure increases and with increasing the ventilation area, the peak pressure decreases. Peak pressure was measured above 45 kPa. Longer combustion time resulted in higher temperatures, increasing an underpressure effect. The experimental results showed agreement with the analytical model results. The model predicts the pressures within reasonable limits ofþ/-2 kPa. The pressure peaking phenomena could be very relevant for hydrogen applications in enclosures with limited ventilation. This could include car garages, ship hull compartments as well as compressor shielding. This work shows that the effect can be modeled and results can be used in design to reduce the consequences.

压力峰值现象（PPP）是指在封闭体积中引入轻质气体至较密气体所引起的效应。此举将导致非平衡压力的产生，因为轻质气体在排出通风口的同时将密集气体推离。为收集相关证据，已进行了大规模实验。实验结果被用于验证分析模型。在恒定体积内测量了压力和温度，同时改变了质量流量和通风面积。该分析模型基于质量守恒和能量守恒原理。实验结果显示，随着质量流量率的增加，峰值压力亦随之上升；而随着通风面积的增大，峰值压力则有所下降。峰值压力测量值超过45 kPa。较长的燃烧时间导致更高的温度，从而加剧了负压效应。实验结果与分析模型结果相符。模型预测的压力值在±2 kPa的合理范围内。压力峰值现象对于在通风受限的空间内应用氢气可能具有重要意义，例如汽车车库、船舶船体隔舱以及压缩机防护装置。本研究表明，该效应可被建模，且实验结果可用于设计，以减轻其后果。