Design of hydrogen leakage detection and alarm processing system for the fuel cell power train lab

The hydrogen leakage detection and alarm processing system is established for the fuel cell （FC） power train lab to meet the hydrogen safety demand of the FC performance test and examination for the project named ＂Research and Development of the Vehicular Technology for the Fuel Cell City Bus＂ by Tsinghua University. The established hydrogen safety system includes the hydrogen supply system, hydrogen leakage detection system, alarm processing system, ventilation system, measures against electrostatic, thunder-arresting and explosion-protection, and the strict hydrogen operation rules. In this safety system, the explosion proof catalytic combustion sensors are used to detect the hydrogen leakage and the electrical control system is designed to process the alarm automatically. The hydrogen safety system plays an important role in the performance, examination of the FC and the assuring the personnel＇ s safety of the fuel cell power train lab.

Leakage and diffusion characteristics of underground hydrogen pipeline

Soil corrosion and hydrogen embrittlement are the main factors of hydrogen pipeline failure. The gas escapes, diffuses and accumulates in the soil and enters the atmosphere when leak occurs. The mechanism of gas diffusion in buried pipelines is very complicated. Mastering the evolution law of hydrogen leakage diffusion is conducive to quickly locating the leakage point and reducing the loss. The leakage model of the underground hydrogen pipeline is established in this paper. The effect of leakage hole, soil type, pipeline pressure, pipeline diameter on hydrogen leakage diffusion were investigated. The results show that when the hydrogen pipeline leaks, the hydrogen concentration increases with the increase of leakage time, showing a symmetrical distribution trend. With the pipeline pressure increase, hydrogen leakage speed is accelerated, and longitudinal diffusion gradually becomes the dominant direction. As the leakage diameter increases, hydrogen leakage per unit of time increases sharply. Hydrogen diffuses more easily in sandy soil, and its diffusion speed, concentration, and range are higher than that in clay soil. The research content provides a reference and basis for the detection and evaluation of buried hydrogen pipeline leakage.

Impacts of wind conditions on hydrogen leakage during refilling hydrogen-powered vehicles

Although hydrogen leakage at hydrogen refueling stations has been a concern,less efforts have been devoted to hydrogen leakage during the refueling of hydrogen-powered vehicles.In this study,hydrogen leakage and dilution from the hydrogen dispenser during the refueling of hydrogen-powered vehicles were numerically investigated under different wind configurations.The shape,size,and distribution of flammable gas clouds(FGC)during the leakage and dilution processes were analyzed.The results showed that the presence of hydrogen-powered vehicles resulted in irregular FGC shapes.Greater wind speeds(v wv)were associated with longer FGC propagation distances.At v_(wv)=2 m·s^(−1)and 10 m·s^(−1),the FGC lengths at the end of the leakage were 7.9 m and 20.4 m,respectively.Under downwind conditions,higher wind speeds corresponded to lower FGC heights.The FGC height was larger under upwind conditions and was slightly affected by the magnitude of the wind speed.In the dilution process,the existence of a region with a high hydrogen concentration led to the FGC volume first increasing and then gradually decreasing.Wind promoted the mixing of hydrogen and air,accelerated FGC dilution,inhibited hydrogen uplifting,and augmented the horizontal movement of the FGC.At higher wind speeds,the low-altitude FGC movements could induce potential safety hazards.

Hydrogen FBG Sensor Using Pd/Ag Film With Application in Propulsion System Fuel Tank Model of Aerospace Vehicle

The high efficiency hydrogen fiber Bragg grating （FBG） sensor is presented. The sensitive film was a new alliance of palladium-silver （Pd-Ag）. In addition, the titanium （Ti） layer was used as the adhesive layer. The presented sensor showed the resolution of more than 60pm/1%H2, and a fast response time of4s - 5s was guaranteed in the 0.1%H2 - 4%H2 range. Moreover, the life time of the sensor was investigated. The obtained results showed that the sensor had an enhanced life time. Furthermore, the sensor was applied in the propulsion system fuel tank model of the aerospace vehicle. The obtained results indicated that it is a prevention system against the disaster aerospace due to hydrogen leakage.