Study Of Dispersion Of Hydrogen Leakage In Air Based On Jet Model

Hydrogen is a kind of promising and clean energy.Nowadays,GH2(gaseous hydrogen)and LH2(liquid hydrogen)has used in aerospace,clean energy and many other fields.Because GH2 burns and explodes easily,it will bring much threaten to surrounding environment and people when it leaks.As a result,before promoting hydrogen energy,it is necessary to study leakage of GH2 and LH2 and to give reasonable and effective measures.In this paper,leakage of GH2 and LH2 is studied by experiment,physical model and numerical simulation.Effects of leakage rate,environmental temperature and humidity are exploded,too.It will provide some guidelines to work out measures and arrange monitoring equipment to deal with leakage of GH2 and LH2 and build appropriate physical model.Firstly,physical model of hydrogen leakage is described clearly.Fluent,governing equations and Realizable 6)- turbulence model which are used in numerical simulation is introduced,too.They are theoretical fundament of comparison between physical model and experiment.They are also theoretical fundament of comparison between physical model and numerical simulation.Secondly,experiments of GH2 leakage are carried out in an environmental chamber.During the experiments,temperature and humidity in the chamber stay constant.No wind exists,neither.The direction of leakage is vertically upward and the rate of leakage is constant.Each hydrogen leakage lasts 1 minutes.There are no obstacles around the leak.From the aspects of safety and feasibility,gaseous hydrogen is replaced by gaseous helium.The result shows that when hydrogen leaks vertically upwardly for a short time in a place where there are no obstacles around the leak,it will form steady concentration field.With increase of leakage rate,hydrogen concentration at the central axis will increase at the same speed.With increase of environmental temperature,hydrogen concentration in height direction decay faster.Increasement of leakage rate will increase the combustible and explosive area.Increasement of environmental temperature will decrease the height of the combustible and explosive area.Increase of environmental humidity will decrease the combustible and explosive area.Thirdly,results of physical model are compared with that of experiments.It shows that when dimensionless height /(9 ranges from 95 to 195,physical model can predict hydrogen concentration at the central axis accurately.When /(9 is above 195,results predicted by physical model is higher than actual results.Leakage rate has an effect on the prediction accuracy.When ranges from 10 to 268,physical model can predict hydrogen concentration at the central axis accurately.When is above 268 or below 10,results predicted by physical model is higher than actual results.Results of physical model are compared with that of numerical simulation.With increase of temperature and humidity,the difference of combustible and explosive area which predicted by them become larger.Physical model is more efficient.The physical model can be used in actual situation.Finally,experiments of LH2 are carried out outdoor by State key laboratory of space cryogenic propellant and Beijing 101 research institute.The results show that dispersion of LH2 leakage is similar to that of GH2 leakage.When height is low,the physical model can well predict the maximum volume fraction of hydrogen.As the physical model lacks description of wind,it still has limitations.According to analysis of experiments of GH2 leakage and LH2 leakage,when GH2 leaks,combustible and explosive area can be narrowed down by decreasing leakage rate.If the leakage rate cannot be controlled,it is also useful to increase environmental humidity.Physical model of hydrogen leakage can be used to estimate combustible and explosive area to determine the minimum safety distance initially.