Study On Evaporation And Dispersion Model Of Liquid Methane Jet Through Large Diameter Pipe

Reusable engine is an important development direction of the aerospace industry in the future.In the choice of propellant for reusable engine,there is a clear advantage for the liquid oxygen/methane compared to the liquid oxygen/hydrogen and other combinations of liquid oxygen and hydrocarbon.Cryogenic or liquid methane security management is one of the important safety problems in the process of the design of liquid oxygen/methane engine and its ground testing.Firstly,the dangerous characteristics of liquid methane are analyzed.The formation mechanism and the law of motion of heavy gas diffusion are described and analyzed in detail,which is the most harmful process in the ground test.After that,related studies on the issue are reviewed.The scenes of the large-scale foreign heavy gas diffusion field tests are briefly described,including classical Burro,Coyote and Falcon series tests.In the aspect of theoretical analysis and numerical simulation,the basic principles and features of classical models are summarized,and the studies on the application of CFD model are introduced in detail.Actually,traditional single phase model is unable to describe the pool formation and phase change,which are essential to risk management.In this paper,we propose an integrated multiphase CFD model to simulate the complete spill process(including liquid methane release,liquid methane-water interaction,evaporation and vapor dispersion),in particular,to capture the mixing and turbulence generated during the spill,based on Falcon-1 and Burro-8 field tests.The simulation results of the new multiphase model are compared with the data from Falcon-1 and Burro-8 test for validation and with other simulation results.It is verified that the multiphase model provides better results than other approaches in accuracy and fully describing the spill process.The significant improvements are obtained due to the more accuracy predictions on the turbulence effect and temperature variations brought by the phase change and other processes in the multiphase model.Then,characteristics of heavy gas dispersion are analyzed.It is demonstrated that the heavy gas diffuses mostly along the surface.Although the atmosphere wind can mitigate the dispersion,the heavy gas dispersion distance is still considerable in the upwind direction and crosswind direction.Finally,the effect of the impoundment on the spill and dispersion is also investigated.Results showed that the impoundment had great effect on dispersion mitigation both in downwind direction and crosswind direction.It is worth mention that the cloud will spread higher for the vertical vortex caused by the impoundment and billboard,therefore shorten the hazard region.