The Mechanism And Characteristics Of Pollution When Discharging Cryogenic Liquid Out Of Container

As the fuel of launch vehicle,the safety of the cryogenic propellant is very important.During the process of discharging cryogenic vessels,it may bring a certain air into the system,cause potential safety hazard.But for the mechanism of the cryogenic liquid discharging process pollution are rarely reported both domestic and abroad.Preventive measures also are mostly experience guidance.Therefore,it is necessary to carry out the cryogenic liquid emptying the air vent pipe in the process of diffusion process mechanism and characteristics of the research.This text set about from two aspects of theory and experiment,the research in the process of liquid hydrogen vent pipe in the diffusion process and its distribution.In theory,according to the principle of gas dynamics and mass transfer theory is deduced from the air in the hydrogen diffusion coefficient and diffusion flux calculation formula.First of all,with the basic equations of fluid dynamics,get different blow-down parameters under cryogenic liquid(gas)in the state in the process of emissions.Based on the boundary layer theory and the analysis of the impact of various physical parameters on Reynolds number,it was given that as the temperature rises,the boundary layer increases and decreases as the flow velocity and size rises.Secondly,probes into the mechanism of material transfer,introduces some molecular diffusion coefficient of the theoretical calculation method,experience method and experimental method,the advantanges and disadvantanges of various methods is given and the error range.Finally,through the analysis and comparison of these methods,the model based on the Lennard-Jones,a potential collision integral correction and temperature calculated formulas of nonpolar gas diffusion coefficient.Through the analysis of empirical formula,it is concluded that the diffusion coefficient and the temperature,pressure,the concrete index of collision integral relationship,for air diffusion behavior in the process of low temperature gas vent provides an important basis for guidance.To simulate liquid hydrogen vent,for different flow rate under normal temperature and low temperature hydrogen empty test have been carried out.Through the vent pipe gas at different positions of the on-line sampling and analysis its oxygen content,it is concluded that the spread of the air in the pipe corresponding conditions.Synthetical consolidation and rehabilitation of groups of experimental data,temperature,rate of emptying the influence law of air pollution.