The Influence Of Dust Particles On Parameters And Properties Of Dc Glow Discharge And Rocket Exhaust Plasmas

Dusty plasma is defined as complex plasma system with lots of dust particles of nanometer or micron scale.The introduction of dust particles in plasmas can significantly change many of plasma parameters and properties,such as electron and ion density,electron temperature,space electric field etc.,and make dusty plasma exhibit many special physical phenomena,such as complex dynamics,wave and instability,special potential structure and abnormal electromagnetic characteristics.Usually,the dusty plasmas generated by human activity are mostly weakly ionized dusty plasmas,such as dusty plasmas produced by gas discharge under laboratory and industrial conditions,the solid rocket exhausts and reentry vehicle sheath in the field of aeronautics and astronautics,etc.And,researches on the influence of dust particles on these weakly ionized plasmas have important practical significance to solve the relevant problems existing in these dusty plasmas.Based on this situation,the effects of dust particles on the main parameters and properties of plasmas are studied for the laboratory dc glow discharge plasmas and solid rocket exhausts in this paper.Firstly,charging process of dust particles is studied under different dust and plasma conditions.Then the fluid and kinetic models are developed for dc glow discharge dusty plasmas,and the influences of dust particles on the properties and parameters of dusty plasmas are investigated under different discharge conditions.At last,the electron kinetic model is used to study rocket exhaust dusty plasmas and the effects of Al₂O₃ particles on the electron energy distribution function and dielectric properties of rocket exhausts are analyzed.The main research contents include:Based on the orbital motion limitation theory,the dust charging model suitable for different plasma and dust parameters is obtained by considering the interaction of dust particles and the quasi-neutrality condition,and the effect of plasma density and dust density and radius on the dust charging process is obtained.The influence of ion-neutral collisions on the ion charging current and dust surface potential is estimated for different plasma parameters.The charge fluctuation of dust particles is analyzed theoretically and the characteristic charging time of dust particles is estimated under laboratory glow discharge conditions.The 1D and 2D axial symmetry fluid models of dusty plasma are developed respectively according to the discharge tube size.The fluid model consists of particle continuity equation,drift diffusion approximate equation,electron energy conservation equation and Poisson's equation,with which the evolution of plasma and dust particle parameters can be described self-consistently in discharge tube.Then the fluid model equations are solved by using the finite element method under conditions of argon dc glow discharge,and the axial distribution of electron dens ity,charge of dust particles,electron temperature and electric field are obtained from the 1D axial symmetry fluid model,meanwhile the radial distribution of these parameters are obtained from the 2D axial symmetry fluid model.The local and nonlocal electron kinetic equations of dusty plasma are deduced based on the Boltzmann equation respectively by using the local field approximation and nonlocal approach,in which the electron-dust elastic and inelastic collisions are considered.The finite difference method is employed to solve the kinetic equations and the dust charging balance equation self-consistently,and the electron energy distribution function,effective electron temperature,electron transport coefficients,the ionization rate coefficients and dust surface potential are obtained for different dust parameters.Also,the calculation results from local and nonlocal kinetic models are compared with each other.The kinetic model is built for solid rocket exhaust dusty plasma.The particle species and the corresponding electron collisions are obtained according to the simulation results in the related reference.Considering the charging processes of Al₂O₃ particles,the electron energy distribution function,the relative permittivity,electrical conductivity and attenuation constant of rocket exhaust are obtained for different density of Al₂O₃ particles.And the calculation results from the kinetic model are compared with those results from Maxwellian distribution.