Four-way Coupling Mo Deling And Numerical Simulation Of Quasi-one Dimensional Gas-solid Two-phase Flow In A Supersonic Nozzle

Laval nozzles are widely used as core components in steam turbines,jet engines,supersonic spraying,needleless injection,fire extinguishers and other devices.Their design quality will have a decisive impact on the device performance.Aiming at the problem of complex two-phase flow when gas and particles interact in a supersonic nozzle,gas-solid phase coupling model,design of numerical calculation and solution method,and analysis of two-phase flow parameter characteristic are developed.Based on this,fully understand the two-phase flow behavior,accurately capture the physical essence,and systematically grasp the influence of parameters,and provide theoretical support for the design and operation of related devices.The main work and conclusion of this thesis are as follows:A mathematical model of single-phase quasi-one-dimensional flow of gas in supersonic nozzle is established by using the modified model of plate turbulent boundary layer and considering the influence of wall friction and heat transfer.Based on flux vector splitting of equation set,the variant form is discretized using the finite difference method.Then using the isentropic flow field as the initial condition and introducing the nozzle inlet constraint conditions,the model constant calibration,accuracy verification and parameter analysis of the single-phase gas flow in the supersonic nozzle were performed.By using the Euler-Lagrange method,considering the interaction between gas and particles and the impact of collision between particles,a quasi-one-dimensional model of gas-solid two-phase four-way coupling is established.Based on the numerical method of gas single-phase flow,the convergence solution of gas single-phase flow is used as the initial field,and the two-phase mass flow ratio at the nozzle inlet is limited.The particle phase data is updated using the particle motion and energy equations,and in the form of "source term" feedback to the gas phase equation in time to achieve the coupling between the gas phase and particle phase.The effects of parameters such as particle diameter,nozzle half expansion angle,total inlet temperature,total inlet pressure,and wall temperature are analyzed numericallyThe numerical calculation results show that the numerical simulations of gas single-phase flow and gas-solid two-phase flow are in good agreement with the previous experiments and numerical simulations respectively,which validates the validity of the mathematical model,numerical calculation and solution method in this thesis.The calculation results of gas-solid two-phase flow in the supersonic nozzle show that when the particle diameter increases,the outlet gas velocity and particle temperature increase,and the outlet gas static temperature and particle velocity decrease.When the nozzle half expansion angle increases,the outlet gas velocity,the particle velocity and Mach number increase,while the static pressure decreases.When the total inlet temperature increases,the outlet gas velocity and particle velocity increase significantly,but the Mach number decreases.When the total inlet pressure increases,the gas velocity,particle velocity,and Mach number increase.When the wall temperature increases,the outlet gas velocity,particle velocity and Mach number decrease.Innovation points in this thesis:(1)Based on the flat turbulent boundary layer model and considering the influence of nozzle channel geometry on the boundary layer,a modified turbulent boundary layer model is proposed.(2)By referring to the concept of calculating particles in Euler-Lagrange method,the statistical strategy of calculating the number of particles in grid cells and the method of calculating the high-order difference value of fluid parameters at the position of particles are designed.(3)A set of stable and efficient numerical calculation method is established by combining the flux vector splitting of the gas phase equation,the space dispersion of the fifth order WENO inner point,the difference construction of the third-order boundary point,and the three-step third-order TVD Runge-Kutta time integral.