Analysis Of The Diesel Exhaust Particle Transport And Deposition In Turbulent Flow

Particles transport and deposition are quite often encountered in diesel exhaust sampling device, the exhaust gas recirculation system and exhaust after treatment devices, which have a significant impact on those devices. Better understanding of diesel exhaust particulate transport and deposition on the walls of a turbulent channel flow is significant.A turbulent flow model is established and the fluid velocity field and temperature field is generated by the FLUENT code. The present results agree well with the available DNS results. The near wall velocity gradient and temperature gradient distribution were analyzed, the results show that Inlet velocity and inlet temperature play an important role on the near wall velocity gradient and temperature gradient.A gas-solid two phase flow model-particle trajectory model is used to reveal particle physical behaviors. The instantaneous fluctuating velocity is generated by a random method. Turbulent dispersion of particle is taken into account by adopting the discrete random walk model. A computational algorithm for solving the motion of a particle in the turbulent flows field is developed. The computation model is applied to study the transport and deposition of spherical particles. Particle equation of motion including Stokes drag, Brownian, Saffman lift, gravitational and Thermophoretic forces is used for trajectory analysis. Trajectory and its influencing factors of spherical particles were calculated and analyzed, Influence of each force, inlet velocity, inlet temperature, channel width and channel length on the particle deposition velocity are investigated.In the second part of the thesis, the kinematics and dynamics of an ellipsoidal particle suspended in the turbulent channel flow field is outlined. On this basis, the motion model of the ellipsoidal particle is established. The particle equations of motion used include the hydrodynamatic forces and torques, the shear-indueed lift, the graviational and the Thermophoretic forces. Trajectory and its influencing factor-aspect ratio of ellipsoidal particles were calculated and analyzed, Influence of aspect ratio and inlet velocity on the particle deposition velocity are investigated.The result, shows that the elongated particles deposition rate increases significantly when the aspect ratio mcreases.The results of this thesis can provide a fundamentnal understanding of transport and deposition of diesel exhaust particulate and particulate trap technology of purification in turbulent channel flows.