Numerical Computation of Fuel-Air Mixing in a Two Phase Axi-Symmetric Coaxial Free Jet Flow

摘要

The problem of hydrodynamic and thermal interactions between a fuel spray and a mixing region of two unconfined coaxial axi-symmetric jets is formulated in terms of a set of parabolic differential equations for the gas phase and a set of Lagrangian ordinary differential equations for the spray. A consistent, second-order accurate hybrid numerical scheme is used to solve these equations. The subsystem of the gas-phase equations have been solved by three different numerical methods: an explicit approach, and iterative implicit method and a non-iterative block implicit method. The subsystem of liquid phase equations are solved along the droplet trajectories by a second order Runge-Kutta scheme. That is, a Lagrangian or method of characteristics approach is employed. The computations have been made to predict the hydrodynamic and thermal mixing regions of the gas phase as well as the trajectories of each individual group of droplets. In addition, the size, velocity and temperature associated with each group are predicted following these trajectories. The relative merits of each of these numerical techniques is discussed in terms of stability, accuracy and efficiency. (ERA citation 09:017079)