The Simulation Of The Process Of Shock Wave And Flame Interaction

This paper is concerned with research into the generation of detonation during the process of shock-flame interaction. It is a part of the Natural Science Foundation of China project (10802077 / A020403): The Simulation of Shock-Flame Interaction and Mechanism of Deflagration-to-Detonation Transition (DDT). Theoretical models, computational program and numerical simulations are presented.The theoretical analysis introduced three instability phenomena including their generative mechanisms: Richtmyer-Meshkov instability, Kelvin-Helmholtz instability and Rayleigh-Taylor instability, particularly the R-M. The generative reasons for the baroclinic effect and the role it plays in the process of the generation and development of vortices and R-M instability is discussed, and the analysis of K-H and R-T joint instability and its impact on fluid interface instability was introduced. Five phases of the development of instabilities were introduced, particularly the nonlinearity processes of the instability. A mathematical model was established. The mathematical model consisted of a long shock tube, maintained at normal temperature and atmospheric pressure, filled with a hydrogen-air mixture. A burning orbicular flame was fixed in the pipe with its central axis just cross the center of flame, an incident shock wave was introduced at left side of the tube, and the shock-flame interaction began once the shock reached flame. Models of adding small flames and obstacles into the flow field were adopted.2-dimensional Euler equations coupled with chemical reactions were used as control equations. Numerical simulation of the process was performed using the space-time conservation method. The detailed hydrogen-oxygen chemical mechanism, which included 9 species and 20 element reactions, was included. The computational program was written using FORTRAN, and run on a high performance computer.An analysis of the results indicated two key parameters Mach number and flame radius for the generation of detonation. When the Mach number was below 1.4, detonation would never appear. A flame with larger radius would generate detonation, when the Mach number was increased to 2.0, but for Mach numbers of 2.3 or larger, all the flames were able to generate detonation no matter how big the flame radius was. Flame radius plays an important role in shock reflection formation and its direction of propagation. Detonation was easily generated in the regions where energy gathered or where there were multiply shocks. The addition of small flames or obstacles to the flow field could increase the chance of these two areas'generation, hence the process of the generation of detonation was shortened in terms of space and time.