After The Step Of Coupling Based On Pdf-the Rsm Steady-state Oxidation Process Of Numerical Simulation

The flow over a back-ward facing step with oxidation reaction is important for the industry and living. There are many experimental and numerical simulation researches on back-ward facing step flow, though, there is little study on the flow with oxidation reaction. The steady oxidation reaction over the back-ward facing step is studied in the paper using the composition PDF (Probability Density Function)–RSM( Reynolds Stress Model)method based on the before researches.Firstly, the Reynolds stress turbulence model is used to simulating the back-ward facing step flow under the cool condition. The influence of different distribute of velocity has been compared and the results is discussed. It shows that the numerical results agree with the experiment's well if the 1/7 power law was used at the entrance. The Reynolds Stress Models can calculate the back-ward facing step flow well.Secondary, the composition PDF transport equations coupled with the Reynolds Stress Model method is used to analyze reaction that the O₂ oxidizes the CH₄ under the low temperature and so that the reaction rate is slow. The two different kinds of reaction mechanisms are considered. The results show that the most influence of velocity magnitude on the oxidation reaction is surveyed at residence time. As the velocity magnitude of come on flow decreasing, the residence time would be increased and the concentration of the products will increase, too. Flow field, reaction mechanisms and the rate of the reaction were impact each other though the temperature field. The different reaction mechanisms show the temperature field likely when the oxidation reactions are slow. CO is produced at the bottom of the back-ward facing step if the two react steps mechanisms are employed.The combustion reactions under the high velocity magnitude between the CH₄ and the O₂ are also considered. It shows that the use of reactants has enlarged more than twenty times compared to the condition under the slow oxidation and the different action mechanisms show the different results. There is about 1000K disparity on the highest temperature of different mechanisms. It is reasonable for there is a large gap on the temperature of the flame of CH4 in the records and the highest temperature of flame under the one step reaction mechanism agrees with the one of the literature well. When it is combustion, the highest concentration of CO appears near the exit and a large amount of CO₂ is produced at the bottom of the back-ward facing step.The researches all conditions emerge that the highest temperature will always appear at the area where the velocity magnitude is the slowest and the back flow has no effect on the temperature field.