Numerical Simulation And Experiment For Venturi Rich/Lean Burner

The separation characteristics and resistance characteristics of venturi rich/lean burners are studied in this dissertation. The methods used to do this are numerical simulation and experiment. This study can be divided into several parts as below:Firstly, detailed summary and evaluation of the international and domestic works on gas-solid two-phase flow in rich/lean burners were reviewed, and some characteristics of those works were sorted out.Secondly, the key to find out resistance characteristics of venturi rich/lean burners is to study resistance in turbulent flow, and this is also the focus of lots of engineering problems. The resistance of hydrodynamically smooth/rough pipe have been calculated using several different turbulent models, the results from those models were compared with Nikuradse's data to find out the best turbulent model in doing this kind of works (all numerical simulation were based on FLUENT software).We found: if the turbulent flow in a pipe is hydrodynamically smooth, the roughness of the pipe shall not be considered, and low Renault number turbulent models , especially Spalart—Allmaras turbulent model, shall be adopted. The results using low Renault number turbulent models with grids of enough fineness are quite good. If the turbulent flow in a pipe is hydrodynamically rough, the roughness of the pipe shall be considered.There are some other important conclusions derived from foregoing study:The flow resistance in a pipe is mainly decided by velocity distribution near the wall, regardless the style of the flow-laminar or turbulent(hydrodynamically smooth) flow. If the sizes of two pipes are the same, the flow resistance in one pipe, in which the grads of axis velocity near the walls is bigger, is bigger than that in the other pipe.The ability to discover the real velocity distribution near the wall is the key whether a turbulent model can calculate the resistance in a smooth/rough pipe correctly or not.Thirdly, the relationships between separation characteristics and resistance characteristics with physical dimensions of venturi rich/lean burners were studied using numerical simulation. The study also shows that: to get good separation characteristics and resistance characteristics of venturi rich/lean burners is to choose a set of suitable physical dimensions. This study is used to design a venturi rich/lean burners with good characteristics.Lastly, a set of tests under controlled conditions were carried out to study the separation characteristics and resistance characteristics of venturi rich/lean burners.