The Experimental And Numerical Simulation Of Self-excited Oscillation Pneumatic Nozzle

Self-excited oscillation pulsed jet is a new type of jet,which has the advantages of high efficiency and energy saving.It can be used in mineral exploitation,dirt cleaning,natural gas transportation and other fields.The self-excited oscillation nozzle has the characteristics of simple structure,small volume,using its own special structure and generating pulsed jet without external excitation.As the core component of the self-excited oscillation pulsed jet system,scholars at home and abroad have made in-depth research on the self-excited oscillation nozzle with water as the medium,but the research on the self-excited oscillation nozzle with complete gas medium is insufficient.Therefore,the jet characteristics of the self-excited oscillation pneumatic pulsed nozzle are studied by combining theoretical analysis,experimental research and numerical simulation.Firstly,the research background,significance and research status of self-excited oscillation pulsed jet were summarized.And the main work of this topic was described.The frequency characteristics of self-excited oscillation pulsed jet and the natural frequency of nozzle were analyzed theoretically,and the frequency expressions were obtained respectively.The effective feedback conditions for self-excited oscillation pulsed jet were obtained.Secondly,the content and purpose of the experiment,the experimental device and the data acquisition system were introduced.Through the experimental study on the flow field of self-excited oscillation pulsed jet,the effects of the chamber length,chamber diameter and other structural parameters,as well as the nozzle inlet pressure on the self-excited oscillation pulsed jet were analyzed,and the optimum structural parameters and operating parameters were determined.Then,the computational fluid dynamics software,numerical model and calculation method were introduced.Based on the Delayed Detached-Eddy Simulation(DDES),ANSYS FLUENT 14.5 was used for numerical simulation.The influence of the structural parameters such as the diameter ratio of upper and lower nozzles,chamber length,chamber diameter and the operating parameters such as nozzle inlet pressure and turbulence intensity were analyzed.The mechanism of self-excited oscillation pulsed jet was revealed by analyzing the pressure and velocity fields in the oscillation chamber.Finally,it summarized the results of the study,points out the shortcomings,and determines the direction of further research.