Research Of Jet Flow Mixing Characteristics Based On Pulse Micro-Jets Controlled

Mixing control of turbulent jet is popular in the field of fluid research,which is used to get a better combustion of the gas jet,reduce pollutant emissions,make use of energy,rapid diffusion for cooling,and reduce the flow noise,etc.The control of mixing in flow flied is divided into active control and passive control technology,and the active control technology is used in this paper.The pulse micro-jets are distributed laterally and vertically to drive round jet.The diffusion and mixing enhancement in turbulent flow is studied by change the distribution of pulse micro-jets and the flow parameters such as actuation frequency,mass flow rate and duty cycle of pulse micro-jets.Firstly,the relation between the mixing characteristics of flow field and the distribution mode of the micro-jets actuation is studied.2,3,4,6 micro-jets are distributed symmetrically around round jet under the condition of each micro-jet flow parameters uniformity.Using the Large Eddy Simulation method of commercial software ANASYS Fluent to simulate the jet flow controlled by micro-jets,and the reliability of the numerical simulation result was verified by the experimental date.By comparing the entrainment mixing enhancement based on the simulation result,it is found that 2 symmetrical pulsed micro-jets actuation has the best effect on mixing enhancement.Second,the excitation effect of micro-jet actuation is analyzed.The ratio of the pulse actuation frequency to the vortex shedding frequency FV/FO is set from the range of 0 to 2.The better flow state is sensitive to the pulse actuation frequency by analyzing the coherent structure and velocity decay rate in external flow field,and the entrainment mixing enhancement is the most obvious when FV is equal to FO.Third,the excitation effect of mass flow rate and duty cycle of micro-jet to the mixing is studied.The mass flow rate and duty cycle of the micro-jet were regulates through the solenoid valve,and the mixing enhancement in external flow field is analyzed.The results shown that the mixing enhanced with the mass flow rate increase when Cm<0.05%,and weaken with the mass flow rate increase when Cm>0.05%.Besides,the mixing weaken when the duty cycle increase from 10% to 20%.At last,this paper explains the physical mechanism of mixing enhance and reveals the process of development and evolution of vertical structure in round jet under micro-jet actuation.