Development Of Self-excited Pulsed Slit Nozzle And Numerical Simulation Of Jet Impact Heat Transfer

Ultra fast cooling(UFC)technology as a core component of the new generation thermo mechanical control process(TMCP)technology has been widely used in industrial production.Ultra fast cooling technology played an important role in organizational performance improvement after the steel rolling.Ultra-fast cooling technology can effectively achieve finegrained strengthening,phase transformation strengthening and precipitation strengthening of steel materials,which can help produce high-quality and high-standard industrial products.The jet cooling in ultra-fast cooling equipment mainly used a combination of a slit nozzle and a high-density quick-cooling nozzle.In this subject,the slot nozzle arrangement can be added a self-excited oscillation pulse jet cavity structure.It is hoped that the heat transfer effect of the self-excited pulse jet will be studied by using the characteristics of the energy storage output of the pulse jet.The main contents of the paper are as follows:(1)The flow characteristics of self-excited pulsed jet inside the nozzle are studied by numerical simulation.By establishing the physical model of jet impact and setting the appropriate parameter conditions,the flow field distribution of slit self-excited pulsed jet,pressure and velocity at the exit center and other parameters were studied.(2)The effect of different structural parameters of self-excited pulse slit nozzle about the fluid flow characteristics inside the nozzle was studied.The different structural parameters inside the nozzle including the width and height of the upper nozzle,the width and height of the lower nozzle,the width and height of the oscillating cavity,the angle of the cone angle of the collision wall was studied.Finally,the different nozzle performances were evaluated by velocity average and velocity Standard deviations,and the optimal structural parameter scheme was selected.(3)Thermal-fluid coupling of self-excited pulse slit jet and continuous slit jet impinging on high temperature steel plate is simulated.The impact pressure and velocity vector changes in the impact line region are compared.The temperature field diagram,temperature drop curve and heat flux density change are analyzed.The simulated heat transfer effects of the two slit jets are compared.Finally,it is concluded that the heat transfer effect of the self-excited pulse jet is better than that of the continuous slit jet.(4)The simulation results of the self-excited pulse jet impinging on the high temperature steel plate were proved by experiments.According to the experimental data,the temperature field distribution of the jet impinging on the high temperature steel plate was analyzed.Temperature drop curve and peak heat flux density of the different structural parameters were obtained by using of the laboratory heat exchange platform.It is verified that the self-excited pulse slit j et has an improvement effect on heat exchange efficiency and heat transfer uniformity.