Research On Characteristics Of The Blue Whirl And Thermal-intensification Effect Of Vortex

The burning of fossil fuel has led to serious environmental and climate issues,and new ways of clean and efficient energy-utilization need to be explored.Swirling combustion is an important technology for energy's clean utilizing,on which the "vortex/flame interaction" has a significant impact.That's why the latter has always been the research frontier and interested in by the community.In this research,attention has been paid to two new phenomena involving vortex/flame interactions:One is the blue whirl,which is inverted cone-shaped flames of blue-color that forms on water surface as a strong fire whirl recedes.Another one is the vortex thermal-intensification effect,that is,when there is a temperature gradient in the periphery,such as the hot environment formed by the flame,the cold vortex gets accelerated.The purpose of the research on the blue whirl is to figure out the formation condition as well as mechanism of it.As to vortex thermal-intensification effct,the principle and critical conditions for a specific vortex are the goals.All the studies are expected to deepen the physical understanding of vortex/flame interaction and provide new ideas for developing potential technologies of high-efficient swirling combustion as well as swirling intensification.For the blue whirl,the structural features and associated formation conditions were investigated and its characteristic was also modeled.For the vortex thermal-intensifaction effect,aspects were studied,including the generating method,vortex geometry,flow characteristics and the modeled description.As well as the mechanism of this effect.The whole research is primarily based on experiments.The results of study for blue whirl show that the circulation and heat-release-rate have decisive influence on the flame geometry and the aspect ratio of the flame ? can be used to distinguish the different flame status quantitively.The lrlation ?=15.49/?f*2 has been figured out,where ?f*is the swirl number,indicating a stable blue whirl forms as 2.4<?f*<5.2.All above suggest that the formation mechanism of the blue whirl is that a circulation-dominated flow is established by a strong fire whirl at first,then an induced bubble-mode vortex breakdown leads to the rapid mixing of fuel and air.The research for the thermal-intensification effect suggest that a high swirl is the key to maintain the hollow structure of the swirling jet while the axially weakening of the swirling intensity leads to its funnel-shape.It is found that the vertical vortex induced by the strong swirling suppresses the radial entrainment significantly.By increasing the temperature gradient at the vortex peripheral when axial flow is constant,the thermal-intensification effect could be excited,which is found significantly depends on how deeply the vortex and flame coupledAll above reveals the formation condition and mechanism of the blue whirl,extends the understanding of its nature.And both a theory of the vortex thermal-intensification and the experimental model for verification are proposed for the deeper exploration for the vortex/flame interaction in future.