Basic Research On Phase Transition Of Droplet Impacting On Periodic Plasma Nanostructure Towards Anti-icing

Supercooled droplets in the clouds will turn into ice after impacting on the aircraft surface.The icing will make the aerodynamic performance of aircraft decline rapidly,which is a major safety hazard during flight.Antiicing is an important method to prevent icing,and it is essential to anti icing the key parts of the aircraft in flight.The main anti-icing methods used in aircraft are hot gas anti-icing and electric heating anti-icing.Nevertheless,the anti-icing area of aircraft is too large,these methods have the problem of high power consumption,which is difficult to be deployed in such large area and used for a long time,and the thermal anti-icing structure used in the wing also affects the aerodynamic performance in some extent.Therefore,reducing the power consumption while ensuring the anti-icing effect,making the anti-icing structure easy to deploy,and less affecting the aerodynamic shape of the aircraft has become an important issue to be solved urgently.As a new anti-icing method,plasma anti-icing has the advantages of fast response,simple geometric structure and easy deployment.Plasma antiicing can solve some problems brought by thermal anti-icing,but its high power consumption and low energy utilization rate remain problems to be solved in its anti-icing application.Considering the problems of plasma antiicing,this thesis introduced periodic plasma structure and proposed a periodic plasma actuator(PPA)with alternating distribution of plasma and metal electrode array.The periodic plasma structure are especially arranged to improve the plasma energy utilization rate,then nanostructures are coupled to the metal electrodes to improve the discharge performance and optimize power consumption.Aircraft icing is a special phase transition phenomenon with droplet dynamics,and anti-icing mainly uses heat exchange to make the temperature of the supercooled droplets reach above the icing critical point,so that it cannot turn into ice or directly evaporated,both of which are droplet phase transition processes.Based on this,this paper sets up a droplet phase transition exploring system to investigate the impact of periodic plasma structure on droplet phase transition,and systematically performs the following innovative research using high-speed cameras and infrared cameras:1)Influence of periodic plasma on droplet phase transition process and evaporation power consumption: When periodic plasma exists,droplets will have a larger spread diameter,lower peak height,and smaller static contact angle,and the density of the plasma will positively promote this phenomenon.When the periodic plasma and electric heating produce the same surface temperature field,the power of periodic plasma heating is 1/3 of electric heating,but the evaporation efficiency of droplets on the surface of PPA is 2.2 times that of electric heating.2)Effect of PPA with nanoelectrode on droplet phase transition and evaporation power consumption: In order to reduce the evaporation power consumption of droplets on the PPA,we tried to grow zinc oxide nanostructure on the PPA metal electrode array.Then the periodic plasma actuator with ZnO nanostructure electrode(ZnO-PPA)is fabricated,which successfully reduced the power per square meter of ZnO-PPA by 1.023 k W compared with PPA under the same discharge parameters,and reduced the required power at the same evaporation efficiency.3)A special spreading morphology of the droplets in the periodic plasma generated by the nano-electrode structure was found: compared with the oval-shaped spreading morphology of the droplets in the periodic plasma,the droplets spread along the periodic plasma region to the droplets' periphery after spreading on the periodic plasma nanostructure,and the overall shape is radial to the surroundings,which will increase the contact area between the droplet and the heat source area and accelerate the evaporation speed of the droplet.Finally,we summarize the current research work,and look forward to the optimization direction of PPA in the next stage and the future anti-icing research.