| Icing is a major threat to aircrafts and large aircrafts are usually equipped with hot gas system to prevent ice formation.However,the flight missions and flight conditions of modern unmanned aerial vehicles(UAVs)are complex and they are mostly not equipped with icing-protection devices.Especially for those small and medium-sized UAVs,the airborne de-icing energy is limited and icing probability is comparably higher than large ones.Therefore,in order to meet the urgent needs of modern UAV’s strong environmental adaptability,it is urgent to develop miniaturized,high efficiency,low energy consumption,and electric control anti-icing and de-icing devices.This dissertation applies the forefront active flow control(AFC)technology to the field of anti-icing and de-icing.As the actuator is the basis of the overall research,a new electro-dynamic dual synthetic jet(DSJ)actuator and heated dual synthetic jet actuator(HDSJ)are designed and studied first.Then a scheme using HDSJ for UAV anti-icing and de-icing is put forward,and the anti-icing mechanism and effect are studied by numerical simulation.Also,de-icing experiments using HDSJ is carried out on the ground.The anti-icing and de-icing technology using HDSJ is primarily studied in the dissertation.Firstly,a new type of electro-dynamic DSJ actuator is designed and manufactured.And the flow field and vortex structure characteristics above the dual exits are studied by PIV experiment and POD(the orthogonal decomposition and reconstruction method)analysis.The contribution rates of different modes to flow field are calculated,in which the first eight modes reconstructs the flow field with satisfaction.Moreover,comparisons in the performance of the piezoelectric and electro-dynamic DSJ actuator are analyzed,through which the piezoelectric DSJ actuator is chosen to design the HDSJ actuator.In order to determine the actuator’s thermal characteristics,the jet temperature measuring experiment is carried out,which lays the basis for numerical simulation of the next step.Secondly,the method of using HDSJ to prevent ice accretion is proposed,and the double anti-icing mechanism is discovered by numerical simulation.Under the condition of low speed incoming flow,the droplet impingement characteristics of the airfoil embedded with SJ/ DSJ actuator in the leading edge are studied individually.And the results show that under the control of SJ/ DSJ,the water droplet in the front edge of airfoil is blocked,thus reducing the ice accretion.The mechanism is that a "vacuum area" of water droplet in a pair of stable closed recirculation zone in front of the leading edge of the airfoil is formed with the help of DSJ.Due to the low velocity and mass fraction of water droplet in the recirculation zone,the water droplet collection rate distribution on the leading edge are changed,which can change the ice shape,playing a role of virtual aerodynamic shape.Additionally,a wedge embedded with a heated DSJA actuator subject to the supercooled flow is investigated.The results show that there is a significant reduction in the instant ice growth by using heated DSJA beacause the hot jet strengthens the heat convection on the wedge surface.Thirdly,under the condition of tense icing environment,the jet exciters may be frozen.In order to investigate the HDSJ actuator’s de-icing ability,microscopic visualization experiment of de-icing on airfoil using a HDSJ actuator has been carried out.The practicability of de-icing using the HDSJ actuator has been proved and the influence of environment temperature and ventilating angle is then studied individually.Compared to heated airfoil model without a HDSJ actuator,the HDSJ actuator helps to decrease the de-icing time by about 25.0% to 36.4%.As the DSJ actuator can promote heat diffusion,which helps accelerating the de-icing process on the airfoil model,it is thus a preferable way to use HDSJ in flight de-icing.What’s more,experiment also reveals that de-icing effect is better when the ventilating angle is close to 90°. |
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