| Since the Wright Brothers invented "Flyer 1" aircraft,propeller propulsion and turbojet propulsion,as two typical power propulsion means of aircraft,have the advantages of large load,long endurance and quick reaction capability.Meanwhile,mechanical rotating parts of the propulsion system will produce sharp working noise and the worn parts are difficult to maintain.In 2018,Barrett’s team at MIT developed the first-generation ionic wind aircraft prototype.Compared with traditional aviation propulsion system,the ionic wind propulsion system has the advantages of simple structure,low noise and miniaturization,and has a broad application prospect as a new aircraft propulsion means.Previous studies on thrust and thrust to power ratio(T/P)of ionic wind propeller are mostly based on a pair of asymmetrical electrodes.There are few studies on the structural and non-structural parameters of propulsion system,as well as the experimental data of multiple electrode arrays in different arrangement.The output thrust and T/P of ionic wind propulsion system also needs to be further improved to expand its application fields.Firstly,the experimental platform of ionic wind propulsion system has been built.The output thrust was measured indirectly by a digital scale.Also,the corona current and T/P of the propulsion system were measured.The simplified corona discharge-airflow coupling model was established using COMSOL Multiphysics for multiple wire-airfoil electrode arrays.The spatial distribution of electric field,charge density and electrohydrodynamics force of different electrode configurations were simulated.The calculation time is reduced by 1-2 orders of magnitude compared with the fluid model.The error between the calculated results and the measured values is within 5%,which was then successfully applied to the optimization and engineering design of the ionic wind propulsion system.Secondly,the influences of structural parameters on thrust and T/P of ionic wind propulsion system were studied experimentally.When the diameter of wire electrode is 0.2-0.6mm,the airfoil electrode chord length 50-70 mm,and the shape NACA0010 or NACA0020,it is found that smaller diameter or higher conductivity wire electrode and larger leading edge radius airfoil electrode increase the thrust,but decrease T/P.Increasing the chord length of airfoil electrode can not only achieve a higher thrust but also a higher T/P.When the electrode array group spacing is 80-240 mm,the smaller the spacing,the higher the thrust and T/P.When the electrode arrays pair spacing 100-200 mm,the smaller the spacing,the lower the thrust and T/P.For the rectangular arrangement,the 1×n structure has the maximum thrust and T/P for a given number of electrodes.Thirdly,the influences of non-structural parameters on thrust and T/P of ionic wind propulsion system were studied experimentally.When the applied voltage amplitude is the same,the negative DC voltage can produce more thrust than the positive DC voltage,but the T/P is slightly smaller.The thrust increase with the applied voltage amplitude when the applied voltage amplitude is between the corona initiation voltage and the breakdown voltage,but the T/P is opposite.The thrust and T/P are not significantly affected when the ambient temperature and relative humidity are 13℃-32℃ and 68%-86%,respectively..In addition,when the wire electrode is coated with graphene,the thrust and T/P can be significantly increased,with a maximum increase of 39% and 35%,respectively.Finally,a 2×4 full-size(3m × 0.45 m × 0.25m)wire-airfoil electrode array is designed and manufactured based on the experimental and simulation results,which is an important part of a light and efficient ionic wind propulsion system.A full-state ground simulated thrust test was carried out for the ionic wind aircraft.The total thrust output of the propulsion system was 3N and the average T/P was 5.4N/k W.After optimization,it was applied to an ionic wind aircraft and achieved the outdoor flight target of about 300 meters within 1 minute. |
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