Scallop ice shape characteristics of swept wing based on large-scale icing wind tunnel experiment

Scallop ice is a special phenomenon that occurs during swept wing aircraft passing through icing clouds.It poses a great challenge for the icing safety assessment that the complex scallop ice shape feature and its mechanism are still unclear.In this work,a large-scale icing wind tunnel experiment of swept wing designed by NACA0012 airfoil is conducted in the Icing Wind Tunnel of China Aerodynamics Research and Development Center.The detailed three-dimensional ice shapes under 0°,15°,30°and 45°swept angles are obtained by laser scanning technology.The experimental results show that with the swept angle increasing from 0°to 45°,the 2D double ice horn structures show certain spanwise variation,and finally transform into complete scallop ice with ice thickness greatly enhanced in the stagnation line region.The empirical mode decomposition of the spanwise ice curve captures the high-frequency fluctuation on the scallop ice caused by the small-scale roughness element,while the trend with low frequency is not obvious.Based on the experimental data,a new complete scallop ice geometric model,named 5Points-5Lines-2Arcs(5P-5L-2A)model,is proposed,which can provide important basis for the quantitative description of complex scallop ice shape.

Experimental study of an anti-icing method over an airfoil based on pulsed dielectric barrier discharge plasma

Aircraft icing has long been a plague to aviation for its serious threat to flight safety. Even though lots of methods for anti-icing have been in use or studied for quite a long time, new methods are still in great demand for both civil and military aircraft. The current study in this paper uses widely used Dielectric Barrier Discharge（DBD） plasma actuation to anti-ice on a NACA0012 airfoil model with a chord length of 53.5 cm in a closed-circuit icing wind tunnel. An actuator was installed at the leading edge of the airfoil model, and actuated by a pulsed low-temperature plasma power source. The actuator has two types of layout, a striped electrode layout and a meshy electrode layout.The ice accretion process or anti-icing process was recorded by a CCD camera and an infrared camera. Instantaneous pictures and infrared contours show that both types of DBD plasma actuators have the ability for anti-ice under a freestream velocity of 90 m/s, a static temperature of -7℃,an Median Volume droplet Diameter（MVD） of 20 lm, and an Liquid Water Content（LWC） of 0.5 g/m^3. The detected variations of temperatures with time at specific locations reveal that the temperatures oscillate for some time after spraying at first, and then tend to be nearly constant values.This shows that the key point of the anti-icing mechanism with DBD plasma actuation is to achieve a thermal equilibrium on the model surface. Besides, the power consumption in the anti-icing process was estimated in this paper by Lissajous figures measured by an oscilloscope, and it is lower than those of existing anti-icing methods. The experimental results presented in this paper indicate that the DBD plasma anti-icing method is a promising technique in the future.

Effects of flow parameters on thermal performance of an inner-liner anti-icing system with jets impingement heat transfer

The multiple jets impingement heat transfer is widely applied in the wing anti-icing system.It is challenging to apply the similarity criterion to carry out the anti-icing experiments due to the complex flow and heat transfer behavior.In the present study,the full-scale slat model is used to carry out anti-icing experimental researches in a 2 m×3 m icing wind tunnel of China Aerodynamics Research and Development Center.The effects of icing parameters Liquid Water Content(LWC)and Median Volume Diameter(MVD)and hot air parameters(mass flow rate and temperature)on the thermal performance of an inner-liner anti-icing system with jets impingement heat transfer are studied.The effects of the experimental parameters are analyzed in detail by combining impingement and evaporation heat transfer mechanisms.The impingement hot air mass flow rate dramatically affects the heat transfer performance of the impingement stagnation region within the range of the experimental parameters.The temperature of impingement hot air and that of wing skin are approximately linear correlated.The experimental results show the effects of LWC and MVD on water film formation and runback ice accretion.The formation of water film is analyzed by an analytical method based on the wing skin temperature difference of dry and wet air conditions.

Flight safety oriented ice shape modulation using distributed plasma actuator units

Ice accretion on the wings seriously threatens the flight safety of an aircraft.From the perspectives of ensuring flight safety and saving power consumption,the ice shape modulation method using distributed plasma is proposed.Distributed plasma actuator units are designed to modulate the spanwise continuous ice at the leading edge into periodically segmented ice pieces,forming a wavy leading edge.Both airfoil and scaled aircraft model,with continuous and modulated ice,are experimentally investigated and simulated.Compared with the continuous ice,ice shape modulation can significantly improve the aerodynamic performance,flight control characteristics and flight safety.This method can save about half electric power,which is very beneficial for application.