| Skin friction drag is an important part of the aerodynamics of modern hypersonic aircraft,and the maximum skin friction drag can account for 50% of the total drag of the aircraft,there is a great significance that reduces the aircraft surface skin friction drag and reduce aircraft energy consumption.At present,there are three main ways to reduce the skin friction drag: low surface energy coating drag reduction technology,micro-blowing/suction technology,rib/groove drag reduction.The application of low surface energy coating drag reduction technology is more extensive,and with the rapid development of nanotechnology,it often combine nano-technology with low surface energy coating method,the preparation of low surface energy with high performance materials.Based on it,this paper aims to develop a nano-modified low surface coating material to achieve drag reduction performance and reduce skin friction drag.This paper mainly research on three parts: fabrication of low surface energy coating,low surface energy coating basic performance test,low surface energy coating drag reduction performance test.The fabrication of low surface energy coating includes pretreatment of substrate,fabrication of nano SiO2/polyurethane mixed dispersion,fabriction of nano SiO2/polyurethane low surface energy coating,and so on.The nano-SiO2/ polyurethane mixed dispersion the fabrication process was such that the nano-particles were 15 nm,30 nm,50 nm,80 nm,100 nm SiO2 0.5 g?mass fraction 1%?,1.0 g,1.5 g,2.0 g,2.5 g,3.5 g,4.0 g,4.5 g,5.0 g were dispersed in 50 g of polyurethane paint curing agent,dispersed by a magnetic stirrer,sonication,high shear emulsification homogenizer,and then mixed with 100 g of polyurethane main agent,The nano-SiO2/polyurethane low-surface coating can be prepared by coating 10 ml of nano-SiO2/polyurethane mixed dispersion on the substrate surface,the spinning machine speed of 2000 r/min,spin coating for 30 seconds.Low surface coating basic performance tests include thickness,hardness,abrasion resistance,surface morphology,contact angle and surface energy.The results show that the thickness of the prepared coating is uniform and the difference is very small when the rotational speed is 2000 rpm and the time is 30 seconds.The hardness of the coating is increased to 4 H,which is much higher than that of the American wheat?HB?;the addition of nano-SiO2 to improve the wear resistance of the coating,when the particle size of 100 nm,the mass fraction of 5% nano-SiO2/polyurethane coating by the wear test after the test the mass reduction rate is 7.5%,the reduction rate of pure polyurethane coating is reduced by 13.2%,and the addition of nano-SiO2 greatly improves the wear resistance of the coating.By observing the microstructure of the coating surface,the low surface of polyurethane the results show that the mass fraction is 5%,the particle size is 100 nm SiO2,and the microstructure of the coating surface is similar to that of the "lotus leaf" effect surface structure.Polyurethane coating its surface energy is only 23.1m J/m2.The results show that the drag reduction performance of SiO2/polyurethane low surface energy coating with different mass fraction and different particle size is different.When the wind speed is 3m/s,5 m/s and 7m/s.Particle size of 100 nm,the mass fraction of 5% nano-SiO2/polyurethane low surface energy coating,drag reduction is the best.By comparing the drag reduction rate with the coating surface energy,it can be seen that there is a negative correlation between the surface energy of the coating and the drag reduction rate.When the surface energy of the coating is low,the coating reduction rate is high. |
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