Supercooled Water Droplet Impingerment Property And Thermal Balance Analysis Under The Condition Of Icing

Ice accretions may occur on certain exposed parts of an airplane, such as the airfoil and aircraft engine when the airplane flies in clouds which contain supercooled water droplets. This is very dangerous since ice accretions can seriously degrade aircraft performance and handling characteristics. Investigation on icing mechanism and effects is the basis of anti/deicing equipments design and the establishment of flight and operation rules in icing condition.The research of droplet impingement property and the caculation of anti-icing surface temperature are the basis of airplane anti-icing study. They are investigated by theoretic analysis and numerical simulation methods in this thesis. It mainly includes the following:Firstly, the Lagrange method is proposed to establish the motion equation of supercooled water droplet, and the CFD software Fluent is applied to calculate the airflow field, and the droplet impingement property on the airfoil surface is investigated, and then a program for the calculation of two-dimensional airfoil and three-dimensional airfoil droplet impingement property is developed.Secondly, the influence of flight velocity, droplet diameter, temperature and droplet gravity on droplet impingement property are investigated. Meanwhile, the droplet impingement property of supercooled large droplet is obtained and its'practical application is discussed. Besides, taking the case of an engine cone section, the impact of modeling method and boundary layer on the local collection coefficient is investigated.At last, based on the calculation of flowfield around the airfoil and the droplet impingement property, the widely used hot air anti-icing system is studied and the Messinger energy balance model of anti-icing study is modified based on the energy balance theory and coupling effect of mass and heat transfer. And based on the modified model, a special program is developed to calculate the temperature of the anti-icing surface. Combined with pratical engineering needs, this thesis also studies the relationship between anti-icing heat requirement and water droplet diameter.The present research involves two aspects, the droplet impingement property and heat flux analysis of the airfoil surface .It is for the first time that the gravity effect on the droplet impingement property is analyzed and the properties of supercooled large droplet are obtained. Some new ideas and methods are presented on the aspect of improving calculation efficiency and result accuracy. The achievements of this paper provide some significant reference for the mechanical analysis of aircraft and engine icing, design of anti/deicing system and perfection of icing wind tunnel technique.