| In aviation, ice accretion on the aircraft will be influenced seriously by the diameter of the supercooled droplets. Aircrafts might suffer supercooled large droplet(SLD) which diameter is bigger than 50 um. SLD icing usually exceeds the present icing protection zone.Under circumstances of SLD, rough ice ridge forms easily, the shape of the airfoil changes,drain field characteristic of the airfoil alters seriously, and the aerodynamic performance of the aircrafts deteriorates tremendously. In SLD icing, the icing area is larger, the frozen rate is faster, the consequences are more seriously, and flight security problem occurs more often, compared to normal icing. At present, the Federal Aviation Administration has amended the original icing envelop to include SLD icing environment.SLD icing detection methods are presented in this thesis. First, characteristics of the SLD are studied. Based on the impact characteristic of SLD, a special structure of the detector which can distinguish SLD icing and normal icing is designed using software simulation. Then, the SLD detection method using optical fiber icing sensor is proposed,and the optical fiber icing detection system is designed. Thickness of ice on the surface of the optical fiber icing sensor can be detected by this detection system. Furthermore,another SLD icing detection system based on image processing technology is proposed in order to get the icing information of the detector better. Ice thickness of the detector and its distribution information can be obtained through the image processing system.In addition, icing wind tunnel experiments and high-low temperature chamber experiments are conducted using the two SLD detection systems. The experimental results show that the detection systems can distinguish SLD icing from normal icing, and get the icing information of the surface of the detector. |
