| Ice may develop on certain exposed parts of an airplane, such as the windscreen, the wings, and the tail when the airplane flys in clouds which contain super-cooled water droplets. This is very dangerous since ice accretion can change the original aerodynamic characteristics of the airpalne and causes loss in lift, a larger resistance, and poorer operating quality. Similiar problem also exists on aircraft engines. For turbo-shaft engine used on helicopters, ice accumulated on the inlet guide vane of the engine can worsen air ingestion. In addition, sheded ice may be sucked into the engine and induces serious damage. In order to reduce the hazards caused by in-flight icing, most modern airplanes have been equipted with de-icing systems or anti-icing systems.This thesis investigates a widely used hot air anti-icing system and tries to find a simple and effective way to evaluate its performance. The research work is carried out both computationally and experimentally. First, an empirical computational method for hot air anti-icing system is introduced. It includes a method which treats the pipelines and vanes as a flow network, a method which calculates heat transfer coefficients on the inner and outer surfaces of a blade, and a method for dividing and simplifying blade surfaces while applying the energy balance eqition. Then, a numerical method for calcultating the water droplet impingement efficient is presented in detail. The temperature distribution on blade surfaces is obtained using the thermal module of a commercial software with the computation results from the empirical method as inputs. As a practical application of the methods introduced above, the hot air ant-icing system for a turbo-shaft engine is analyzed at two anti-icing states. The hot air anti-icing is tested in an ice tunnel. Results of the measured temperature on the blade surface validate both the actual performance of the hot air anti-icing system and the computational methods employed in the thesis. |
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