Infrared Nondestructive Testing In Turbine Blade Cooling Duct Blockage

Aero-engine turbine blade is the main part of the engine, which to provide high impetus for aircraft. Blade working environment is extremely bad. High temperature, high pressure, high speed load makes the blade is very easy to be damaged. Especially cooling air-duct of the blade is easily to be blocked, this situation can cause damage to the engine and make big aircraft accident. X-ray detection commonly used for air duct blockage, but the test has extremely complicated procedure, include filling the lead powder into cooling air-duct of the turbine blade.Considering the limitations of other detection methods, this topic take advantage of thermal imaging, suggest using infrared nondestructive testing methods in detecting turbine blade cooling air-duct blockage.According to the internal structure of turbine blade, material properties, the cooling mechanism of in-service blade, this paper established the heat transfer model of blocked cooling air-duct, and quantitative analysis the relationship between air duct blockage parameter, the experiment control parameters and infrared thermal imaging parameters, temperature. Deduced the formula of defective area and the non-defective area temperature difference on the surface of the blade with the time, heat transfer coefficient, water stimulation temperature difference, and the relation between block size. After comparing a variety of experimental thermal excitation mode, considering that the water has a large heat capacity, which can bring enough heat and also has less viscous coefficient., which would not cause secondary pollution to the blade air-duct, we choice hot and cold water alternately as the infrared detection of thermal excitation carrier. Based on the hot and cold water to simulate the thermal excitation way, take the gradient search optimization algorithm in the air duct blockage parameter specific cases to achieve the best result of the test to determine the experiment control parameters value area, which provides a theoretical basis for the selection of experimental parameters.The experimental results shows that in the optimization time parameter range from surface observations to a maximum temperature difference, so that the temperature field model and its optimization is effective.