High-pressure turbine blades are key components in aero-engine turbines and operate in a very harsh environment. In the engine cycle, the high-pressure turbine blades are subjected to the impact of high-temperature and high-pressure gas generated after combustion. The effective cooling measures can ensure safe and reliable operation of the engine, prolong the service life of the engine, and reduce the wood formation of high-temperature materials. The performance of the engine depends to a large extent on the temperature of the turbine inlet, which is limited by the material and construction of the turbine blades. The turbine blades are thus continuously cooled so that they can operate safely and reliably beyond the melting point of the material at the permissible working ambient temperature.
The film cooling technology is one of the representative important structural improvements, which greatly improves the performance of the engine: air film cooling is to distribute n rows of cooling film holes in the blade height on the turbine blade leaves, and eject from the film holes. The cooling airflow forms a gas film on the surface of the blade body to block high temperature gas, thereby improving the high temperature resistance of the blade material. The processing quality of the cooling film hole directly affects the cooling effect of the high pressure turbine blade and affects the working life of the blade.
The processing method of the film cooling hole usually has a method such as laser processing or electric discharge machining (EDM). The former has a fast processing speed and low cost, but due to the laser melting effect, the roughness in the hole is not uniform, forming a thick remelted layer, and the actually measured hole diameter is smaller than the actual flow diameter of the hole; the latter has high processing precision. The roughness in the hole is uniform, and the remelted layer is thin, and the formed hole can be processed, but the processing time is long and the cost is high.
In order to obtain better quality of film hole processing, most of the high-vortex blade film holes in the aviation industry are processed by electric spark. In the EDM process of the film hole, there are the following problems: 1 the working fluid pressure is reduced, the matrix impurities, the residual surface of the inner cavity surface core, etc., which will lead to prolonged processing time, resulting in thickening of the remelted layer, and even Microcracks appear. 2 When the film is filled, the electrode and the original hole are completely overlapped, and secondary discharge is likely to occur, which may affect the surface state of the part. 3 At present, there is no mature processing technology in which the sharp corner of the slanting hole of the air film hole is rounded. It can be seen that the thickness of the remelted layer is a key factor affecting the quality of the film hole. The optimization of the process parameters can minimize the thickness of the remelted layer to improve the processing quality of the film hole.
The thickness of the remelted layer is the finger used to measure the quality of the film hole in the parameter design. It is the core factor of the parameter design. The basic idea is to make the processing quality of the film hole by selecting the best horizontal combination of all the parameters in the system. Preferably, the smaller the thickness of the remelted layer, the better the processing quality of the film hole. The analysis process of the remelted layer is actually a preferred problem. It uses the orthogonal table to measure the thickness of the remelted layer T as the evaluation index of the processing quality of the film hole, and uses statistical techniques to analyze and determine the optimal level combination. The greater the difference in the thickness of the remelted layer, the higher the level of influencing factors.
Screwing skills
"First Screw a screw, not all screwed in, screwed in one-third, and then screwed in the diagonal screw, so as to maintain the balance, and then use the diagonal approach to screw in the Other one-third. All screwed in and then tighten the remaining two-thirds of all. END 1 1, when it comes to this kind of thing, we first take out the wide rubber band prepared, is usually very common some rubber band on. 2 2, then the prepared rubber band on the head of the screw has been damaged or rusted 3 3, then the rubber band flat on the interface of the screw needs to be dealt with.
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