Topical issues of gas turbine engine friction unit reliability

Operation of bearings and seals of gas turbine engines (GTE) is associated with adverse wear effects of friction parts. Boundary friction occuring in startup - shutdown and extreme engine operating modes is characterized by high values of the friction ratio and damage of friction surfaces in the contact zone. This results in damage accumulation, wear and changes in the geometry of the friction surfaces, which leads to degraded performance properties of the product and functional failure. In this case the requirements for fixed geometry in turbomachinery bearings and seals are very strong, since any undesirable change in the shape or size of the working gap leads to a decrease in unit efficiency and engine efficiency as a whole. In addition to the boundary friction regime, the efficiency of bearing and sealing units is decreased due to power friction losses. These losses are always present in friction units, but they can have a significant effect on the unit performance in off-optimum operation (including the turbulent flow regime in the working gap and the wrong choice of lubricant). Some of these problems are solved constructively by changes in the shape of working surfaces, use of special materials and advanced coatings, as well as timely control of the lubricant purity.