Developing Approaches to the Cut-In Assessment in the Labyrinth Seals

Aeronautical and Space-Rocket Engineering


Аuthors

Matveev A. A.*, Falaleev S. V.**, Tisarev A. Y.***, Kul'kov S. D.****

Samara National Research University named after Academician S.P. Korolev, Moskovskoe shosse, 34, Samara, Russia

*e-mail: 2018-00957@students.ssau.ru
**e-mail: falaleev.sv@ssau.ru
***e-mail: tisarev@ssau.ru
****e-mail: Kulkov2002@yandex.ru

Abstract

ormal operation. Necessary cooling is being ensured by the secondary air system. Labyrinth seals are being emmployed to regulate the amount of air to cooling and have great influence on the performance of engine. Labyrinth seals wear during engine transients. Labyrinth seals are being employed for regulating the quantity of air incoming for cooling, and greatly affect the engine operating characteristics. Labyrinth seals wear during the engine transients. The labyrinth seals wear reduces their hydraulic resistance, which increases leakages and reduces the engine components efficiency.
The presented article considers causes of friction in the wearable stator elements. The main cause of the cut-in can be attributed to the temperature mismatch between the stator and rotor during transients. The moment after takeoff and during reacceleration are most indicative moments in the flight cycle, when the cut-in may occur.
The following wear parameters can be identified. These are the depth and width of the wear groove. Factors affecting the wear parameters have been identified. They are the size of the radial mounting gap, the cutting-in time, the rate of the operating modes variation, the pitch of the combs, and the seal-to-bearings distance.
The authors considered experimental methods for the wear output parameters determining. Internal gauges are employed for the penetration into smooth coatings measuring. 3D-scanning and casts making are being applied for the honeycomb coatings. With ideal visibility, the grooves can be identified and their depth can be determined, though under bad conditions the honeycomb surface becomes inaccessible for scanning, and wear cannot be identified. The wear parameters obtaining with casts involves obtaining a wear profile and the depth of the grooves determining by a microscope. The article considers various materials for the casts making. Inferences were drawn on the methods considered applicability.
The engine thermomechanical model should be elaborated to compute the gap in the labyrinth seals and wearable coating wear. This model application allows, as the result of the non-stationary computations, determining the gap in the labyrinth seals during the cycle and fixing the wear. All models were developed in the ANSYS Mechanical APDL. The obtained results accuracy will depend on the computation model correctness and the boundary conditions, namely thermodynamic and gas-dynamic parameters.

Keywords:

wear forming, labyrinth seal, cut-in, wear grooves in seals, non-stationary thermal process, thermo-mechanical model, wearable coating wear, cut-in determining technique

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