The test bench development improvement of the gas turbine engine due to the application of the new method for axial force determining impact on the radial-thrust bearing

Aeronautical and Space-Rocket Engineering

Thermal engines, electric propulsion and power plants for flying vehicles


Аuthors

Khramin R. V.*, Slobodskoi D. A.**, Lebedev M. V.***, Sobul’ A. V.****

United Engine Corporation “Saturn”, 163, Lenin av., Rybinsk, Yaroslavl region, 152903, Russia

*e-mail: roman.khramin@ues-saturn.ru
**e-mail: denis.slobodskoy@uec-saturn.ru
***e-mail: maksim.lebedev@uec-saturn.ru
****e-mail: aleksandr.sobul@uec-saturn.ru

Abstract

A radial-thrust bearing of rotor supports is one of the most critical elements of aviation gas-turbine engine, as its failure leads to the engine destruction. To ensure the required reliability of such bearings, experimental studies allowing increase the accuracy of design models employed for the bearing life determination under engine operating conditions were performed. One of the main factors affecting the endurance of radial-thrust bearings is the axial load.

The current quantitative method of axial load determination during engine tests employs the technological supports with dynamometric rings. Qualitative methods of axial load determination based on vibration sensor readings do not allow correct determining of the axial load.

This article presents the method used to measure the axial force applied to radial-thrust bearing. The method is based on dynamic strain gauging of bearing rings. Strain gauges are installed into special slots in the bearing rings. The slot width should be maximum possible but not exceeding the distance between the adjacent rolling elements. The slot depth should comply with the requirements for admissible deformation of raceways and sensitivity of the strain gauges.

The strain gauges readings are taken in the values of relative strain (mm/mm). For ease of use, these values are converted into stresses values (kgf/mm2) by multiplying them by the elasticity modulus of the bearing ring material.

To determine the dependency of the strain gauge readings on the axial load, calibration on a special installation is performed. During calibration, the strain gauges measure the variable stresses in the slot. The amplitude of variable stresses with flicker frequency of the rolling elements is proportional to the axial load, and is a key parameter. To determine it, the signal from the strain gauge, at any given moment, is represented as a Fourier series, and spectrum of the signal amplitude-frequency response is formed. This spectrum is being used to determine the amplitude on flicker frequency of the rolling element. Based on the test results, the calibration factor is determined which characterizes the dependency of axial load on the amplitude of the strain gauge reading signal. Then, by the measured dynamic stresses recalculation, the axial load applied to the bearing is determined.

The accuracy of axial load measurement by dynamic strain gauging of bearing rings does not exceed ±1% of the reference load. The above­described method has been applied during engine tests together with the current method with temporary supports and dynamometric rings.

Based on the test results, the accuracy of axial load determination has been increased and the number of the required engine tests has been reduced.

Keywords:

aviation gas-turbine engine, test bench development, accuracy of axial load determining, dynamic strain gauging, radial-thrust bearing, calibration

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