DE2915200A1 - Vibration testing of turbine rotor blades - using periodic compressed air injection via mounting rotating in centrifugal - Google Patents

Abstract

A vibration tester for axial flow turbine engine rotor blades using periodic compresed air injection induced resonant vibrations produces representative loadings including superimposed aircraft dependent loads not conventionally applied during test. The most operationally highly stressed components are accurately test loaded to produce more reliable results than conventionally achieved. A disc (2) carrying a blade (1) is mounted coaxially in a rotation symmetrical housing (3) to which it is rigidly attached via a stub axle (2'). The axle and disc have compressed air inlet channels (6, 6') and housing and axle have outlet channels (7, 7'). The disc has peripheral compressed air outlet nozzles. The disc stub axle and a corresp. stub axle (3') on the housing itself (3) run in bearings in an evacuated centrifugal stand chamber (5) within which the disc and housing assembly rotates.

Description

Vibration testing device for rotor blades

of turbo machines, with excited by periodic compressed air flow Resonance vibration of rotor blades of axial flow turbomachinery, i.e. of turbines or compressors, often break during operation due to vibration fatigue. this leads to usually to high damage costs and often to the endangerment of people, z. B.

due to engine failure.

So far, one has had one when examining vibration resistance firmly clamped stationary blade either mechanically, electrodynamically or by means of periodically supplied compressed air excited to resonance vibrations. The results Such examinations are for the load actually occurring in the company however only limited meaningful, because the centrifugal force, which superimposed one Stress caused is not taken into account.

In such laboratory tests, the one that is subjected to the highest stress in operation Component zone not properly checked, so that the determined service life is often quite out of service lies.

The object of the invention is to provide a test device of the aforementioned To show a way that avoids these disadvantages, that is, a very operational one Vibration testing of the blade is permitted.

This task is with the characterizing features of the claim 1 solved, while claims 2 to 5 indicate further improvements.

The invention is based on the drawing with an exemplary embodiment explained; 1 shows the test device according to the invention in longitudinal section and FIG. 2 shows a modified vibration excitation device.

According to Fig. 1, the test blade 1 is suspended in a disk 2, which has then been balanced. The disc is coaxial in a rotationally symmetrical one Housing 3 with Radially outwardly reduced width used and firmly connected to it by means of a shaft stub 2 '. The housing 3 is means of the disc shaft stub 2 'with a drive device not specifically shown is connected and by means of its own shaft stub attached to the opposite side 3 'rotatably mounted in a centrifugal chamber 5, preferably with vertical standing axis.

This centrifugal stand chamber is used to reduce friction losses 5 designed to be evacuable.

Through that drive device, the housing 3 together with the disk 2 can also Test blade 1 can be brought to the desired test speed. The shovel will then periodically via discharge nozzles (4) attached to the outer area of the pane pressurized with compressed air and thereby excited to resonance vibrations. The to it The required compressed air is supplied via channels 6, 6 'in the stub shaft 2' and in the disk 2 supplied, while the exhaust air through the housing interior 7 'and a separate Channel 7 is discharged.

The oscillation amplitude of the blade is determined by the air pressure or the Air volume controlled and by known optical or electronic devices measured.

If the blade breaks, only a controllable imbalance occurs on; Broken blade pieces are attached to the circumferential wall of the circumferential rotationally symmetrical Housing 3 caught.

Because of the excitation of vibrations by compressed air, I also do a test no problems at high temperatures.

According to Fig. 2, the discharge nozzles 4 for the compressed air in a be designed as a separate device, which in addition to the test blade 1 on dovetail or fir tree grooves is releasably suspended. Such a device can also be used. be attached to its own disk or to the rotationally symmetrical housing 3.

Blank page

Claims (5)

Claims 1. Vibration testing device for rotor blades of axial flow turbomachines, with excited by periodic - compressed air flow Resonance oscillation, characterized in that a) a disc (2) with a suspended Test blade (1) inserted coaxially into a rotationally symmetrical housing (3) and is firmly connected to it by means of a shaft stub (2 ') that b) in this disc shaft stub (2 ') and separate channels (6, 6' or 7.7 ') are designed for the compressed air supply or the air discharge that c) on the radial Outside of the disc (2) there are outflow nozzles (4) for the compressed air and that d) the rotationally symmetrical housing (3) by means of the a drive device connected disc shaft stub (2 ') and by means of a own shaft stub (3 ') attached to the opposite side in a centrifugal stand chamber (5) is rotatably mounted. 2. Test device according to claim 1, characterized in that the rotationally symmetrical housing (3) with a radially outwardly reduced width is. 3. Test device according to claim 1 or 2, characterized that the centrifugal stand chamber (5) can be evacuated. 4. Test device according to one of claims 1 to 3, characterized in that that the discharge nozzles (4) for the compressed air are formed in a separate device that are next to the test shovel (1) on dovetail or fir tree grooves is releasably suspended (Fig. 2). 5. Test device according to one of claims 1 to 3, characterized in that that the discharge nozzles (4) in a separate device formed are attached to a separate disk or to the rotationally symmetrical housing (3) is.