SU879361A2 - Turbo-machine testing method - Google Patents

Description

one

FIELD OF THE INVENTION The invention relates to methods for the investigation of vibrations in scapular cavities.

According to the main author. St. In 735948, a method is known in which the pulse sensor is moved around the body circumferentially in a plane perpendicular to the axis of the turbomachine, and fixes its position in the places of maximum deflection of the ends of the blades 1.

However, this method does not accurately determine the resonant oscillation frequency of the blades.

The purpose of the invention is to improve the accuracy of determining the resonant frequency of oscillation of the blades.

This goal is achieved by the fact that at the moment of fixing the pulse sensor, the rotational speed of the rotor of the turbomachine is measured, and the frequency of resonant oscillations is determined as the product of the average value of the measured rotational frequencies and the number of sources of disturbing force.

FIG. 1 shows the dependence of the amplitude A of the oscillations of the working blades on the rotation frequency (1 turbomachine; FIG. 2 shows the dependence of the phase shift V on the rotation frequency

V) turbomachines; in fig. 3 - offset of the end of the blade from the neutral position, i.e., the amplitude A depending on the angle of rotation oi per revolution of the impeller; in fig. 4 shows the dependence of the amplitude A of oscillations of the working blades on the frequency of rotation uJ at three values of the angle сС.

ten

The resonant vibrations of the working blades are usually caused by fixed elements located in the gas-air duct of the turbomachine. -With this the scapula commits

15 forced resonant oscillations with an amplitude which is a function of the frequency of rotation of the turbomachine (see Fig. 1). And at the moment of resonance, i.e. at Cf Schro, where Cf ro is a pe20 resonant frequency, the phase shift is -75/2 (see Fig. 2).

If the pulse sensor is located at points 1 and 2 around the circumference

25 (see Fig. 3), the dependence of the amplitude A on the rotational speed will be characterized by curves 3 and 4, respectively (see Fig. 4), i.e., the moment of resonance of the SU - c} p corresponds to the amplitude value ± f.

If the pulse sensor is located at point 5 around the circumference (see Fig. 3), then at the moment of resonance the amplitude A "O (curve 6 in Fig. 4).

Thus, to determine the oscillation frequency of the blade, it is necessary:

during the passage of the resonant mode, measure the maximum values of the time intervals characterizing the movement of the end of the blade at different positions of the pulse sensor located on the body circumferentially in a plane perpendicular to the axis of the turbomachine;

fix the sensor positions at which extreme time interval values are reached;

measure the rotor speed corresponding to these extremes;

determine the number of sources of perturbation (multiplicity), while it should be borne in mind that the integer, the number of waves (see Fig. 3) fit along the wheel circumference.

The product of the average value of the measured rotational frequency by the magnitude of the multiplicity gives the desired value of the frequency of resonant oscillations.

Thus, the accuracy of the measurement of the frequency of the resonant oscillations is improved, since it is determined by the accuracy of the measurement of the speed of rotation of the rotor.

Claims (1)

1. USSR author's certificate 735948, cl. G 01 M 15/00, 01/26/1976. 0tfi.f / / R