Technique of experiment and data processing

The experimental information on a few structure in the compressor at var­ious circumferential positions of stator rows was obtained as follows. On a constant operation mode of the compressor on the given frequency of the R rotation and the air fbw rate by circumferential shift of IGV relative S the rel­ative mutual circumferential position of stators (parameter v) is changed from 0 (some starting position of stators) up to 1 (shift of IGV relative S on one full pitch of stator vanes Hst) with the pitch Д v = 0,1. In turn at each of 11 values V by simultaneous circumferential shift of IGV and S value of the relative cir­cumferential position of stators (parameter Yst) is changed from 0 up to 1 with the pitch ДУ^ = 0,1. Thus, the received files of measured parameters pro­vided the information on their circumferential distortion and on their change in dependence on mutual stators position.

At measurements by high-response sensors the information on change of fbw parameters on time within 1 second with phase synchronization of mea­surements with the help of the R blade passing frequency (BPF) mark was provided. After amplification of electric signals of sensors and their transfor­mation to physical values with the help of analog-digital converters measured parameters entered in a digital kind to PC. Frequency of interrogation of high – response sensor made 19,2kHz, that at BPF 1,2kHz provided 15 measurements on the period of BPF. It is enough received volume of the experimental infor­mation for obtaining of change of flow parameters as in steady (connected with stators), and rotating (connected with a rotor) systems of references by results of measurements by high-response sensors in the steady system of reference, realized in experiment. The technique of recalculation of the measured pa­rameters for their representation in rotating system of reference is described in [12,14]. For allocation of a periodic signal the indications of sensors were av­eraged on ensemble on 114 periods of BPF (3 revolutions of R). Random fbw pulsations were determined by subtraction of periodic components of pulsa­tions from the measured values. It is necessary to notice, that random pul­sations are caused not only by flow turbulence, but also small deviations in geometry of the R blades and operation mode of the compressor.

Any few parameter n(r, x,y, t,v) (for example, pressure, velocity and etc.) generally is the function, dependent from radial r, axial x and circumferential y coordinates of a considered point, time t and a mutual circumferential position of stators v. For reception of integrated estimations of interactions of rows effects by results of experiment or calculation at fixed values r, x and v were determined the following generalized parameters:

(n)t – averaged on time value П;

П >t – mean root square (RMS) deviation of П from its average on time value (n)t;

((n)t )y, (< П >t)y – averaged on period H (pitch of stators or rotor) values (n)t and < П >t;

П >y, << П >t>y – RMS deviations of values (П) and < П >t from their averaged values ((n)t)y and (< П >t)y on circumferential period H.

Averaged on circumferential period H values ((n)t )y and (< П >t )y char­acterize some stationary fbw, obtained by averaging of real unsteady fbw, and RMS deviations < П >y and << П >t >y determines a level of unsteady in­teractions of mutually moving rows and for the isolated row of identical blades < П >y and << П >t >y are equal to zero. The specified parameters may be determined in the R and S systems of reference. Conformity between the parameters, determined in different systems of reference, is given in [14].