The purpose and volume of experiments
The purposes of a series of the experiments, executed in work, are the determination of inflience of axial gaps between rows and numbers of IGV vanes on unsteady fhw parameters of the R blades and an experimental estimation of inflrence of unsteadiness on losses in the compressor. Practical result of the analysis is definition of optimization criteria of mutual circumferential position of stators.
Axial gaps Д12 (between IGV and R) and Д23 (between R and S) at researches of the clocking effect are chosen, recognizing that according to Refs. [1,2,7,8,9,12], the source of the clocking effect in system of rows IGV-RK – S is change of flow in the R at mutual circumferential shift of the IGV and S. As criteria of an estimation of a unsteadiness level and clocking effect the generalized parameters were used:
(< Гя >t )v – averaged on mutual circumferential position of stators v (0 < v < 1) of RMS deviation on time t of velocity circulation on the R blade
Гя = rR (t);
<< Гя >t>v – RMS deviation < Гя >t from (< Гя >t)v for all mutual circumferential position of stators. Values (< Гя >t)v and << Гя >t>v were calculated under the theory of potential-vortical interaction for cascades on mean radius of the compressor at various combinations of axial gaps Д12 and Д23 in a wide range of their change from 5 up to 60mm (from 0,05 up to 0,62 from the R blade axial projection length).
By results of calculations 2 assembly of the compressor were chosen for research, providing essentially various levels of parameter << Г я >t >v at close values of parameter < Гя >t, i. e. essentially various levels of clocking effect at close values of fbw unsteadiness on the R blades:
1-st compressor assembly – Д12 = Д23 = 15mm (Д12 = Д23 = 0,15), << TR >t>v= 41%, (< TR >t)v = 4,2%; _
3-th compressor assembly – Д12 = 60mm, Д23 = 5mm (Д12 = 0,62, Д23 = 0, 05), « TR >t>v= 15%, (< TR >t)v = 4,3%;
Besides the specified configurations of the compressor, for which experiment was carried out at numbers of blades 36-38-36, 2-nd compressor assembly was executed at numbers of blades 18-38-36. By a calculated estimation reduction of numbers of the IGV vanes in 2 times results in increase of common ft>w unsteadiness on the R blades, however considerably reduces clocking effect.