PSI - Issue 50

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Diana D. Popova et al. / Procedia Structural Integrity 50 (2023) 236–250 Popova, Popov, Samoylenko / Structural Integrity Procedia 00 (2022) 000 – 000 Fig. 11. RB domain grid model: a) general view; b) TC area section.

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In total, two cases were considered: in the first case, the value of the tip clearance in the rotor blade domain is constant along the profile at the periphery and equals 0.5 mm, which is the ideal case; in the second, the value of the tip clearance is not constant along the profile, which is a real case. The described calculation model is tuned according to the results of the experiment. 9. CFD Results The TC non-uniformity value along the RB end perimeter introduces local changes in the flow structure, which affects the distribution of static pressure in the area of the blade end and, accordingly, on the flow velocity vectors.

Table 2. Distribution of Mach number ( ideal parallel gap; real non-parallel gap).

Point number (according fig.6)

Mach number (ideal parallel gap)

Mach number (real non-parallel gap)

1 2 3 4 5 6 7 8

0.92 0.94 0.63 0.33 0.19 0.17 0.49 0.71

0.90 0.95 0.74 0.35 0.25 0.18 0.56 0.75

Table 12 shows the velocity (Mach number) in points 1-8. It can be seen that there are practically no differences in the features of the flow, with the exception of a decrease in speed from the PS, and, as a result, a redistribution of static pressure. Figure 12 shows the relative total pressure circuit in relative motion at the outlet of the working crown. It can be seen that in the case of a real non-parallel gap, the magnitude and intensity of the leakage vortex through the tip clearance "A" decreased, and the vortex structures of the horseshoe-shaped vortex "B" are also reduced.

a

b

Fig. 12. Relative total pressure in relative motion at the outlet of the working crown: a) ideal parallel gap; b) real non-parallel gap.

For a detailed analysis of the flow at the RB periphery, control surfaces were built in the TC area, formed by the elements of the airfoil profile - the leading edge, PS,SS and trailing edge (see Figure 13). The relative flow rate of the working fluid through each surface is determined, according to the figure. The results are presented in table 2.