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Fig. 20. Detailed view of y+ contour plot around the LSMB snubber (a) suctior side (bottom half) (b) pressure side (top half).

Figure 20 Detailed view of y+ contour plot around the LSMB snubber (a) suctior side (bottom half) (b) pressure side (top half).

Related Figures (33)

Fig. 1. Schematic representation of Flow Reversal Phenomenon.
Fig. 1. Schematic representation of Flow Reversal Phenomenon.
Fig. 2. Cross section of the model scaled steam turbine [11].
Fig. 2. Cross section of the model scaled steam turbine [11].
Fig. 3. Exhaust hood of the investigated model scaled steam turbine [11].
Fig. 3. Exhaust hood of the investigated model scaled steam turbine [11].
Fig. 4. (a) Cross-sectional view of the model steam turbine rear stages, (b) upstream view of plane 62, probe traverse and location marked in red.(For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 4. (a) Cross-sectional view of the model steam turbine rear stages, (b) upstream view of plane 62, probe traverse and location marked in red.(For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 5. Five-hole probe used for flow field measurements.
Fig. 5. Five-hole probe used for flow field measurements.
Fig. 7. Measured ventilation power for a given test case.
Fig. 7. Measured ventilation power for a given test case.
Fig. 6. Detailed view of the snubber geometry (67% blade span).
Fig. 6. Detailed view of the snubber geometry (67% blade span).
Test cases summary. However, at the end, the absolute velocity in the active area is ra- ther similar between the two LSMB, Fig. 11. Table 1
Test cases summary. However, at the end, the absolute velocity in the active area is ra- ther similar between the two LSMB, Fig. 11. Table 1
Fig. 9. Measured axial velocity distribution for freestanding and snubber blades on plane 62 at different circumferential locations for test case 1. The reverse flow height is about 60% of the blade span. The pressure distribution along the circumference at the LSMB outlet seems to be uniform for both sets of rear stages (Fig. 12). In fact, the difference in measured static pressure is for most of the blade span
Fig. 9. Measured axial velocity distribution for freestanding and snubber blades on plane 62 at different circumferential locations for test case 1. The reverse flow height is about 60% of the blade span. The pressure distribution along the circumference at the LSMB outlet seems to be uniform for both sets of rear stages (Fig. 12). In fact, the difference in measured static pressure is for most of the blade span
Fig. 8. Measured average ventilation power at different test cases for the freestanding and snubber rear stages.
Fig. 8. Measured average ventilation power at different test cases for the freestanding and snubber rear stages.
Fig. 10. Measured radial velocity distribution for freestanding and snubber blades on plane 62 at different circumferential locations for test case 1
Fig. 10. Measured radial velocity distribution for freestanding and snubber blades on plane 62 at different circumferential locations for test case 1
Fig. 11. Measured absolute velocity distribution for freestanding and snubber blades on plane 62 at different circumferential locations for test case 1
Fig. 11. Measured absolute velocity distribution for freestanding and snubber blades on plane 62 at different circumferential locations for test case 1
Fig. 12. Measured static pressure distribution for freestanding and snubber blades on plane 62 at different circumferential locations for test case 1
Fig. 12. Measured static pressure distribution for freestanding and snubber blades on plane 62 at different circumferential locations for test case 1
Fig. 13. Measured total pressure distribution for freestanding and snubber blades on plane 62 at different circumferential locations for test case 1.
Fig. 13. Measured total pressure distribution for freestanding and snubber blades on plane 62 at different circumferential locations for test case 1.
Fig. 14. Measured temperature distribution for freestanding and snubber blades on plane 62 for different test cases
Fig. 14. Measured temperature distribution for freestanding and snubber blades on plane 62 for different test cases
Fig. 15. CFD model with 4 sectors (left), detailed view of the multiple mixing plane used as interface between the LSMB and diffuser (right).
Fig. 15. CFD model with 4 sectors (left), detailed view of the multiple mixing plane used as interface between the LSMB and diffuser (right).
Number of nodes used in different grid domains for the last stage only. Table 2
Number of nodes used in different grid domains for the last stage only. Table 2
Fig. 17. Sensitivity analysis on element span-wise distributed at the LSMB outlet.
Fig. 17. Sensitivity analysis on element span-wise distributed at the LSMB outlet.
Fig. 16. Grid details of last stage rotor blade.
Fig. 16. Grid details of last stage rotor blade.
Fig. 18. LSMB tip gap mash [11].
Fig. 18. LSMB tip gap mash [11].
Fig. 19. Detailed view of the snubber mesh. 106 elements span-wise distributed, Fig. 17. The box mesh type does not lead to any significant difference in results. The automatic wall function has been used for near wall calcula- tions. This option offers a formulation which automatically switch from wall-functions to a low-RE near wall formulation as the mesh is refined. The k- w model of Wilcox (and therefore the SST turbulence model), has the advantage that an analytical expression is known for the w sublayer, which can be exploited to achieve the target. The main idea behind the present formulation is to blend the wall value for w between the The tip gap has been considered in modelling the LSMB (see Fig. 18). The exhaust box has been discretized with all the furniture, stiffening plates, pipes etc. For the snubber last stage blade, the mesh has been refined in cor- respondence of the snubber, as shown in Fig. 19.
Fig. 19. Detailed view of the snubber mesh. 106 elements span-wise distributed, Fig. 17. The box mesh type does not lead to any significant difference in results. The automatic wall function has been used for near wall calcula- tions. This option offers a formulation which automatically switch from wall-functions to a low-RE near wall formulation as the mesh is refined. The k- w model of Wilcox (and therefore the SST turbulence model), has the advantage that an analytical expression is known for the w sublayer, which can be exploited to achieve the target. The main idea behind the present formulation is to blend the wall value for w between the The tip gap has been considered in modelling the LSMB (see Fig. 18). The exhaust box has been discretized with all the furniture, stiffening plates, pipes etc. For the snubber last stage blade, the mesh has been refined in cor- respondence of the snubber, as shown in Fig. 19.
Fig. 21. y+ contour plot for last stage blades in correspondence of the hub and tip regions (stator and runner blades).
Fig. 21. y+ contour plot for last stage blades in correspondence of the hub and tip regions (stator and runner blades).
Fig. 22. Comparison of steam turbine inlet pressure between measurements and CFD calculations for snubber LSMB
Fig. 22. Comparison of steam turbine inlet pressure between measurements and CFD calculations for snubber LSMB
Fig. 23. Comparison of last two stages ventilation power between measurements and CFD calculations for the snubber LSMB
Fig. 23. Comparison of last two stages ventilation power between measurements and CFD calculations for the snubber LSMB
Fig. 24. Comparison of span-wise blade axial velocity distribution for freestanding and snubber blades on plane 62, test case1
Fig. 24. Comparison of span-wise blade axial velocity distribution for freestanding and snubber blades on plane 62, test case1
Fig. 25. Measurements vs CFD of temperature distribution for freestanding and snubber blades on plane 62 for test case
Fig. 25. Measurements vs CFD of temperature distribution for freestanding and snubber blades on plane 62 for test case
Fig. 26. Meridional view of the axial velocity flow field for LSMB (a) with snubber (b) freestanding.
Fig. 26. Meridional view of the axial velocity flow field for LSMB (a) with snubber (b) freestanding.
Fig. 27. Meridional view of the axial velocity flow field without blade wireframe for LSMB (a) with snubber (b) freestanding
Fig. 27. Meridional view of the axial velocity flow field without blade wireframe for LSMB (a) with snubber (b) freestanding
Fig. 28. Meridional view of the radial velocity field for LSMB (a) with snubber (b) freestanding with emphasis on the magnitude of the radial velocity in corre- spondence of the reverse flow height.
Fig. 28. Meridional view of the radial velocity field for LSMB (a) with snubber (b) freestanding with emphasis on the magnitude of the radial velocity in corre- spondence of the reverse flow height.
Fig. 29. Meridional view of the flow field of the snubber last stage blades with and without wireframe
Fig. 29. Meridional view of the flow field of the snubber last stage blades with and without wireframe
Fig. 30. Meridional view of the flow temperature distribution of the snubber last stage blades with and without wireframe.
Fig. 30. Meridional view of the flow temperature distribution of the snubber last stage blades with and without wireframe.
Fig. 31. Meridional view of the flow field of the freestanding last stage blades with and without wireframe.
Fig. 31. Meridional view of the flow field of the freestanding last stage blades with and without wireframe.
Fig. 32. Meridional view of the flow temperature distribution of the freestanding last stage blades with and without wireframe
Fig. 32. Meridional view of the flow temperature distribution of the freestanding last stage blades with and without wireframe
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