Numerical Study of the Purge Flow’s Effect on the Loss Mechanism of the Blocking and Shear Effects
Abstract
:1. Introduction
2. Numerical Method
2.1. Computational Models
2.2. Numerical Approach and Mesh
2.3. Boundary Conditions
2.4. Validation of Numerical Method
3. Results and Discussion
3.1. Definition of Loss Parameters and Variation of Turbine Loss along Flow Direction
3.2. Blocking Effect
3.3. Viscous Shear Effect
4. Conclusions
- (1)
- The blocking effect of the purge flow on the upstream and the shear effect between the purge flow and the mainstream are responsible for the change of the stator loss. Both are sensitive to the sealing flow rate and sealing structure.
- (2)
- The blocking effect is mainly affected by the radial and the tangential velocity at the exit of the cavity. The blocking effect is positively correlated with sealing efficiency. Thus, it is most apparent for the Chute_30 structure with a sealing efficiency of 99.9%. The tangential velocity, which is affected by gas ingestion, is the main factor in determining the blocking effect under the same sealing flow rate.
- (3)
- The shear mixing loss is mainly affected by the tangential velocity gradient along the radial and the axial direction, and the axial velocity gradient along the radial. The rim shear vortex formed by the gas intrusion at the rim gap reduces the tangential velocity gradient and increases the axial velocity gradient for the gas transport from the rotor side to the stator side. With the increase in sealing efficiency, the proportion of tangential velocity gradient increases obviously, which accounts for 66.5% of the axial sealing structure with IR = 1.5, and 69.5% for the Chute_30 sealing structure with IR = 1.0%. The tangential velocity gradient becomes the dominant factor of shear loss for the higher sealing efficiency situation. Thus, using the mixing shear model Sharon and Wilcox et al. proposed may be more accurate to evaluate the shear loss for the high sealing efficiency situation. In addition, the influence of the axial velocity gradient on the shear loss needs to be considered when the sealing efficiency is relatively low.
- (4)
- Increasing the tangential velocity is an effective way to reduce the upstream blocking effect and shear loss. Although the blocking effect reduces the upstream stator loss, it is still significant to alleviate the blockage effect from the perspective of the turbine as a whole because the blockage will affect the upstream and downstream flow fields simultaneously.
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
References
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Parameter | S1 | R1 | S2 |
---|---|---|---|
Blade numbers | 36 | 54 | 36 |
Span/mm | 70 | 70 | 70 |
Chord length/mm | 80.88 | 59.72 | 85.50 |
Pitch/mm | 63.7 | 42.5 | 63.7 |
Inlet angle/° | 0.0 | 52.4 | −35.4 |
Exit angle/° | 72.0 | −66.6 | 66.0 |
Exit Ma | 0.54 | 0.50 | 0.48 |
Re/×105 | 7.1 | 3.8 | 5.1 |
Boundary Condition | Value |
---|---|
Total pressure in the mainstream inlet (Kpa) | 140 |
Total temperature in mainstream inlet (K) | 328 |
Total temperature in the cavity inlet(K) | 308 |
Rim seal flow IR in cavity inlet | 0%,0.5%,1.0%,1.5% |
The concentration of CO2 in mainstream inlet | 0 |
The concentration of CO2 in cavity inlet | 1 |
The rotation speed of rotor wall(r/min) | 2700 |
Axial | Radial | Chute_60 | Chute_45 | Chute_30 | |
---|---|---|---|---|---|
0% | −0.003 | — | — | — | — |
0.5% | −0.009 | — | — | — | — |
1.0% | −0.018 | −0.020 | −0.021 | −0.026 | −0.028 |
1.5% | −0.026 | — | — | — | — |
| Axial | Radial | Chute_60 | Chute_45 | Chute_30 |
---|---|---|---|---|---|
0% | 10.4% | — | — | — | — |
0.5% | 42.0% | — | — | — | — |
1.0% | 77.3% | 82.3% | 86.4% | 94.1% | 99.9% |
1.5% | 95.3% | — | — | — | — |
Axial | Radial | Chute_60 | Chute_45 | Chute_30 | |
---|---|---|---|---|---|
0% | 0.0467 | — | — | — | — |
0.5% | 0.0534 | — | — | — | — |
1.0% | 0.0670 | 0.0863 | 0.0734 | 0.0924 | 0.095 |
1.5% | 0.0855 | — | — | — | — |
Mass Average | 0% | 0.5% | 1% | 1.5% |
---|---|---|---|---|
121.0 (32.8%) | 226.7 (36.2%) | 319.7 (39.7%) | 448.4 (39.1%) | |
23.14 (6.3%) | 121.2 (19.4%) | 204.2 (25.3%) | 314.82 (27.4%) | |
117.0 (31.7%) | 133.5 (21.3%) | 119.7 (14.9%) | 148.62 (13%) | |
Total proportion | 70.8% | 76.9% | 79.9% | 79.5% |
Mass Average | Axial | Radial | Chute_60 | Chute_45 | Chute_30 |
---|---|---|---|---|---|
319.66 (39.7%) | 265.95 (33.1%) | 426.4 (46.3%) | 440.9 (48.4%) | 482.0 (51.7%) | |
204.214 (25.3%) | 215.362 (26.8%) | 183.2 (19.9%) | 171.76 (18.9%) | 165.4 (17.8%) | |
119.74 (14.9%) | 154.05 (19.2%) | 108.417 (11.8%) | 98.65 (10.8%) | 68.82 (7.4%) | |
Total proportion | 79.9% | 79.1% | 78% | 78.1% | 76.9% |
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Bai, T.; Yang, Q.; Liu, J. Numerical Study of the Purge Flow’s Effect on the Loss Mechanism of the Blocking and Shear Effects. Processes 2023, 11, 50. https://doi.org/10.3390/pr11010050
Bai T, Yang Q, Liu J. Numerical Study of the Purge Flow’s Effect on the Loss Mechanism of the Blocking and Shear Effects. Processes. 2023; 11(1):50. https://doi.org/10.3390/pr11010050
Chicago/Turabian StyleBai, Tao, Qingzhen Yang, and Jian Liu. 2023. "Numerical Study of the Purge Flow’s Effect on the Loss Mechanism of the Blocking and Shear Effects" Processes 11, no. 1: 50. https://doi.org/10.3390/pr11010050
APA StyleBai, T., Yang, Q., & Liu, J. (2023). Numerical Study of the Purge Flow’s Effect on the Loss Mechanism of the Blocking and Shear Effects. Processes, 11(1), 50. https://doi.org/10.3390/pr11010050