| 1. |
- Du, Kun, et al.
(författare)
-
Effect of non-axisymmetric endwall contouring and swirling inlet flow on film cooling performance of turbine endwall
- 2024
-
Ingår i: International Journal of Heat and Mass Transfer. - 0017-9310. ; 229
-
Tidskriftsartikel (refereegranskat)abstract
- Non-axisymmetric endwall contouring (NEC) is one of the verified approaches to suppress secondary flows and improve aerodynamic performance. However, the design of NEC brings significant challenges to the design of endwall cooling structures. Herein, a pressure-sensitive paint experimental approach was used to obtain the film cooling effectiveness of the NEC endwall with a purge slot in this study. Three NEC types were adopted: NEC (COS), NEC (SIN), and NEC (−SIN). In addition, lean premixed combustion technology was used to achieve lower levels of NOx emissions. The turbine inlet was characterized by high turbulence and strong swirling. The effects of different swirling angles (±10, ±20, and ±30°) and densities were further explored. Due to the NEC profiling changing the secondary flow near the endwall area, coolant from the purge slot was better attached to the slot exit position, leading to a significant increase in the size of the high-cooling-efficiency region. With the mass flow ratio (MFR) varying from 0.5 to 2%, the film cooling effectiveness of the flat and NEC endwalls had similar variation characteristics. When the MFR = 0.5%, the area-averaged cooling efficiencies of the NEC (COS), NEC (SIN), and NEC (−SIN) endwalls could be improved by 2, 12.5, and 20%, respectively. Positive swirling and smaller negative swirling inflow could improve the film cooling effectiveness inside the channel. The case of SA = +20° had the best improvement, where the film cooling effectiveness of the NEC (COS), NEC (SIN), and NEC (−SIN) endwalls could reach up to 29, 35, 36, and 34%, respectively. The NEC (−SIN) endwall was less sensitive to the effects of the swirling inflow.
|
|
| 2. |
- Du, Kun, et al.
(författare)
-
Non-axisymmetric Endwall film cooling characteristics considering the influences of cylindrical holes and laidback fan-shaped holes
- 2024
-
Ingår i: International Journal of Heat and Mass Transfer. - 0017-9310. ; 225
-
Tidskriftsartikel (refereegranskat)abstract
- Flow fields near the turbine vane endwall are complicated due to the endwall cross flows. The use of a non-axisymmetric endwall is regarded as an efficient technique to reduce the lateral pressure difference, decreasing the endwall cross flow. Numerical analysis was performed to determine how the non-axisymmetric endwall affected the vortex structure and heat transfer level. The cooling performance was investigated with cylindrical and laidback fan-shaped holes (7–7–7), which were arranged in rows aligned in the axial direction. The results showed that the non-axisymmetric endwall could significantly reduce the circumferential pressure difference and suppress the growth of the passage vortex, and the area-averaged heat transfer coefficient was reduced by 3.34%. The outlet area of the film hole was altered by the non-axisymmetric endwall, and the over-cooled regions may have appeared as a result of the excessive area increase. The influence of the non-axisymmetric endwall was concentrated at 0.4 < Z/Cax < 1.0 for the cylindrical hole. With the increase in M, the film cooling effectiveness of the non-axisymmetric endwall attained a higher level than that of the flat endwall. For the laidback fan-shaped hole, the effect of the non-axisymmetric endwall was confined within 0.25 < Z/Cax < 1.0. The half-period trigonometric function of the non-axisymmetric endwall (HTFN) achieved the optimal cooling performance for three blowing ratios. However, the periodic trigonometric function of the non-axisymmetric endwall (PTFN) only outperformed the flat endwall when M= 1.5.
|
|
