Numerical Study of the Effects of Thermal Barrier Coating and Turbulence Intensity on Cooling Performances of a Nozzle Guide Vane
Abstract
:1. Introduction
2. Thermal Parameters
- (1)
- Overall cooling effectiveness (φ):
- (2)
- TBC effectiveness (τ):
- (3)
- Percentage of temperature reduction (R):
- (4)
- Increment of overall cooling effectiveness (Δφ):
- (5)
- Variation of heat transfer coefficient (Δh):Δh = h − hTBC
3. Geometric Configuration
4. Computational Procedures
4.1. Computational Mesh
4.2. Calculation Techniques
4.3. Boundary Conditions
4.4. Validation of the Turbulence Model
5. Results and Discussions
5.1. Overall Cooling Effectiveness and TBC Effectiveness
5.2. Effects of TBC and Tu on Overall Cooling Effectiveness
5.3. Effects of TBC and Tu on Heat Transfer Coefficient
6. Conclusions
- (1)
- TBC increases significantly the overall cooling effectiveness on the basis of the vane metal surface, but it does not alter the trends of distribution of the overall cooling effectiveness for all three Tus.
- (2)
- For this test case, with only two rows of film holes on the SS, TBC is more effective on the PS than on the SS. The role of TBC on the increment in the overall cooling effectiveness is relatively higher in the ineffectively cooled regions, i.e., the tip and hub of the vane, but is relatively lower in the regions close to the exits of film holes, the downstream of the diffusion shaped-holes on the SS, and the TE.
- (3)
- When Tu increases, the increment in the overall cooling effectiveness due to TBC in the ineffectively cooled regions can reach up to 24% or 38 K at Tu = 20%, but increases slightly in the exits and downstream of the diffusion shaped-holes on the SS, as well as the TE.
- (4)
- TBC can block heat flux from mainstream into the vane, but it can also blocks the heat flux transferred from the solid vane into the mixing fluid of cooling air and the mainstream. When Tu increases, these effects becomes more significant.
Acknowledgments
Author Contributions
Conflicts of Interest
Nomenclature
cp,f | specific heat capacity of fluid (J/kg·K) |
cp,m | specific heat capacity of solid (J/kg·K) |
cp,TBC | specific heat capacity of TBC (J/kg·K) |
h | heat transfer coefficient at metal surface (W/m2·K) |
hTBC | heat transfer coefficient at TBC surface (W/m2·K) |
Δh | variation of heat transfer coefficient (W/m2·K) |
kf | thermal conductivity of fluid (W/m·K) |
km | thermal conductivity of solid (W/m·K) |
kTBC | thermal conductivity of TBC (W/m·K) |
Lu | turbulence length scale (m) |
P | pressure (Pa) |
PR | pressure ratio |
Ps | static pressure (Pa) |
PT,c | total pressure at coolant inlet (Pa) |
PT,∞ | total pressure at mainstream inlet (Pa) |
Pref | reference pressure (3.44740 × 105 Pa) |
qflux | heat flux at the interface of solid and fluid (W/m2) |
R | percentage of metal temperature reduction (%) |
T | metal surface temperature without TBC (K) |
Tc | inlet temperature of cooling air (K) |
Tref | reference temperature (709 K) |
TTBC | metal surface temperature with TBC (K) |
Tw | vane local wall temperature (K) |
T∞ | inlet temperature of mainstream (K) |
T′ | TBC surface temperature (K) |
Tu | free-stream turbulence intensity (%) |
ΔT | temperature reduction in metal surface |
temperature gradient at the interface of solid and fluid (K/m) | |
Greek Symbols | |
ρf | density of mainstream and coolant (kg/m3) |
ρm | density of metal (kg/m3) |
ρTBC | density of TBC (kg/m3) |
φ | overall cooling effectiveness on the metal surface without TBC |
φTBC | overall cooling effectiveness on the metal surface with TBC |
τ | TBC effectiveness |
Δφ | increment of overall cooling effectiveness on the vane surface |
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Row | Number of Holes | Hole Diameter (cm) | Type/Angle |
---|---|---|---|
1 | 22 | 0.061 | Axial, Diffusion shaped |
2 | 23 | 0.061 | Axial, Diffusion shaped |
3 | 12 | 0.048 | Radial |
4 | 12 | 0.048 | Radial |
5 | 12 | 0.048 | Radial |
6 | 12 | 0.048 | Radial |
7 | 12 | 0.048 | Radial |
8 | 12 | 0.048 | Radial |
9 | 12 | 0.048 | Radial |
10 | 20 | 0.036 | Compound Angle 45° |
11 | 16 | 0.061 | Compound Angle 60° |
12 | 16 | 0.048 | Axial |
13 | 18 | 0.061 × 0.155 | Pressure side slot |
Property of Material | Air: Mainstream and Cooling Air | Steel: Vane Structure | ZrO2: TBC |
---|---|---|---|
Density (kg·m−3) | ρf = ideal gas assumption | ρm = 8055 | ρTBC = 5500 |
Specific heat capacity (J·kg−1·K−1) | cp,f = 938 + 0.196 T | cp,m = 438.5 + 0.177 T | cp,TBC = 418 |
Thermal conductivity (W·m−1·K−1) | kf = 0.0102 + 5.8 × 10−5 T | km = 11.2 + 0.0144 T | kTBC = 1.04 |
Viscosity (kg·m−1·s−1) | Three-equation of Sutherland model | - | - |
Boundary | Condition |
---|---|
Mainstream inlet | T∞ = 709 K, PT,∞ = 3.44740 × 105 Pa, Lu = 6 cm, Tu = 3.3%, 10% and 20% |
Mainstream outlet | PR = 1.67, Intended PR of Timko [26] |
Forward coolant inlet | Tc = 339 K, PT,c = 3.50950 × 105 Pa |
Forward coolant outlet | Adiabatic wall with non-slip condition |
Aft coolant inlet | Tc = 339 K, PT,c = 3.50950 × 105 Pa |
Aft coolant outlet | Adiabatic wall with non-slip condition |
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Prapamonthon, P.; Xu, H.; Yang, W.; Wang, J. Numerical Study of the Effects of Thermal Barrier Coating and Turbulence Intensity on Cooling Performances of a Nozzle Guide Vane. Energies 2017, 10, 362. https://doi.org/10.3390/en10030362
Prapamonthon P, Xu H, Yang W, Wang J. Numerical Study of the Effects of Thermal Barrier Coating and Turbulence Intensity on Cooling Performances of a Nozzle Guide Vane. Energies. 2017; 10(3):362. https://doi.org/10.3390/en10030362
Chicago/Turabian StylePrapamonthon, Prasert, Huazhao Xu, Wenshuo Yang, and Jianhua Wang. 2017. "Numerical Study of the Effects of Thermal Barrier Coating and Turbulence Intensity on Cooling Performances of a Nozzle Guide Vane" Energies 10, no. 3: 362. https://doi.org/10.3390/en10030362