# Numerical Study on Cooling Performance of a Steam-Cooled Blade Based on Response Surface Method
## 3 Effect of Working Parameters on the Cooling Performance of the Blade
### Influence of Mainstream Outlet Pressure  
Figure 10 presents the influence law of the mainstream outlet pressure on the cooling efficiency distribution of the steam-cooled blade, from Figure 10a-c, it can be observed that when the mainstream outlet pressure changes, the distribution of the surface cooling efficiency of the steam-cooled blade is in the range of 0.26-0.67. When the mainstream outlet pressure increases, the area of the high cooling efficiency area in the middle chord area of the steam-cooled blade slightly decreases, while the area of the low cooling efficiency area in the leading and trailing edges of the blade slightly increases. The area of cooling efficiency region in the leading and trailing edges of the blade increases slightly. The cooling efficiency of the steam-cooled blade surface decreases with the increase of the mainstream outlet pressure, but at the same time the temperature of the blade surface is more uniform, which indicates that the mainstream outlet pressure reduces the temperature non-uniformity of the steam-cooled blade. After calculation, it can be seen that when the mainstream outlet pressure increases from 120 kPa to 160 kPa, the average cooling efficiency of the steam-cooled blade decreases by 3.76% and the temperature non-uniformity decreases by 1.03%. From Figure 10d, it can be known that the mainstream outlet pressure on the average cooling efficiency and temperature non-uniformity of air-cooled and steam-cooled blades have the same effect law, that is, the increase of the mainstream outlet pressure will reduce the average cooling efficiency and temperature non-uniformity of both. From Figure 10d, it is also clear that the steam-cooled blade has higher cooling efficiency and temperature non-uniformity compared with the air-cooled blade at the same mainstream outlet pressure. In the studied parameter range, the average cooling efficiency of the former is higher than that of the latter by about 15.38-16.02%, with an average of about 15.60%; the temperature non-uniformity of the former is higher than that of the latter by about 21.96-22.65%, with an average of about 22.26%. Figure 9: Influence of mainstream inlet temperature on dimensionless temperature distribution: (**a**) \(T_{\text{gi}}=680\) K; (**b**) \(T_{\text{gi}}=695\) K; (**c**) \(T_{\text{gi}}=710\) K; (**d**) Variation law of the mean value. Figure 11 presents the influence law of the mainstream outlet pressure on the distribution of the dimensionless temperature of the steam cooled blade, from Figure 11a-c, it can be found that when the mainstream outlet pressure increases, the distribution of the dimensionless temperature on the surface of the steam cooled blade is in the range of 0.78-0.92, and the area of the low dimensionless temperature region in the middle chord area of the steam cooled blade is slightly reduced, while the area of the high dimensionless temperature region at the leading and trailing edges of the blade is slightly increased. This indicates that the increase of the mainstream outlet pressure will slightly increase the dimensionless temperature of the steam cooled blade. In addition, from Figure 11a-c, it can be known that the change of the mainstream outlet pressure has a greater effect on the dimensionless temperature of the chordal area in the suction surface of the steam cooking blade compared with other areas. After calculation, it can be seen that when the mainstream outlet pressure increases from 120 kPa to 160 kPa, the average dimensionless temperature of the steam cooled blade increases by 0.52%. From Figure 11d, it can be seen that the average dimensionless temperature of both air-cooled and steam-cooled blade increases with the increase of the main stream outlet pressure, but the steam-cooled blade is about 2.15-2.28% lower compared with the air-cooled blade at the same mainstream outlet pressure, and the average is about 2.20% lower.