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In order to explore the similarities and differences of the loss characteristics of carbon dioxide and steam in turbine cascades, the flow characteristics of the two kinds of working fluids in stator cascade and stage were studied by numerical methods. And the optimal Mach number for efficient operation of turbine stage under subsonic condition was obtained. The results show that with the increase of Mach number, the flow loss first increases and then decreases. When the Mach number is lower, the diffuser has a large range and is easy to backflow, which makes the wall boundary layer thicken and separate, and increases the overall flow loss. When the Mach number is higher, the strength of the secondary vortex in passage is larger, and the shock wave will be generated near the trailing edge of blades. The reason for the larger flow loss is the secondary flow and shock wave. Compared with steam, the dynamic viscosity of carbon dioxide is slightly higher, and its density is about twice that of steam. Under the same Mach number condition, the mainstream velocity is lower, the boundary layer is thicker, and the overall loss is larger. When the Mach number is lower than 0.30, the total-total efficiency of turbine stages with carbon dioxide is lower. While the Mach number is higher than 0.50, the efficiency of carbon dioxide is slightly higher than that of steam. When the optimal outlet Mach number of balde is about 0.60, the efficiency of both is the highest. The research results will provide a reference for further improving the design level for axial flow turbines of steam and carbon dioxide, and further understanding the loss characteristics of different medium in turbine stage.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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