Numerical calculation of conjugate heat transfer was carried out to study the effect of combined film and swirl cooling at the leading edge of a gas turbine vane with a cooling chamber inside. Two cooling chambers (C1 and C2 cases) were specially designed to generate swirl in the chamber, which could enhance overall cooling effectiveness at the leading edge. A simple cooling chamber (C0 case) was designed as a baseline. The effects of different cooling chambers were studied. Compared with the C0 case, the cooling chamber in the C1 case consists of a front cavity and a back cavity and two cavities are connected by a passage on the pressure side to improve the overall cooling effectiveness of the vane. The area-averaged overall cooling effectiveness of the leading edge () was improved by approximately 57%. Based on the C1 case, the passage along the vane was divided into nine segments in the C2 case to enhance the cooling effectiveness at the leading edge, and was enhanced by 75% compared with that in the C0 case. Additionally, the cooling efficiency on the pressure side was improved significantly by using swirl-cooling chambers. Pressure loss in the C2 and C1 cases was larger than that in the C0 case.
Numerical calculation of conjugate heat transfer is carried out to study the effect of combined film and swirl cooling at the leading edge of a gas turbine vane with a a cooling chamber inside, in which 3-D steady RANS approach with the k-ω SST turbulence model is used. Two different kinds of coolant chamber configuration (C1 and C2) are selected. In C2, the cooling chamber is composed of a front cavity and a back cavity, and the two cavities are connected by a passage which is divided into 16 segments. The comparative investigations between C1 and C2 cases have been carried out to study the effect of different cooling chambers at M = 0.25, 0.5, 1 and 2. For two cases, overall cooling effectiveness increases with M increasing. In C1 case, with increasing M, differences of mass flow through film holes rows will decrease. The variation of mass flow from holes changes by less than 26.7% at M = 2. However, in C2 case, mass flow through S1 and S2 is significantly larger than that through other film holes rows. Area-averaged overall effectiveness in C2 is larger by 2.5% at M = 0.25 compared to C1 case.
The optimization of turbine cooling design has become a new research field of gas turbine. The swirl chamber is a prospect cooling concept. In this paper, the numerical simulation of the swirl chamber is carried out by FLUENT. The influence of inlet size parameters, temperature ratio and inlet Reynolds number on the enhanced heat transfer of swirl chamber is studied. The results show that, in the range of the studied condition, Nusselt number decreases with the height, the width, the ratio of width to height and Reynolds number. It also shows that comprehensive heat transfer effect is best at d=20 mm and enhances observably with the enlargement of width, width height ratio, and Reynolds number. Friction factor increases with height, width, temperature ratio and Reynolds number decreases. It is increased by increasing width height ratio. Nusselt number and comprehensive heat transfer effect decrease a little with aggrandizement of temperature ratio.
With the rapid development of renewable energy generation, the requirement for operational flexibility of power plants has increased. This has led to steam turbine operating frequently at low load flow conditions. This paper focuses on the investigation of unsteady aerodynamic excitation in the last stage of LP under low load flow, which was conducted by assuming one single passage, to provide detailed flow information for optimization design. We present a numerical investigation of unsteady pressure forces on Multi-passage LP last blade rows caused by flow separation under low load flow. The flow field of the turbine was calculated by transient 3D computational fluid dynamic (ANSYS CFX16.0). The results indicate the vortex strength induced by high incidence angle under low load flow having the characteristic of spatial non-uniformity and time non-uniformity. We found that the unsteady pressure forces on the rotor are significantly influenced by the separation vortex and have different phase pressure fluctuation between neighboring two rotor blades. The variation in the forces indicates that the neighboring rotor blades experience a load imbalance at every time step which may results in oscillation in the last long moving blades. In particular, the tip vortex plays a crucial part in unsteady aerodynamics.
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