Comparative investigation of unsteady flow interactions in endwall regions of shrouded and unshrouded turbines

Gao, Jie; Zheng, Qun

doi:10.1016/j.compfluid.2014.09.004

Cited by 9 publications

(6 citation statements)

References 40 publications

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“…The pressure ratio p t,in / p shows a good agreement with the results of Gao et al. 22 Although there are some errors in the trailing edge because of the differences of blade profiles, those results show the similar trend. Besides, considering there is a very complex flow occurs in the tip clearance, a validation was also performed using the numerical data of Lin et al.…”

Section: Resultssupporting

confidence: 88%

“…In order to verify the reliability of the simulation results in this paper, Figure 16 shows the pressure ratio p t,in /p on the rotor surface at 50%, 80%, 90%, and 98% blade height. The pressure ratio p t,in /p shows a good agreement with the results of Gao et al 22 Although there are some errors in the trailing edge because of the differences of blade profiles, those results show the similar trend. Besides, considering there is a very complex flow occurs in the tip clearance, a validation was also performed using the numerical data of Lin et al 24 Figure 17 shows the comparison of the current predictions with the numerical data for S dis distributions taken at a staggered labyrinth seal.…”

Section: Comparison Of Mixing Loss Under Different Tip Clearancessupporting

confidence: 88%

“…The number of grids affects the accuracy of calculation results. Therefore, the grid dependence is examined by the tip leakage flow rate and the isentropic efficiency when the tip clearance is 0.25 mm, which can be calculated from Gao and Zheng 22 as expressed in the following where T is the temperature and κ is the specific heat ratio.…”

Section: Model and Methodsmentioning

confidence: 99%

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Effects of leakage vortex on aerodynamic performance and loss mechanism of steam turbine

Cao

Wang

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part A:

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To avoid friction, a clearance between the rotor blade tip and the cylinder is needed in a steam turbine. As a result, the leakage flow is formed under the pressure difference which mixes with the main flow and causes the mixing loss. So, a numerical calculation was conducted based on a high-pressure 1.5-stage steam turbine with the tip labyrinth seal. The leakage vortex system and the mixing progress at different tip clearances were analyzed. The related leakage losses were calculated. The results show that the leakage flow will lead to the steam deflecting at the rotor exit and cause incidence loss. Furthermore, in the downstream stator, the leakage flow near the suction side with high radial velocity causes the deflection of the outflow angles. The main influence region of leakage flow is distributed above 75% of blade height, whereas the most intense region is distributed at approximately 95% of blade height. It is found that the mixing loss is related to the size of the backflow vortex. The related leakage losses increase with tip clearance, in which the mixing loss is the major part and the mass-averaged entropy mixing loss coefficient is 7–11%.

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Section: Resultssupporting

confidence: 88%

Section: Comparison Of Mixing Loss Under Different Tip Clearancessupporting

confidence: 88%

Section: Model and Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Effects of leakage vortex on aerodynamic performance and loss mechanism of steam turbine

Cao

Wang

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part A:

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show abstract

“…It is very difficult to directly arrange test points on the seal, which makes it impossible to monitor the wear condition of the seal in stage, and it is impossible to judge the influence of the leakage on the flow characteristics in stage. Since it is not easy to directly measure the seal leakage in steam turbine stage [5], this paper chooses to use numerical simulation methods for research.…”

Section: Introductionmentioning

confidence: 99%

Research on the Influence of Steam Turbine Seal Leakage

Pingguo

Zhang

2021

E3S Web Conf.

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CFD was employed to simulate the steam flow in 1.5-stage cascades with three different seal clearances. When the seal clearance is 0, there is no steam seal leakage, no obvious secondary flow in the cascade, and the stage efficiency reaches 88.27%. When the clearance of diaphragm seal and rotor tip seal is 1mm, the leakage of diaphragm seal strongly interferes with the flow in the cascade, which promotes the formation and development of the end-wall secondary flow near rotor hub, and the rotor tip leakage flow has little effect on next stage, and the stage efficiency drops by about 2 percentage points. When the seal clearance is 4mm, the end-wall secondary flow near rotor hub and next stator casing is strengthened significantly, and the attack angle loss increases, so the stage efficiency decreases by about 13 percentage points.

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“…The unsteady flow characteristics reflect that the strong radially inward migration of vane wake reduces the circumferential variation of flow conditions at rotor inlet near the tip region. Gao and Zheng 11 have performed an unsteady calculation of shrouded and unshrouded turbines. They found that the streamwise vorticity plays a major role in the development of secondary vortices and the streamwise vorticity of rotor secondary vortices depends on the upstream wake.…”

Section: Introductionmentioning

confidence: 99%

Unsteady winglet-cavity tip on leakage flow in a high-pressure turbine stage of low-aspect ratio

Zhou

Chen

Wang

2017

Proceedings of the Institution of Mechanical Engineers, Part C:

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In an unshrouded high-pressure turbine, the upstream vane wake, vane–blade interaction and blade tip leakage flow indicate complex and unsteady flow characteristics. Considering a high-pressure turbine stage of low-aspect ratio, the effects of the flat tip, cavity tip and winglet-cavity tip on the unsteady flow characteristics are investigated by numerical simulation. The exit Mach number and Reynolds number based on the chord of vane are 0.9 and 5.5×105, respectively. The pressure ratio of stage is 2.4. The time-resolved results indicate that the winglet-cavity tip scheme has smaller time variation of the total performance parameters and obtains a smaller tip leakage mass flow and a higher turbine stage efficient than the other cases. The vane–rotor interaction affects the pressure distribution at the region of blade leading edge remarkably and leads to a large time variation of tip leakage mass flow at the front of blade tip. The unsteady aerodynamic performance is analyzed with entropy-increase distribution at stage outlet and the vane–rotor interaction is discussed by the entropy-increase phase–time and phase–phase diagrams at blade outlet. Compared with the flat tip and cavity tip, the upper passage vortex loss is reduced obviously by the winglet-cavity tip. Thus, it is evaluated that the improvement of turbine stage coefficient with winglet-cavity tip results from the reduction of the upper passage vortex loss.

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Comparative investigation of unsteady flow interactions in endwall regions of shrouded and unshrouded turbines

Cited by 9 publications

References 40 publications

Effects of leakage vortex on aerodynamic performance and loss mechanism of steam turbine

Effects of leakage vortex on aerodynamic performance and loss mechanism of steam turbine

Research on the Influence of Steam Turbine Seal Leakage

Unsteady winglet-cavity tip on leakage flow in a high-pressure turbine stage of low-aspect ratio

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