Impact of Gas Turbine Outflow on Diffuser Performance: A Numerical Study

Kluß, David; Wiedermann, Alexander; Volgmann, W.

doi:10.1115/gt2004-53043

Cited by 5 publications

(3 citation statements)

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“…Figure 10 displays the circumferential nonuniformity coefficients of C p at locations T1, H4, and C4 at the three operational conditions, where x-axis represents the flow coefficient and y-axis represents C Cp cnu , which is defined in equation (5). In addition, higher C Cp cnu means higher circumferential non-uniformity.…”

Section: Resultsmentioning

confidence: 99%

“…turbulent kinetic energy and secondary flow, have to be captured in order to estimate the realistic boundary conditions at the diffuser inlet for uncoupled computations. Kluβ et al [5] carried out the systematic numerical study of a coupled arrangement of the turbine stage and diffuser flow field. With a frozen rotor approach at the rotor-diffuser interface plane, the real effect of the rotor wakes and secondary flow on the diffuser can be captured if there is no strut in the diffuser passage.…”

Section: Introductionmentioning

confidence: 99%

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Experimental and numerical investigation of interaction between turbine stage and exhaust hood

Liu

Zhou

2007

Proceedings of the Institution of Mechanical Engineers, Part A:

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The current article describes the experimental and numerical studies on the flow field in a coupled turbine stage and exhaust hood model. The low subsonic stage with 22 stator blades and 30 rotor blades is especially designed for the hood model, which is a typical design for a 300/600 MW steam turbine. Velocity distributions at the inlet, outlet, and hood exit stages, in addition to static pressure distributions at the diffuser tip and hub end-walls and at the hood outer casing, are measured and compared with the numerical prediction. The flow details in the exhaust system with the whole annulus stator and rotor blade rows are simulated by employing the computational fluid dynamics software. Good agreements between numerical and experimental results are demonstrated. It is found that the swirl angle profile and total pressure profile due to the upstream turbine stage at the diffuser inlet have an unfavourable effect on the exhaust hood performance.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental and numerical investigation of interaction between turbine stage and exhaust hood

Liu

Zhou

2007

Proceedings of the Institution of Mechanical Engineers, Part A:

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“…The dependency between the inlet swirl and static pressure recovery performance of the diffuser is caused by the flow separation near the struts and corresponding the different incidence angles. Klub et al 14 numerically investigated the effect of turbine outflow on the static pressure recovery performance of the diffuser. The optimum distance between the rotor exit and the diffuser inlet for the specific work was obtained.…”

Section: Introductionmentioning

confidence: 99%

Effects of struts profiles and skewed angles on the aerodynamic performance of gas turbine exhaust diffuser

Dong

et al. 2021

Proceedings of the Institution of Mechanical Engineers, Part A:

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The strut structure directly affects the flow field characteristics and aerodynamic performance of the gas turbine exhaust diffuser. The effects of the strut profiles and strut skewed angles on the aerodynamic performance of the exhaust diffuser at different inlet pre-swirls were numerically investigated using three-dimensional Reynolds-Averaged Navier-Stokes(RANS) and Realizable k-ε turbulence model. The numerical static pressure recovery coefficient of the exhaust diffuser is in agreement with the experimental data well. The reliability of the numerical method for the exhaust diffuser performance analysis was demonstrated. Exhaust diffusers with four kinds of vertical strut profiles obtain the highest static pressure recovery coefficient at the inlet pre-swirl of 0.35. The similar static pressure recovery coefficient of exhaust diffusers with four kinds of vertical strut airfoils are observed when the inlet pre-swirl is less than 0.48. The static pressure recovery coefficient of exhaust diffusers with vertical b1 and b2 struts are higher than that with the a1 and a2 struts when the inlet pre-swirl is greater than 0.48. At the inlet pre-swirl of 0.35, The static pressure recovery coefficient of the exhaust diffuser with the a1 strut decreases with the increasing of the strut skewed angles. The static pressure recovery coefficient of the exhaust diffuser with the b1 strut increases with the increasing of the strut skewed angles, and the static pressure recovery coefficient increases by 3.6% compared with the vertical design when the skewed angle of b1 strut is 40[Formula: see text]. At the inlet pre-swirl of 0.64. The static pressure recovery coefficient of the exhaust diffuser with the a1 strut increases by 8.7% compared with the vertical design when the skewed angle of a1 strut is greater than 20°. In addition, the static pressure recovery coefficient of the exhaust diffuser with the b1 strut decreases by 3.8% compared with the vertical design when the skewed angle of b1 strut is 40°. The method to improve the aerodynamic performance of the exhaust diffuser by appropriate increase the strut maximum thickness and design the strut skewed angle is proposed in this work.

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Effect of Wakes and Secondary Flow on Re-attachment of Turbine Exit Annular Diffuser Flow

Kluß

Stoff

Wiedermann

2009

Journal of Turbomachinery

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In this paper numerical results of wake and secondary flow interaction in diffuser flow fields are discussed. The wake and secondary flow are generated by a rotating wheel equipped with 30 cylindrical spokes with a diameter of 10 mm as a first approach to the turbine exit flow environment. The apex angle of the diffuser is chosen such that the flow is strongly separated according to the well-known performance charts of Sovran and Klomp (1967, “Experimentally Determined Optimum Geometries for Rectilinear Diffusers With Rectangular, Conical or Annular Cross-Section,” in Fluid Mechanics of Internal Flow, Elsevier, New York, pp. 272–319). This configuration has been tested in an experimental test rig at the Leibniz University Hannover (Sieker and Seume 2007, “Influence of Rotating Wakes on Separation in Turbine Exhaust Diffusers,” Paper No. ISAIF8-54). According to these experiments, the flow in the diffuser separates as free jet for low rotational speeds of the spoke-wheel, as expected by theory. However, if the 30 spokes of the upstream wheel rotate beyond the value of 500 rpm the measurements indicate that the flow remains attached to the outer diffuser wall. It will be shown by the present numerical analysis with the commercial solver ANSYS CFX-10.0 that only an unsteady approach using the elaborate scale adaptive simulation with the shear stress transport turbulence model is capable of predicting the stabilizing effect of the rotating wheel to the diffuser flow at larger rotational speeds. The favorable comparison with the experimental data suggests that the mixing effect of wakes and secondary flow pattern is responsible for the reattachment. As a result of our studies, it can be stated that the considerably higher numerical costs associated with unsteady calculations must be accepted in order to increase the understanding of the physical flow phenomena in turbine exit flow and its interaction with the downstream diffuser.

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Impact of Gas Turbine Outflow on Diffuser Performance: A Numerical Study

Cited by 5 publications

References 0 publications

Experimental and numerical investigation of interaction between turbine stage and exhaust hood

Experimental and numerical investigation of interaction between turbine stage and exhaust hood

Effects of struts profiles and skewed angles on the aerodynamic performance of gas turbine exhaust diffuser

Effect of Wakes and Secondary Flow on Re-attachment of Turbine Exit Annular Diffuser Flow

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