The Role of Rotor Tip Clearance on the Aerodynamic Interaction of a Last Gas Turbine Stage and an Exhaust Diffuser

Willinger, Reinhard; Haselbacher, H.

doi:10.1115/98-gt-094

Cited by 10 publications

(5 citation statements)

References 10 publications

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“…C Di4−3 tpl and C Di4−3 pr at three operational conditions are also compared in Table 1. It can be seen that the total pressure loss coefficient is reduced and is defined in equation (3). The inflow is relatively uniform along the radial direction with a small swirl angle.…”

Section: Resultsmentioning

confidence: 99%

“…A number of experimental and numerical studies on turbine stage-diffuser or turbine stage-hood interactions have been carried out. Willinger and Hasselbacher [3] studied the effect of rotor tip clearance flow on diffuser performance with an N-S solver, in which the turbulence behaviour of the flow field was simulated by a k-ε model. Several turbulence models were evaluated byVassiliev et al [4].…”

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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“…Note that the flow angle of the blade tip vortex is higher than the flow angle of the main flow. This overturning is caused by the momentum of the tip flow, as described by Willinger and Hasselbacher [21]. In the experiments, the inlet of the diffuser is located about 0.5 of axial chord length downstream of the rotor, where the Reynolds shear stresses were found to influence the boundary layer, therefore in the following paragraph the focus is on the propagation of the stresses downstream of the rotor.…”

Section: Origin and Propagation Of Reynolds Shear Stressesmentioning

confidence: 99%

On the Numerical Prediction of the Influence of Tip Flow on Diffuser Stability

Drechsel

Joerg

Herbst

2016

JGPP

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In previous studies, the pressure recovery of highly-loaded annular diffusers was identified to correlate with the Reynolds shear stresses at rotor outlet in the blade tip region. The origin and propagation of the Reynolds shear stresses, however, have not been experimentally clarified yet due to measurement probe constraints. Hence in the present work, the origin of these stresses, as well as the transport throughout the flow channel is analyzed by simulating the rotor with the scale adaptive turbulence model SAS-SST is used. Using the SAS approach, the Reynolds shear stress characteristics of the simulation are validated by the experimental results, whereas common RANS approaches are shown not to be appropriate. The tip leakage vortex is found to be the source of the Reynolds shear stress production. The interaction between vortex and mean flow leads to turbulent momentum transport. The Reynolds shear stresses propagate into the rotor far-field connected to the blade tip vortices which mix about four chord lengths downstream of the rotor trailing edge.

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“…Finally, it is assumed that all the turbine designs feature an outlet diffuser characterized by a semi-opening angle of 0.175 rad (10 degree) and a length of 1 m [41]. Thus, once the outlet geometry of the last stage is known (i.e., mean diameter and blade height) from the design model, it is possible to compute the crosssectional area ratio (outlet/inlet) of the diffuser and then its efficiency according to the experimental data reported in [42].…”

Section: Casementioning

confidence: 99%

A Code for the Preliminary Design of Cooled Supercritical CO2 Turbines and Application to the Allam Cycle

Scaccabarozzi

Martelli

Pini

et al. 2022

Journal of Engineering for Gas Turbines and Power

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This paper documents a thermo-fluid-dynamic mean-line model for the preliminary design of multi-stage axial turbines with blade cooling applicable to supercritical CO2 turbines. Given the working fluid and coolant inlet thermodynamic conditions, blade geometry, number of stages and load criterion, the model computes the stage-by-stage design along with the cooling requirement and ultimately provides an estimate of turbine efficiency via a semi-empirical loss model. Different cooling modes are available and can be selected by the user (stand-alone or combination): convective cooling, film cooling, thermal barrier coating. The model is applied to attain the preliminary aero-thermal design of the 600 MW cooled axial supercritical CO2 turbine of the Allam cycle. Results show that a load coefficient varying from 3 to 1 throughout the machine, and a reaction degree ranging from 0.1 to 0.5 lead to the maximum total-to-static turbine efficiency of about 85 %. Consequently, as opposed to uncooled CO2 turbines, a repeated stage configuration is an unsuited design choice for cooled sCO2 machines. Moreover, the study highlights that film cooling is considerably less effective compared to conventional gas turbines, while increasing the number of stages from 5 to 6 and adopting higher rotational speeds leads to an increased efficiency.

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The Role of Rotor Tip Clearance on the Aerodynamic Interaction of a Last Gas Turbine Stage and an Exhaust Diffuser

Abstract: Ra

Cited by 10 publications

References 10 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

On the Numerical Prediction of the Influence of Tip Flow on Diffuser Stability

A Code for the Preliminary Design of Cooled Supercritical CO2 Turbines and Application to the Allam Cycle

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