Effect of Turbine Tip Leakage Flows on Exhaust Diffuser Performance

Babu, Mohan; Bhatia, Dinesh; Shukla, Ram Krishna; Pradeep, A. M.; Roy, Bishnupada

doi:10.1115/gt2011-45457

Cited by 10 publications

(5 citation statements)

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“…The scope of this paper comprises the total pressure losses produced in the shroud boundary layer of the annular diffuser downstream of the rotor. Babu et al (2011) were able to demonstrate that rotor tip leakage, achieved by means of flow injection in the shroud region, allow to decrease total pressure loss in comparison to an idealised uniform inflow. In the investigation presented here, the tip jet is achieved by a rotor instead.…”

Section: Total Pressure Loss Coefficientmentioning

confidence: 97%

Correlation between total pressure losses of highly loaded annular diffusers and integral stage design parameters

Mimic

Jätz

Herbst

2018

J. Glob. Power Propuls. Soc.

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Diffusers convert kinetic flow energy into a rise in static pressure. This pressure recovery is the primary aerodynamic design objective for exhaust gas diffusers in power-generating steam and gas turbines. The total pressure loss is an equally important diffuser design parameter. It is strongly linked to the pressure recovery and the residual kinetic energy of the diffuser outlet flow. A reduction benefits the overall thermodynamic cycle, which requires the adjacent components of a diffuser to be included in the design process. This paper focuses on the total pressure losses in the boundary layer of a highly loaded annular diffuser. Due to its large opening angle the diffuser is susceptible to flow separation under uniform inlet conditions, which is a major source for total pressure losses. However, the unsteady tip leakage vortices of the upstream rotor, which are a source of losses, stabilise the boundary layer and prevent separation. Experiments and unsteady numerical simulation conducted show that the total pressure loss reduction caused by the delayed boundary layer separation exceed the vortex-induced losses by far. This flow interaction between the rotor and diffuser consequently decreases the overall total pressure losses. The intensity of the tip leakage vortex is linked to three rotor design parameters, namely work coefficient, flow coefficient and reduced blade-passing frequency. Based on these parameters, we propose a semi-empiric correlation to predict and evaluate the change in total pressure losses with regards to design operating conditions.

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Section: Total Pressure Loss Coefficientmentioning

confidence: 97%

Correlation between total pressure losses of highly loaded annular diffusers and integral stage design parameters

Mimic

Jätz

Herbst

2018

J. Glob. Power Propuls. Soc.

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“…For the effects of turbine tip leakage flows on the exhaust diffuser performance, Babu et al 16 found that the turbine exit flow was simulated by combining an injection scheme from the casing into the main flow that changes the uniform diffuser inlet velocity profile to that of a typical turbine exit flow profile. It was observed that typical axial turbine exit flows carry a thin tip-induced casing boundary layer (tipstrong flow), which energizes and enables the casing endwall flows to overcome adverse pressure gradients, and the current study also reinforces the fact that the volute diffuser performance is highly sensitive to inlet conditions.…”

Section: Effect Of Turbine Exit Conditions Simulated On the Nonaxisymmetric Exhaust Volutementioning

confidence: 99%

Advances in coupled axial turbine and nonaxisymmetric exhaust volute aerodynamics for turbomachinery

Gao

Tao

Huo

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part G:

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Marine, industrial, turboprop and turboshaft gas turbine engines use nonaxisymmetric exhaust volutes for flow diffusion and pressure recovery. These processes result in a three-dimensional complex turbulent flow in the exhaust volute. The flows in the axial turbine and nonaxisymmetric exhaust volute are closely coupled and inherently unsteady, and they have a great influence on the turbine and exhaust aerodynamic characteristics. Therefore, it is very necessary to carry out research on coupled axial turbine and nonaxisymmetric exhaust volute aerodynamics, so as to provide reference for the high-efficiency turbine-volute designs. This paper summarizes and analyzes the recent advances in the field of coupled axial turbine and nonaxisymmetric exhaust volute aerodynamics for turbomachinery. This review covers the following topics that are important for turbine and volute coupled designs: (1) flow and loss characteristics of nonaxisymmetric exhaust volutes, (2) flow interactions between axial turbine and nonaxisymmetric exhaust volute, (3) improvement of turbine and volute performance within spatial limitations and (4) research methods of coupled turbine and exhaust volute aerodynamics. The emphasis is placed on the turbine-volute interactions and performance improvement. We also present our own insights regarding the current research trends and the prospects for future developments.

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“…Great efforts have been made for understanding the effect of the turbine outlet flow field on diffuser performance, particularly that of tip jets induced upstream of the diffuser. Numerous authors, such as Babu et al (2011) and Volkmer et al (2011) found an increase in diffuser pressure recovery for increasing jet intensity. Mimic et al (2017) were able to correlate the diffuser pressure recovery with stage parameters of the blading, demonstrating a direct correlation between the intensity of tipgap vortices and boundary layer stabilization for an engine-like test rig.…”

Section: Introductionmentioning

confidence: 95%

Effect of Diffuser Inhomogeneity on Full-Annulus Axial Turbine Performance

Oettinger¹,

Henke²,

Seume³

2020

Proceedings of Global Power &Amp; Propulsion Society

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Gas-turbine stacks are typically designed to be as short as possible, often featuring an aggressive diffuser and an exit plenum with a radial bend in order to reduce transmission shaft length. This can, however, cause flow inhomogeneity at the turbine outlet affecting performance. In this paper, the effect of such inhomogeneity is investigated utilizing experimentally supported full-annulus simulations of the turbine and exhaust sections. It is demonstrated that an inhomogeneous static pressure distribution can cause variation in upstream blade loading of up to 1.3 % in the Zweifel coefficient. This effect becomes stronger for higher diffuser inlet swirl angles, stressing the importance of interlocked turbine-exhaust section design.

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Effect of Turbine Tip Leakage Flows on Exhaust Diffuser Performance

Cited by 10 publications

References 0 publications

Correlation between total pressure losses of highly loaded annular diffusers and integral stage design parameters

Correlation between total pressure losses of highly loaded annular diffusers and integral stage design parameters

Advances in coupled axial turbine and nonaxisymmetric exhaust volute aerodynamics for turbomachinery

Effect of Diffuser Inhomogeneity on Full-Annulus Axial Turbine Performance

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