Multistage Aspects and Unsteady Effects of Stator and Rotor Clocking in an Axial Turbine With Low Aspect Ratio Blading

Behr, Thomas; Porreca, L.; Mokulys, Thomas; Kalfas, A. I.; Abhari, Reza S.

doi:10.1115/gt2004-53612

Cited by 11 publications

(6 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It can be seen that as this vortex region passes the stator leading edge, the turbulence intensity reduces by factor 2. The same effect has been described in more detail in the article by Behr et al [6]. Depending on the relative Fig.…”

Section: Unsteady Rotor Secondary Flowsupporting

confidence: 56%

“…In these studies the circumferential position of the wake of the upstream stator relative to the leading edge of the subsequent stator was mainly held responsible for the effect on efficiency. Contrary effects of clocking positions on different span regions have been found by Behr et al [6], Huber et al [1], Schennach et al [7], and Arnone et al [8]. Consequently, they all suggested to focus more on the three-dimensionality of the flow for explaining clocking phenomena.…”

Section: Introductionmentioning

confidence: 90%

See 1 more Smart Citation

Stator-clocking effects on the unsteady interaction of secondary flows in a 1.5-stage unshrouded turbine

Behr

Kalfas

Abhari

2007

Proceedings of the Institution of Mechanical Engineers, Part A:

Self Cite

View full text Add to dashboard Cite

Effects of stator clocking on the unsteady interaction of stator and rotor secondary flows and performance are investigated in a 1.5-stage, high-pressure turbine. Due to the low aspect ratio design of the blade rows, vortical structures dominate the inlet flow field of the second stator row. Therefore the interaction of first stator and rotor secondary flows in relation to the stator-clocking position must be considered in order to achieve an optimized multi-stage performance. Four different stator-clocking positions are studied in this experimental investigation. The data comprise unsteady and steady probe measurements, which are acquired downstream of the rotor and the second stator blade row of a 1.5-stage, unshrouded turbine. A two-sensor fast response aerodynamic probe technique is used in the measurement campaign. It is found that multi-row interaction effects of vortical secondary flow features dominate the loss creation in turbine stages having low aspect ratio geometries. The periodic interaction of shed passage vortices of the first stator with secondary flow structures of the rotor creates regions characterized by reduced total pressure and increased turbulence, and entropy at fixed locations relative to the subsequent stator. Circumferential position of these interaction regions defines the spanwise distribution of total pressure loss in the downstream stator. Stator-clocking controls the spanwise distribution of loss in high-pressure turbines. However, the potential of reducing the loss is limited due to the three-dimensional nature of the flow, and hence, the non-uniform effect of a clocking position on the spanwise performance of a downstream stator.

show abstract

Section: Unsteady Rotor Secondary Flowsupporting

confidence: 56%

Section: Introductionmentioning

confidence: 90%

Stator-clocking effects on the unsteady interaction of secondary flows in a 1.5-stage unshrouded turbine

Behr

Kalfas

Abhari

2007

Proceedings of the Institution of Mechanical Engineers, Part A:

Self Cite

View full text Add to dashboard Cite

show abstract

“…These models, which consist of the algebraic Baldwin-Lomax model [16], the one-equation Spalart-Allmaras model [17], and the k−ω model of Wilcox [18], will be compared on the CASCADE. Further descriptions of the solver and its unsteady features as well as turbulence modelling can be found in references [19][20][21][22]. Especially the code's ability to model the unsteady wake correctly in terms of wake depth and diffusion has been the core of interest.…”

Section: Computational Fluid Dynamics-modelling/unsteady Lossesmentioning

confidence: 99%

Unsteady numerical investigation of the effect of wakes with eddy shedding in different axial turbine aerofoils

Mokulys

Congiu

Rose

et al. 2009

Proceedings of the Institution of Mechanical Engineers, Part A:

View full text Add to dashboard Cite

In the past it was found experimentally and numerically that eddy shedding on trailing edges of turbine aerofoils has significant effect on the aerodynamic performance. Aerofoils of gas turbines usually have relatively thick trailing edges for reasons of mechanical integrity, and hence strong unsteady wakes are created. The current investigation considers trailing edges without cooling injection; hence the area of application is limited to the low-and medium-pressure stages of a gas turbine. In this work a numerical investigation is performed with the aim to weigh the loss production inside these unsteady wakes against the available kinetic energy of the unsteady fluid to formulate a so-called unsteady recovery factor. Furthermore, several design exercises are presented on a gas-turbine rotor profile, which is interacting with the unsteady wake of an upstream vane with eddy shedding. This shows that the stage performance is quite significantly influenced comparing frontloaded, midloaded, and aftloaded profile designs in contradiction to standard steady design approaches. It was found that a frontloaded rotor design under consideration of interaction with an unsteady wake can increase the stage performance of a two-dimensional midsection considerably, while under steady assumptions it has about the same or worse performance. This result shows the importance of unsteady methods in turbine design and also potential new ways for improved profile design.

show abstract

“…2 Other clocking investigations on the turbines obtained similar results, the maximum efficiency variation influenced by vane clocking varied from 0.3 to 2.0 points. [3][4][5] Besides, vane clocking effect experiment was conducted on compressors. The experiment in NASA's Four-Stage Axial Compressor Facility showed that the impact of stator indexing produced a change of 0.2 points in overall efficiency, but the change was in the band of uncertainty due to manufacturing variations and assembly tolerances.…”

Section: Introductionmentioning

confidence: 99%

An experimental investigation of the vane clocking effects on the centrifugal compressor time-averaged performance

Wuqi

Zhang

et al. 2013

Proceedings of the Institution of Mechanical Engineers, Part A:

View full text Add to dashboard Cite

The clocking effect, known as a potential means to improve the aerodynamic performance of the turbomachinery, has been investigated widely in the multistage axial turbomachinery, but little reported on the radial turbomachinery. In the present paper, an experimental investigation was made on the vane clocking effect between the inlet guide vanes and the vaned diffuser in a medium-speed centrifugal compressor. The measured data show that the vane clocking has an effect on the aerodynamic performance of the researched centrifugal compressor stage. At the design point, the maximum efficiency variation is about 0.52 points and the maximum total pressure ratio variation is 0.004. When the inlet guide vane’s stagger angle was adjusted to −45°, the vane clocking effect is strengthened. The maximum efficiency and total pressure ratio variation for the design point, respectively, are 0.67 points and 0.006, and for the low flow rate point even, respectively, increases to 0.90 points and 0.007. The wake characteristics show that the maximum efficiency variation always arises at a similar clocking configuration, in which the upstream inlet guide vanes wake was detected to impinge on the diffuser blade leading edge. In addition, the profile pressure distribution on the diffuser blade was measured in detail and the blade loading analysis shows that there is no measureable variation for the vane clocking effect on the steady diffuser blade loading.

show abstract

Multistage Aspects and Unsteady Effects of Stator and Rotor Clocking in an Axial Turbine With Low Aspect Ratio Blading

Cited by 11 publications

References 19 publications

Stator-clocking effects on the unsteady interaction of secondary flows in a 1.5-stage unshrouded turbine

Stator-clocking effects on the unsteady interaction of secondary flows in a 1.5-stage unshrouded turbine

Unsteady numerical investigation of the effect of wakes with eddy shedding in different axial turbine aerofoils

An experimental investigation of the vane clocking effects on the centrifugal compressor time-averaged performance

Contact Info

Product

Resources

About