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:10.1115/1.2101855

Cited by 30 publications

(9 citation statements)

References 18 publications

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“…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:

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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.

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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:

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“…This probe is a modified version of the conventional single sensor probe already used in previous investigations [16][17][18] and has a second sensor sensitive of pitch angle variation of the flow. The dimensions of each piezoresistive sensor are 0:4 0:8 mm, the distance between the two sensors is approximately 2.2 mm and the tip diameter of the probe is 1.8 mm.…”

Section: B Measurement Technologymentioning

confidence: 99%

“…This paper follows a series of studies on unsteady flows in a multistage environment, conducted on the same shrouded turbine geometry and focused on blade interaction [16][17][18][19]. A methodology is proposed to derive turbulence quantities along the three spatial directions.…”

mentioning

confidence: 99%

Turbulence Measurements and Analysis in a Multistage Axial Turbine

Porreca

Hollenstein

Kalfas

et al. 2007

Journal of Propulsion and Power

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This paper presents turbulence measurements and detailed flow analysis in an axial turbine stage. Fast response aerodynamic probes were used to resolve aperiodic fluctuations along the three directions. Assuming incompressible flow, the effective turbulence level and Reynolds stress are retrieved by evaluating the stochastic velocity component out of the measured time-resolved pressure and flow angle fluctuations along the streamwise, radial, and circumferential direction. A comparison between turbulence intensity and measured total pressure shows that flow structures with higher turbulence level are identified in the region of loss cores at the exit of the second stator passage. Turbulence intensity is evaluated under isotropic and nonisotropic assumption in order to quantify the departure from isotropic conditions. The measurements show that locally the streamwise fluctuating component can be twice bigger than the radial and tangential component. The current analysis shows that multisensor fast response aerodynamic probes can be used to provide information about the mean turbulence levels in the flow and the Reynolds stress tensor, in addition to the measurements of unsteady total pressure loss. Nomenclature c = absolute velocity vector e = mean unit vector in the secondary flow definition p = static pressure p d = dynamic head s, , r = streamwise, circumferential, and radial directions T=T 0 = blade passing period fraction t = time u = streamwise velocity component u,ṽ,w = periodic velocity component: phase-lock averaged u 0 , v 0 , w 0 = stochastic (aperiodic) velocity components v = circumferential velocity component w = radial velocity component = yaw angle = pitch angle x = absolute uncertainty of quantity x = density Subscripts/superscripts 1 = probe position 1 iso = isotropic assumption NS = nonsimultaneous sec = secondary flow vector

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“…The turbine stage maximum efficiency condition occurs when the wake from the upstream vane row is positioned such that it impinges on the leading edge of the downstream vane. The minimum efficiency condition, typically out of phase with the optimum configuration by half a passage, occurs when the wake convects through the middle of the downstream vane passage [9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Vane Clocking in a Three-Stage Compressor: Frequency Domain Data Analysis

Key

Lawless

Fleeter

2009

Journal of Propulsion and Power

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Blade row interactions affect compressor performance and durability. As design systems expand to account for these interactions, a better understanding of the underlying physics is necessary. In this paper, results from a vane clocking experiment in a three-stage compressor are discussed. Efforts are focused on the second stage, specifically the change in stator 2 wake profiles with respect to the placement of the stator 1 wake. The two clocking conditions presented position the wake from stator 1 at the leading edge of stator 2 and in the middle of the stator 2 passage. The time-accurate data are Fourier decomposed to determine the relative magnitudes of the frequencies in the spectrum. With data acquired at 50 circumferential locations spanning one vane passage for each clocking configuration, an enormous amount of data is collected, and a useful method for synthesizing this information is presented. Results show that, by placing the stator 1 wake at the leading edge of stator 2, the stator 2 boundary-layer response to the large incidence variations associated with the rotor 2 wakes is dampened, resulting in a thinner and more shallow stator 2 wake. Nomenclature CL LE = clocking configuration that positions stator 1 wake at leading edge of stator 2 CL MP = clocking configuration that positions stator 1 wake in the middle of the stator 2 passage f = frequency m c = corrected mass flow rate P o = total pressure R = rotor S = stator U = wheel speed V = flow velocity in the absolute reference frame = absolute flow angle = adiabatic efficiency

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

Cited by 30 publications

References 18 publications

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

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

Turbulence Measurements and Analysis in a Multistage Axial Turbine

Vane Clocking in a Three-Stage Compressor: Frequency Domain Data Analysis

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