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.
StrouhalV., ‘Ueber eine besondere Art der Tonerregung’Ann. Phys. Chemie, Neue Folge510 (1878): 216–251.
2.
Von KármánT.RubachH., ‘Ueber den Mechanismus des Fluessigkeits- und Luftwiderstandes’Phys. Zeitschr.132 (1912): 49–59.
3.
EckertE. R. G.WeiseW., ‘Messungen der Temperaturverteilung auf der Oberfläche schnell angeströmter umbeheizter Körper’Jahrbuch 1940 der Deutschen Luftfahrtforschung2 (1940): 25–31.
4.
EckertE. R. G., ‘Energy separation in fluid streams’Int. Commun. Heat Mass Transf.13 (1987): 127–143.
5.
CarscallenW. E.OosthuizenP. H., ‘The effect of secondary flow on the redistribution of the total temperature field downstream of a stationary turbine cascade’ (1989): 1-18 AGARD Report CP 469.
6.
CarscallenW. E.CurrieT. C.HoggS. I.GostelowJ. P., ‘Measurement and computation of energy separation in the vortical wake flow of a turbine nozzle cascade’J. Turbomach.121 (1999): 703–708.
7.
HoggS. I.CarscallenW. E.GostelowJ. P.ButtsworthD. R.JonesT. V., ‘Wide bandwidth stagnation temperature measurements in vortical flows behind turbine vanes’ (1997): 389–400 IEEE; Instrumentation in Aerospace Simulation Facilities, ICIAFS.
8.
SieverdingC. H.RichardH.DesseJ.-M., ‘Turbine blade trailing edge flow characteristics at high subsonic oulet Machnumber’ASME/IGTI J. Turbomach.125 (2003): 298–309.
9.
SieverdingC. H.OttoliaD.BagneraC.ComadoroA.BrouckaertJ. F.DesseJ. -M., ‘Unsteady turbine blade wake characteristics’ASME/IGTI J. Turbomach.1264 (2004): 551–559.
10.
XuL.DentonJ. D., ‘The base pressure and loss of a family of four turbine blades’ASME/IGTI J. Turbomach.110 (1988): 9–17.
11.
KeoghR., Aerodynamic performance measurements of a film-cooled turbine stage (Massachusetts Institute of Technology 1998) Thesis, Aeronautics and Astronautics.
12.
HummelF., ‘Wake-wake interaction and its potential for clocking in a transonic high-pressure turbine’ASME J. Turbomach.124 (2002): 69–76.
13.
RoseM. G.HarveyN. W., ‘Turbomachinery wakes: Differential work and mixing losses’ASME/IGTI J. Turbomach.122 (2000): 68–77.
14.
LeeE. S.DulikravichG. S.DennisB. H., ‘Rotor cascade shape optimization with unsteady passing wakes using implicit dual-time stepping and a genetic algorithm’Int. J. Rotat. Mach.9 (2003): 353–361.
15.
Van de WallA. G.KadambiJ. R.AdamczykJ. J., ‘A transport model for the deterministic stress associated with turbomachinery blade row interactions’ASME/IGTI J. Turbomach.122 (2000): 593–603.
16.
BaldwinB.LomaxH., ‘Thin layer approximation and algebraic model for separated turbulent flows’ (1978): 78–257 AIAA paper.
17.
SpalartP. R.AllmarasS. R., ‘A one-equation turbulence model for aerodynamic flows’ (1992): AIAA report 92-0439.
18.
WilcoxD. C., ‘A half century historical review of the k–ω-model’ (1991): AIAA paper 91-0615.
19.
MokulysT.DewhurstS. C.AbhariR. S., ‘Numerical validation of characteristic and linearized unsteady boundary conditions for non-integer blade ratios in a non-linear Navier Stokes solver’ (2005) Proceedings of the IGTI TurboExpo, Reno, Nevada, 2005, GT2005-68670.
20.
MokulysT.FerrariF.HaertelC.AbhariR. S., ‘Uncertainty analysis of predicted heat transfer for turbomachinery flows’ In Proceedings of the Conference of Modelling Fluid Flow, CMFF, Budapest, September 2003.
21.
MokulysT., On the development and application of accurate numerical models for the computation of steady and unsteady flowfields in turbomachinery (2007): Dissertation ETH No. 17152.
22.
BehrT.PorrecaL.MokulysT.KalfasA. I.AbhariR. S., ‘Multistage aspects and unsteady flow effects of stator and rotor clocking in an axial turbine with low aspect ratio blading’ASME J. Turbomach.128 (2006): 11–22.
23.
MeeD. J.BainesN. C.OldfieldM. L. G.DickensT. E., ‘An examination of the contributions to loss on a transonic turbine blade in cascade’ASME/IGTI J. Turbomach.114 (1992): 155–162.
24.
DrelaM.GilesM. B., ‘ISES: A two-dimensional viscous aerodynamic design and analysis code’ (1987): AIAA paper 87-0424.
DentonJ. D., ‘The 1993 IGTI scholar lecture: Loss mechanisms in turbomachines’ASME J. Turbomach.115 (1993): 621–656.
27.
DentonJ. D.XuL., ‘The trailing edge loss of transonic turbine blades’Trans. ASME, J. Turbomach.1122 (1989): 277–285.
28.
FalkE. A.DarbeR. P.GorrellS. E., ‘Influence of IGV trailing edge geometry on blade-row aerodynamic interactions in a transsonic compressor’ In proceedings of the 40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, July 2004, AIAA paper 2004-3757.
29.
HeL.ChenT.WellsR. G.LiY. S.NingW., ‘Analysis of rotor—rotor and stator—stator interferences in multi-stage turbomachines’ASME J. Turbomach.124 (2002): 564–571.
30.
KorakianitisT., ‘Influence of stator—rotor gap on axial turbine unsteady forcing functions’AIAA J.317 (1993): 1256–1264.
31.
KreitmeierF., ‘Space averaging 3D flows using strictly formulated balance equations in turbomachinery’ (1992) In proceedings of the ASME Cogen—Turbo, 1992, IGTI-vol.7, Book no., 100333-1992.
32.
Lavante vonE.MoczalaM.ParvizinaM., ‘Numerical investigation of losses due to unsteady effects in axial turbines’ (2003) In Proceedings of the ASME/IGTI Turbo Expo, Atlanta, Paper GT2003–38838.
33.
MikolajczakA. A., ‘The practical importance of unsteady flow’ (Unsteady Phenomena in Turbomachinery, North Atlantic Treaty Organization 1976) AGARD CP-144.
34.
SharmaO. P.StetsonG. M.DanielsW. A.GreitzerE. M.BlairM. F.DringR. P., ‘Impact of periodic unsteadiness and heat load in axial flow turbomachines’ (Final report from United Technologies Corporation, Pratt & Whitney for NASA Lewis Research Center 1996).
35.
SmithL. H., ‘Wake dispersion in turbomachines’ASME J. Basic Eng.88 (1996): 688–690.
36.
SondakD. L.DorneyD. J., ‘Simulation of vortex shedding in a turbine stage’ASME/IGTI J. Turbomach.1213 (1999): 428–435.
37.
WalraevensR. E.GallusH. E., ‘Stator—rotor—stator interaction in an axial flow turbine and its influence on loss mechanisms’ (1996) In Proceedings of the AGARD, 1996, pp. 39, 571.
38.
YuW. S.LakshminarayanaB., ‘Numerical simulation of the effects of rotor-stator spacing and wake/blade count ratio on turbomachinery flows’J. Fluids Eng.117 (1995): 639–646.
