Effects of Tip Endwall Contouring on the Three-Dimensional Flow Field in an Annular Turbine Nozzle Guide Vane: Part 1—Experimental Investigation

1985 ◽  
Vol 107 (4) ◽  
pp. 983-990 ◽  
Author(s):  
E. Boletis
Keyword(s):  
Experimental Investigation ◽  
Aspect Ratio ◽  
Guide Vane ◽  
Three Dimensional ◽  
Three Dimensional Flow ◽  
Low Aspect Ratio ◽  
Dimensional Flow ◽  
Nozzle Guide Vane ◽  
Endwall Contouring ◽  
Nozzle Guide

Tip endwall contouring is one of the most effective methods to improve the performance of low aspect ratio turbine vanes [1]. In view of the wide variety of geometric parameters, it appears that only the physical understanding of the three-dimensional flow field will allow us to evaluate the probable benefits of a particular endwall contouring. The paper describes the experimental investigation of the three-dimensional flow through a low-speed, low aspect ratio, high-turning annular turbine nozzle guide vane with meridional tip endwall contouring. The full impact of the effects of tip contouring is evaluated by comparison with the results of a previous study in an annular turbine nozzle guide vane of the same blade and cascade geometry with cylindrical endwalls [12]. In parallel, the present experimental study provides a fully three-dimensional test case for comparison with advanced theoretical calculation methods [15]. The flow is explored by means of double-head, four-hole pressure probes in five axial planes from far upstream to downstream of the blade row. The results are presented in the form of contour plots and spanwise pitch-averaged distributions.

scholarly journals Effects of Tip Endwall Contouring on the Three Dimensional Flow Field in an Annular Turbine Nozzle Guide Vane: Part 2 — Numerical Investigation

1985 ◽  
Author(s):  
Tony Arts
Keyword(s):  
Flow Field ◽  
Numerical Investigation ◽  
Guide Vane ◽  
Three Dimensional ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Nozzle Guide Vane ◽  
Contour Plots ◽  
Endwall Contouring ◽  
Nozzle Guide

This paper describes the numerical investigation of the three dimensional flow through a low speed, low aspect ratio, high turning annular turbine nozzle guide vane with meridional tip endwall contouring. This rotational flow field has been simulated using a finite volume discretization and a time marching technique to solve the three dimensional, time dependent Euler equations expressed in a cylindrical coordinates system. The results are presented under the form of contour plots, spanwise pitch-averaged distributions and blade static pressure distributions. Detailed comparisons with the measurements described in part I of the paper are also provided.

Numerical Analysis on Effects of the Contoured Endwall on the Three Dimensional Flow Characteristics in an Annular Turbine Nozzle Vane

2007 ◽  
Author(s):  
Wu Sang Lee ◽  
Jin Taek Chung ◽  
Dae Hyun Kim ◽  
Seung Joo Choe
Keyword(s):  
Guide Vane ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Leading Edge ◽  
Secondary Flows ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

The three-dimensional flow in a turbine nozzle guide vane passage causes large secondary loss through the passage and increased heat transfer on the blade surface. In order to reduce or control these secondary flows, a linear turbine with contoured endwall configurations was used and changes in the three-dimensional flow field were analyzed and discussed. Contoured endwalls are installed at a location downstream of the saddle point near the leading edge of the pressure side blade and several positions along the centerline of the passage at constant distance. The objective of this study is to document the development of the three-dimensional flow in a turbine nozzle guide vane cascade with modified endwall. In addition, it proposes and appropriates endwall contouring which shows best overall loss reduction performance among the simulated contoured endwall. The results of this study show that the development of passage vortex and cross flow in the cascade composed of one flat and one contoured endwalls are affected by the acceleration which occurs in contoured endwall side. The overall loss is reduced near the flat endwall rather than contoured endwall, the best performance was shown for the case of 10–15% contoured for span-wise, 40–70% length of chord from trailing edge.

Flow Measurements in a Nozzle Guide Vane Passage With a Low Aspect Ratio and Endwall Contouring

2000 ◽  
Author(s):  
Steven W. Burd ◽  
Terrence W. Simon
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Guide Vane ◽  
Flow Measurements ◽  
Vast Number ◽  
Aspect Ratios ◽  
Nozzle Guide Vane ◽  
Endwall Contouring ◽  
Nozzle Guide

The vast number of turbine cascade studies in the literature has been performed in straight-endwall, high-aspect-ratio, linear cascades. As a result, there has been little appreciation for the role of, and added complexity imposed by, reduced aspect ratios. There also has been little documentation of endwall profiling at these reduced spans. To examine the role of these factors on cascade hydrodynamics, a large-scale nozzle guide vane simulator was constructed at the Heat Transfer Laboratory of the University of Minnesota. This cascade is comprised of three airfoils between one contoured and one flat endwall. The geometries of the airfoils and endwalls, as well as the experimental conditions in the simulator, are representative of those in commercial operation. Measurements with hot-wire anemometry were taken to characterize the flow approaching the cascade. These measurements show that the flow field in this cascade is highly elliptic and influenced by pressure gradients that are established within the cascade. Exit flow field measurements with triple-sensor anemometry and pressure measurements within the cascade indicate that the acceleration imposed by endwall contouring and airfoil turning is able to suppress the size and strength of key secondary flow features. In addition, the flow field near the contoured endwall differs significantly from that adjacent to the straight endwall.

The Influence of Endwall Contouring on the Performance of a Turbine Nozzle Guide Vane

1998 ◽  
Author(s):  
Vincenzo Dossena ◽  
Antonio Perdichizzi ◽  
Marco Savini
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Guide Vane ◽  
Three Dimensional ◽  
Angle Distribution ◽  
Secondary Effects ◽  
Three Dimensional Flow ◽  
Nozzle Height ◽  
Dimensional Flow ◽  
Endwall Contouring

The paper presents the results of a detailed investigation of the flow field in a gas turbine linear cascade. A comparison between a contoured and a planar configuration of the same cascade has been performed, and differences in the three-dimensional flow field are here analyzed and discussed. The flow evolution downstream of the trailing edge was surveyed by means of probe traversing while a 3-D Navier-Stokes solver was employed to obtain information on flow structures inside the vaned passages. The experimental measurements and the numerical simulation of the three-dimensional flow field has been performed for two cascades; one with planar endwalls, and the other with one planar and one profiled endwall, so as to present a reduction of the nozzle height. The investigation was carried out at an isentropic downstream Mach number of 0.6. Airfoils of both cascades were scaled from the same high pressure gas turbine inlet guide vane. Measurements of the three-dimensional flow field have been performed on five planes downstream of the cascades by means of a miniaturized five-hole pressure probe. The presence of endwall contouring strongly influences the secondary effects; the vortex generation and their development is inhibited by the stronger acceleration taking place throughout the cascade. The results show that the secondary effects on the contoured side of the passage are confined in the endwall region, while on the flat side the secondary vortices display characteristics similar to the ones occurring downstream of the planar cascade. The spanwise outlet angle distribution presents a linear variation for most of the nozzle height, with quite low values approaching the contoured endwall. The analysis of mass averaged losses shows a significant performance improvement in the contoured cascade. This has to be ascribed not only to lower secondary losses but also to a reduction of the profile losses.

The Influence of Endwall Contouring on the Performance of a Turbine Nozzle Guide Vane

1999 ◽  
Vol 121 (2) ◽  
pp. 200-208 ◽  
Author(s):  
V. Dossena ◽  
A. Perdichizzi ◽  
M. Savini
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Guide Vane ◽  
Three Dimensional ◽  
Angle Distribution ◽  
Secondary Effects ◽  
Three Dimensional Flow ◽  
Nozzle Height ◽  
Dimensional Flow ◽  
Endwall Contouring

The paper presents the results of a detailed investigation of the flow field in a gas turbine linear cascade. A comparison between a contoured and a planar configuration of the same cascade has been performed, and differences in the three-dimensional flow field are here analyzed and discussed. The flow evolution downstream of the trailing edge was surveyed by means of probe traversing while a three-dimensional Navier–Stokes solver was employed to obtain information on flow structures inside the vaned passages. The experimental measurements and the numerical simulation of the three-dimensional flow field have been performed for two cascades; one with planar endwalls, and the other with one planar and one profiled endwall, so as to present a reduction of the nozzle height. The investigation was carried out at an isentropic downstream Mach number of 0.6. Airfoils of both cascades were scaled from the same high-pressure gas turbine inlet guide vane. Measurements of the three-dimensional flow field have been performed on five planes downstream of the cascades by means of a miniaturized five-hole pressure probe. The presence of endwall contouring strongly influences the secondary effects; the vortex generation and their development are inhibited by the stronger acceleration taking place throughout the cascade. The results show that the secondary effects on the contoured side of the passage are confined in the endwall region, while on the flat side the secondary vortices display characteristics similar to the ones occurring downstream of the planar cascade. The spanwise outlet angle distribution presents a linear variation for most of the nozzle height, with quite low values approaching the contoured endwall. The analysis of mass-averaged losses shows a significant performance improvement in the contoured cascade. This can be ascribed not only to lower secondary losses but also to a reduction of the profile losses.

scholarly journals Study of a Low Aspect Ratio Low Pressure Turbine Nozzle Guide Vane With High Outer Annulus Wall Slope

1997 ◽  
Author(s):  
G. Siden ◽  
S. Schlechtriem ◽  
E. Johann ◽  
H. Klinger
Keyword(s):  
Aspect Ratio ◽  
Pressure Distribution ◽  
Pressure Loss ◽  
Guide Vane ◽  
Low Aspect Ratio ◽  
Nozzle Guide Vane ◽  
Outer Annulus ◽  
Unsteady Loading ◽  
Nozzle Guide ◽  
Wall Slope

This paper presents the results of a combined experimental and CFD investigation of a first stage low pressure (LP) turbine nozzle guide vane (NGV). The configuration is characterized by a small number of low aspect ratio vanes in a strongly diverging annulus. The experimental part of the study has been conducted in a two-stage rotating rig environment with detailed area traverse measurements upstream and downstream of the NGV. The inlet whirl to the NGV has been varied by a row of pre-swirl vanes (PSV) located in the turbine rig inlet. The effect of inlet whirl angle on the development of the passage vortices and on the NGV pressure loss is assessed by using measurements and steady state 30 CFD predictions. The area traverse results, which neglect any mixing loss downstream of the traverse plane, show the traditional airfoil loss-loop characteristic with minimum loss at design incidence and increased loss at both positive and negative incidence. By considering the turbine overall performance, however, it is observed that the isentropic turbine efficiency increases for negative incidence and decreases for positive incidence to an extent that cannot be explained by the measured NGV total pressure loss only. This leads us to believe that the non-uniform flow field at the exit of the NGV generated by the wake and secondary flow impacts significantly on the loss generation further downstream in the turbine. Unsteady 3D CFD predictions of the NGV and the downstream rotor passage aerodynamics have been conducted in order to study the convection of the NGV wake and passage vortices through the rotor passage and the resulting unsteady loading on the rotor. The strongest interaction takes place in the hub region. The unsteady loading in the tip region is characterized by incidence variations which typically only affect the rotor unsteady pressure distribution in the leading edge region up to 40% axial chord. In the hub, however, the strong three-dimensional character of the flow forces large amplitude fluctuations to occur in the rotor unsteady pressure distribution at the throat region. These fluctuations affect the character and the level of diffusion on the suction surface and are therefore likely to have significant impact on the rotor loss. In striving to reduce manufacturing cost and engine weight by exploiting high outer annulus wall slope and smaller gap-to-chord ratios these types of effects are bound to become increasingly important. The application of advanced prediction tools, such as used in this paper, will inevitably play an important role in this development.

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