Experimental and Numerical Investigation of the Influence of Rotor Blades on Hot Gas Ingestion Into the Upstream Cavity of an Axial Turbine Stage

2000 ◽  
Author(s):  
Dieter Bohn ◽  
Bernd Rudzinski ◽  
Norbert Sürken ◽  
Wolfgang Gärtner
Keyword(s):  
Carbon Dioxide ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Positive Influence ◽  
Rotor Blades ◽  
Gas Concentration ◽  
Hot Gas ◽  
Carbon Dioxide Gas ◽  
Static Pressure Distribution ◽  
Nozzle Guide

The phenomenon of hot gas ingestion through turbine rim seals is experimentally and numerically investigated for a complete stage with nozzle guide vanes and uncooled helicopter turbine rotor blades. In the experimental part, two different geometrical rim seal configurations are examined: 1. a simple axial gap between rotor and stator disk and 2. an axial gap between the rotor disk and a rim seal lip at the periphery of the stator disk. The results obtained are compared to experiments carried out for the same geometry but without rotor blades. The influence of the presence of rotor blades on hot gas ingestion is examined for different parameters such as nondimensional seal flow rate, Reynolds number in the turbine annulus and rotational speed. For the determination of the sealing efficiency measurements of carbon dioxide gas concentration are carried out in the wheelspace. The static pressure distribution in the cavity is measured by means of pressure taps at the stator disk. It is shown that for configuration 1 the presence of rotor blades causes a considerable drop in sealing efficiency whereas for configuration 2 the sealing efficiency increases significantly. In the numerical part results of three-dimensional unsteady CFD calculations for configuration 2 are compared to steady calculations for the same configuration without blades. Predictions of hot gas ingestion and carbon dioxide gas concentration in the hub region and inside the cavity are presented. Special emphasis is put on unsteady effects arising from rotor movement. A local ingestion zone rotating at approximately half rotor speed is numerically predicted. As indicated by the experimental results the rotor blades have a positive influence on the predicted sealing efficiency.

Influence of an Axial and Radial Rim Seal Geometry on Hot Gas Ingestion Into the Upstream Cavity of a 1.5-Stage Turbine

2006 ◽  
Author(s):  
Dieter E. Bohn ◽  
Achim Decker ◽  
Nils Ohlendorf ◽  
Ralf Jakoby
Keyword(s):  
Carbon Dioxide ◽  
Gas Turbines ◽  
Static Pressure ◽  
Turbine Rotor ◽  
Gas Concentration ◽  
Hot Gas ◽  
Carbon Dioxide Gas ◽  
Flow Parameters ◽  
Pressure Distributions ◽  
Rotor Disk

In gas turbines hot gas ingestion into the cavities between rotor and stator disks has to be avoided almost completely in order to ensure that the guaranteed lifetime of the turbine rotor disk will be reached. The influence of an axial and radial rim seal configuration geometry on the phenomenon of hot gas ingestion into the rim seal section and inside the front cavity of a 1.5-stage axial turbine is experimentally investigated. The results obtained for the reference axial configuration are compared to those for the radial configuration in the upstream cavity of the turbine. The hot gas ingestion phenomenon is examined for different flow parameters such as non-dimensional seal flow rate, Reynolds number in the main annulus and rotational speed. The sealing efficiency is determined by measurements of the carbon dioxide gas concentration in the cavity. Static pressure distributions are measured using pressure taps at the stator disk and rim seal lip. It will be shown for the axial rim seal geometry that the guide vanes mainly influence the flow field in the rim seal gap and inside the cavity whereas for the radial rim seal geometry such an influence is limited almost exclusively to the rim seal gap. For the radial rim seal a higher sealing efficiency was detected, mainly due to the different type of the rim seal.

scholarly journals Influence of Rim Seal Geometry on Hot Gas Ingestion Into the Upstream Cavity of an Axial Turbine Stage

1999 ◽  
Author(s):  
Dieter Bohn ◽  
Bernd Rudzinski ◽  
Norbert Sürken ◽  
Wolfgang Gärtner
Keyword(s):  
Mach Number ◽  
Gas Turbines ◽  
Three Dimensional ◽  
Main Flow ◽  
Rotor Blades ◽  
Flow Rates ◽  
Hot Gas ◽  
Carbon Dioxide Gas ◽  
Industrial Gas Turbines ◽  
Rotor Disk

The ingestion of hot gas at the rim seal of a turbine has been investigated for a complete stage with nozzle guide vanes and rotor blades for two types of geometry: 1. the simple axial gap between a flat rotor disk and a flat stator disk, commonly used for industrial gas turbines and 2. an axial lip of the rim seal on the stator combined with a flat rotor disk, often found in aero engine applications. The clearance of the axial gap has been varied for the second type. The efficiency of the rim seal has been examined for different seal flow rates, rotational Reynolds numbers and Mach numbers in the main flow. For the determination of the sealing effectiveness carbon dioxide gas concentration measurements have been carried out in the wheelspace. The distribution of the static pressure in the vicinity of the seal and inside the wheelspace has been measured by means of pressure taps at the stator disk. It is shown that the external flow Mach number in the main flow has a significant effect on the sealing efficiency. As Mach number increases sealing efficiency goes down. The rotational Reynolds number has a distinct effect on the rim seal efficiency depending on the examined configuration. Even for high seal flow rates the ingestion of hot gas can not be fully avoided. The experimental results were the motivation for a three-dimensional CFD approach neglecting the influence of the rotor blades. The results give further insight into aerodynamic features of the ingestion phenomenon.

Influence of Leading Edge Fillet and Nonaxisymmetric Contoured Endwall on Turbine NGV Exit Flow Structure and Interactions With the Rim Seal Flow

2013 ◽  
Author(s):  
Özhan H. Turgut ◽  
Cengiz Camcı
Keyword(s):  
Flow Structure ◽  
Total Pressure ◽  
Guide Vane ◽  
Axial Flow ◽  
Leading Edge ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Constant Thickness ◽  
Computational Evaluation ◽  
Nozzle Guide

Three different ways are employed in the present paper to reduce the secondary flow related total pressure loss. These are nonaxisymmetric endwall contouring, leading edge (LE) fillet, and the combination of these two approaches. Experimental investigation and computational simulations are applied for the performance assessments. The experiments are carried out in the Axial Flow Turbine Research Facility (AFTRF) having a diameter of 91.66cm. The NGV exit flow structure was examined under the influence of a 29 bladed high pressure turbine rotor assembly operating at 1300 rpm. For the experimental measurement comparison, a reference Flat Insert endwall is installed in the nozzle guide vane (NGV) passage. It has a constant thickness with a cylindrical surface and is manufactured by a stereolithography (SLA) method. Four different LE fillets are designed, and they are attached to both cylindrical Flat Insert and the contoured endwall. Total pressure measurements are taken at rotor inlet plane with Kiel probe. The probe traversing is completed with one vane pitch and from 8% to 38% span. For one of the designs, area averaged loss is reduced by 15.06%. The simulation estimated this reduction as 7.11%. Computational evaluation is performed with the rotating domain and the rim seal flow between the NGV and the rotor blades. The most effective design reduced the mass averaged loss by 1.28% over the whole passage at the NGV exit.

Ingestion Into the Upstream Wheelspace of an Axial Turbine Stage

1994 ◽  
Vol 116 (2) ◽  
pp. 327-332 ◽  
Author(s):  
T. Green ◽  
A. B. Turner
Keyword(s):  
Pressure Distribution ◽  
Static Pressure ◽  
Three Dimensional ◽  
Computer Code ◽  
Rotor Blades ◽  
Rotor Speed ◽  
Turbine Stage ◽  
Flow Rates ◽  
Static Pressure Distribution ◽  
Axial Clearance

The upstream wheelspace of an axial air turbine stage complete with nozzle guide vanes (NGVs) and rotor blades (430 mm mean diameter) has been tested with the objective of examining the combined effect of NGVs and rotor blades on the level of mainstream ingestion for different seal flow rates. A simple axial clearance seal was used with the rotor spun up to 6650 rpm by drawing air through it from atmospheric pressure with a large centrifugal compressor. The effect of rotational speed was examined for several constant mainstream flow rates by controlling the rotor speed with an air brake. The circumferential variation in hub static pressure was measured at the trailing edge of the NGVs upstream of the seal gap and was found to affect ingestion significantly. The hub static pressure distribution on the rotor blade leading edges was rotor speed dependent and could not be measured in the experiments. The Denton three-dimensional C.F.D. computer code was used to predict the smoothed time-dependent pressure field for the rotor together with the pressure distribution downstream of the NGVs. The level and distribution of mainstream ingestion, and thus the seal effectiveness, was determined from nitrous oxide gas concentration measurements and related to static pressure measurements made throughout the wheelspace. With the axial clearance rim seal close to the rotor the presence of the blades had a complex effect. Rotor blades in connection with NGVs were found to reduce mainstream ingestion seal flow rates significantly, but a small level of ingestion existed even for very high levels of seal flow rate.

Experimental Measurements of Ingestion Through Turbine Rim Seals: Part 1—Externally-Induced Ingress

2011 ◽  
Author(s):  
Carl M. Sangan ◽  
Kunyuan Zhou ◽  
J. Michael Owen ◽  
Oliver J. Pountney ◽  
Mike Wilson ◽  
...  
Keyword(s):  
Three Dimensional ◽  
External Pressure ◽  
Operating Conditions ◽  
Turbine Stage ◽  
Research Facility ◽  
Three Dimensional Flow ◽  
Co2 Gas ◽  
Gas Concentration ◽  
Hot Gas ◽  
New Research

This paper describes a new research facility which experimentally models hot gas ingestion into the wheel-space of an axial turbine stage. Measurements of CO2 gas concentration in the rim-seal region and inside the cavity are used to assess the performance of two generic (though engine-representative) rim-seal geometries in terms of the variation of concentration effectiveness with sealing flow rate. The variation of pressure in the turbine annulus, which governs this externally-induced (EI) ingestion, was obtained from steady pressure measurements downstream of the vanes and near the rim seal upstream of the rotating blades. Although the ingestion through the rim seal is a consequence of an unsteady, three-dimensional flow field and the cause-effect relationship between pressure and the sealing effectiveness is complex, the experimental data is shown to be successfully calculated by simple effectiveness equations developed from a previously published orifice model. The data illustrate that, for similar turbine-stage velocity triangles, the effectiveness can be correlated using a non-dimensional sealing parameter, Φo. In principle, and within the limits of dimensional similitude, these correlations should apply to a geometrically-similar engine at the same operating conditions. Part 2 of this paper describes an experimental investigation of rotationally-induced (RI) ingress, where there is no mainsteam flow and consequently no circumferential variation of external pressure.

The Importance of Circumferential Non-uniformities in a Passage-Averaged Quasi-Three-Dimensional Turbomachinery Design System

1986 ◽  
Vol 108 (2) ◽  
pp. 240-245 ◽  
Author(s):  
I. K. Jennions ◽  
P. Stow
Keyword(s):  
Pressure Gradient ◽  
Guide Vane ◽  
Three Dimensional ◽  
Radial Pressure ◽  
Turbine Rotor ◽  
Design System ◽  
Radial Pressure Gradient ◽  
Flow Effects ◽  
Nozzle Guide ◽  
Turbomachinery Design

The purpose of this paper is to show, for both rotating and non-rotating blade rows, the importance of including circumferential non-uniform flow effects in a quasi-three-dimensional blade design system. The paper follows from previous publications on the system in which the mathematical analysis and computerized system are detailed. Results are presented for a different stack of the nozzle guide vane presented previously and for a turbine rotor. In the former case it is again found that the blade force represents a major contribution to the radial pressure gradient, while for the rotor the radial pressure gradient is dominated by centrifugal effects. In both examples the effects of circumferential non-uniformities are detailed and discussed.

Measurements and Predictions of Heat Transfer on Rotor Blades in a Transonic Turbine Cascade

2004 ◽  
Vol 126 (1) ◽  
pp. 110-121 ◽  
Author(s):  
Paul W. Giel ◽  
Robert J. Boyle ◽  
Ronald S. Bunker
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Thin Foil ◽  
Reynolds Numbers ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Maximum Point ◽  
Stagnation Region ◽  
Design Point ◽  
Laminar To Turbulent Transition

Detailed heat transfer measurements and predictions are given for a power generation turbine rotor with 127 deg of nominal turning and an axial chord of 130 mm. Data were obtained for a set of four exit Reynolds numbers comprised of the facility maximum point of 2.50×106, as well as conditions which represent 50%, 25%, and 15% of this maximum condition. Three ideal exit pressure ratios were examined including the design point of 1.443, as well as conditions which represent −25% and +20% of the design value. Three inlet flow angles were examined including the design point and ±5deg off-design angles. Measurements were made in a linear cascade with highly three-dimensional blade passage flows that resulted from the high flow turning and thick inlet boundary layers. Inlet turbulence was generated with a blown square bar grid. The purpose of the work is the extension of three-dimensional predictive modeling capability for airfoil external heat transfer to engine specific conditions including blade shape, Reynolds numbers, and Mach numbers. Data were obtained by a steady-state technique using a thin-foil heater wrapped around a low thermal conductivity blade. Surface temperatures were measured using calibrated liquid crystals. The results show the effects of strong secondary vortical flows, laminar-to-turbulent transition, and also show good detail in the stagnation region.

scholarly journals A Numerical Method for the Analysis of 3D Viscous Compressible Flow in Turbine Cascades: Application to Secondary Flow Development in a Cascade With and Without Dihedral

1986 ◽  
Author(s):  
W. N. Dawes
Keyword(s):  
Secondary Flow ◽  
Compressible Flow ◽  
Three Dimensional ◽  
Leading Edge ◽  
Computer Code ◽  
Horseshoe Vortex ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Flow Development ◽  
Viscous Compressible Flow

The present paper describes a computer code, currently under development, aimed at solving the equations of three-dimensional viscous compressible flow in turbomachinery goemetries. The code uses a simple, novel pre-processed implicit algorithm. An outline of the method is given and the current capabilities of the code are assessed. The code is applied to the study of the flowfield in a cascade of transonic gas turbine rotor blades. The geometry and the presence of inlet end-wall boundary layers lead to significant three-dimensional effects. The pattern of secondary flow development, including the details of the leading edge horseshoe vortex and associated saddle point, are clearly resolved and correspond to experimental experience. A computation is also presented to show the influence of dihedral (non-linear stacking) on the secondary flow development.

Influence of Hot Streak/Airfoil Count Ratios on High Pressure Stage of a Vaneless Counter-Rotating Turbine

2008 ◽  
Author(s):  
Qingjun Zhao ◽  
Huishe Wang ◽  
Fei Tang ◽  
Xiaolu Zhao ◽  
Jianzhong Xu
Keyword(s):  
High Pressure ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Peak Temperature ◽  
Combined Effects ◽  
High Pressure Turbine ◽  
Flow Angle ◽  
Count Ratio ◽  
Hot Streak

In order to reveal the effects of the hot streak/airfoil count ratio on the heating patterns of high pressure turbine rotor blades in a Vaneless Counter-Rotating Turbine, three-dimensional unsteady Navier-Stokes simulations have been performed. In these simulations, the ratio of the number of hot streaks to the number of the high pressure turbine vanes and rotors is 1:3:3, 1:2:2, 2:3:3 and 1:1:1, respectively. The numerical results show that the migration characteristics of the hot streak in the high pressure turbine rotor are predominated by the combined effects of secondary flow and buoyancy. The combined effects induce the high temperature fluid migrate towards the hub in the high pressure turbine rotor. And the combined effects become more intensified when the hot streak/airfoil count ratio increases. The results also indicate that the peak temperature of the hot streak is dissipated as the hot streak goes through the high pressure turbine vane or the rotor. The dissipated extent of the peak temperature in the high pressure turbine stator and the rotor is increased as the hot streak-to-airfoil ratio increases. And the increase of the hot streak/airfoil count ratio trends to increase the relative Mach number at the high pressure turbine outlet. The relative flow angle from 23% to 73% span at the high pressure turbine outlet decreases as the hot streak-to-airfoil ratio increases. The results also indicate that the isentropic efficiency of the Vaneless Counter-Rotating Turbine is decreased as the hot streak/airfoil count ratio increases.

An Experimental and Computational Study of Transonic Three-Dimensional Flow in a Turbine Cascade

1984 ◽  
Vol 106 (2) ◽  
pp. 414-420 ◽  
Author(s):  
J.-J. Camus ◽  
J. D. Denton ◽  
J. V. Soulis ◽  
C. T. J. Scrivener
Keyword(s):  
Computational Study ◽  
Three Dimensional ◽  
Inviscid Flow ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Turbine Rotor Blade ◽  
Dimensional Effects ◽  
Blade Section ◽  
Exit Mach Number ◽  
End Wall

Detailed experimental measurements of the flow in a cascade of turbine rotor blades with a nonplanar end wall are reported. The cascade geometry was chosen to model as closely as possible that of a H.P. gas turbine rotor blade. The blade section is designed for supersonic flow with an exit Mach number of 1.15 and the experiments covered a range of exit Mach numbers from 0.7–1.2. Significant three-dimensional effects were observed and the origin of these is discussed. The measurements are compared with data for the same blade section in a two-dimensional cascade and also with the predictions of two different fully three-dimensional inviscid flow calculation methods. It is found that both these calculations predict the major three-dimensional effects on the flow correctly.

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