Experimental Investigation of the Upstream Effect of Different Low Pressure Turbine Exit Guide Vane Designs on Rotor Blade Vibration

2016 ◽  
Author(s):  
F. Schönleitner ◽  
T. Selic ◽  
C. Schitter ◽  
F. Heitmeir ◽  
A. Marn
Keyword(s):  
Rotor Blade ◽  
Guide Vane ◽  
Low Pressure ◽  
Operating Conditions ◽  
Numerical Code ◽  
Noise Emission ◽  
Blade Vibration ◽  
Vibration Measurements ◽  
Guide Vanes ◽  
Low Pressure Turbine

Exit guide vanes of turbine exit casings are designed to meet aerodynamic, structural and acoustic criteria. New low pressure turbine architectures of aero engines try to optimize components weight in order to decrease the fuel consumption and reduce noise emissions. For this purpose different designs of turbine exit guide vanes (TEGV) exist which vary geometry as well as the number of vanes in the casing. In the subsonic test turbine facility at the Institute for Thermal Turbomachinery and Machine Dynamics of Graz University of Technology, which represents a 1 ½ low pressure turbine stage, the upstream effect of these innovative turbine exit casings (TEC) designs is under investigation. Up to now the influence of the turbine exit casing in relation to the aerodynamic vibration excitation of the rotor blading is not well known. For rotor blade vibration measurements a telemetry system in combination with strain gauges is applied. The present paper is a report of blade vibration measurements within a rotating system in the area of low pressure turbines under engine relevant operating conditions. Within the test phase different turbine exit casings are under investigation at two different operating points (OP). These turbine exit casings represent different design goals, e.g. aerodynamically optimization was performed to reduce losses at the aero design point or an acoustically optimization was done to reduce noise emission at the operating point approach. All these different design intents lead to a changed upstream effect, thus changing rotor blade vibrations. To identify parameters affecting blade vibration attention is paid to aerodynamic measurements as well. Selected results of steady and unsteady flow field measurements are analyzed to draw conclusions. The upstream effect of different turbine exit casings can be quantified at OP1. Depending on the vane number both the potential effect of the TEGV increase and the upstream effect as well. Aerodynamic as well as acoustic improvements as wanted with H-TEC and inverse-cut-off TEC lead to unfavorable conditions and higher blade loading in comparison to the referenced TEC. OP2 provides additional information of downstream effects. Due to the stator vane number the rotor blading is excited in its 4th eigenfrequency. The comparison between all investigated turbine exit casings with respect to the referenced configuration provides a basis for numerical code validation and future developments.

On the Effect of Axial Spacing Between Rotor and Stator Onto the Blade Vibrations of a Low Pressure Turbine Stage at Engine Relevant Operating Conditions

2016 ◽  
Author(s):  
Andreas Marn ◽  
Florian Schönleitner ◽  
Mathias Mayr ◽  
Thorsten Selic ◽  
Franz Heitmeir
Keyword(s):  
Rotor Blade ◽  
Low Pressure ◽  
Forced Response ◽  
Operating Conditions ◽  
Turbine Stage ◽  
Blade Vibration ◽  
Structural Dynamic ◽  
Flow Measurements ◽  
Vibration Measurements ◽  
Excitation Mechanisms

In order to achieve the ACARE targets regarding reduction of emissions, it is essential to reduce fuel consumption drastically. Reducing engine weight is supporting this target and one option to reduce weight is to reduce the overall engine length (shorter shafts, nacelle). However, to achieve a reduction in engine length, the spacing between stator and rotor can be minimised, thus changing the rotor blade excitation. Related to the axial spacing, a number of excitation mechanisms with respect to the rotor blading must already be considered during the design process. Based on these facts several setups have been investigated at different engine relevant operating points and axial spacing between the stator and rotor in the subsonic test turbine facility (STTF-AAAI) at the Institute for Thermal Turbomachinery and Machine Dynamics at Graz University of Technology. In order to avoid upstream effects of supporting struts, these struts are located far downstream of the stage which is under investigation. For rotor blade vibration measurements, a novel telemetry system in combination with strain gauges is applied. To the best of the author’s knowledge, the present paper is the first report of blade vibration measurements within a rotating system in the area of low pressure turbines under engine relevant operating conditions. In addition, aerodynamic measurements including unsteady flow measurements have been conducted, but will not be presented in this paper. By analysing the flow field, aerodynamic excitation mechanisms can be identified and assigned to the blade vibration. However, this is not presented in this paper. Within this paper, the flow fields are analysed in both upstream and downstream of the turbine stage, visualised for two axial gaps and then compared to the forced response of the blading. Detailed structural dynamic investigations show critical modes during the operation which are identified by the telemetry measurements as well. Finally the influence of the axial spacing regarding the rotor blade excitation and vibration can be elaborated and is prepared to get a better understanding of basic mechanisms. The paper shows that reducing axial spacing is a promising option for reducing engine weight, but aeroelasticity must be carefully taken into account.

Noise Attenuation Potential Using Helmholtz Absorbers Integrated in Low Pressure Turbine Exit Guide Vanes and Turbine Exit Casing End Walls

2020 ◽  
Author(s):  
Manuel Zenz ◽  
Loris Simonassi ◽  
Philipp Bruckner ◽  
Simon Pramstrahler ◽  
Franz Heitmeir ◽  
...  
Keyword(s):  
Suction Side ◽  
Aircraft Engine ◽  
Low Pressure ◽  
Flow Channel ◽  
Operating Conditions ◽  
Noise Attenuation ◽  
Beneficial Result ◽  
Guide Vanes ◽  
Acoustic Liners ◽  
Low Pressure Turbine

Abstract To further reduce the noise emitted from modern aircrafts, every possibility has to be taken into account. Acoustic liners are successfully used in the inlet or the bypass duct of aircraft engines to mitigate the noise emitted by the fan. Due to the rough environment (high temperature, flow velocity, higher order duct modes), the exhaust duct is of limited use concerning the application of acoustic liners. It is well known that the last stage low pressure turbine (LPT) has a dominant influence onto the emitted noise of an aircraft engine especially at low load conditions such as approach. A noise reduction in this area could lead to a beneficial result of decreasing the noise content which is directly emitted in the environment. This paper is about noise attenuation using Helmholtz absorbers in various parts of a turbine exit casing (TEC). These single degree of freedom absorbers have been integrated in turbine exit guide vanes (TEGVs), with the openings on the vanes suction side, as well as in the inner and outer duct end walls. Different absorber neck diameters were investigated and combined with different vane designs. The vane designs studied included a state of the art set-up as well as vanes with a lean. Test runs were performed with altered combinations of vanes and end walls under engine relevant operating conditions in a subsonic test turbine facility for aerodynamic, aeroacoustic and aeroelastic investigations (STTF-AAAI) located at the Institute of Thermal Turbomachinery and Machine Dynamics at Graz University of Technology. Comparisons between all these setups and the respective hard wall reference cases were done. The resulting sound pressure levels as well as sound power levels of all investigated combinations are listed and compared concerning each configurations noise attenuation potential. Additionally, the flow field downstream of every setup is analysed if the aerodynamic behaviour is changing. The investigated operating point is the noise certification point Approach (APP) which is of high importance because of the high acoustical impact onto the environment around airports during the landing procedure of an aircraft. The acoustical data has been obtained by using flush mounted condenser microphones located downstream of the TEC. The whole test section was rotated over 360 deg around the flow channel. To detect if the aerodynamical behaviour changes by including openings into the flow channel end walls as well as into the vanes, aerodynamic measurements have been performed downstream of the TEC. The aerodynamical data was obtained by using an aerodynamic five-hole-probe (5HP) as well as a trailing edge probe.

Modal Characterization, Strain Gauge Setup and 1-Way FSI of a Low Pressure Turbine Rotor Blading

2015 ◽  
Author(s):  
F. Schönleitner ◽  
L. Traussnig ◽  
F. Heitmeir ◽  
A. Marn
Keyword(s):  
Strain Gauge ◽  
Interaction Analysis ◽  
Low Pressure ◽  
Turbine Rotor ◽  
Operating Conditions ◽  
Detailed Knowledge ◽  
Telemetry System ◽  
Vibration Measurements ◽  
Low Pressure Turbine ◽  
Set Up

New designs of low pressure turbines show optimized geometries of stator and rotor blading as well as reduced axial spacing between stator and rotor due to the main target of saving weight which is directly related to the fuel consumption of the aero engine. An important step during the realization process is to investigate altered excitation mechanism. For this purpose aero elastic investigations will be performed at the test rig of Graz University of Technology. In general for a serious prediction of vibration characteristics under operating conditions of any structure a detailed knowledge of the dynamic behavior is essential. In preparation of upcoming strain gauge vibration measurements in combination with a telemetry system of the low pressure turbine rotor blading, modal characteristics as well as a realistic estimation of blade deformation are mandatory. Within this paper different methods of evaluating modal characteristic numerical as well as experimental such as impact hammer and shaker tests, respectively are presented. Numerical investigations show different models and mathematical contact formulation and should provide a better understanding for using correct contact models additionally. When comparing numerical with experimental results a prediction of an optimal strain gauge setup for vibration measurements as well as a simplified numerical model for further aero elastic investigations, such as fluid structure interaction analysis (FSI), complete previous investigations. In order to set up the telemetry system the knowledge of blade deformation at operating conditions is of particular importance. Therefore finally in this paper a 1-way FSI coupling is presented.

LM9000 Passive Clearance Control (PCC)

2020 ◽  
Author(s):  
Simone Marchetti ◽  
Duccio Nappini ◽  
Roberto De Prosperis ◽  
Paolo Di Sisto
Keyword(s):  
Control System ◽  
Low Pressure ◽  
Industrial Applications ◽  
Flow Path ◽  
Operating Conditions ◽  
Low Pressure Turbine ◽  
Power Turbine ◽  
Extensive Test ◽  
First Time ◽  
Clearance Control

Abstract This paper describes the design of the Free Power Turbine (FPT) of the LM9000, in particularly the design of its Passive Clearance Control (PCC) system. The LM9000 is the aero-derivative version of the GE90-115B jet engine. Its core engine has many common parts with the GE90; what differs is the booster (low pressure compressor) and the lower pressure turbine (LPT). The booster of the LM9000 is without fan because the engine is not used to provide thrust but torque only, subsequently it has a new flow path [5]. The LPT has instead been replaced by an intermediate pressure turbine (IPT) and by the FPT. The IPT drives the booster, while the FPT is a free low-pressure turbine designed for both power generation and mechanical drive industrial applications, including LNG production plants. Due to its different application, the LM9000 FPT flow path differs sensibly from the GE90 LPT, however as the GE90 it is provided of a clearance control system that cools the casing in order to reduce its radial deflection. It is not the first time that a clearance control system has been used in industrial applications; in GE aero-derivative power turbines is already present in the LM6000 and LMS100. Design constraints, system complexity, high environment variability because the PCC is located outside the GT, harsh environments and long periods of usage still make the design of this component challenging. The design of the PCC has been supported by extensive heat transfer and mechanical simulations. Each PCC component has been addressed with a dedicated life calculation and all the blade and seal clearances have been estimated for all the operating conditions of the engine. Simulations have been validated by an extensive test campaign performed on the first engine.

Aerodynamic Effects of an Unshrouded Low Pressure Turbine on a Low Aspect Ratio Exit Guide Vane

2012 ◽  
Author(s):  
Thorsten Selic ◽  
Davide Lengani ◽  
Andreas Marn ◽  
Franz Heitmeir
Keyword(s):  
Aspect Ratio ◽  
Guide Vane ◽  
Low Pressure ◽  
Tip Clearance ◽  
Pressure Probe ◽  
Model Parameters ◽  
Leakage Flow ◽  
Low Pressure Turbine ◽  
Low Aspect Ratio ◽  
The Impact

This paper presents the effects of an unshrouded low pressure turbine (LPT) onto the following exit guide vane row (EGV). The measurement results were obtained in the subsonic test turbine facility at Graz University of Technology by means of a fast response pressure probe in planes downstream of the rotor as well as oil flow visualisation. The test rig was designed in cooperation with MTU Aero Engines and represents the last 1.5 stages of a commercial aero engine. Considerable efforts were put into the adjustment of all relevant model parameters to reproduce the full scale LPT situation. Different tip clearances were evaluated by means of CFD obtained using a commercial Navier-Stokes code and validated with experimental results. The goal is to evaluate the effect of the varying leakage flow on the flow in the low aspect ratio EGV. Special attention is given to the impact on the development of secondary flows as well as the flow structures downstream of the EGV. The effect of the leakage flow causes a change of the flow structure of the EGV, particularly losses. Considering the largest investigated tip-clearance, the losses increased by 71% when compared to a zero-leakage case.

Investigation of the Impact of Unsteady Turbulence Effects on the Aeroelastic Analysis of a Low-Pressure Turbine Rotor Blade

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Jan Philipp Heners ◽  
Damian M. Vogt ◽  
Christian Frey ◽  
Graham Ashcroft
Keyword(s):  
Rotor Blade ◽  
Numerical Study ◽  
Turbulence Models ◽  
Gibbs Phenomenon ◽  
Low Pressure ◽  
Turbine Rotor ◽  
Filter Method ◽  
Turbine Rotor Blade ◽  
Low Pressure Turbine ◽  
The Impact

Abstract The impact of the unsteadiness in the considered turbulence quantities on the numerical prediction of the aeroelastic behavior of a low-pressure turbine (LPT) rotor blade is evaluated by means of a numerical study. In this context, one of the main objectives of this work is to compare different nonlinear harmonic balance (HB) approaches—one neglecting and one considering the unsteadiness in the employed turbulence models—with a conventional nonlinear solver of the unsteady Reynolds-averaged Navier–Stokes (URANS) equations in the time domain. In order to avoid unphysical oscillations in the turbulence quantities caused by the Gibbs phenomenon in the chosen HB approach, a filter method based on the Lanczos filter is developed. The developed filter method is applied in the course of the HB simulations considering the unsteadiness in the underlying turbulence model. Furthermore, the impact of its application on the solution of the flow field and on the unsteady surface pressure of the rotor blade, in particular, is discussed in the context of this work.

A Comparison of Turbulence Levels From Particle Image Velocimetry and Constant Temperature Anemometry Downstream of a Low-Pressure Turbine Cascade at High-Speed Flow Conditions

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Silvio Chemnitz ◽  
Reinhard Niehuis
Keyword(s):  
Particle Image Velocimetry ◽  
Constant Temperature ◽  
High Speed ◽  
Particle Image ◽  
Low Pressure ◽  
Operating Conditions ◽  
Stereoscopic Particle Image Velocimetry ◽  
Turbine Cascade ◽  
Low Pressure Turbine ◽  
Image Velocimetry

Abstract The development and verification of new turbulence models for Reynolds-averaged Navier–Stokes (RANS) equation-based numerical methods require reliable experimental data with a deep understanding of the underlying turbulence mechanisms. High accurate turbulence measurements are normally limited to simplified test cases under optimal experimental conditions. This work presents comprehensive three-dimensional data of turbulent flow quantities, comparing advanced constant temperature anemometry (CTA) and stereoscopic particle image velocimetry (PIV) methods under realistic test conditions. The experiments are conducted downstream of a linear, low-pressure turbine cascade at engine relevant high-speed operating conditions. The special combination of high subsonic Mach and low Reynolds number results in a low density test environment, challenging for all applied measurement techniques. Detailed discussions about influences affecting the measured result for each specific measuring technique are given. The presented time mean fields as well as total turbulence data demonstrate with an average deviation of ΔTu<0.4% and ΔC/Cref<0.9% an extraordinary good agreement between the results from the triple sensor hot-wire probe and the 2D3C-PIV setup. Most differences between PIV and CTA can be explained by the finite probe size and individual geometry.

The Off-Design Performance of a Low-Pressure Turbine Cascade

1987 ◽  
Vol 109 (2) ◽  
pp. 201-209 ◽  
Author(s):  
H. P. Hodson ◽  
R. G. Dominy
Keyword(s):  
Reynolds Numbers ◽  
Low Pressure ◽  
Turbine Rotor ◽  
Surface Flow ◽  
Operating Conditions ◽  
Turbine Cascade ◽  
Linear Cascade ◽  
Design Performance ◽  
Low Pressure Turbine ◽  
Wide Range

The ability of a given blade profile to operate over a wide range of conditions is often of the utmost importance. This paper reports the off-design performance of a low-pressure turbine rotor root section in a linear cascade. Data were obtained using pneumatic probes and surface flow visualization. The effects of incidence (+9, 0, −20 deg), Reynolds (1.5, 2.9, 6.0 × 105), pitch-chord ratio (0.46, 0.56, 0.69), and inlet boundary layer thickness (0.011, 0.022 δ*/C) are discussed. Particular attention is paid to the three dimensionality of the flow field. Significant differences in the detail of the flow occur over the range of operating conditions investigated. It is found that the production of new secondary loss is greatest at lower Reynolds numbers, positive incidence, and the higher pitch-chord ratios.

Computational Fluid Dynamics Analysis of a Steam Power Plant Low-Pressure Turbine Downward Exhaust Hood

1996 ◽  
Vol 118 (1) ◽  
pp. 214-224 ◽  
Author(s):  
R. H. Tindell ◽  
T. M. Alston ◽  
C. A. Sarro ◽  
G. C. Stegmann ◽  
L. Gray ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Integrated Approach ◽  
Low Pressure ◽  
Operating Conditions ◽  
Exhaust Hood ◽  
Steam Power ◽  
Low Pressure Turbine ◽  
Computational Fluid Dynamics Analysis ◽  
Turbine Exhaust

Computational fluid dynamics (CFD) methods are applied to the analysis of a low-pressure turbine exhaust hood at a typical steam power generating station. A Navier-Stokes solver, capable of modeling all the viscous terms, in a Reynolds-averaged formulation, was used. The work had two major goals. The first was to develop a comprehensive understanding of the complex three-dimensional flow fields that exist in the exhaust hood at representative operating conditions. The second was to evaluate the relative benefits of a flow guide modification to optimize performance at a selected operating condition. Also, the influence of simulated turbine discharge characteristics, relative to uniform hood entrance conditions, was evaluated. The calculations show several interesting and possibly unique results. They support use of an integrated approach to the design of turbine exhaust stage blading and hood geometry for optimum efficiency.

Sign in / Sign up

Export Citation Format

Share Document