Correction: Minimization of Pressure Fluctuations in an Axial Turbine Stage Under Periodic Inflow Conditions

A clear understanding of the flow characteristics in the older generation of industrial gas turbines operating with silo combustors is important for potential upgrades. Non-uniformities in the form of circumferential and radial variations in internal flow properties can have a significant impact on the gas turbine stage performance and durability. This paper presents a comprehensive study of the underlying internal flow features involved in the advent of non-uniformities from twin-silo combustors and their propagation through a single axial turbine stage of the Siemens v94.2 industrial gas turbine. Results indicate the formation of strong vortical structures alongside large temperature, pressure, velocity, and flow angle deviations that are mostly located in the top and bottom sections of the turbine stage caused by the excessive flow turning in the upstream tandem silo combustors. A favorable validation of the simulated exhaust gas temperature (EGT) profile is also achieved via comparison with the measured data. A drop in isentropic efficiency and power output equivalent to 2.28% points and 2.1 MW, respectively is observed at baseload compared to an ideal straight hot gas path reference case. Furthermore, the analysis of internal flow topography identifies the underperforming turbine blading due to the upstream non-uniformities. The findings not only have implications for the turbine aerothermodynamic design, but also the combustor layout from a repowering perspective.

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Development of a generalized physical and mathematical model of working substance processes in an axial turbine stage

Journal of Physics Conference Series ◽

10.1088/1742-6596/1843/1/012017 ◽

2021 ◽

Vol 1843 (1) ◽

pp. 012017

Author(s):

V A Kalytka ◽

M V Korovkin ◽

P Sh Madi ◽

A D Mekhtiyev ◽

A V Bashirov ◽

...

Keyword(s):

Mathematical Model ◽

Turbine Stage ◽

Axial Turbine

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Some Aspects of Wake-Wake Interactions Regarding Turbine Stator Clocking

Journal of Turbomachinery ◽

10.1115/1.1370158 ◽

2000 ◽

Vol 123 (3) ◽

pp. 526-533 ◽

Cited By ~ 20

Author(s):

Maik Tiedemann ◽

Friedrich Kost

Keyword(s):

Total Pressure ◽

Guide Vane ◽

Pressure Fluctuations ◽

Fast Response ◽

Turbine Stage ◽

Flow Angle ◽

Wake Interactions ◽

Turbulence Data ◽

Number Flow ◽

Nozzle Guide

This investigation is aimed at an experimental determination of the unsteady flowfield downstream of a transonic high pressure turbine stage. The single stage measurements, which were part of a joined European project, were conducted in the windtunnel for rotating cascades of the DLR Go¨ttingen. Laser-2-focus (L2F) measurements were carried out in order to determine the Mach number, flow angle, and turbulence distributions. Furthermore, a fast response pitot probe was utilized to determine the total pressure distribution. The measurement position for both systems was 0.5 axial rotor chord downstream of the rotor trailing edge at midspan. While the measurement position remained fixed, the nozzle guide vane (NGV) was “clocked” to 12 positions covering one NGV pitch. The periodic fluctuations of the total pressure downstream of the turbine stage indicate that the NGV wake damps the total pressure fluctuations caused by the rotor wakes. Furthermore, the random fluctuations are significantly lower in the NGV wake affected region. Similar conclusions were drawn from the L2F turbulence data. Since the location of the interaction between NGV wake and rotor wake is determined by the NGV position, the described effects are potential causes for the benefits of “stator clocking” which have been observed by many researchers.

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Design of a Transonic High-Pressure Turbine Stage 2D Section With Reduced Rotor/Stator Interaction

Volume 5: Turbo Expo 2004, Parts A and B ◽

10.1115/gt2004-53520 ◽

2004 ◽

Cited By ~ 1

Author(s):

Michele Vascellari ◽

Re´my De´nos ◽

Rene´ Van den Braembussche

Keyword(s):

Rotor Blade ◽

Static Pressure ◽

Aerodynamic Force ◽

Pressure Fluctuations ◽

Uniform Field ◽

Turbine Stage ◽

Rotor Stator Interaction ◽

Transonic Turbine ◽

Blade Failure ◽

Rotor Profiles

In transonic turbine stages, the exit static pressure field of the vane is highly non-uniform in the pitchwise direction. The rotor traverses periodically this non-uniform field and large static pressure fluctuations are observed around the rotor section. As a consequence the rotor blade is submitted to significant variations of its aerodynamic force. This contributes to the high cycle fatigue and may result in unexpected blade failure. In this paper an existing transonic turbine stage section is redesigned in the view of reducing the rotor stator interaction, and in particular the unsteady rotor blade forcing. The first step is the redesign of the stator blade profile to reduce the stator exit pitchwise static pressure gradient. For this purpose, a procedure using a genetic algorithm and an artificial neural network is used. Next, two new rotor profiles are designed and analysed with a quasi 3D Euler unsteady solver in order to investigate their receptivity to the shock interaction. One of the new profiles allows reducing the blade force variation by 50%.

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Influence of Detailing on Aerodynamic Forcing of a Transonic Axial Turbine Stage and Forced-Response Prediction for Low-Engine-Order (LEO) Excitation

Volume 7B: Structures and Dynamics ◽

10.1115/gt2017-64502 ◽

2017 ◽

Cited By ~ 1

Author(s):

Tobias R. Müller ◽

Damian M. Vogt ◽

Klemens Vogel ◽

Bent A. Phillipsen ◽

Peter Hönisch

Keyword(s):

Numerical Study ◽

Response Prediction ◽

Forced Response ◽

Resonance Excitation ◽

Response Analysis ◽

Turbine Stage ◽

Flow Induced Vibration ◽

Axial Turbine ◽

Timing Data ◽

Generalized Force

The effects of detailing on the prediction of forced-response in a transonic axial turbine stage, featuring a parted stator design, asymmetric inlet and outlet casings as well as rotor cavities, is investigated. Ensuring the mechanical integrity of components is of paramount importance for the safe and reliable operation of turbomachines. Among others, flow induced resonance excitation can lead to high-cycle fatigue (HCF) and potentially to damage of components unless properly damped. This numerical study is assessing the necessary degree of detailing in terms of spatial and temporal discretization, boundary conditions of the pre-stressed rotor geometry as well as geometrical detailing for the reliable prediction of the aerodynamic excitation of the structure. In this context, the sensitivity of the aerodynamic forcing is analyzed by means of the generalized force criterion, showing a significant influence for some of the investigated variations of the numerical model. Moreover, the origin and further progression of several low-engine-orders (LEO) within the flow field, as well as their interaction with different geometric details has been analyzed based on the numerical results obtained from a full 360° CFD-calculation of the investigated turbine stage. The predicted flow induced vibration of the structure has been validated by means of a full forced-response analysis, where a good agreement with tip-timing data has been found.

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Multi-Disciplinary Design Optimization of a Axial Turbine Stage of Aircraft Auxiliary Power Unit

12th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference ◽

10.2514/6.2008-6055 ◽

2008 ◽

Author(s):

G.B Ashakiran ◽

Aishwarjya Gogoi ◽

Q Nagpurwala

Keyword(s):

Design Optimization ◽

Power Unit ◽

Turbine Stage ◽

Axial Turbine ◽

Auxiliary Power Unit ◽

Auxiliary Power

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Axial Turbine Design for a Twin-Turbine Heavy-Duty Turbocharger Concept

Volume 2B: Turbomachinery ◽

10.1115/gt2018-75453 ◽

2018 ◽

Cited By ~ 1

Author(s):

Nicholas Anton ◽

Magnus Genrup ◽

Carl Fredriksson ◽

Per-Inge Larsson ◽

Anders Christiansen-Erlandsson

Keyword(s):

Engine Performance ◽

Operating Conditions ◽

Single Stage ◽

Flow Coefficient ◽

Speed Ratio ◽

Heavy Duty ◽

Turbine Stage ◽

Axial Turbine ◽

Radial Turbine ◽

Turbine Design

In the process of evaluating a parallel twin-turbine pulse-turbocharged concept, the results considering the turbine operation clearly pointed towards an axial type of turbine. The radial turbine design first analyzed was seen to suffer from sub-optimum values of flow coefficient, stage loading and blade-speed-ratio. Modifying the radial turbine by both assessing the influence of “trim” and inlet tip diameter all concluded that this type of turbine is limited for the concept. Mainly, the turbine stage was experiencing high values of flow coefficient, requiring a more high flowing type of turbine. Therefore, an axial turbine stage could be feasible as this type of turbine can handle significantly higher flow rates very efficiently. Also, the design spectrum is broader as the shape of the turbine blades is not restricted by a radially fibred geometry as in the radial turbine case. In this paper, a single stage axial turbine design is presented. As most turbocharger concepts for automotive and heavy-duty applications are dominated by radial turbines, the axial turbine is an interesting option to be evaluated for pulse-charged concepts. Values of crank-angle-resolved turbine and flow parameters from engine simulations are used as input to the design and subsequent analysis. The data provides a valuable insight into the fluctuating turbine operating conditions and is a necessity for matching a pulse-turbocharged system. Starting on a 1D-basis, the design process is followed through, resulting in a fully defined 3D-geometry. The 3D-design is evaluated both with respect to FEA and CFD as to confirm high performance and durability. Turbine maps were used as input to the engine simulation in order to assess this design with respect to “on-engine” conditions and to engine performance. The axial design shows clear advantages with regards to turbine parameters, efficiency and tip speed levels compared to a reference radial design. Improvement in turbine efficiency enhanced the engine performance significantly. The study concludes that the proposed single stage axial turbine stage design is viable for a pulse-turbocharged six-cylinder heavy-duty engine. Taking into account both turbine performance and durability aspects, validation in engine simulations, a highly efficient engine with a practical and realizable turbocharger concept resulted.

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Numerical Studies on the Effect of Tip Clearance and Tip Cooling Flow on Endwall Losses of an Unshrouded Axial Turbine Rotor

ASME 2013 Gas Turbine India Conference ◽

10.1115/gtindia2013-3568 ◽

2013 ◽

Author(s):

K. Asgar Ali ◽

Quamber H. Nagpurwala ◽

Abdul Nassar ◽

S. V. Ramanamurthy

Keyword(s):

Flow Rate ◽

Layer Growth ◽

Coolant Flow ◽

Tip Clearance ◽

Coolant Flow Rate ◽

Total Efficiency ◽

Turbine Stage ◽

Suction Surface ◽

Axial Turbine ◽

Ejection Rate

This paper deals with the numerical investigations on a low pressure axial turbine stage to assess the effect of variation in rotor tip clearance and tip coolant ejection rate on the end wall losses. The rotor, along with the NGV, was modeled to represent the entire turbine stage. The CFX TASCflow software was used to perform steady state analysis for different rotor tip clearances and different tip coolant ejection rates. The locations of the cooling slots were identified on the blade tip and the coolant ejection rate was specified at these areas. The simulations were carried out with tip clearances of 0%, 1% and 2% of blade height and ejection flow rates of 0.5%, 0.75% and 1% of main turbine flow rate. It is shown that the size and strength of the leakage vortex is directly related to the tip clearance. The reduction in efficiency is not in linearity with the tip clearance owing to the effect of boundary layer growth on the end walls. Introduction of the tip coolant flow shows increased total–total efficiency compared to that of the uncooled tip. This is attributed to a reduction in the strength of the leakage vortex due to reduced cross-flow over the tip clearance from pressure surface to suction surface. At a coolant flow rate of 0.75% of the main flow rate, there is significant increase in efficiency of about 0.5%. Optimum tip clearance and coolant flow rate are obtained based on the results of the present analysis.

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