Interaction of Wheelspace Coolant and Main Flow in a New Aeroderivative LPT

Increased computational capabilities make available for the aero/thermal designers new powerful tools to include more geometrical details, improving the accuracy of the simulations, and reducing design costs and time. In the present work, a low-pressure turbine was analyzed, modeling the rotor-stator including the wheel space region. Attention was focused on the interaction between the coolant and the main flow in order to obtain a more detailed understanding of the behavior of the angel wings, to evaluate the wall heat flux distribution, and to prevent hot gas ingestion. Issues of component reliability related to thermal stress require accurate modeling of the turbulence and unsteadiness of the flow field. To satisfy this accuracy requirement, a full 3D URANS simulation was carried out. A reduced count ratio technique was applied in order to decrease numerical simulation costs. The study was carried out to investigate a new two-stage Low Pressure Turbine from GE Infrastructure Oil&Gas to be coupled to a new aeroderivative gas generator, the LM2500+G4, developed by GE Infrastructure, Aviation.

Download Full-text

Interaction of Wheelspace Coolant and Main Flow in a New Aeroderivative Low Pressure Turbine

Journal of Turbomachinery ◽

10.1115/1.3195036 ◽

2010 ◽

Vol 132 (3) ◽

Cited By ~ 4

Author(s):

F. Montomoli ◽

M. Massini ◽

N. Maceli ◽

M. Cirri ◽

L. Lombardi ◽

...

Keyword(s):

Flux Distribution ◽

Low Pressure ◽

Main Flow ◽

Space Region ◽

Heat Flux Distribution ◽

Gas Generator ◽

Component Reliability ◽

Accuracy Requirement ◽

Low Pressure Turbine ◽

Hot Gas

Increased computational capabilities make available for the aero/thermal designers new powerful tools to include more geometrical details, improving the accuracy of the simulations and reducing design costs and time. In the present work, a low-pressure turbine was analyzed, modeling the rotor-stator including the wheel space region. Attention was focused on the interaction between the coolant and the main flow in order to obtain a more detailed understanding of the behavior of the angel wings, to evaluate the wall heat flux distribution, and to prevent hot gas ingestion. Issues of component reliability related to thermal stress require accurate modeling of the turbulence and unsteadiness of the flow field. To satisfy this accuracy requirement, a full 3D URANS simulation was carried out. A reduced count ratio technique was applied in order to decrease numerical simulation costs. The study was carried out to investigate a new two-stage low-pressure turbine from GE Infrastructure Oil & Gas to be coupled to a new aeroderivative gas generator (the LM2500+G4) developed by GE Infrastructure, Aviation.

Download Full-text

Transition Mechanisms in Laminar Separated Flow Under Simulated Low Pressure Turbine Aerofoil Conditions

Journal of Turbomachinery ◽

10.1115/1.4006393 ◽

2012 ◽

Vol 135 (1) ◽

Cited By ~ 12

Author(s):

Jerrit Dähnert ◽

Christoph Lyko ◽

Dieter Peitsch

Keyword(s):

Reynolds Number ◽

Separation Bubble ◽

Separated Flow ◽

Low Pressure ◽

Main Flow ◽

Test Facility ◽

Flow Conditions ◽

Laminar Separation ◽

Free Stream Turbulence ◽

Low Pressure Turbine

Based on detailed experimental work conducted at a low speed test facility, this paper describes the transition process in the presence of a separation bubble with low Reynolds number, low free-stream turbulence, and steady main flow conditions. A pressure distribution has been created on a long flat plate by means of a contoured wall opposite of the plate, matching the suction side of a modern low-pressure turbine aerofoil. The main flow conditions for four Reynolds numbers, based on suction surface length and nominal exit velocity, were varied from 80,000 to 300,000, which covers the typical range of flight conditions. Velocity profiles and the overall flow field were acquired in the boundary layer at several streamwise locations using hot-wire anemometry. The data given is in the form of contours for velocity, turbulence intensity, and turbulent intermittency. The results highlight the effects of Reynolds number, the mechanisms of separation, transition, and reattachment, which feature laminar separation-long bubble and laminar separation-short bubble modes. For each Reynolds number, the onset of transition, the transition length, and the general characteristics of separated flow are determined. These findings are compared to the measurement results found in the literature. Furthermore, the experimental data is compared with two categories of correlation functions also given in the literature: (1) correlations predicting the onset of transition and (2) correlations predicting the mode of separated flow transition. Moreover, it is shown that the type of instability involved corresponds to the inviscid Kelvin-Helmholtz instability mode at a dominant frequency that is in agreement with the typical ranges occurring in published studies of separated and free-shear layers.

Download Full-text

The Influence of Different Rim Seal Geometries on Hot-Gas Ingestion and Total Pressure Loss in a Low-Pressure Turbine

Volume 7: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2010-22205 ◽

2010 ◽

Cited By ~ 6

Author(s):

P. Schuler ◽

W. Kurz ◽

K. Dullenkopf ◽

H.-J. Bauer

Keyword(s):

Pressure Loss ◽

Total Pressure ◽

Gas Flow ◽

Low Pressure ◽

Total Pressure Loss ◽

Pressure Loss Coefficient ◽

Low Pressure Turbine ◽

Hot Gas ◽

Flow Through ◽

Total Pressure Loss Coefficient

In order to prevent hot-gas ingestion into the rotating turbo machine’s inside, rim seals are used in the cavities located between stator- and rotor-disc. The sealing flow ejected through the rim seal interacts with the boundary layer of the main gas flow, thus playing a significant role in the formation of secondary flows which are a major contributor to aerodynamic losses in turbine passages. Investigations performed in the EU project MAGPI concentrate on the interaction between the sealing flow and the main gas flow and in particular on the influence of different rim seal geometries regarding the loss-mechanism in a low-pressure turbine passage. Within the CFD work reported in this paper static simulations of one typical low-pressure turbine passage were conducted containing two different rim seal geometries, respectively. The sealing flow through the rim seal had an azimuthal velocity component and its rate has been varied between 0–1% of the main gas flow. The modular design of the computational domain provided the easy exchange of the rim seal geometry without remeshing the main gas flow. This allowed assessing the appearing effects only to the change of rim seal geometry. The results of this work agree with well-known secondary flow phenomena inside a turbine passage and reveal the impact of the different rim seal geometries on hot-gas ingestion and aerodynamic losses quantified by a total pressure loss coefficient along the turbine blade. While the simple axial gap geometry suffers considerable hot-gas ingestion upstream the blade leading edge, the compound geometry implying an axial overlapping presents a more promising prevention against hot-gas ingestion. Furthermore, the effect of rim seals on the turbine passage flow field has been identified applying adequate flow visualisation techniques. As a result of the favourable conduction of sealing flow through the compound geometry, the boundary layer is less lifted by the ejected sealing flow, thus resulting in a comparatively reduced total pressure loss coefficient over the turbine blade.

Download Full-text

Transition Mechanisms in Laminar Separated Flow Under Simulated Low Pressure Turbine Airfoil Conditions

Volume 7: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2011-45690 ◽

2011 ◽

Author(s):

Jerrit Da¨hnert ◽

Christoph Lyko ◽

Dieter Peitsch

Keyword(s):

Reynolds Number ◽

Separation Bubble ◽

Separated Flow ◽

Low Pressure ◽

Main Flow ◽

Test Facility ◽

Flow Conditions ◽

Laminar Separation ◽

Free Stream Turbulence ◽

Low Pressure Turbine

Based on detailed experimental work conducted at a low speed test facility, this paper describes the transition process in the presence of a separation bubble with low Reynolds number, low free-stream turbulence, and steady main flow conditions. A pressure distribution has been created on a long flat plate by means of a contoured wall opposite of the plate, matching the suction side of a modern low-pressure turbine aerofoil. The main flow conditions for four Reynolds numbers, based on suction surface length and nominal exit velocity, were varied from 80,000 to 300,000, which covers the typical range of flight conditions. Velocity profiles and the overall flow field were acquired in the boundary layer at several streamwise locations using hot-wire anemometry. The data given is in the form of contours for velocity, turbulence intensity, and turbulent intermittency. The results highlight the effects of Reynolds number, the mechanisms of separation, transition, and reattachment, which feature laminar separation-long bubble and laminar separation-short bubble modes. For each Reynolds number, the onset of transition, the transition length, and the general characteristics of separated flow are determined. These findings are compared to the measurement results found in the literature. Furthermore, the experimental data is compared with two categories of correlation functions also given in the open literature: (1) correlations predicting the onset of transition and (2) correlations predicting the mode of separated flow transition. Moreover, it is shown that the type of instability involved corresponds to the inviscid Kelvin-Helmholtz instability mode at a dominant frequency that is in agreement with the typical ranges occurring in published studies of separated and free-shear layers.

Download Full-text

Inverse Fin Arrangement in a Low Pressure Turbine to Improve the Interaction Between Shroud Leakage Flows and Main Flow

Volume 7: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2011-45250 ◽

2011 ◽

Cited By ~ 2

Author(s):

Inga Mahle ◽

Roman Schmierer

Keyword(s):

Axial Velocity ◽

Gas Turbines ◽

Low Pressure ◽

Flow Path ◽

Main Flow ◽

Leakage Flow ◽

Wall Region ◽

Leakage Flows ◽

Low Pressure Turbine ◽

Mixing Losses

The paper deals with the geometry of the shroud cavities in low pressure gas turbines and presents a design which helps to reduce the losses that arise when the shroud leakage flows interact with the main flow. The fins in low pressure gas turbines are usually attached to the shroud of the blades. They are therefore rotating while the non-rotating honeycomb or abrasive coating is mounted into the casing. The shroud leakage flow, after passing the rear fin, is decelerated in the rear cavity chamber and enters the main flow path with an axial velocity that is smaller than the axial velocity of the main flow. This difference in axial velocity, together with differences in the circumferential velocity, leads to increased turbulence, mixing losses and an unfavorable incidence of the subsequent vane row in the wall region. Contrarily to the usual configuration, the inverse fins in the turbine presented in the paper are attached to the casing while the honeycomb is mounted onto the rotating blades. This arrangement results in the location of the gap between the fin and the honeycomb being very close to the position of re-entry of the leakage flow into the main flow. Therefore, the leakage flow keeps a high velocity resulting from the narrow fin gap until re-entry which reduces the velocity difference with respect to the main flow. Consequently, the mixing losses and subsequent row losses are reduced. Due to the favorable position of the gap and a particular shaping of the honeycomb, the leakage flow is kept close to the surface of the shroud and enters the main flow with little perturbations. The paper presents numerical results of steady 3D simulations of a three-stage low pressure turbine. Results with an ideal flow path (no cavities), with shroud cavities with conventionally rotating fins and with shroud cavities with inverse fins are compared.

Download Full-text

Contribution of Tip Shroud Cavity to Loss Generation in the Main Flow of a Low Pressure Turbine Using Steady and Unsteady Numerical Approach

Volume 2B: Turbomachinery ◽

10.1115/gt2020-15422 ◽

2020 ◽

Author(s):

Maxime Perini ◽

Nicolas Binder ◽

Yannick Bousquet ◽

Eric Schwartz

Keyword(s):

Low Pressure ◽

Numerical Approach ◽

Main Flow ◽

Time Resolved ◽

Flow Angle ◽

Pressure Losses ◽

Low Pressure Turbine ◽

Steady Simulation ◽

Tip Shroud ◽

Additional Losses

Abstract A lot of studies on turbomachinery main flow optimisation have been performed in order to reach current efficiencies. To go further in the study of aerodynamic losses sources, a better understanding of technological effects is required. Tip shroud cavities in low pressure turbine is an example. Indeed, the by-pass flow causes additional pressure losses. In addition, interactions between main flow and cavity flows, as well as the re-entering flow, cause mixing losses and modifications of flow angle. This paper investigates the contribution of tip shroud cavities in a low pressure turbine stage on the overall performance and flow structures. The ability of a steady simulation to predict this kind of flow by comparison with time-resolved results is poorly documented in the literature, and is an objective of this paper. Computations are compared with experimental data from low speed turbine test rig. Entropy production shows that a large amount of additional losses comes from the cavities themselves whichever the steady or unsteady treatment of the simulation. Additional losses generated in the rotor are more dependent on the presence of the shroud or not than the unsteady feature of the simulations.

Download Full-text

Investigation of the Influence of Different Rim Seal Geometries in a Low-Pressure Turbine

Volume 7: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2011-45682 ◽

2011 ◽

Cited By ~ 3

Author(s):

P. Schuler ◽

K. Dullenkopf ◽

H.-J. Bauer

Keyword(s):

Mass Flow ◽

Total Pressure ◽

Gas Flow ◽

Low Pressure ◽

Flow Rates ◽

Low Pressure Turbine ◽

Hot Gas ◽

Seal Design ◽

Compound Design ◽

Mass Flow Rates

The sealing of the machine’s inside against hot-gas ingestion is commonly provided by blowing relative cold compressor air radially out through the turbine wheelspace. Rim-seals located inside the wheelspace are primarily designed to keep the required amount of sealing at a minimum. A further possible function of the rim-seal follows from the desire to reduce the aerodynamic losses contributed by the interaction of the emerging sealing flow with the boundary layer of the incoming main flow. Investigations performend in the EU project MAGPI concentrate on the interaction between the sealing flow and the main gas flow and in particular on the effect of different rim seal designs regarding the loss-mechanism in a low-pressure turbine passage. Two different rim seal designs inside a linear low-pressure turbine cascade rig have been analysed in detail. Both, the simple axial gap and the more complex compound design were investigated under the influence of different sealing mass flow rates. Furthermore, a configuration without any cavity in the main gas flow served as a reference case. Extensive measurements of the total pressure loss over the turbine blade have been conducted by means of a five-hole probe. Additionally, the blade loading has been measured at several blade heights. A considerable increase of total pressure losses was observed due to the presence of a cavity with any rim seal design, even for no sealing flow. Higher sealing mass flow rates intensified this effect which becomes manifested in a strengthening of the secondary flows downstream the cascade. Experiments revealed also significant differences in loss-increment depending on the rim seal design used. Deeper insight into the interaction of the flows close to the rim seal is given by results of Laser-Doppler-Velocimetry measurements. The rounded shape of the compound design, which implies an axial overlapping, represents a promising prevention against hot-gas ingestion. While the axial gap design is characterized by higher losses, it also suffers considerable hot-gas ingestion in front of the blade leading edge. A parametric study regarding a possible optimization of the axial gap design is presented in this work.

Download Full-text