scholarly journals Novel high-pressure turbine purge control features for increased stage efficiency

2017 ◽  
Vol 1 ◽  
pp. 68MK5V ◽  
Author(s):  
Rainer Schädler ◽  
Anestis I. Kalfas ◽  
Reza S. Abhari ◽  
Gregor Schmid ◽  
Tilmann auf dem Kampe ◽  
...  
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Gas Turbines ◽  
High Pressure Turbine ◽  
Axial Turbine ◽  
Seal Design ◽  
Geometrical Features ◽  
Purge Flow ◽  
The Impact ◽  
Stage Efficiency

AbstractRim seals throttle flow and have shown to impact the aerodynamic performance of gas turbines. The results of an experimental investigation of a rim seal exit geometry variation and its impact on the high-pressure turbine flow field are presented. A one-and-a-half stage, unshrouded and highly loaded axial turbine configuration with 3-dimensionally shaped blades and non-axisymmetric end wall contouring has been tested in an axial turbine facility. The exit of the rotor upstream rim seal was equipped with novel geometrical features which are termed as purge control features (PCFs) and a baseline rim seal geometry for comparison. The time-averaged and unsteady aerodynamic effects at rotor inlet and exit have been measured with pneumatic probes and the fast-response aerodynamic probe (FRAP) for three rim seal purge flow injection rates. Measurements at rotor inlet and exit reveal the impact of the geometrical features on the rim seal exit and main annulus flow field, highlighting regions of reduced aerodynamic losses induced by the modified rim seal design. Measurements at the rotor exit with the PCFs installed show a benefit in the total-to-total stage efficiency up to 0.4% for nominal and high rim seal purge flow rates. The work shows the potential to improve the aerodynamic efficiency by means of a well-designed rim seal exit geometry without losing the potential to block hot gas ingestion from the main annulus.

Aerodynamic Robustness of End Wall Contouring Against Rim Seal Purge Flow

2014 ◽  
Author(s):  
K. Regina ◽  
A. I. Kalfas ◽  
R. S. Abhari ◽  
A. Lohaus ◽  
S. Voelker ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Flow Field ◽  
Gas Turbines ◽  
Fast Response ◽  
Axial Turbine ◽  
Purge Flow ◽  
The One ◽  
End Wall ◽  
Stage Efficiency ◽  
Higher Sensitivity

In the present study, the results of an experimental investigation are presented, which have been undertaken in the axial turbine facility LISA at ETH Zurich. The two test configurations consist of a one-and-a-half stage, unshrouded, highly loaded axial turbine with 3-dimensionally shaped blading representative of modern high pressure gas turbines. The two test configurations differ in the hub end walls: while one design has cylindrical end walls, the other design features non-axisymmetric end wall contouring (EWC). Both turbine designs have not been especially designed for the unsteady and complex interaction mechanisms of the hub rim seal purge flow with the main annulus flow. However, these turbine designs have been subject to measurements without (nominal) and with purge flow (0.8% of the main mass flow) with the purpose of studying the aerodynamic robustness of the performance of the stages with respect to the rim seal purge flow. In order to further analyze the robustness of both turbine designs, also measurements at off-design conditions have been taken. The steady and unsteady aerodynamic effects are measured, respectively, with pneumatic probes as well as with the in-house developed and manufactured Fast Response Aerodynamic Probe (FRAP) technology. With the aim of evaluating the aerodynamic performance and robustness of the end wall design, the one result of the experimental investigation is the quantification of the sensitivity of the stage efficiency with respect to the case with and without purge flow for both turbine designs. By means of the analysis of the time-resolved flow field and characterization of the secondary flow features, their reaction to the presence of purge flow is highlighted and used as an explanation for the efficiency deficits caused by the purge flow. The measurements show a benefit in stage efficiency of +0.2% by using the end wall contouring in the nominal case, confirming the design intention and effectiveness of the contoured end walls. However, the beneficial impact of the end wall contouring is taken back by a higher sensitivity of the stage efficiency with respect to the purge flow, which causes the efficiency benefit to vanish with the investigated purge flow injection rate of 0.8%. The off-design measurements show that also the sensitivity of the stage with end wall contouring with respect to the reduction of stage loading factor is by 1/3 higher than the one of the cylindrical end walls. The measurements imply that the cost of higher stage efficiency at nominal conditions by the use of end wall contouring is paid with a higher sensitivity of the stage to changes in the rotor incoming flow field and thus with a lower aerodynamic robustness of the turbine design.

Experimental Investigation of Purge Flow Effects on a High Pressure Turbine Stage

2014 ◽  
Vol 137 (4) ◽  
Author(s):  
K. Regina ◽  
A. I. Kalfas ◽  
R. S. Abhari
Keyword(s):  
Experimental Investigation ◽  
High Pressure ◽  
Gas Turbines ◽  
Radial Displacement ◽  
Secondary Flows ◽  
Turbine Stage ◽  
Flow Factor ◽  
Purge Flow ◽  
The Impact ◽  
Stage Efficiency

In the present paper, an experimental investigation of the effects of rim seal purge flow on the performance of a highly loaded axial turbine stage is presented. The test configuration consists of a one-and-a-half stage, unshrouded, turbine, with a blading representative of high pressure (HP) gas turbines. Efficiency measurements for various purge flow injection levels have been carried out with pneumatic probes at the exit of the rotor and show a reduction of isentropic total-to-total efficiency of 0.8% per percent of injected mass flow. For three purge flow conditions, the unsteady aerodynamic flow field at rotor inlet and rotor exit has been measured with the in-house developed fast response aerodynamic probe (FRAP). The time-resolved data show the unsteady interaction of the purge flow with the secondary flows of the main flow and the impact on the radial displacement of the rotor hub passage vortex (HPV). Steady measurements at off-design conditions show the impact of the rotor incidence and of the stage flow factor on the resulting stage efficiency and the radial displacement of the rotor HPV. A comparison of the effect of purge flow and of the off-design conditions on the rotor incidence and stage flow factor shows that the detrimental effect of the purge flow on the stage efficiency caused by the radial displacement of the rotor HPV is dominated by the increase of stage flow factor in the hub region rather than by the increase of negative rotor incidence.

Impact of Individual High-Pressure Turbine Rotor Purge Flows on Turbine Center Frame Aerodynamics

2017 ◽  
Author(s):  
S. Zerobin ◽  
C. Aldrian ◽  
A. Peters ◽  
F. Heitmeir ◽  
E. Göttlich
Keyword(s):  
High Pressure ◽  
Pressure Loss ◽  
Turbine Rotor ◽  
Flow Conditions ◽  
High Pressure Turbine ◽  
Reference Case ◽  
University Of Technology ◽  
Purge Flow ◽  
Generation Mechanisms ◽  
The Impact

This paper presents an experimental study of the impact of individual high-pressure turbine purge flows on the main flow in a downstream turbine center frame duct. Measurements were carried out in a product-representative one and a half stage turbine test setup, installed in the Transonic Test Turbine Facility at Graz University of Technology. The rig allows testing at engine-relevant flow conditions, matching Mach, Reynolds, and Strouhal number at the inlet of the turbine center frame. The reference case features four purge flows differing in flow rate, pressure, and temperature, injected through the hub and tip, forward and aft cavities of the high-pressure turbine rotor. To investigate the impact of each individual cooling flow on the flow evolution in the turbine center frame, the different purge flows were switched off one-by-one while holding the other three purge flow conditions. In total, this approach led to six different test conditions when including the reference case and the case without any purge flow ejection. Detailed measurements were carried out at the turbine center frame duct inlet and outlet for all six conditions and the post-processed results show that switching off one of the rotor case purge flows leads to an improved duct performance. In contrast, the duct exit flow is dominated by high pressure loss regions if the forward rotor hub purge flow is turned off. Without the aft rotor hub purge flow, a reduction in duct pressure loss is determined. The purge flows from the rotor aft cavities are demonstrated to play a particularly important role for the turbine center frame aerodynamic performance. In summary, this paper provides a first-time assessment of the impact of four different purge flows on the flow field and loss generation mechanisms in a state-of-the-art turbine center frame configuration. The outcomes of this work indicate that a high-pressure turbine purge flow reduction generally benefits turbine center frame performance. However, the forward rotor hub purge flow actually stabilizes the flow in the turbine center frame duct and reducing this purge flow can penalize turbine center frame performance. These particular high-pressure turbine/turbine center frame interactions should be taken into account whenever high-pressure turbine purge flow reductions are pursued.

Time-Averaged and Time-Accurate Aerodynamic Effects of Forward Rotor Cavity Purge Flow for a High-Pressure Turbine: Part I—Analytical and Experimental Comparisons

2012 ◽  
Author(s):  
Brian R. Green ◽  
Randall M. Mathison ◽  
Michael G. Dunn
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Film Cooling ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Flow Path ◽  
Field Analysis ◽  
High Pressure Turbine ◽  
Purge Flow

The effect of rotor purge flow on the unsteady aerodynamics of a high-pressure turbine stage operating at design corrected conditions has been investigated both experimentally and computationally. The experimental configuration consisted of a single-stage high-pressure turbine with a modern film-cooling configuration on the vane airfoil as well as the inner and outer end-wall surfaces. Purge flow was introduced into the cavity located between the high-pressure vane and the high-pressure disk. The high-pressure blades and the downstream low-pressure turbine nozzle row were not cooled. All hardware featured an aerodynamic design typical of a commercial high-pressure ratio turbine, and the flow path geometry was representative of the actual engine hardware. In addition to instrumentation in the main flow path, the stationary and rotating seals of the purge flow cavity were instrumented with high frequency response, flush-mounted pressure transducers and miniature thermocouples to measure flow field parameters above and below the angel wing. Predictions of the time-dependent flow field in the turbine flow path were obtained using FINE/Turbo, a three-dimensional, Reynolds-Averaged Navier-Stokes CFD code that had the capability to perform both steady and unsteady analysis. The steady and unsteady flow fields throughout the turbine were predicted using a three blade-row computational model that incorporated the purge flow cavity between the high-pressure vane and disk. The predictions were performed in an effort to mimic the design process with no adjustment of boundary conditions to better match the experimental data. The time-accurate predictions were generated using the harmonic method. Part I of this paper concentrates on the comparison of the time-averaged and time-accurate predictions with measurements in and around the purge flow cavity. The degree of agreement between the measured and predicted parameters is described in detail, providing confidence in the predictions for flow field analysis that will be provided in Part II.

Time-Averaged and Time-Accurate Aerodynamic Effects of Rotor Purge Flow for a Modern, One and One-Half Stage High-Pressure Turbine—Part II: Analytical Flow Field Analysis

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Brian R. Green ◽  
Randall M. Mathison ◽  
Michael G. Dunn
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Film Cooling ◽  
Gas Flow ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Field Analysis ◽  
High Pressure Turbine ◽  
Purge Flow

The detailed mechanisms of purge flow interaction with the hot-gas flow path were investigated using both unsteady computationally fluid dynamics (CFD) and measurements for a turbine operating at design corrected conditions. This turbine consisted of a single-stage high-pressure turbine and the downstream, low-pressure turbine nozzle row with an aerodynamic design equivalent to actual engine hardware and typical of a commercial, high-pressure ratio, transonic turbine. The high-pressure vane airfoils and inner and outer end walls incorporated state-of-the-art film cooling, and purge flow was introduced into the cavity located between the high-pressure vane and disk. The flow field above and below the blade angel wing was characterized by both temperature and pressure measurements. Predictions of the time-dependent flow field were obtained using a three-dimensional, Reynolds-averaged Navier–Stokes CFD code and a computational model incorporating the three blade rows and the purge flow cavity. The predictions were performed to evaluate the accuracy obtained by a design style application of the code, and no adjustment of boundary conditions was made to better match the experimental data. Part I of this paper compared the predictions to the measurements in and around the purge flow cavity and demonstrated good correlation. Part II of this paper concentrates on the analytical results, looking at the primary gas path ingestion mechanism into the cavity as well as the effects of the rotor purge on the upstream vane and downstream rotor aerodynamics and thermodynamics. Ingestion into the cavity is driven by high static pressure regions downstream of the vane, high-velocity flow coming off the pressure side of the vane, and the blade bow waves. The introduction of the purge flow is seen to have an effect on the static pressure of the vane trailing edge in the lower 5% of span. In addition, the purge flow is weak enough that upon exiting the cavity, it is swept into the mainstream flow and provides no additional cooling benefits on the platform of the rotating blade.

Time-Averaged and Time-Accurate Aerodynamic Effects of Forward Rotor Cavity Purge Flow for a High-Pressure Turbine—Part I: Analytical and Experimental Comparisons

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Brian R. Green ◽  
Randall M. Mathison ◽  
Michael G. Dunn
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Film Cooling ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Flow Path ◽  
Field Analysis ◽  
High Pressure Turbine ◽  
Purge Flow

The effect of rotor purge flow on the unsteady aerodynamics of a high-pressure turbine stage operating at design corrected conditions has been investigated, both experimentally and computationally. The experimental configuration consisted of a single-stage high-pressure turbine with a modern film-cooling configuration on the vane airfoil and the inner and outer end wall surfaces. Purge flow was introduced into the cavity located between the high-pressure vane and the high-pressure disk. The high-pressure blades and the downstream low-pressure turbine nozzle row were not cooled. All of the hardware featured an aerodynamic design typical of a commercial high-pressure ratio turbine and the flow path geometry was representative of the actual engine hardware. In addition to instrumentation in the main flow path, the stationary and rotating seals of the purge flow cavity were instrumented with high frequency response flush-mounted pressure transducers and miniature thermocouples in order to measure the flow field parameters above and below the angel wing. Predictions of the time-dependent flow field in the turbine flow path were obtained using FINE/Turbo, a three-dimensional Reynolds-averaged Navier–Stokes computational fluid dynamics CFD code that had the capability to perform both a steady and unsteady analysis. The steady and unsteady flow fields throughout the turbine were predicted using a three blade-row computational model that incorporated the purge flow cavity between the high-pressure vane and disk. The predictions were performed in an effort to mimic the design process with no adjustment of boundary conditions to better match the experimental data. The time-accurate predictions were generated using the harmonic method. Part I of this paper concentrates on the comparison of the time-averaged and time-accurate predictions with measurements in and around the purge flow cavity. The degree of agreement between the measured and predicted parameters is described in detail, providing confidence in the predictions for the flow field analysis that will be provided in Part II.

Aerodynamic Performance of Turbine Center Frames With Purge Flows—Part II: The Influence of Individual Hub and Tip Purge Flows

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Stefan Zerobin ◽  
Christian Aldrian ◽  
Andreas Peters ◽  
Franz Heitmeir ◽  
Emil Göttlich
Keyword(s):  
High Pressure ◽  
Operating Conditions ◽  
High Pressure Turbine ◽  
Flow Rates ◽  
Purge Flow ◽  
Flow Evolution ◽  
Generation Mechanisms ◽  
The Impact ◽  
First Time ◽  
Time Assessment

The aerodynamic behavior of turbine center frame (TCF) ducts under the presence of high-pressure turbine (HPT) purge flows was experimentally investigated in this two-part paper. While the first part of the paper demonstrated the impact of varying the purge flow rates (PFR) on the loss behavior of two different TCF designs, the second part concentrates on the influence of individual hub and tip purge flows on the main flow evolution and loss generation mechanisms through the TCF ducts. Therefore, measurements were conducted at six different operating conditions in a one and a half stage turbine test setup, featuring four individual purge flows injected through the hub and tip, forward and aft cavities of the HPT rotor. The outcomes of this first-time assessment indicate that a HPT purge flow reduction generally benefits TCF performance. Decreasing one of the rotor case PFRs leads to an improved duct pressure loss. The purge flows from the rotor aft hub and tip cavities are demonstrated to play a particularly important role for improving the duct aerodynamic behavior. In contrast, the forward rotor hub purge flow actually stabilizes the flow in the TCF duct and reducing this purge flow can penalize TCF performance. These particular HPT/TCF interactions should be taken into account whenever high-pressure turbine purge flow reductions are pursued.

Time-Averaged and Time-Accurate Aerodynamic Effects of Rotor Purge Flow for a Modern, One and One-Half Stage High-Pressure Turbine: Part II—Analytical Flow Field Analysis

2012 ◽  
Author(s):  
Brian R. Green ◽  
Randall M. Mathison ◽  
Michael G. Dunn
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Film Cooling ◽  
Gas Flow ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Field Analysis ◽  
High Pressure Turbine ◽  
Purge Flow

The detailed mechanisms of purge flow interaction with the hot-gas flow path were investigated using both unsteady CFD and measurements for a turbine operating at design corrected conditions. This turbine consisted of a single-stage high-pressure turbine and the downstream, low-pressure turbine nozzle row with an aerodynamic design equivalent to actual engine hardware and typical of a commercial, high-pressure ratio, transonic turbine. The high-pressure vane airfoils and inner and outer endwalls incorporated state-of-the-art film cooling, and purge flow was introduced into the cavity located between the high-pressure vane and disk. The flow field above and below the blade angel wing was characterized by both temperature and pressure measurements. Predictions of the time-dependent flow field were obtained using a three-dimensional, Reynolds-Averaged Navier-Stokes CFD code and a computational model incorporating the three blade rows and the purge flow cavity. The predictions were performed to evaluate the accuracy obtained by a design style application of the code, and no adjustment of boundary conditions was made to better match the experimental data. Part I of this paper compared the predictions to the measurements in and around the purge flow cavity and demonstrated good correlation. Part II of this paper concentrates on the analytical results, looking at the primary gas path ingestion mechanism into the cavity as well as the effects of the rotor purge on the upstream vane and downstream rotor aerodynamics and thermodynamics. Ingestion into the cavity is driven by high static pressure regions downstream of the vane, high-velocity flow coming off the pressure side of the vane, and the blade bow waves. The introduction of the purge flow is seen to have an effect on the static pressure of the vane trailing edge in the lower 5% of span. In addition, the purge flow is weak enough that upon exiting the cavity, it is swept into the mainstream flow and provides no additional cooling benefits on the platform of the rotating blade.

A Systematic Experimental Study on the Aerodynamics of Leading Edge Film Cooling on a Large Scale High Pressure Turbine Cascade

1998 ◽  
Author(s):  
Sabine Ardey ◽  
Leonhard Fottner
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Injection Site ◽  
Film Cooling ◽  
Gas Turbines ◽  
Large Scale ◽  
Three Dimensional ◽  
Leading Edge ◽  
Turbine Cascade ◽  
High Pressure Turbine

Systematic isothermal investigations on the aerodynamic effects of leading edge film cooling were carried out on a large scale high pressure turbine cascade named AGTB. In the vicinity of the stagnation point the AGTB turbine cascade has one injection site on the suction side and one on the pressure side. Three injection geometries were tested: Slots (two dimensional geometry), streamwise inclined holes (symmetrical three dimensional geometry) and compound angle holes (fully three dimensional geometry). The injection angle in streamwise direction, the blowing ratio, the inlet turbulence intensity, the inlet Mach number, and the inlet Reynolds number were kept constant at values typically found in modern gas turbines. The measured data comprise the coolant plenum state, the cascade inlet conditions, the flow field in the cascade exit plane including secondary flows, the static pressure distribution in the mid span section of the blade and in the near hole region, the coolant flow field close to the injection site on the leading edge, Schlieren images of the coolant penetration height and oil-and-dye flow visualizations of the blade surface. The experimental data are summarized and documented as a test case that can be used for validation purposes of prediction methods.

Unsteady Effects due to Rotor Purge Flow Variations in a Dual-Spool Turbine Setup

2020 ◽  
Author(s):  
F. Merli ◽  
P. Z. Sterzinger ◽  
M. Dellacasagrande ◽  
L. Wiesinger ◽  
A. Peters ◽  
...  
Keyword(s):  
Flow Field ◽  
Gas Turbines ◽  
Pressure Probe ◽  
Wall Region ◽  
Two Stage ◽  
Reference Case ◽  
Time Resolved ◽  
Aerodynamic Pressure ◽  
Purge Flow ◽  
The Impact

Abstract The paper discusses the impact of rotor purge flows on the unsteady flow field downstream of a two-stage, two-spool test turbine. The analyzed setup is representative of the second high-pressure turbine (HPT) and the first low-pressure turbine (LPT) stage in a modern turbofan aero-engine, with a turbine center frame (TCF) with non-turning struts in-between the two turbines. All measurements were carried out for an engine-representative test vehicle setup at the Transonic Test Turbine Facility at Graz University of Technology. The test rig features a secondary air system delivering five purge flows with independent temperature and mass flow control to the HPT and LPT cavities. This work extends the results shown in two recent publications analyzing the time-resolved flow through the same two-stage setup at fixed purge flow rates. The paper aims to provide additional input about the driving sources of unsteadiness in gas turbines for aeronautic applications, by isolating the HPT and LPT purge air contributions. The time-resolved flow field at the LPT exit was acquired with a Fast Response Aerodynamic Pressure Probe (FRAPP) for three different purge conditions (reference case, no HPT purge case, no LPT purge case), to separate and quantify the impact of HPT and LPT purge contributions on the main flow field. The so-called Rotor Synchronic Averaging (RSA) technique was used as phase-averaging approach, to account for the unsteadiness due to both rotors. Proper Orthogonal Decomposition (POD) was then applied to isolate the most important structures and identify their origins. The comparison of the three data-sets shows a significant influence of the HPT purge on the entire flow field at the LPT exit, even though the HPT is located far upstream, while the LPT purge impact appears to mostly affect the end-wall region.

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