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

2012 ◽  
Author(s):  
K. Regina ◽  
A. I. Kalfas ◽  
R. S. Abhari
Keyword(s):  
High Pressure ◽  
Mass Flow ◽  
Radial Displacement ◽  
Turbine Stage ◽  
Test Configuration ◽  
Flow Factor ◽  
Passage Vortex ◽  
Purge Flow ◽  
The Impact ◽  
Stage Efficiency

In the present paper an experimental investigation of the effects of hub purge flow on the performance of a high pressure axial turbine stage is presented. The test configuration consists of a one-and-a-half stage, unshrouded, highly loaded axial turbine, with a blading representative of high pressure gas turbines. The test configuration has the capability of integrating purge flow from the cavity under the rotor/stator platform. 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): one condition is with sucking at a mass flow fraction of −0.1 % and two conditions are with injection at a mass flow fraction of 0.8 % and 1.2 %. The time-resolved data shows 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. 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 hub passage vortex is dominated by the increase of stage flow factor in the hub region rather than by the increase of negative rotor incidence.

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.

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.

Heat Transfer and Pressure Measurements for the Forward Purge Cavity, Inner Endwall, and Rotor Platform of a Cooled Transonic Turbine Stage

2018 ◽  
Author(s):  
Jeremy Nickol ◽  
Matthew Tomko ◽  
Randall Mathison ◽  
Jong S. Liu ◽  
Mark Morris ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Pressure ◽  
Fourier Transforms ◽  
Pressure Measurements ◽  
Turbine Stage ◽  
Cooling Flow ◽  
Complex Interactions ◽  
Purge Flow ◽  
The Impact

An experiment is performed using a cooled transonic high-pressure turbine stage operating at design-corrected conditions. Pressure measurements are taken at several locations within the forward purge cavity between the high-pressure stator and rotor, as well as on the blade platforms and vane inner endwalls. Double-sided Kapton heat-flux gauges are installed on the upper surface of the rotor blade platform (open to the hot gas path flow) and underneath the platform (exposed to coolant and leakage flow). The blade airfoil and purge flow cooling are supplied by the same flow circuit and must be varied together, but the influence of the airfoil cooling has previously been shown to be negligible in the platform region flow of interest to this study. A separate cooling circuit supplies the aft purge flow between the rotor and downstream components. The vane cooling holes have been blocked off for this experiment to simplify analysis. In order to determine the effect of the purge flow on the blade aerodynamics and heat transfer, the forward and aft cooling flow rates are varied independently. Both time-averaged and time-accurate results are presented for the pressure and heat-flux data to illustrate the complex interactions between the purge cavity flow structures and the external flow. Time-accurate data are presented using both Fast-Fourier Transforms (FFTs) to identify driving frequencies and ensemble average plots to highlight the impact of different wake shapes.

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.

Numerical Investigation of the Effect of Purge Flow on Aerodynamic Performance and Film Cooling Effectiveness on a Rotating Turbine With Non-Axisymmetric Endwall Contouring

2012 ◽  
Author(s):  
M. T. Schobeiri ◽  
K. Lu ◽  
J. C. Han
Keyword(s):  
Numerical Investigation ◽  
Mass Flow ◽  
Flow Injection ◽  
Film Cooling ◽  
Preceding Paper ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Purge Flow ◽  
Endwall Contouring ◽  
The Impact

The impact of the purge flow injection on aerodynamics and film cooling effectiveness of a high pressure turbine with non-axisymmetric endwall contouring has been numerically investigated. For this purpose, the geometry and boundary condition of a three-stage turbine at the Turbomachinery Performance and Flow Research Laboratory (TPFL), Texas A&M University is utilized. The turbine is being prepared to experimentally verify the results of the current numerical investigations. Its rotor includes non-axisymmetric endwall contouring on the first and second rotor row. In the preceding paper [1] it was shown that the endwall contouring of the second rotor contouring was able to substantially increase the turbine efficiency. To investigate the film cooling in conjunction with a purge flow injection, the first turbine rotor hub was contoured. Applying the same contouring method, however, different aerodynamic behavior of the first rotor was observed due to its immediate exposure to the purge flow injection. Consequently, the endwall design of the first rotor row required particular attention. The purge flow investigation involves the reference case without endwall contouring followed by the investigation with endwall contouring. The turbine used for this numerical investigation has two independent cooling loops. The first loop supplies coolant air to the stator-rotor gap, while the second loop provides cooling air to the downstream discrete film-cooling holes and blade tip cooling injection holes. For the current investigations the second loop is closed. Film cooling effectiveness is numerically simulated for rotor frequency of 2400 rpm. Efficiency, pressure, temperature and film cooling effectiveness distributions are determined for purge mass flow ratios of MFR = 0.5%, 1.0% and 2.0%. The small amount of the injected mass flow drastically changes the development of the secondary flow structure of the contoured first turbine row partially reversing the improvement tendency obtained from the endwall contouring.

Aerothermal Impact of the Interaction Between Hub Leakage and Mainstream Flows in Highly-Loaded HP Turbine Blades

2010 ◽  
Author(s):  
I. Popovic´ ◽  
H. P. Hodson
Keyword(s):  
Mass Flow ◽  
Vortical Structure ◽  
Turbine Blades ◽  
Outer Part ◽  
Suction Surface ◽  
Leakage Flows ◽  
Passage Vortex ◽  
Purge Flow ◽  
Mass Flow Rates ◽  
Highly Loaded

This paper describes experimental and numerical investigations of a highly-loaded rotor blade with leakage (purge) flow injection through an upstream overlapping seal. The effects of both leakage mass flow rates and swirl have been studied to examine their effects on the aerothermal performance. As the leakage mass flow rate was increased, the loss generally increased. The increase in the losses was found to be non-linear with the three distinct regimes of leakage-mainstream interaction being identified. The varying sensitivity of the losses to the leakage fraction was linked to the effects of the upstream potential field of the blade on a vortical structure originating from the outer part of the seal. This vortical structure affected the interaction between the leakage and mainstream flows as it grew to become the hub passage vortex. Very limited cooling was provided by the leakage flows. The coolant was mainly concentrated close to the suction surface in the front part of the rotor platform and on the blade suction surface in the path of the passage vortex. However, the regions benefiting from cooling were also characterized by higher values of the heat transfer coefficient. As a consequence, the net heat flux reduction was small and the leakage injection was thus deemed thermally neutral.

The Effect of Secondary Air Injection on the Performance of a Transonic Turbine Stage

2002 ◽  
Author(s):  
S. Girgis ◽  
E. Vlasic ◽  
J.-P. Lavoie ◽  
S. H. Moustapha
Keyword(s):  
Turbine Stage ◽  
Cfd Simulations ◽  
Secondary Air Injection ◽  
Flow Test ◽  
Mainstream Flow ◽  
Purge Flow ◽  
Simulated Test ◽  
Transonic Turbine ◽  
Secondary Air ◽  
Stage Efficiency

This paper presents results of rig testing of a transonic, single stage turbine with various modifications made to the injection of secondary air into the mainstream. Results show that significant improvements in stage efficiency can be realized by optimizing the injection of upstream disk purge and rotor upstream shroud leakage flow into the mainstream flow. Results of CFD simulations of the rotor upstream disk purge flow test conditions and closely simulated test geometry agree well with test data.

The Impact of Rotor Inlet Cavity Volume and Length Scale on Efficiency

2012 ◽  
Author(s):  
Konstantinos G. Barmpalias ◽  
Reza S. Abhari ◽  
Anestis I. Kalfas ◽  
Naoki Shibukawa ◽  
Takashi Sasaki
Keyword(s):  
Experimental Work ◽  
Computational Analysis ◽  
Cavity Length ◽  
Cavity Wall ◽  
Length Scale ◽  
Cavity Volume ◽  
Turbine Stage ◽  
Flow Interactions ◽  
The Impact ◽  
Stage Efficiency

The interaction between the cavity and the main flows accounts for a considerable amount of the overall aerodynamic losses in axial turbomachinery. Experimental work supplemented by a computational analysis is presented in this paper on the impact of rotor inlet cavity volume and length scale on turbine stage efficiency. Inlet cavity volume and geometry have been systematically varied. The flow interactions occurring at the cavity inlet between the cavity and main flows and their subsequent impact on efficiency were studied. Five different configurations have been examined within this study. The radial cavity wall has been shortened by 13% and 25% compared to the initial cavity length. Cavity volume has been reduced by 14% and 28% respectively. An additional rounding introduced at the upper right corner of the cavity generated two more variations. Efficiency was increased by 1.1% and 1.6% for the 14% and 28% cavity volume reductions, respectively. The rounding introduced led only to efficiency deficits as the strengthening of the cavity vortex caused increased interaction at the cavity inlet area.

scholarly journals Numerical Investigation of the Hub-Seal Mass Flow Rate Effect on the Axial Turbine Stage Efficiency

2019 ◽  
Vol 213 ◽  
pp. 02080
Author(s):  
Petr Straka
Keyword(s):  
Numerical Simulation ◽  
Mass Flow Rate ◽  
Compressible Flow ◽  
Mass Flow ◽  
Flow Rate ◽  
Turbine Stage ◽  
Axial Turbine ◽  
Flow Through ◽  
Stage Efficiency ◽  
Flow Rate Effect

The contribution deals with numerical simulation of compressible flow through the axial turbine stage equipped with the hub-seal. The current flowing from the hub-seal has a major impact on the secondary flow in the hub-region of the blade span. The aim of this work is to found a dependency of the efficiency-drop on the hub-seal mass flow rate. Numerical simulation has been made for configuration of experimental axial single-stage reaction turbine.

The Effect of Thermal Barrier Coating Surface Temperature on the Adhesion Behavior of CMAS Deposits

2020 ◽  
Author(s):  
Robert A. Clark ◽  
Nicholas Plewacki ◽  
Pritheesh Gnanaselvam ◽  
Jeffrey P. Bons ◽  
Vaishak Viswanathan
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Surface Temperature ◽  
Mass Flow ◽  
Experimental Results ◽  
Thermal Barrier ◽  
Back Side ◽  
Surface Temperatures ◽  
The Impact ◽  
Side Flow

Abstract The interaction of thermal barrier coating’s surface temperature with CMAS (calcium magnesium aluminosilicate) like deposits in gas turbine hot flowpath hardware is investigated. Small Hastelloy X coupons were coated in TBC using the air plasma spray (APS) method and then subjected to a thermal gradient via back-side impingement cooling and front-side impingement heating using the High Temperature Deposition Facility (HTDF) at The Ohio State University (OSU). A 1-D heat transfer model was used to estimate TBC surface temperatures and correlate them to intensity values taken from infrared (IR) images of the TBC surface. TBC frontside surface temperatures were varied by changing back-side mass flow (kept at a constant temperature), while maintaining a constant hot-side gas temperature and jet velocity representative of modern commercial turbofan high-pressure turbine (HPT) inlet conditions (approximately 1600K and 200 m/s, or Mach 0.25). In this study, Arizona Road Dust (ARD) was utilized to mimic the behavior of CMAS attack on TBCs. To identify the minimum temperature at which particles adhere, the back-side cooling mass flow was set to the maximum amount allowed by the test setup, and trace amounts of 0–10 μm ARD particles were injected into the hot-side flow to impinge on the TBC surface. The TBC surface temperature was increased through coolant reduction until noticeable deposits formed, as evaluated through an IR camera. Accelerated deposition tests were then performed where approximately 1 gram of ARD was injected into the hot side flow while the TBC surface temperature was held at various points above the minimum observed deposition temperature. Surface deposition on the TBC coupons was evaluated using an infrared camera and a backside thermocouple. Coupon cross sections were also evaluated under a scanning electron microscope for any potential CMAS ingress into the TBC. Experimental results of the impact of surface temperature on CMAS deposition and deposit evolution and morphology are presented. In addition, an Eulerian-Lagrangian solver was used to model the hot-side impinging jet with particles at four TBC surface temperatures and deposition was predicted using the OSU Deposition model. Comparisons to experimental results highlight the need for more sophisticated modeling of deposit development through conjugate heat transfer and mesh morphing of the target surface. These results can be used to improve physics-based deposition models by providing valuable data relative to CMAS deposition characteristics on TBC surfaces, which modern commercial turbofan high pressure turbines use almost exclusively.

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