scholarly journals Effects of a combined hot-streak and swirl profile on cooled 1.5-stage turbine aerodynamics: an experimental and computational study

2020 ◽  
pp. 1-24
Author(s):  
Maxwell G. Adams ◽  
Paul F. Beard ◽  
Mark R. Stokes ◽  
Fredrik Wallin ◽  
Kam S. Chana ◽  
...  
Keyword(s):  
Performance Studies ◽  
Gas Turbines ◽  
Computational Study ◽  
Inlet Temperature ◽  
Lean Burn ◽  
Flow Angle ◽  
Rotor Aerodynamics ◽  
Total Temperature ◽  
Hot Streak ◽  
Profile Area

Abstract Recently developed lean-burn combustors offer reduced NOx emissions for gas turbines. The flow at exit of lean-burn combustors is dominated by hot-streaks and residual swirl, which have been shown–individually–to impact turbine aerodynamic performance. Studies have shown that residual swirl at inlet to the high-pressure (HP) stage predominantly affects the vane aerodynamics, while hot-streaks affect the rotor aerodynamics. Studies have also shown that these changes to the HP stage aerodynamics can affect the downstream intermediate-pressure (IP) vane aerodynamics. Yet, to date, there have been no published studies presenting experimental turbine test data with both swirl and hot-streaks simultaneously present at inlet. This paper presents the first experimental and computational investigation into the effects of combined hot-streaks and swirl on turbine aerodynamics. Measurements were conducted in the Oxford Turbine Research Facility, a short-duration rotating transonic facility that matches non-dimensional engine conditions. Two turbine inlet flows are considered. The first is uniform in total pressure, total temperature, and flow angle. The second features a non-uniform total temperature (hot-streak) profile featuring strong radial and weak circumferential variation superimposed on a swirling velocity profile. Area surveys of the flow were conducted throughout the turbine. Measurements and URANS predictions suggest that the inlet temperature non-uniformity was relatively well preserved upon being convected through the turbine, and relatively poor comparisons between URANS and experiment highlight the challenge of accurately predicting the complex IP vane flow.

scholarly journals Numerical Investigation on the Influence of Hot Streak Temperature Ratio in a High-Pressure Stage of Vaneless Counter-Rotating Turbine

2007 ◽  
Vol 2007 ◽  
pp. 1-14 ◽  
Author(s):  
Zhao Qingjun ◽  
Wang Huishe ◽  
Zhao Xiaolu ◽  
Xu Jianzhong
Keyword(s):  
High Pressure ◽  
Secondary Flow ◽  
Heat Load ◽  
Rotor Blades ◽  
Inlet Temperature ◽  
Combined Effects ◽  
Temperature Ratio ◽  
Flow Angle ◽  
Hot Streak ◽  
Relative Flow

The results of recent studies have shown that combustor exit temperature distortion can cause excessive heat load of high-pressure turbine (HPT) rotor blades. The heating of HPT rotor blades can lead to thermal fatigue and degrade turbine performance. In order to explore the influence of hot streak temperature ratio on the temperature distributions of HPT airfoil surface, three-dimensional multiblade row unsteady Navier-Stokes simulations have been performed in a vaneless counter-rotating turbine (VCRT). The hot streak temperature ratios from 1.0 (without hot streak) to 2.4 were used in these numerical simulations, including 1.0, 1.2, 1.6, 2.0, and 2.4 temperature ratios. The hot streak is circular in shape with a diameter equal to 25%of the span. The center of the hot streak is located at 50%of span and 0%of pitch (the leading edge of the HPT stator vane). The predicted results show that the hot streak is relatively unaffected as it migrates through the HPT stator. The hot streak mixes with the vane wake and convects towards the pressure surface (PS) of the HPT rotor when it moves over the vane surface of the HPT stator. The heat load of the HPT rotor increases with the increase of the hot streak temperature ratio. The existence of the inlet temperature distortion induces a thin layer of cooler air in the HPT rotor, which separates the PS of the HPT rotor from the hotter fluid. The numerical results also indicating the migration characteristics of the hot streak in the HPT rotor are predominated by the combined effects of secondary flow and buoyancy. The combined effects that induce the high-temperature fluid migrate towards the hub on the HPT rotor. The effect of the secondary flow on the hotter fluid increases as the hot streak temperature ratio is increased. The influence of buoyancy is directly proportional to the hot streak temperature ratio. The predicted results show that the increase of the hot streak temperature ratio trends to increase the relative Mach number at the HPT rotor outlet, and decrease the relative flow angle from 25%to 75%span at the HPT rotor outlet. In the other region of the HPT outlet, the relative flow angle increases when the hot streak temperature ratio is increased. The predicted results also indicate that the isentropic efficiency of the VCRT decreases with the increase of the hot streak temperature ratio.

Influence of Hot Streak Circumferential Length-Scale in Transonic Turbine Stage

2004 ◽  
Author(s):  
L. He ◽  
V. Menshikova ◽  
B. R. Haller
Keyword(s):  
Heat Transfer ◽  
Computational Study ◽  
Guide Vane ◽  
Strong Dependence ◽  
Rotor Blades ◽  
Inlet Temperature ◽  
Turbine Stage ◽  
Blade Vibration ◽  
Nozzle Guide ◽  
Hot Streak

A computational study is carried out on the influence of turbine inlet temperature distortion (hot streak). The hot streak effects are examined from both aeromechanical (forced blade vibration) and aero-thermal (heat transfer) points of view. Computations are firstly carried out for a transonic HP turbine stage, and the steady and unsteady surface pressure results are compared with the corresponding experimental data. Subsequent analysis is carried out for hot-streaks with variable circumferential wavelength, corresponding to different numbers of combustion burners. The results show that the circumferential wavelength of the temperature distortion can significantly change unsteady forcing as well as the heat-transfer to rotor blades. In particular, when the hot-streak wavelength is the same as the nozzle guide vane (NGV) blade pitch, there is a strong dependence of the preferential heating characteristics on the relative clocking position between hot-streak and NGV blade. However, this clocking dependence is shown to be qualitatively weakened for the cases with fewer hot streaks with longer circumferential wavelengths.

Effect of NGV Lean Under Influence of Inlet Temperature Traverse

2013 ◽  
Author(s):  
A. Rahim ◽  
B. Khanal ◽  
L. He ◽  
E. Romero
Keyword(s):  
Heat Transfer ◽  
Computational Study ◽  
Navier Stokes ◽  
Tangential Displacement ◽  
Inlet Temperature ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Inlet Conditions ◽  
Hot Streak ◽  
The Impact

One of the most widely studied parameters in turbine blade shaping is blade lean, i.e. the tangential displacement of spanwise sections. However, there is a lack of published research that investigates the effect of blade lean under non-uniform temperature conditions (commonly referred to as a ‘hot-streak’) that are present at the combustor exit. Of particular interest is the impact of such an inflow temperature profile on heat transfer when the NGV blades are shaped. In the present work a computational study has been carried out for a transonic turbine stage using an efficient unsteady Navier-Stokes solver (HYDRA). The configurations with a nominal vane and a compound leaned vane under uniform and hot-streak inlet conditions are analysed. After confirming the typical NGV loading and aero-loss redistributions as seen in previous literature on blade lean, the focus has been directed to the rotor aerothermal behavior. Whilst the overall stage efficiencies for the configurations are largely comparable, the results show strikingly different rotor heat transfer characteristics. For a uniform inlet, a leaned NGV has a detrimental effect on the rotor heat transfer. However, once the hot-streak is introduced, the trend is reversed; the leaned NGV leads to favourable heat transfer characteristics in general and for the rotor tip region in particular. The possible causal links for the observed aerothermal features are discussed. The present findings also highlight the significance of evaluating NGV shaping designs under properly conditioned inflow profiles, rather than extrapolating the wisdom derived from uniform inlet cases. The results also underline the importance of including rotor heat transfer and coolability during the NGV design process.

Rotor Blade Heat Transfer of High Pressure Turbine Stage Under Inlet Hot-Streak and Swirl

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
A. Rahim ◽  
L. He
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Heat Load ◽  
Design Space Exploration ◽  
Role Reversal ◽  
Dominant Factor ◽  
Inlet Temperature ◽  
Turbine Stage ◽  
Lean Burn ◽  
Hot Streak

A key consideration in high pressure (HP) turbine designs is the heat load experienced by rotor blades. Impact of turbine inlet nonuniformity of combined temperature and velocity traverses, typical for a lean-burn combustor exit, has rarely been studied. For general turbine aerothermal designs, it is also of interest to understand how the behavior of lean-burn combustor traverses (with both hot-streak and swirl) might contrast with those for a rich-burn combustor (largely hot-streak only). In the present work, a computational study has been carried out on the aerothermal performance of a HP turbine stage under nonuniform temperature and velocity inlet profiles. The analyses are primarily conducted for two combined hot-streak and swirl inlets, with opposite swirl directions. In addition, comparisons are made against a hot-streak only case and a uniform inlet. The effects of three nozzle guide vane (NGV) shape configurations are investigated: straight, compound lean (CL) and reverse CL (RCL). The present results reveal a qualitative change in the roles played by heat transfer coefficient (HTC) and fluid driving (“adiabatic wall”) temperature, Taw. It has been shown that the blade heat load for a uniform inlet is dominated by HTC, whilst a hot-streak only case is largely influenced by Taw. However, in contrast to the hot-streak only case, a combined hot-streak and swirl case shows a role reversal with the HTC being a dominant factor. Additionally, it is seen that the swirling flow redistributes radially the hot fluid within the NGV passage considerably, leading to a much ‘flatter’ rotor inlet temperature profile compared to its hot-streak only counterpart. Furthermore, the rotor heat transfer characteristics for the combined traverses are shown to be strongly dependent on the NGV shaping and the inlet swirl direction, indicating a potential for further design space exploration. The present findings underline the need to clearly define relevant combustor exit temperature and velocity profiles when designing and optimizing NGVs for HP turbine aerothermal performance.

scholarly journals Commissioning of a Combined Hot-Streak and Swirl Profile Generator in a Transonic Turbine Test Facility

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Maxwell G. Adams ◽  
Thomas Povey ◽  
Benjamin F. Hall ◽  
David N. Cardwell ◽  
Kam S. Chana ◽  
...  
Keyword(s):  
Boundary Condition ◽  
Reynolds Number ◽  
Gas Turbines ◽  
Test Facility ◽  
Lean Burn ◽  
Numerical Predictions ◽  
Turbine Inlet ◽  
Total Temperature ◽  
Inlet Conditions ◽  
Inlet Boundary Condition

Abstract By enhancing the premixing of fuel and air prior to combustion, recently developed lean-burn combustor systems have led to reduced NOx and particulate emissions in gas turbines. Lean-burn combustor exit flows are typically characterized by nonuniformities in total temperature, or so-called hot-streaks, swirling velocity profiles, and high turbulence intensity. While these systems improve combustor performance, the exiting flow-field presents significant challenges to the aerothermal performance of the downstream turbine. This paper presents the commissioning of a new fully annular lean-burn combustor simulator for use in the Oxford Turbine Research Facility (OTRF), a transonic rotating facility capable of matching nondimensional engine conditions. The combustor simulator can deliver engine-representative turbine inlet conditions featuring swirl and hot-streaks either separately or simultaneously. To the best of our knowledge, this simulator is the first of its kind to be implemented in a rotating turbine test facility.The combustor simulator was experimentally commissioned in two stages. The first stage of commissioning experiments was conducted using a bespoke facility exhausting to atmospheric conditions (Hall and Povey, 2015, “Experimental Study of Non-Reacting Low NOx Combustor Simulator for Scaled Turbine Experiments,” ASME Paper No. GT2015-43530.) and included area surveys of the generated temperature and swirl profiles. The survey data confirmed that the simulator performed as designed, reproducing the key features of a lean-burn combustor. However, due to the hot and cold air mixing process occurring at lower Reynolds number in the facility, there was uncertainty concerning the degree to which the measured temperature profile represented that in OTRF. The second stage of commissioning experiments was conducted with the simulator installed in the OTRF. Measurements of the total temperature field at turbine inlet and of the high-pressure (HP) nozzle guide vane (NGV) loading distributions were obtained and compared to measurements with uniform inlet conditions. The experimental survey results were compared to unsteady numerical predictions of the simulator at both atmospheric and OTRF conditions. A high level of agreement was demonstrated, indicating that the Reynolds number effects associated with the change to OTRF conditions were small. Finally, data from the atmospheric test facility and the OTRF were combined with the numerical predictions to provide an inlet boundary condition for numerical simulation of the test turbine stage. The NGV loading measurements show good agreement with the numerical predictions, providing validation of the stage inlet boundary condition imposed. The successful commissioning of the simulator in the OTRF will enable future experimental studies of lean-burn combustor–turbine interaction.

Numerical and Experimental Investigations of the Influence of Different Swirl Ratios on the Temperature Streak Development in a 4-Stage Turbine

2000 ◽  
Author(s):  
Dieter Bohn ◽  
Harald Funke ◽  
Tom Heuer ◽  
Jürg Bütikofer
Keyword(s):  
Gas Turbines ◽  
Experimental Investigations ◽  
Inlet Temperature ◽  
Temperature Inhomogeneity ◽  
Radial Temperature ◽  
Blade Cooling ◽  
Hot Gas ◽  
Segregation Effect ◽  
Temperature Equalization ◽  
Hot Streak

In the development of modern gas turbines the increase in the turbine inlet temperature is restricted by the need for cooling the first stages of the turbine. In addition, the flow leaving the combustor is thermally inhomogeneous. Since the blade cooling has to be designed for the actual local hot gas temperatures, it is important to know how these temperature inhomogeneities develop and attenuate inside the multistage flow passage. In this investigation the development of a circumferential and a radial temperature inhomogeneity inside a 4-stage turbine is analyzed at three different swirl ratios. Since the experimental setup allows a circumferential temperature streak, a radial temperature streak has also been applied at different swirl ratios to the same geometrical configuration for a numerical investigation. The first stage has a significant impact on the attenuation and change in form of a circumferential temperature streak depending on the swirl. For the radial streak the hot streak segregation effect can be eliminated by increasing the swirl. Consequently, the temperature equalization process is weakened.

CFD Investigation of the Performance of a Military HP Axial Turbine Subjected to Inlet Temperature Distortion

2005 ◽  
Author(s):  
Andrea Zilli ◽  
Vassilios Pachidis ◽  
Anthony Jackson ◽  
Pericles Pilidis
Keyword(s):  
High Pressure ◽  
Fluid Dynamic ◽  
Axial Flow ◽  
Inlet Temperature ◽  
High Pressure Turbine ◽  
Cfd Simulations ◽  
Axial Turbine ◽  
Total Temperature ◽  
Steady State Simulation ◽  
Hot Streak

It is known that the exit flow from the combustor entering a turbine stage will have wide spatial variations in temperature both radially and circumferentially. This phenomenon is amplified in military engines, due to the higher temperatures involved, and can affect also the performance of a highly loaded, high-pressure axial turbine. Computational Fluid Dynamic (CFD) simulations are an innovative and powerful tool for studying inlet temperature distortion and can be integrated in the early phases of the design process. This paper discusses the 3D CFD steady state simulation of the performance of a single stage axial flow high pressure turbine at design point, off design and on several constant speed lines. The study also addresses the behaviour of the turbine when subjected to uneven inlet total temperature distribution. In addition to the ideal case (uniform inlet temperature), three types of distorted inlet temperature conditions have been investigated. These are: simple radial distortion, hot streak aligned to the mid passage of the stator and hot streak impinging on the leading edges of the stator. The analysis demonstrated that temperature distortion does not have a significant effect on the performance of the high pressure turbine apart from a small reduction in efficiency. It has been found that this drop in efficiency can be reduced by directing (clocking) the hot streaks towards the stator blades. The commercial CFD package, CFX-TASCflow, has been used in this study.

Two-Dimensional Inlet Temperature Profile Attenuation in a Turbine Stage

1991 ◽  
Author(s):  
Daniel J. Dorney ◽  
Roger L. Davis ◽  
Om P. Sharma
Keyword(s):  
Turbine Blade ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Numerical Procedure ◽  
Inlet Temperature ◽  
Two Dimensional ◽  
Dimensional Solution ◽  
Airfoil Surface ◽  
Data Set ◽  
Hot Streak

Experimental evidence has shown that hot streaks which are emitted from the combustors of gas turbines are often largely responsible for the burning of first stage turbine blades. Designers have attempted to counteract the effects of these hot streaks through the use of complex internal and film cooling schemes. Unfortunately, due to the lack of accurate predictive tools which account for temperature non-uniformities in the gas path, as well as a lack of detailed understanding of the physical mechanisms which control the migration and accumulation of the hot streak gases, turbine blade “hot spots” still occasionally occur. In an effort to increase understanding of the interaction mechanisms between combustor hot streaks and turbine blade heat transfer, a numerical investigation has been conducted to determine if a two-dimensional solution procedure can accurately predict rotor airfoil surface heating for flows which include planar hot streaks. A two-dimensional Navier-Stokes analysis is used to predict unsteady viscous flow through a 1-stator/1-rotor configuration with a planar hot streak introduced at the stator inlet. Comparison of the predicted results with a new experimental data set demonstrates that the two-dimensional numerical procedure can be used to accurately predict time-averaged rotor pressure surface temperatures for flows which include planar hot streaks.

Rotor Blade Heat Transfer Characteristics for High Pressure Turbine Stage Under Inlet Temperature and Velocity Traverses

2014 ◽  
Author(s):  
A. Rahim ◽  
L. He ◽  
E. Romero
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Heat Load ◽  
Inlet Temperature ◽  
Turbine Stage ◽  
Heat Transfer Characteristics ◽  
Lean Burn ◽  
Transfer Characteristics ◽  
Hot Streak ◽  
The Impact

One of the key considerations in high pressure (HP) turbine design is the heat load experienced by rotor blades. The impact of turbine inlet non-uniformities on the blades in the form of combined temperature and velocity traverses, typical for a lean burn combustor exit, has rarely been studied. For general HP turbine aerothermal designs, it is also of interest to understand how the behavior of a lean burn combustor traverses (hot streak and swirl) might contrast with those for rich burn combustion (largely hot streak only). In the present work, a computational study has been carried out on the aerothermal performance of a HP turbine stage under non-uniform temperature and velocity inlet profiles. The analyses are primarily conducted for two combined hot streak and swirl inlets, with opposite swirl directions. In addition, comparisons are made against a hot streak only case and a uniform inlet. The effects of three NGV shape configurations are investigated; namely, straight, compound lean (CL) and reverse compound lean (RCL). The present results show that there is a qualitative change in the roles played by heat transfer coefficient (HTC) and fluid driving (‘adiabatic wall’) temperature, Taw. It has been shown that the blade heat load distribution for a uniform inlet is dominated by HTC, whilst for a hot streak only case it is wholly influenced by Taw. However, in contrast to the hot streak only case, the case with a combined hot streak and swirl shows a role reversal with the HTC being dominant in determining the heat load. Additionally, it is seen that the swirling flow radially redistributes the hot fluid within the NGV passage considerably, leading to a much ‘flatter’ rotor inlet temperature profile compared to its hot streak only counterpart. Further, the rotor heat transfer characteristics for the cases with the combined traverses are shown to be strongly dependent on the NGV shaping and the inlet swirl direction, indicating the potential for future design space exploration. The present findings underline the need to clearly define relevant combustor exit temperature and velocity profiles when designing and optimizing NGVs for HP turbine aerothermal performance.

Numerical investigation of non-uniform flow in twin-silo combustors and impact on axial turbine stage performance

2021 ◽  
pp. 095765092199394
Author(s):  
Hafiz M Hassan ◽  
Adeel Javed ◽  
Asif H Khoja ◽  
Majid Ali ◽  
Muhammad B Sajid
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Internal Flow ◽  
Large Temperature ◽  
Clear Understanding ◽  
Gas Temperature ◽  
Turbine Stage ◽  
Flow Angle ◽  
Axial Turbine ◽  
Stage Performance

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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