Influence of Mainstream Turbulence Intensity on Heat Transfer Characteristics of a High Pressure Turbine Stage With Inlet Hot Streak

2015 ◽  
Vol 138 (4) ◽  
Author(s):  
Zhiduo Wang ◽  
Zhaofang Liu ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Pressure ◽  
Turbulence Intensity ◽  
Computational Study ◽  
Leading Edge ◽  
Adiabatic Wall ◽  
Airfoil Surface ◽  
Turbulence Decay ◽  
Hot Streak

An unsteady computational study was carried out on GE-E3 high pressure (HP) turbine at inflow turbulence intensities of 5%, 10%, and 20% accompanying with inlet hot streak (HS) at two circumferential positions (impinging and nonimpinging relative to vane leading edge) to analyze the interacted turbulence and HS influences. Turbulence decay mechanisms in turbine passage were presented, and the airfoil heat transfer behaviors were explored by means of adiabatic wall temperature, heat transfer coefficient (HTC), and wall heat flux. The results indicate that the elevated turbulence leads to favorable turbine airfoil temperature distributions, and turbulence induced HS attenuation mainly occurs in vane passage. In addition, the HS dispersion is related directly to the temperature gradients. Although the endwall temperature increases by more than 20 K (2.8% inlet mass-averaged temperature) and midregion temperature decreases by 16 K at blade leading edge, the hot region on blade pressure surface (PS) is only weakened by about 7 K, when turbulence intensity is increased from 5% to 20%. Higher turbulence significantly affects the airfoil HTC, excepting the regions secondary and leakage flow effects are dominating. Therefore, the tip and blade suction surface (SS) trailing edge heat flux is decreased for the temperature decline at higher turbulence, which is beneficial to tip cooling. HS position not only affects the airfoil surface temperature variations but also slightly affects the vane and blade midspan HTC for the variation of heat transfer driving temperature.

Numerical Study on Aero-Thermal Performance of HP Turbine Endwalls Under Influence of Hot Streak and High Mainstream Turbulence

2016 ◽  
Author(s):  
Zhiduo Wang ◽  
Wenhao Zhang ◽  
Zhaofang Liu ◽  
Chen Zhang ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Turbulence Intensity ◽  
Wall Temperature ◽  
Numerical Study ◽  
Leading Edge ◽  
Heat Transfer Characteristics ◽  
Adiabatic Wall ◽  
Transfer Characteristics ◽  
Hot Streak

In this paper, unsteady RANS simulations were performed at two hot streak (HS) circumferential positions with inlet turbulence intensity of 5% and 20%. The interacted HS and high mainstream turbulence effects on endwall heat transfer characteristics of a high-pressure (HP) turbine were discussed by analyzing the flow structures and presenting the endwall adiabatic wall temperature, heat transfer coefficient (HTC) and heat flux distributions. The results indicate that both the wall temperature and HTC increase with the turbulence intensity at most stator endwall regions. In addition, the increase of wall temperature plays a greater role than HTC of influencing the wall heat flux. However, higher turbulence intensity decreases the intensity of the stator passage horse-shoe vortex, also the corresponding region HTC and heat flux are reduced. In rotor passage, the variation of HS circumferential position would alter the hub and casing endwall temperature, however, the discrepancy is weakened at higher turbulence. The elevated HS attenuation at higher turbulence results in temperature augmentation at the leading edge of rotor hub and casing endwalls, while temperature decrease after 50% axial chord, thus obtains more uniform temperature distributions on the endwalls. However, the rotor endwall HTC is only augmented significantly at the leading edge on hub endwall, and pressure side and downstream of trailing edge on casing endwall. Variation of HTC and adiabatic wall temperature jointly determines the rotor hub and casing endwall heat flux, and the temperature variation has dominant effects in the most regions. In general, the variation of adiabatic wall temperature and HTC should be considered simultaneously when analyzing the turbine endwall heat transfer characteristics.

Influence of Mainstream Turbulence Intensity on Heat Transfer Characteristics of a HP Turbine Stage With Inlet Hot Streak

2015 ◽  
Author(s):  
Zhiduo Wang ◽  
Zhaofang Liu ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Turbulence Intensity ◽  
Computational Study ◽  
Temperature Drop ◽  
Suction Surface ◽  
Airfoil Surface ◽  
Prediction Ability ◽  
Turbulence Decay ◽  
Inflow Turbulence ◽  
Hot Streak

An unsteady computational study were carried out for the GE-E3 HP turbine at inflow turbulence intensities of 5%, 10% and 20% accompanying with inlet hot streak (HS) at two circumferential positions (impinging and non-impinging relative to vane leading edge) to analyze the interacted turbulence and HS influences. Several validation studies were performed to investigate the heat transfer prediction ability of shear stress transport (SST) turbulence model coupled with γ-θ transition model. Turbulence decay mechanisms in turbine passage were presented, and the airfoil heat transfer behaviors were explored by means of both time-averaged adiabatic wall temperature and heat transfer coefficient (HTC). The results indicate that increase of inflow turbulence leads to favorable turbine temperature distributions in general, and on the blade and tip surface in particular, especially for the non-impinging case and inflow turbulence increasing from 10% to 20%. While the vane and blade surface area-averaged temperatures are hardly changed, a maximum area-averaged temperature drop of 8.9 K is induced at the tip surface. Higher HTC is observed at vane, blade pressure surface, and suction surface mid region at higher turbulence. However, HTCs at endwall regions of blade suction surface and blade tip are insensitive to the turbulence effect, thus the heat load of these regions is not critical when the inflow turbulence intensity is increased. HS position not only affects the airfoil surface temperature variations, but also slightly affects the vane and blade midspan HTC for the variation of fluid driving temperature.

Aerodynamics and Heat Transfer for a Cooled One and One-Half Stage High-Pressure Turbine—Part III: Impact of Hot-Streak Characteristics on Blade Row Heat Flux

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
R. M. Mathison ◽  
C. W. Haldeman ◽  
M. G. Dunn
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Pressure ◽  
Radial Profile ◽  
Leading Edge ◽  
Coolant Temperature ◽  
High Pressure Turbine ◽  
Blade Row ◽  
Hot Streak ◽  
The Impact

The influence of hot-streak magnitude and alignment relative to the vane leading edge on blade row heat flux is investigated for a one and one-half stage high-pressure turbine with a film-cooled vane, purge cooling, and uncooled blades. The full-stage turbine is operated at design-corrected conditions. In addition to investigating the impact of different hot-streak characteristics, this study also looks at the interaction of cooling flow with the hot streaks. This paper builds on the investigation of profile migration utilizing temperature measurements presented in Part I and the heat transfer measurements presented in Part II. Hot streaks aligned with the vane midpitch have a greater impact on blade temperatures and heat-flux values than hot streaks aligned with the vane leading edge. The leading edge hot streaks tend to be mixed out over the surface of the vane. The magnitude of the hot streak is observed to have the largest influence on the temperature and heat flux for the downstream blade. Time-accurate measurements confirm these conclusions and indicate that further analysis of the time-accurate data is warranted. Film cooling is found to impact a hot-streak profile in a way similar to that observed for a radial profile. Differences in core to coolant temperature ratio cause the uniform profile to show different coolant effects, but the overall spread of the cooling appears similar.

Aerodynamics and Heat Transfer for a Cooled One and One-Half Stage High-Pressure Turbine: Part III—Impact of Hot Streak Characteristics on Blade Row Heat Flux

2010 ◽  
Author(s):  
R. M. Mathison ◽  
C. W. Haldeman ◽  
M. G. Dunn
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Pressure ◽  
Radial Profile ◽  
Leading Edge ◽  
Coolant Temperature ◽  
High Pressure Turbine ◽  
Blade Row ◽  
Hot Streak ◽  
The Impact

The influence of hot streak magnitude and alignment relative to the vane leading edge on blade row heat flux are investigated for a one and one-half stage high-pressure turbine with a film-cooled vane, purge cooling, and un-cooled blades. The full-stage turbine is operated at design-corrected conditions. In addition to investigating the impact of different hot-streak characteristics, this study also looks at the interaction of cooling flow with the hot streaks. This paper builds on the investigation of profile migration utilizing temperature measurements presented in Part I and the heat transfer measurements presented in Part II. Hot streaks aligned with the vane mid-pitch have a greater impact on blade temperatures and heat-flux values than hot streaks aligned with the vane leading edge. The leading edge hot streaks tend to be mixed out over the surface of the vane. The magnitude of the hot streak is observed to have the largest influence on the temperature and heat flux for the downstream blade. Time-accurate measurements confirm these conclusions and indicate that further analysis of the time-accurate data is warranted. Film cooling is found to impact a hot streak profile in a way similar to that observed for a radial profile. Differences in core to coolant temperature ratio cause the uniform profile to show different coolant effects, but the overall spread of the cooling appears similar.

Effects of Shock Wave Passage on Heat Transfer in a Transonic Turbine Cascade

1994 ◽  
Author(s):  
D. G. Holmberg ◽  
T. Reid ◽  
T. Kiss ◽  
H. L. Moses ◽  
W. F. Ng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Shock Wave ◽  
Heat Flux ◽  
Leading Edge ◽  
Main Flow ◽  
Suction Surface ◽  
Adiabatic Wall ◽  
Blow Down ◽  
Long Run ◽  
Transonic Turbine

Results from a new facility for measuring heat transfer in transonic turbine cascades are repotted. An air heater has been built into the blow-down wind tunnel to heat the main flow for a 20 second run time. This allows control of the direction and magnitude of the heat transfer into the blade throughout the tests. A Heat Flux Microsensor was inserted into the blade to measure simultaneous surface heat flux and temperature. Measurements were made on the suction surface of the blades toward the trailing edge. Because of the long run times (20 s), the adiabatic wall temperature could be determined directly from the measured surface temperature and heat flux. Simultaneous pressure measurements were made with a Kulite transducer at the same distance from the leading edge to document shock passage. A separate shock tube was used to generate a shock wave which was introduced into the test section in front of the cascade. This shock was carried over the blade by the main flow. The resulting changes in heat flux correlated strongly with the unsteady pressure changes. An overall increase of 1.5 W/cm2 in heat flux was recorded for a pressure increase of 7 kPa during the initial passage of the shock.

Influence of High Mainstream Turbulence on Leading Edge Heat Transfer

1991 ◽  
Vol 113 (4) ◽  
pp. 843-850 ◽  
Author(s):  
A. B. Mehendale ◽  
J. C. Han ◽  
S. Ou
Keyword(s):  
Heat Transfer ◽  
Turbulence Intensity ◽  
Leading Edge ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Turbulence Decay ◽  
High Turbulence

The influence of high mainstream turbulence on leading edge heat transfer was studied. High mainstream turbulence was produced by a bar grid (Tu = 3.3–5.1 percent), passive grid (Tu = 7.6–9.7 percent), and jet grid (Tu = 12.9–15.2 percent). Experiments were performed using a blunt body with a semicylinder leading edge and flat sidewalls. The mainstream Reynolds numbers based on leading edge diameter were 25,000, 40,000, and 100,000. Spanwise and streamwise distributions of local heat transfer coefficients on the leading edge and flat sidewall were obtained. The results indicate that the leading edge heat transfer increases significantly with increasing mainstream turbulence intensity, but the effect diminishes at the end of the flat sidewall because of turbulence decay. Stagnation point heat transfer results for high turbulence intensity flows agree with the Lowery and Vachon correlation, but the overall heat transfer results for the leading edge quarter-cylinder region are higher than their overall correlation for the entire circular cylinder region. High mainstream turbulence tends not to shift the location of the separation-reattachment region. The reattachment heat transfer results are about the same regardless of mainstream turbulence levels and are much higher than the turbulent flat plate correlation.

Heat Transfer for the Blade of a Cooled Stage and One-Half High-Pressure Turbine—Part I: Influence of Cooling Variation

2011 ◽  
Vol 134 (3) ◽  
Author(s):  
R. M. Mathison ◽  
C. W. Haldeman ◽  
M. G. Dunn
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Pressure ◽  
Inlet Temperature ◽  
Temperature Profiles ◽  
High Pressure Turbine ◽  
Suction Surface ◽  
Adiabatic Wall ◽  
Cooling Flows ◽  
Cooling Flow

Heat-flux measurements are presented for a one-and-one-half stage high-pressure turbine operating at design-corrected conditions with modulated cooling flows in the presence of different inlet temperature profiles. Coolant is supplied from a heavily film-cooled vane and the purge cavity (between the rotor disk and the upstream vane) but not from the rotor blades, which are solid metal. Thin-film heat-flux gauges are located on the uncooled blade pressure and suction surface (at multiple span locations), on the blade tip, on the blade platform, and on the disk and vane sides of the purge cavity. These measurements provide a comprehensive picture of the effect of varying cooling flow rates on surface heat transfer to the turbine blade for uniform and radial inlet temperature profiles. Part I of this paper examines the macroscopic influence of varying all cooling flows together, while Part II investigates the individual regions of influence of the vane outer and purge cooling circuits in more detail. The heat-flux gauges are able to track the cooling flow over the suction surface of the airfoil as it wraps upwards along the base of the airfoil for the uniform vane inlet temperature profile. A similar comparison for the radial profile shows the same coolant behavior but with less pronounced changes. From these comparisons, it is clear that cooling impacts each temperature profile similarly. Nearly all of the cooling influence is limited to the blade suction surface, but small changes are observed for the pressure surface. In addition to the cooling study, a novel method of calculating the adiabatic wall temperature is demonstrated. The derived adiabatic wall temperature distribution shows very similar trends to the Stanton number distribution on the blade.

Accuracy of Conventional Adiabatic Effectiveness and Heat Transfer Augmentation Factors in Predicting Heat Flux Into a Turbine Blade Leading Edge

2010 ◽  
Author(s):  
Laurene D. Dobrowolski ◽  
David G. Bogard ◽  
Silvia Ravelli
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Wall Temperature ◽  
Conjugate Heat Transfer ◽  
Density Ratio ◽  
Leading Edge ◽  
Adiabatic Wall ◽  
Stagnation Line ◽  
Conducting Wall ◽  
Heat Transfer Simulation

This paper focuses on the legitimacy of using conventional predictions, based on adiabatic wall temperature (Taw) and heat transfer coefficient (HTC) augmentation, of heat flux into a film cooled leading edge. To answer this question, the heat flux predicted using Taw was compared to the heat flux into a conducting leading edge. The study used numerical simulations with the k-ε turbulence model of FLUENT. The model simulated was a three-row leading edge with one row of holes on the stagnation line and two additional rows located at ±25°, which has been experimentally studied extensively. The adiabatic wall temperature was obtained from an adiabatic simulation. External heat transfer coefficients were determined from a constant heat flux simulation using a density ratio of DR = 1.0, as is commonly done experimentally. A conjugate heat transfer simulation was also run to give the surface temperature and heat flux into the conducting leading edge. Overall, the heat transfer was well predicted with the use of Taw and HTC augmentation. However, between the holes, conventional predictions of heat transfer were poor, with disparity up to 30% when compared with the conducting wall heat flux obtained from the conjugate heat transfer simulation. Thermal boundary layer profiles were used to understand the disparity between the heat fluxes obtained from the conventional prediction and the conducting wall simulation.

Heat Transfer for the Blade of a Cooled Stage and One-Half High-Pressure Turbine: Part I—Influence of Cooling Variation

2010 ◽  
Author(s):  
R. M. Mathison ◽  
C. W. Haldeman ◽  
M. G. Dunn
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Pressure ◽  
Inlet Temperature ◽  
Temperature Profiles ◽  
High Pressure Turbine ◽  
Suction Surface ◽  
Adiabatic Wall ◽  
Cooling Flows ◽  
Cooling Flow

Heat-flux measurements are presented for a one-and-one-half stage high-pressure turbine operating at design corrected conditions with modulated cooling flows in the presence of different inlet temperature profiles. Coolant is supplied from a heavily film cooled vane and the purge cavity (between the rotor disk and the upstream vane) but not from the rotor blades, which are solid metal. Thin-film heat-flux gauges are located on the un-cooled blade pressure and suction surface (at multiple span locations), on the blade tip, on the blade platform, and on the disk and vane sides of the purge cavity. These measurements provide a comprehensive picture of the effect of varying cooling flow rates on surface heat transfer to the turbine blade for uniform and radial inlet temperature profiles. Part I of this paper examines the macroscopic influence of varying all cooling flows together, while Part II investigates the individual regions of influence of the vane outer and purge cooling circuits in more detail. The heat-flux gauges are able to track the cooling flow over the suction surface of the airfoil as it wraps upwards along the base of the airfoil for the uniform vane inlet temperature profile. A similar comparison for the radial profile shows the same coolant behavior but with less pronounced changes. From these comparisons, it is clear that cooling impacts each temperature profile similarly. Nearly all of the cooling influence is limited to the blade suction surface, but small changes are observed for the pressure surface. In addition to the cooling study, a novel method of calculating the adiabatic wall temperature is demonstrated. The derived adiabatic wall temperature distribution shows very similar trends to the Stanton Number distribution on the blade.

Experimental investigation of wall heat transfer due to spray combustion in a high-pressure/high-temperature vessel

2021 ◽  
pp. 146808742110072
Author(s):  
Karri Keskinen ◽  
Walter Vera-Tudela ◽  
Yuri M Wright ◽  
Konstantinos Boulouchos
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Pressure ◽  
High Temperature ◽  
High Speed ◽  
Transfer Problem ◽  
Wall Heat Transfer ◽  
Gas Temperature ◽  
Reference Case ◽  
High Pressure High Temperature

Combustion chamber wall heat transfer is a major contributor to efficiency losses in diesel engines. In this context, thermal swing materials (adapting to the surrounding gas temperature) have been pinpointed as a promising mitigative solution. In this study, experiments are carried out in a high-pressure/high-temperature vessel to (a) characterise the wall heat transfer process ensuing from wall impingement of a combusting fuel spray, and (b) evaluate insulative improvements provided by a coating that promotes thermal swing. The baseline experimental condition resembles that of Spray A from the Engine Combustion Network, while additional variations are generated by modifying the ambient temperature as well as the injection pressure and duration. Wall heat transfer and wall temperature measurements are time-resolved and accompanied by concurrent high-speed imaging of natural luminosity. An investigation with an uncoated wall is carried out with several sensor locations around the stagnation point, elucidating sensor-to-sensor variability and setup symmetry. Surface heat flux follows three phases: (i) an initial peak, (ii) a slightly lower plateau dependent on the injection duration, and (iii) a slow decline. In addition to the uncoated reference case, the investigation involves a coating made of porous zirconia, an established thermal swing material. With a coated setup, the projection of surface quantities (heat flux and temperature) from the immersed measurement location requires additional numerical analysis of conjugate heat transfer. Starting from the traces measured beneath the coating, the surface quantities are obtained by solving a one-dimensional inverse heat transfer problem. The present measurements are complemented by CFD simulations supplemented with recent rough-wall models. The surface roughness of the coated specimen is indicated to have a significant impact on the wall heat flux, offsetting the expected benefit from the thermal swing material.

Sign in / Sign up

Export Citation Format

Share Document