Experimental study on aerodynamic loss and heat transfer for various squealer tips

2021 ◽  
pp. 1-31
Author(s):  
Jin-sol Jung ◽  
Inkyom Kim ◽  
Jin Sung Joo ◽  
Sang-woo Lee
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Thermal Load ◽  
Suction Side ◽  
Tip Clearance ◽  
Pressure Side ◽  
Loss Reduction ◽  
Turbine Cascade ◽  
Low Speed ◽  
Aerodynamic Loss

Abstract This paper presents aerodynamic loss data for five squealer configurations of a full squealer (FS), a pressure-side squealer (PS), a suction-side squealer (SS), a camberline squealer (CS), and a full-camberline squealer (FCS) in a low speed turbine cascade. In addition, tip thermal load data are also reported for the FS, PS, and SS tips. The results show that when h/s (tip clearance-to-span ratio) ≥ 0.96%, the mass-averaged loss for the FS tip decreases, has a minimum value, and then increases, as the squealer height (hst) increases. For h/s = 0.48%, however, the loss changes with hst/s is found to be minute. For the FS tip, the loss tends to increase, as the squealer thickness increases. Adding a camberline squealer to the FS tip is not beneficial in the loss reduction. When hst/s < 3.82% for h/s = 0.96%, the FS tip has the lowest mass-averaged loss, the SS tip has the second lowest loss, the PS tip has higher loss compared to the SS tip, and the CS tip loss is highest, regardless of hst/s. For h/s = 0.96%, the average tip thermal load for the FS tip is lower than the PS tip one but is higher than the SS tip one. Thus, the SS tip delivers the lowest average thermal load, irrespective of hst/s.

Experimental Study on Aerodynamic Loss and Heat Transfer for Various Squealer Tips

2020 ◽  
Author(s):  
Jin-sol Jung ◽  
Inkyom Kim ◽  
Jin Sung Joo ◽  
Sang Woo Lee
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Thermal Load ◽  
Suction Side ◽  
Tip Clearance ◽  
Pressure Side ◽  
Loss Reduction ◽  
Turbine Cascade ◽  
Low Speed ◽  
Aerodynamic Loss

Abstract This paper presents aerodynamic loss data for five squealer configurations of a full squealer (FS), a pressure-side squealer (PS), a suction-side squealer (SS), a camberline squealer (CS), and a full-camberline squealer (FCS) in a low speed turbine cascade. In addition, tip thermal load data are also reported for the FS, PS, and SS tips. The results show that when h/s (tip clearance-to-span ratio) ≥ 0.96%, the mass-averaged loss for the FS tip decreases, has a minimum value, and then increases, as the squealer height (hst) increases. For h/s = 0.48%, however, the loss changes with hst/s is found to be minute. For the FS tip, the loss tends to increase, as the squealer thickness increases. Adding a camberline squealer to the FS tip is not beneficial in the loss reduction. When hst/s < 3.82% for h/s = 0.96%, the FS tip has the lowest mass-averaged loss, the SS tip has the second lowest loss, the PS tip has higher loss compared to the SS tip, and the CS tip loss is highest, regardless of hst/s. For h/s = 0.96%, the average tip thermal load for the FS tip is lower than the PS tip one but is higher than the SS tip one. Thus, the SS tip delivers the lowest average thermal load, irrespective of hst/s.

scholarly journals Effects of Tip Clearance Gap and Exit Mach Number on Turbine Blade Tip and Near-Tip Heat Transfer

2013 ◽  
Author(s):  
K. Anto ◽  
S. Xue ◽  
W. F. Ng ◽  
L. J. Zhang ◽  
H. K. Moon
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Turbine Blade ◽  
Leading Edge ◽  
Suction Side ◽  
Tip Clearance ◽  
Pressure Side ◽  
Engine Blade ◽  
Blade Tip ◽  
Exit Mach Number

This study focuses on local heat transfer characteristics on the tip and near-tip regions of a turbine blade with a flat tip, tested under transonic conditions in a stationary, 2-D linear cascade with high freestream turbulence. The experiments were conducted at the Virginia Tech transonic blow-down wind tunnel facility. The effects of tip clearance and exit Mach number on heat transfer distribution were investigated on the tip surface using a transient infrared thermography technique. In addition, thin film gages were used to study similar effects in heat transfer on the near-tip regions at 94% height based on engine blade span of the pressure and suction sides. Surface oil flow visualizations on the blade tip region were carried-out to shed some light on the leakage flow structure. Experiments were performed at three exit Mach numbers of 0.7, 0.85, and 1.05 for two different tip clearances of 0.9% and 1.8% based on turbine blade span. The exit Mach numbers tested correspond to exit Reynolds numbers of 7.6 × 105, 9.0 × 105, and 1.1 × 106 based on blade true chord. The tests were performed with a high freestream turbulence intensity of 12% at the cascade inlet. Results at 0.85 exit Mach showed that an increase in the tip gap clearance from 0.9% to 1.8% translates into a 3% increase in the average heat transfer coefficients on the blade tip surface. At 0.9% tip clearance, an increase in exit Mach number from 0.85 to 1.05 led to a 39% increase in average heat transfer on the tip. High heat transfer was observed on the blade tip surface near the leading edge, and an increase in the tip clearance gap and exit Mach number augmented this near-leading edge tip heat transfer. At 94% of engine blade height on the suction side near the tip, a peak in heat transfer was observed in all test cases at s/C = 0.66, due to the onset of a downstream leakage vortex, originating from the pressure side. An increase in both the tip gap and exit Mach number resulted in an increase, followed by a decrease in the near-tip suction side heat transfer. On the near-tip pressure side, a slight increase in heat transfer was observed with increased tip gap and exit Mach number. In general, the suction side heat transfer is greater than the pressure side heat transfer, as a result of the suction side leakage vortices.

Heat Transfer and Aerodynamics of Turbine Blade Tips in a Linear Cascade

2004 ◽  
Vol 128 (2) ◽  
pp. 300-309 ◽  
Author(s):  
P. J. Newton ◽  
G. D. Lock ◽  
S. K. Krishnababu ◽  
H. P. Hodson ◽  
W. N. Dawes ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Flow Visualization ◽  
Turbine Blade ◽  
Pressure Coefficient ◽  
Suction Side ◽  
Tip Clearance ◽  
Pressure Side ◽  
Linear Cascade ◽  
Side Edge ◽  
High Heat Transfer

Local measurements of the heat transfer coefficient and pressure coefficient were conducted on the tip and near tip region of a generic turbine blade in a five-blade linear cascade. Two tip clearance gaps were used: 1.6% and 2.8% chord. Data was obtained at a Reynolds number of 2.3×105 based on exit velocity and chord. Three different tip geometries were investigated: A flat (plain) tip, a suction-side squealer, and a cavity squealer. The experiments reveal that the flow through the plain gap is dominated by flow separation at the pressure-side edge and that the highest levels of heat transfer are located where the flow reattaches on the tip surface. High heat transfer is also measured at locations where the tip-leakage vortex has impinged onto the suction surface of the aerofoil. The experiments are supported by flow visualization computed using the CFX CFD code which has provided insight into the fluid dynamics within the gap. The suction-side and cavity squealers are shown to reduce the heat transfer in the gap but high levels of heat transfer are associated with locations of impingement, identified using the flow visualization and aerodynamic data. Film cooling is introduced on the plain tip at locations near the pressure-side edge within the separated region and a net heat flux reduction analysis is used to quantify the performance of the successful cooling design.

Heat Transfer and Aerodynamics of Turbine Blade Tips in a Linear Cascade

2005 ◽  
Author(s):  
P. J. Newton ◽  
S. K. Krishnababu ◽  
G. D. Lock ◽  
H. P. Hodson ◽  
W. N. Dawes ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Pressure Coefficient ◽  
Suction Side ◽  
Tip Clearance ◽  
Flow Visualisation ◽  
Pressure Side ◽  
Linear Cascade ◽  
Side Edge ◽  
High Heat Transfer

Local measurements of the heat transfer coefficient and pressure coefficient were conducted on the tip and near tip region of a generic turbine blade in a five-blade linear cascade. Two tip clearance gaps were used: 1.6% and 2.8% chord. Data was obtained at a Reynolds number of 2.3 × 105 based on exit velocity and chord. Three different tip geometries were investigated: a flat (plain) tip, a suction-side squealer, and a cavity squealer. The experiments reveal that the flow through the plain gap is dominated by flow separation at the pressure-side edge and that the highest levels of heat transfer are located where the flow reattaches on the tip surface. High heat transfer is also measured at locations where the tip-leakage vortex has impinged onto the suction surface of the aerofoil. The experiments are supported by flow visualisation computed using the CFX CFD code which has provided insight into the fluid dynamics within the gap. The suction-side and cavity squealers are shown to reduce the heat transfer in the gap but high levels of heat transfer are associated with locations of impingement, identified using the flow visualisation and aerodynamic data. Film cooling is introduced on the plain tip at locations near the pressure-side edge within the separated region and a net heat flux reduction analysis is used to quantify the performance of the successful cooling design.

scholarly journals Tip gap size effects on thermal performance of cavity-winglet tips in transonic turbine cascade with endwall motion

2017 ◽  
Vol 1 ◽  
pp. CR5JBC ◽  
Author(s):  
Fangpan Zhong ◽  
Chao Zhou
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Tip Clearance ◽  
Pressure Side ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
High Heat Transfer ◽  
The Heat Transfer Coefficient

AbstractThe thermal performance of two cavity-winglet tips with endwall motion is investigated in a transonic high pressure turbine cascade, which operates at an engine representative exit Mach number of 1.2 and an exit Reynolds number of 1.7 × 106. The numerical method is first validated with experimental data and then used to investigate blade heat transfer at three different tip clearances of 1.1, 2.1 and 3.1% chord. The effects of relative endwall motion are considered. The present results show that as the size of the tip gap increases, the heat transfer coefficient and heat load on the tip increases. The winglet geometries on the blade tip mainly affect the tip flow structure close to them. At a larger tip clearance, the size of the separation bubble above the pressure side winglet increases. The heat transfer coefficient is high on the pressure side winglet due to the flow reattachment at all tip clearances. Within the tip gap, when the size of the tip clearance increases, the size of the cavity vortex increases and the cavity scraping vortex due to relative endwall motion becomes smaller. The impingement of the both two vortexes can lead to high heat transfer coefficient on the cavity floor surface. On the blade suction surface, when the size of the tip clearance increases, the heat transfer coefficient of the cavity tip increases, but those of the winglet tips decreases. The heat transfer coefficient is high on the side surface of the suction side winglet at all tip clearances because of the tip leakage flow impingement.

Investigation of Innovative Trailing Edge Cooling Configurations With Enlarged Pedestals and Square or Semicircular Ribs: Part 1—Experimental Results

2008 ◽  
Author(s):  
Bruno Facchini ◽  
Lorenzo Tarchi
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Suction Side ◽  
Pressure Side ◽  
Wall Heat Transfer ◽  
Transfer Enhancement ◽  
Trailing Edge ◽  
Cooling Performance ◽  
Flow Acceleration ◽  
Pressure Losses

This paper describes a heat transfer experimental study of several trailing edge cooling configurations based on the combination of two different heat transfer enhancing devices: enlarged pedestals and ribs. The baseline geometry consists of a wedge shaped duct with two arrays of enlarged pedestals. Square or semicircular turbulators were arranged in between the pedestals of the first row in three different positions: first on the pressure side (PS), then on the suction side (SS) and finally on both end-walls of the duct. For each configuration heat transfer and pressure loss measurements were made keeping the Mach number at 0.3 and varying the Reynolds number from 9000 to 27000. Detailed maps of heat transfer coefficient over the PS surface were measured using the transient technique with thermo-chromic liquid crystals. Results show that the combined effect of flow acceleration and turbulators lead to a significant increase of the heat transfer. The comparison between square and semicircular ribs shows that the wall heat transfer enhancement capability of the former shape is definitely higher only in the configuration with both ribbed surfaces; in like manner, square ribs generate higher pressure losses. In the configurations with one ribbed surface there are no remarkable differences between the two shapes. It is anyway interesting that the ribs placed on one side do not affect significantly the opposite smooth endwall behavior while they enhance HTC on their side, highlighting the possibility to increase cooling performance only on the airfoil side exposed to higher temperatures.

Numerical Investigation of Effects of Non-Uniform Tip Clearance on Flow Field Inside a Turbine Cascade

2016 ◽  
Author(s):  
Hongwei Ma ◽  
Yangtao Tian
Keyword(s):  
Flow Field ◽  
Suction Side ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Pressure Side ◽  
Turbine Cascade ◽  
Leakage Loss ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Turbine Performance

In the unshrouded axial turbine, the tip clearances can result in the loss of turbine efficiency and the penalty of turbine performance. Therefore, investigating the blade tip geometry of improving the turbine performance has a great significance. This paper is to study the effects of non-uniform tip clearance on the flow field in a turbine cascade. The numerical works are performed at the incidence angle of 0 degree and the exit Reynolds number of 1.7 × 105 based on the blade chord. In the investigations, the flat tip (Basic) geometry was employed as a benchmark, and three different tip geometries, including the pressure side squealer (PSQ), suction side squealer (SSQ) and grooved tip (Grooved), were studied. The tip clearances are all specified as 1.18% of the chord. The squealer height is set to 2.94% of the chord. The endwall static pressure, tip leakage loss, flow capacity and the development of tip leakage vortex are discussed. And the numerical results show that the grooved tip which can obtain the least total pressure loss, is helpful to smooth the pressure change from pressure side to suction side and suppress the intensity of tip leakage vortex. The tip clearance flow in the pre semi-passage is mainly involved in the passage vortex, and in the post semi-passage it is added to the tip leakage vortex. Compared with the Basic, PSQ and SSQ tips, the Grooved tip contributes to reducing the tip leakage flow and the tip leakage loss. And the leakage flow can be strengthened in the middle passage for the PSQ. The difference between the area averaged streamwise coefficient and mass averaged loss is almost opposite for the SSQ and Grooved tip, which is uncertain the performance of the turbine cascade with the SSQ and Grooved tip is better than the Basic tip.

Influence of tip clearance and cavity depth on heat transfer in a cutback squealer tip

2020 ◽  
pp. 095441002096469
Author(s):  
Weijie Wang ◽  
Shaopeng Lu ◽  
Hongmei Jiang ◽  
Qiusheng Deng ◽  
Jinfang Teng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Suction Side ◽  
High Heat ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Trailing Edge ◽  
Cavity Depth ◽  
High Heat Transfer ◽  
Blade Tip ◽  
High Heat Transfer Coefficient

Numerical simulations are conducted to present the aerothermal performance of a turbine blade tip with cutback squealer rim. Two different tip clearance heights (0.5%, 1.0% of the blade span) and three different cavity depths (2.0%, 3.0%, and 6.0% of the blade span) are investigated. The results show that a high heat transfer coefficient (HTC) strip on the cavity floor appears near the suction side. It extends with the increase of tip clearance height and moves towards the suction side with the increase of cavity depth. The cutback region near the trailing edge has a high HTC value due to the flush of over-tip leakage flow. High HTC region shrinks to the trailing edge with the increase of cavity depth since there is more accumulated flow in the cavity for larger cavity depth. For small tip clearance cases, high HTC distribution appears on the pressure side rim. However, high HTC distribution is observed on suction side rim for large tip clearance height. This is mainly caused by the flow separation and reattachment on the squealer rims.

scholarly journals Measurement of Unsteady Flow and Heat Transfer in a Linear Turbine Cascade

1992 ◽  
Author(s):  
X. Liu ◽  
W. Rodi
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Unsteady Flow ◽  
Boundary Layers ◽  
Suction Side ◽  
Turbine Cascade ◽  
Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Background Turbulence ◽  
Hot Film

A detailed experimental study has been conducted on the wake-induced unsteady flow and heat transfer in a linear turbine cascade. The unsteady wakes with passing frequencies in the range zero to 240 Hz were generated by moving cylinders on a squirrel cage device. The velocity fields in the blade-to-blade flow and in the boundary layers were measured with hot-wire anemometers, the surface pressures with a pressure transducer and the heat transfer coefficients with a glue-on hot film. The results were obtained in ensemble-averaged form so that periodic unsteady processes can be studied. Of particular interest was the transition of the boundary layer. The boundary layer remained laminar on the pressure side in all cases and in the case without wakes also on the suction side. On the latter, the wakes generated by the moving cylinders caused transition, and the beginning of transition moves forward as the cylinder-passing frequency increases. Unlike in the flat-plate study of Liu and Rodi (1991a) the instantaneous boundary layer state does not respond to the passing wakes and therefore does not vary with time. The heat transfer increases under increasing cylinder-passing frequency even in the regions with laminar boundary layers due to the increased background turbulence.

Heat Transfer and Aerodynamics of Over-Shroud Leakage Flows in a High-Pressure Turbine

2009 ◽  
Author(s):  
Knut Lehmann ◽  
Richard Thomas ◽  
Howard Hodson ◽  
Vassilis Stefanis
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Large Scale ◽  
Suction Side ◽  
Surface Flow ◽  
Tip Clearance ◽  
Flow Visualisation ◽  
Leakage Flow ◽  
High Pressure Turbine ◽  
High Heat Transfer

An experimental study has been conducted to investigate the distribution of the convective heat transfer on the shroud of a high pressure turbine blade in a large scale rotating rig. A continuous thin heater foil technique has been adapted and implemented on the turbine shroud. Thermochromic Liquid Crystals were employed for the surface temperature measurements to derive the experimental heat transfer data. The heat transfer is presented on the shroud top surfaces and the three fins. The experiments were conducted for a variety of Reynolds numbers and flow coefficients. The effects of different inter-shroud gap sizes and reduced fin tip clearance gaps were also investigated. Details of the shroud flow field were obtained using an advanced Ammonia-Diazo surface flow visualisation technique. CFD predictions are compared with the experimental data and used to aid interpretation. Contour maps of the Nusselt number reveal that regions of highest heat transfer are mostly confined to the suction side of the shroud. Peak values exceed the average by as much as 100 percent. It has been found that the interaction between leakage flow through the inter-shroud gaps and the fin tip leakage jets are responsible for this high heat transfer. The inter-shroud gap leakage flow causes a disruption of the boundary layer on the turbine shroud. Furthermore, the development of the large recirculating shroud cavity vortices is severely altered by this leakage flow.

Sign in / Sign up

Export Citation Format

Share Document