Cooling Efficiency for Assessing the Cooling Performance of an Effusion Cooled Combustor Liner

2013 ◽  
Author(s):  
B. Wurm ◽  
A. Schulz ◽  
H.-J. Bauer ◽  
M. Gerendas
Keyword(s):  
Heat Fluxes ◽  
Main Flow ◽  
Wall Pressure ◽  
Pressure Measurements ◽  
Cooling Efficiency ◽  
Transfer Coefficients ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Thermal Investigations ◽  
The Impact

Based on experimental results on a liner of a modern direct lean injection combustion chamber using coolant ejection from both effusion cooling holes and a starter film, a method is presented that allows the assessment of the cooling performance of the liner. As the main focus of the present study is a deeper understanding of the interaction of swirl flow and near wall cooling flow, wall pressure measurements are performed for the calculation of local blowing ratios and local coolant mass fluxes. Thermal investigations allow the calculation of adiabatic film cooling effectiveness and heat transfer coefficients. The pressure drop across the effusion cooled liner is varied between 1% and 3% of the total pressure of the main flow. As experiments are performed without combustion and at low temperature, the influence of radiation is neglected. Results show the impact of the swirled main flow on the stability of the starter film and on the effusion cooling performance. Stagnation areas which could be identified by wall pressure measurements are confirmed by detailed PIV measurements. Thermal investigations reveal reduced cooling performance in the respective stagnation areas. For the definition of the non dimensional cooling efficiency the measurement area is sub divided into rhombic sections, which are located around each effusion cooling hole. Based on the measurement results presented, heat fluxes per unit area can then be calculated and put together to the cooling efficiency.

Impact of Swirl Flow on the Cooling Performance of an Effusion Cooled Combustor Liner

2012 ◽  
Vol 134 (12) ◽  
Author(s):  
B. Wurm ◽  
A. Schulz ◽  
H.-J. Bauer ◽  
M. Gerendas
Keyword(s):  
Swirl Flow ◽  
Main Flow ◽  
Heat Shield ◽  
Pressure Measurements ◽  
Cooling Performance ◽  
Hot Gas ◽  
Thermal Investigations ◽  
The Impact ◽  
Combustor Liner ◽  
Near Wall

An experimental study on combustor liner cooling of modern direct lean injection combustion chambers using coolant ejection from both effusion cooling holes and a starter film has been conducted. The experimental setup consists of a generic scaled three sector planar rig in an open loop hot gas wind tunnel, which has been described earlier in Wurm et al. (2009, “A New Test Facility for Investigating the Interactions Between Swirl Flow and Wall Cooling Films in Combustors, Investigating the Interactions Between Swirl Flow and Wall Cooling Films in Combustors,” ASME Paper No. GT2009-59961). Experiments are performed without combustion. Realistic engine conditions are achieved by applying engine-realistic Reynolds numbers, Mach numbers, and density ratios. A particle image velocimetry (PIV) measurement technique is employed, which has been adjusted to allow for high resolution near wall velocity measurements with and without coolant ejection. As the main focus of the present study is a deeper understanding of the interaction of swirl flows and near wall cooling flows, wall pressure measurements are performed for the definition of local blowing ratios and to identify the impact on the local cooling performance. For thermal investigations an infrared thermography measurement technique is employed that allows high resolution thermal studies on the effusion cooled liner surface. The effects of different heat shield geometry on the flow field and performance of the cooling films are investigated in terms of near wall velocity distributions and film cooling effectiveness. Two different heat shield configurations are investigated which differ in shape and inclination angle of the so called heat shield lip. Operating conditions for the hot gas main flow are kept constant. The pressure drop across the effusion cooled liner is varied between 1% and 3% of the total pressure. Results show the impact of the swirled main flow on the stability of the starter film and on the effusion cooling performance. Stagnation areas which could be identified by wall pressure measurements are confirmed by PIV measurements. Thermal investigations reveal reduced cooling performance in the respective stagnation areas.

Impact of Swirl Flow on the Cooling Performance of an Effusion Cooled Combustor Liner

2012 ◽  
Author(s):  
B. Wurm ◽  
A. Schulz ◽  
H.-J. Bauer ◽  
M. Gerendas
Keyword(s):  
High Resolution ◽  
Main Flow ◽  
Heat Shield ◽  
Pressure Measurements ◽  
Cooling Performance ◽  
Hot Gas ◽  
Thermal Investigations ◽  
The Impact ◽  
Combustor Liner ◽  
Near Wall

An experimental study on combustor liner cooling of modern direct lean injection (DLI) combustion chambers using coolant ejection from both effusion cooling holes and a starter film has been conducted. The experimental setup consists of a generic scaled three sector planar rig in an open loop hot gas wind tunnel, which has been described earlier in Wurm et al. [1]. Experiments are performed without combustion. Realistic engine conditions are achieved by applying engine-realistic Reynolds numbers, Mach numbers, and density ratios. A Particle Image Velocimetry (PIV) measurement technique is employed, which has been adjusted to allow for high resolution near wall velocity measurements with and without coolant ejection. As the main focus of the present study is a deeper understanding of the interaction of swirl flows and near wall cooling flows, wall pressure measurements are performed for the definition of local blowing ratios and to identify the impact on the local cooling performance. For thermal investigations an infrared thermography measurement technique is employed that allows high resolution thermal studies on the effusion cooled liner surface. The effects of different heat shield geometry on the flow field and performance of the cooling films are investigated in terms of near wall velocity distributions and film cooling effectiveness. Two different heat shield configurations are investigated which differ in shape and inclination angle of the so called heat shield lip. Operating conditions for the hot gas main flow are kept constant. The pressure drop across the effusion cooled liner is varied between 1% and 3% of the total pressure. Results show the impact of the swirled main flow on the stability of the starter film and on the effusion cooling performance. Stagnation areas which could be identified by wall pressure measurements are confirmed by PIV measurements. Thermal investigations reveal reduced cooling performance in the respective stagnation areas.

Rib Turbulator Effects on Crossflow-Fed Shaped Film Cooling Holes

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Dale W. Fox ◽  
Fraser B. Jones ◽  
John W. McClintic ◽  
David G. Bogard ◽  
Thomas E. Dyson ◽  
...  
Keyword(s):  
Film Cooling ◽  
Velocity Ratio ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Smooth Channel ◽  
Cooling Hole ◽  
Film Cooling Holes ◽  
Inlet Position ◽  
The Impact

Most studies of turbine airfoil film cooling in laboratory test facilities have used relatively large plenums to feed flow into the coolant holes. However, a more realistic inlet condition for the film cooling holes is a relatively small channel. Previous studies have shown that the film cooling performance is significantly degraded when fed by perpendicular internal crossflow in a smooth channel. In this study, angled rib turbulators were installed in two geometric configurations inside the internal crossflow channel, at 45 deg and 135 deg, to assess the impact on film cooling effectiveness. Film cooling hole inlets were positioned in both prerib and postrib locations to test the effect of hole inlet position on film cooling performance. A test was performed independently varying channel velocity ratio and jet to mainstream velocity ratio. These results were compared to the film cooling performance of previously measured shaped holes fed by a smooth internal channel. The film cooling hole discharge coefficients and channel friction factors were also measured for both rib configurations with varying channel and inlet velocity ratios. Spatially averaged film cooling effectiveness is largely similar to the holes fed by the smooth internal crossflow channel, but hole-to-hole variation due to inlet position was observed.

Film Cooling Downstream of a Row of Discrete Holes With Compound Angle

2000 ◽  
Vol 123 (2) ◽  
pp. 222-230 ◽  
Author(s):  
R. J. Goldstein ◽  
P. Jin
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Film Cooling ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Mass Transfer Coefficients ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Compound Angle

A special naphthalene sublimation technique is used to study the film cooling performance downstream of one row of holes of 35 deg inclination angle and 45 deg compound angle with 3d hole spacing and relatively small hole length to diameter ratio (6.3). Both film cooling effectiveness and mass/heat transfer coefficients are determined for blowing rates from 0.5 to 2.0 with density ratio of unity. The mass transfer coefficient is measured using pure air film injection, while the film cooling effectiveness is derived from comparison of mass transfer coefficients obtained following injection of naphthalene-vapor-saturated air with that of pure air injection. This technique enables one to obtain detailed local information on film cooling performance. General agreement is found in local film cooling effectiveness when compared with previous experiments. The laterally averaged effectiveness with compound angle injection is higher than that with inclined holes immediately downstream of injection at a blowing rate of 0.5 and is higher at all locations downstream of injection at larger blowing rates. A large variation of mass transfer coefficients in the lateral direction is observed in the present study. At low blowing rates of 0.5 and 1.0, the laterally averaged mass transfer coefficient is close to that of injection without compound angle. At the highest blowing rate used (2.0), the asymmetric vortex motion under the jets increases the mass transfer coefficient drastically ten diameters downstream of injection.

Film Cooling From a Row of Holes With Both Ends Embedded in Transverse Slots

2008 ◽  
Author(s):  
D. H. Zhang ◽  
L. Sun ◽  
Q. Y. Chen ◽  
M. Lin ◽  
M. Zeng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Aerodynamic Performance ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Discharge Coefficients ◽  
Cylindrical Holes

Embedding a row of typical cylindrical holes in a transverse slot can improve the cooling performance. Rectangular slots can increase the cooling effectiveness but is at the cost of decreasing of discharge coefficients. An experiment is conducted to examine the effects of an overlying transverse inclined trench on the film cooling performance of axial holes. Four different trench configurations are tested including the baseline inclined cylindrical holes. The influence of the geometry of the upstream lip of the exit trench and the geometry of the inlet trench on cooling performance is examined. Detailed film cooling effectiveness and heat transfer coefficients are obtained separately using the steady state IR thermography technique. The discharge coefficients are also acquired to evaluate the aerodynamic performance of different hole configurations. The results show that the film cooling holes with both ends embedded in slots can provide higher film cooling effectiveness and lower heat transfer coefficients; it also can provide higher discharge coefficients whilst retaining the mechanical strength of a row of discrete holes. The cooling performance and the aerodynamic performance of the holes with both ends embedded in inclined slots are superior to the holes with only exit trenched. To a certain extent, the configuration of the upstream lip of the exit trench affects the cooling performance of the downstream of the trench. The filleting for the film hole inlet avail the improvement of the cooling effect, but not for the film hole outlet. Comparing film cooling with embedded holes to unembedded holes, the overall heat flux ratio shows that the film holes with both ends embedded in slots and filleting for the film hole inlet can produce the highest heat flux reduction.

Impact of Swirl Flow on the Penetration Behaviour and Cooling Performance of a Starter Cooling Film in Modern Lean Operating Combustion Chambers

2014 ◽  
Author(s):  
B. Wurm ◽  
A. Schulz ◽  
H.-J. Bauer ◽  
M. Gerendas
Keyword(s):  
Optical Measurement ◽  
Measurement Techniques ◽  
Swirl Flow ◽  
Main Flow ◽  
Heat Shield ◽  
Fuel Injector ◽  
Combustion Chambers ◽  
Cooling Performance ◽  
The Impact ◽  
Penetration Behaviour

An experimental and numerical study is presented that deals with the impact of the swirled hot gas main flow on the penetration behaviour and cooling performance of a starter cooling film. Within modern combustion chambers designed for lean combustion the whole fuel/air mixing process is done by the fuel injectors without any additional mixing ports. Typically swirl stabilization is used within this kind of combustion chambers. The swirl flow interacts in a particular way with near wall cooling flows like starter cooling films which assure a proper wall cooling near the fuel injector. Experiments without combustion show the impact of the swirled main flow on the stability of the starter cooling film. Thermal analyses reveal a reduced cooling performance of the starter film near the stagnation area of the swirl flow. Laser optical measurement techniques reveal a significant reduced penetration of the starter cooling film close to the stagnation area. Numerical simulations show the reason for the reduced starter film performance in areas which cannot be accessed by optical measurement techniques. Based on experimental and numerical data different adaptive hole geometries where tested in combination with heat shield ribs in order to improve the starter film cooling performance. Results show that the combined application of heat shield ribs and adaptive cooling holes stabilize the starter cooling film and lead to a homogenous cooling performance.

Film Cooling Effectiveness and Mass/Heat Transfer Coefficient Downstream of One Row of Discrete Holes

1999 ◽  
Vol 121 (2) ◽  
pp. 225-232 ◽  
Author(s):  
R. J. Goldstein ◽  
P. Jin ◽  
R. L. Olson
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness

A special naphthalene sublimation technique is used to study the film cooling performance downstream of one row of holes of 35 deg inclination angle with 3d hole spacing and relatively small hole length to diameter ratio (L/d = 6.3). Both film cooling effectiveness and mass/heat transfer coefficient are determined for blowing rates from 0.5 to 2.0 with density ratio of 1.0. The mass transfer coefficient is measured using pure air film injection, while the film cooling effectiveness is derived from comparison of mass transfer coefficients obtained following injection of naphthalene-vapor-saturated air with those from pure air injection. This technique enables one to obtain detailed local information on film cooling performance. The laterally averaged and local film cooling effectiveness agree with previous experiments. The difference between mass/heat transfer coefficients and previous heat transfer results indicates that conduction error may play an important role in the earlier heat transfer measurements.

A Novel Method for Designing Fan-Shaped Holes With Short Length-to-Diameter Ratio in Producing High Film Cooling Performance for Thin-Wall Turbine Airfoil

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Weihong Li ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Film Cooling ◽  
Diameter Ratio ◽  
Short Length ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Shaped Hole ◽  
Length To Diameter Ratio

An experimental investigation of the geometrical parameter effects on the film cooling performance of a fan-shaped hole was conducted on a low speed flat-plate facility. The pressure sensitive paint (PSP) technique and steady liquid crystal (SLC) technique were employed to determine the adiabatic film cooling effectiveness and heat transfer coefficients, respectively, for a blowing ratio ranging from 0.3 to 3 and a density ratio of DR = 1.5. Several geometrical parameters were investigated, including lateral expansion angle, length-to-diameter ratio, and hole entrance shape. Local, laterally averaged, and area-averaged adiabatic film cooling effectiveness, heat transfer coefficients, and net heat flux reduction (NHFR) were shown to provide a comprehensive understanding on the geometrical parameter effects on the thermal performance. A novel method was proposed for designing a fan-shaped hole with short length-to-diameter ratio to design to achieve high film cooling performance. The original and optimized fan-shaped holes were compared in terms of adiabatic film cooling effectiveness, heat transfer coefficients, and NHFR. Results showed that the optimized fan-shaped hole with short length-to-diameter ratio, large lateral diffusion angle, and slot hole entrance shape obtained highest overall thermal performance. It demonstrated the feasibility of adopting the proposed design method to design fan-shaped holes applied in thin wall gas turbine blades.

Comparison the Cooling Performance of Cylindrical and Fan-Shaped Cooling Holes With Special Emphasis on the Effect of Internal Coolant Cross-Flow

2008 ◽  
Author(s):  
Christian Saumweber ◽  
Achmed Schulz
Keyword(s):  
Film Cooling ◽  
Symmetry Plane ◽  
Cross Flow ◽  
Transfer Coefficients ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Cooling Flow ◽  
Heat Transfer Coefficients ◽  
Expansion Angle ◽  
Cooling Hole

Cooling holes in real gas turbine applications are prevalently exposed to cross-flow in the coolant passage. The majority of the studies available in literature do not consider the effects of flow in the coolant passage. Our own studies however reveal that especially diffuser holes are very susceptible in respect to cross-flow at the hole entrance, if the orientation of the cross-flow is perpendicular to the symmetry plane of the cooling hole. The effect of coolant cross-flow will be discussed in detail. The superordinate target is to identify the dominating mechanisms, which determine the flow field within the diffuser hole and hence limit the potential of cooling performance augmentation. For this reason a fan-shaped hole with 14° expansion angle will be compared to a simple cylindrical hole. Both holes have a length-to-diameter ratio of 6 and an inclination angle of 30°. The comparison will be performed by means of experimentally gained discharge coefficients, local and laterally averaged adiabatic film cooling effectiveness, and heat transfer coefficients. Numerical simulations of the cooling flow will support the interpretation of the experimental results.

RELATIVE CASING MOTION EFFECT ON SQUEALER TIP COOLING PERFORMANCE AT TIGHT TIP CLEARANCE

2020 ◽  
pp. 1-18
Author(s):  
Diwei Zhu ◽  
Qiang Zhang ◽  
Shaopeng Lu ◽  
Jinfang Teng
Keyword(s):  
Thermal Load ◽  
Tip Clearance ◽  
Cooling Efficiency ◽  
Suction Surface ◽  
Cooling Performance ◽  
High Thermal Load ◽  
Blade Tip ◽  
Motion Effect ◽  
Cfd Method ◽  
The Impact

Abstract The effect of relative motion between the casing and turbine blade tip has been recognized as an important factor for tip aerothermal performance evaluation. Tight tip clearance is becoming one of the main objectives of engine manufacturers. This paper provides some insights on the topic that the impact of casing motion on the blade tip thermal performance could be different between nominal and tight tip clearances. A typical squealer tip geometry was employed, with coolant holes on the cavity floor near the pressure side rim. Three tip clearances, 1.1%, 0.6% and 0.2% of the span, are compared. The CFD method was validated against experimental data in the previous study. The results suggest that, in the tight tip situation, the effect of casing motion on cooling efficiency and flow structure is distinguished from the larger clearance situations. The scraping effect drives the leakage flow towards the blade suction surface, inducing high thermal load at tight clearance. The findings in this study highlight the importance of relative casing motion, especially at tight clearance.

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