scholarly journals Percussion Drilling of Deep Holes Using Picosecond Ultrashort Pulse Laser in Ni-Based Superalloy Coated with Ceramic Thermal Barrier Coatings

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3570
Author(s):  
Haodong Liu ◽  
Wanqin Zhao ◽  
Lingzhi Wang ◽  
Xiaowei Shen ◽  
Ning Wang ◽  
...  
Keyword(s):  
Thermal Barrier Coatings ◽  
Pulse Laser ◽  
Ultrashort Pulse ◽  
Film Cooling ◽  
Morphological Characteristics ◽  
Side Wall ◽  
Thermal Barrier ◽  
Ultrashort Pulse Laser ◽  
Barrier Coatings ◽  
Percussion Drilling

Ni-based superalloy with ceramic thermal barrier coatings (TBCs) is a composite material, which can be used in special environments with high temperature and high pressure such as aeroengine blade. In order to improve the cooling effect of the aeroengine, it is necessary to perform multi-size and large-area holes processing on the surface of blades. As a non-contact processing method with fast processing speed, good processing quality and almost no deformation, laser processing has been one of the important processing methods for film cooling hole processing of aeroengine blades. Percussion drilling is presented using picosecond ultrashort pulse laser in order to explore processing of deep holes in Ni-based superalloy, ceramic TBCs, and ceramic TBCs/substrate multilayer material. The effects of pulses, threshold and wavelength on hole diameter have been discussed, and the experiment on the deep hole ablation with 1064 nm wavelength has been performed. By analyzing the hole size and morphological characteristics of multiple processing parameters, the variation of hole cylindricity is obtained. A high-quality hole, without spatters around the periphery of hole entrance and without recast layer on the side-wall surface, in Ni-based superalloy coated with ceramic TBCs has been drilled. This research has potential applications to blade film cooling holes.

Percussion drilling on nickel-based alloy with thermal barrier coatings using femtosecond laser

Optik ◽  
2019 ◽  
Vol 194 ◽  
pp. 163066 ◽  
Author(s):  
Zhaoyang Zhai ◽  
Wenjun Wang ◽  
Xuesong Mei ◽  
Ming Li ◽  
Xun Li
Keyword(s):  
Femtosecond Laser ◽  
Thermal Barrier Coatings ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Nickel Based Alloy ◽  
Percussion Drilling

Conjugate heat transfer modeling of a turbine vane endwall with thermal barrier coatings

2019 ◽  
Vol 123 (1270) ◽  
pp. 1959-1981 ◽  
Author(s):  
Xing Yang ◽  
Zhenping Feng ◽  
Terrence W. Simon
Keyword(s):  
Heat Transfer ◽  
Thermal Barrier Coatings ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Thermal Protection ◽  
Design Stage ◽  
Thermal Barrier ◽  
Cooling Effectiveness ◽  
Barrier Coatings ◽  
Turbine Vane

ABSTRACTAdvanced cooling techniques involving internal enhanced heat transfer and external film cooling and thermal barrier coatings (TBCs) are employed for gas turbine hot components to reduce metal temperatures and to extend their lifetime. A deeper understanding of the interaction mechanism of these thermal protection methods and the conjugate thermal behaviours of the turbine parts provides valuable guideline for the design stage. In this study, a conjugate heat transfer model of a turbine vane endwall with internal impingement and external film cooling is constructed to document the effects of TBCs on the overall cooling effectiveness using numerical simulations. Experiments on the same model with no TBCs are performed to validate the computational methods. Round and crater holes due to the inclusion of TBCs are investigated as well to address how film-cooling configurations affect the aero-thermal performance of the endwall. Results show that the TBCs have a profound effect in reducing the endwall metal temperatures for both cases. The TBC thermal protection for the endwall is shown to be more significant than the effect of increasing coolant mass flow rate. Although the crater holes have better film cooling performance than the traditional round holes, a slight decrement of overall cooling effectiveness is found for the crater configuration due to more endwall metal surfaces directly exposed to external mainstream flows. Energy loss coefficients at the vane passage exit show a relevant negative impact of adding TBCs on the cascade aerodynamic performance, particularly for the round hole case.

Blockage Effects From Simulated Thermal Barrier Coatings for Cylindrical and Shaped Cooling Holes

2014 ◽  
Author(s):  
Christopher A. Whitfield ◽  
Robert P. Schroeder ◽  
Karen A. Thole ◽  
Scott D. Lewis
Keyword(s):  
Gas Turbine ◽  
Thermal Barrier Coatings ◽  
Film Cooling ◽  
Pressure Ratio ◽  
Flux Ratio ◽  
Thermal Barrier ◽  
Flow Area ◽  
Barrier Coatings ◽  
Combustion Gas ◽  
Cooling Hole

Film cooling and sprayed thermal barrier coatings (TBCs) protect gas turbine components from the hot combustion gas temperatures. As gas turbine designers pursue higher turbine inlet temperatures, film cooling and thermal barrier coatings are critical in protecting the durability of turbomachinery hardware. One obstacle to the synergy of these technologies is that TBC coatings can block cooling holes when applied to the components, causing a decrease in the film cooling flow area thereby reducing coolant flow for a given pressure ratio. In this study the effect of TBC blockages was simulated on film cooling holes for widely spaced cylindrical and shaped holes. At low blowing ratios for shaped holes the blockages were found to have very little effect on adiabatic effectiveness. At high blowing ratios, the area-averaged effectiveness of shaped and cylindrical holes decreased as much as 75% from blockage. The decrease in area-averaged effectiveness was found to scale best with the effective momentum flux ratio of the jet exiting the film cooling hole for the shaped holes.

scholarly journals Hole Formation Process in Ultrashort Pulse Laser Percussion Drilling

2013 ◽  
Vol 41 ◽  
pp. 431-440 ◽  
Author(s):  
S. Döring ◽  
T. Ullsperger ◽  
F. Heisler ◽  
S. Richter ◽  
A. Tünnermann ◽  
...  
Keyword(s):  
Pulse Laser ◽  
Formation Process ◽  
Ultrashort Pulse ◽  
Hole Formation ◽  
Ultrashort Pulse Laser ◽  
Laser Percussion Drilling ◽  
Percussion Drilling

Millisecond pulse laser machining of thermal barrier coatings

2020 ◽  
Vol 28 ◽  
pp. 107-117 ◽  
Author(s):  
Sundar Marimuthu ◽  
Bethan Smith ◽  
Aislinn Kiely ◽  
Yijun Liu
Keyword(s):  
Thermal Barrier Coatings ◽  
Pulse Laser ◽  
Laser Machining ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Millisecond Pulse

Blockage Effects From Simulated Thermal Barrier Coatings for Cylindrical and Shaped Cooling Holes

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Christopher A. Whitfield ◽  
Robert P. Schroeder ◽  
Karen A. Thole ◽  
Scott D. Lewis
Keyword(s):  
Gas Turbine ◽  
Thermal Barrier Coatings ◽  
Film Cooling ◽  
Pressure Ratio ◽  
Flux Ratio ◽  
Thermal Barrier ◽  
Flow Area ◽  
Barrier Coatings ◽  
Combustion Gas ◽  
Cooling Hole

Film cooling and sprayed thermal barrier coatings (TBCs) protect gas turbine components from the hot combustion gas temperatures. As gas turbine designers pursue higher turbine inlet temperatures, film cooling and TBCs are critical in protecting the durability of turbomachinery hardware. One obstacle to the synergy of these technologies is that TBC coatings can block cooling holes when applied to the components, causing a decrease in the film cooling flow area thereby reducing coolant flow for a given pressure ratio (PR). In this study, the effect of TBC blockages was simulated on film cooling holes for widely spaced cylindrical and shaped holes. At low blowing ratios for shaped holes, the blockages were found to have very little effect on adiabatic effectiveness. At high blowing ratios, the area-averaged effectiveness of shaped and cylindrical holes decreased as much as 75% from blockage. The decrease in area-averaged effectiveness was found to scale best with the effective momentum flux ratio of the jet exiting the film cooling hole for the shaped holes.

Finite Element Analysis of Thermal-Mechanical Behavior in the Thermal Barrier Coatings With Cooling Hole Structure

2017 ◽  
Author(s):  
Jishen Jiang ◽  
Zhenwei Cai ◽  
Weizhe Wang ◽  
Yingzheng Liu
Keyword(s):  
Mechanical Behavior ◽  
Thermal Barrier Coatings ◽  
Film Cooling ◽  
Operating Conditions ◽  
Thermal Barrier ◽  
Transfer Coefficients ◽  
Adiabatic Wall ◽  
Element Analysis ◽  
Barrier Coatings ◽  
Cooling Hole

The present work aims to investigate the thermal-mechanical behavior in thermal barrier coatings (TBCs) with a round film cooling hole under gas turbine operating conditions. The adiabatic wall temperatures and surface heat transfer coefficients are firstly calculated for thermal boundary conditions. Subsequently, stress analyses during both thermal exposure and cooling down period are presented. The results show that: although the cooling hole has lower temperature, large stress concentration still appears because of the geometry of cooling holes and thermal mismatch between TBCs and substrate. The huge thermal stress may lead to pre-mature failure of TBCs, which should be carefully considered in the design of film cooling-TBC system.

scholarly journals Effects of Thermal Barrier Coatings on Approaches to Turbine Blade Cooling

2006 ◽  
Author(s):  
R. J. Boyle
Keyword(s):  
Thermal Barrier Coatings ◽  
Film Cooling ◽  
Thermal Design ◽  
Thermal Barrier ◽  
Inlet Temperature ◽  
Internal Cooling ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Barrier Coatings ◽  
Component Efficiency

Reliance on Thermal Barrier Coatings (TBC) to reduce the amount of air used for turbine vane cooling is beneficial both from the standpoint of reduced NOx production, and as a means of improving cycle efficiency through improved component efficiency. It is shown that reducing vane cooling from 10% to 5% of mainstream air can lead to NOx reductions of nearly 25% while maintaining the same rotor, inlet temperature. An analysis is given which shows that, when a TBC is relied upon in the vane thermal design process, significantly less coolant is required using internal cooling alone compared to film cooling. This is especially true for small turbines where internal cooling without film cooling permits the surface boundary layer to remain laminar over a significant fraction of the vane surface.

An Experimental Study of Thermal Barrier Coatings and Film Cooling on an Internally Cooled Simulated Turbine Vane

2011 ◽  
Author(s):  
F. Todd Davidson ◽  
Jason E. Dees ◽  
David G. Bogard
Keyword(s):  
Thermal Barrier Coatings ◽  
Film Cooling ◽  
Thermal Protection ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Blowing Ratio ◽  
Turbine Vane ◽  
Internally Cooled ◽  
Detailed Assessment ◽  
Overall Effectiveness

This study investigated the interaction of thermal barrier coatings (TBC) and various film cooling configurations to provide a detailed assessment of the thermal protection on a first stage turbine vane. The internally cooled, scaled-up turbine vane used for this study was designed to properly model the conjugate heat transfer effects found in a real engine. The TBC material was selected to properly scale the thicknesses and thermal conductivities of the model to those of the engine. External surface temperatures, TBC-vane interface temperatures and internal temperatures were all measured over a range of internal coolant Reynolds numbers and mainstream turbulence intensities. The blowing ratio of the various film-cooling designs was also varied. The addition of TBC on the vane surface was found to increase the overall effectiveness of the vane surface just downstream of the coolant holes by up to 0.25 when no film cooling was present. The presence of the TBC significantly dampened the variations in overall effectiveness due to changes in blowing ratio which mitigated the detrimental effects of coolant jet separation. It was also discovered that with the presence of TBC standard round holes showed equivalent, if not better, performance when compared to round holes embedded in a shallow transverse trench.

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