scholarly journals Evaluation of thermal barrier coatings and surface roughness in a single-cylinder light-duty diesel engine

2019 ◽  
pp. 146808741987583 ◽  
Author(s):  
Joop Somhorst ◽  
Michael Oevermann ◽  
Mirko Bovo ◽  
Ingemar Denbratt
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Diesel Engine ◽  
Thermal Barrier Coatings ◽  
Heat Losses ◽  
Operating Conditions ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Single Cylinder ◽  
Light Duty

The effect of two thermal barrier coatings and their surface roughness on heat transfer, combustion, and emissions has been investigated in a single-cylinder light-duty diesel engine. The evaluated thermal barrier coating materials were plasma-sprayed yttria-stabilized zirconia and hard anodized aluminum, which were applied on the piston top surface. The main tool for the investigation was cylinder pressure analysis of the high-pressure cycle, from which the apparent rate of heat release, indicated efficiency, and heat losses were derived. For verification of the calculated wall heat transfer, the heat flow to the piston cooling oil was measured as well. Application of thermal barrier coatings can influence engine operating conditions like charge temperature and ignition delay. Therefore, extra attention was paid to choosing stable and repeatable engine operating points. The experimental data were modeled using multiple linear regression to isolate the effects of the coatings and of the surface roughness. The results from this study show that high surface roughness leads to increased wall heat losses and a delayed combustion. However, these effects are less pronounced at lower engine loads and in the presence of soot deposits. Both thermal barrier coatings show a reduction of cycle-averaged wall heat losses, but no improvement in indicated efficiency. The surface roughness and thermal barrier coatings had a significant impact on the hydrocarbon emissions, especially for low-load engine operation, while their effect on the other exhaust emissions was relatively small.

Microstructure and Heat Transfer Phenomena in Ceramic Thermal Barrier Coatings

2001 ◽  
Vol 84 (4) ◽  
pp. 827-835 ◽  
Author(s):  
Paolo Scardi ◽  
Matteo Leoni ◽  
Federico Cernuschi ◽  
Angelamaria Figari
Keyword(s):  
Heat Transfer ◽  
Thermal Barrier Coatings ◽  
Thermal Barrier ◽  
Barrier Coatings

High Temperature Radiation Heat Transfer Performance of Thermal Barrier Coatings With Multiple Layered Structures

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Xiao Huang
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Thermal Barrier Coatings ◽  
Wavelength Range ◽  
Coating Thickness ◽  
Single Layer ◽  
Layered Structures ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Layered Coating

Meeting the demands for ever increasing operating temperatures in gas turbines requires concurrent development in cooling technologies, new generations of superalloys, and thermal barrier coatings (TBCs) with increased insulation capability. In the case of the latter, considerable research continues to focus on new coating material compositions, the alloying/doping of existing yttria stabilized zirconia ceramics, and the development of improved coating microstructures. The advent of the electron beam physical vapor deposition coating process has made it possible to consider the creation of multiple layered coating structures to meet specific performance requirements. In this paper, the advantages of layered structures are first reviewed in terms of their functions in impeding thermal conduction (via phonons) and thermal radiation (via photons). Subsequently, the design and performance of new multiple layered coating structures based on multiple layered stacks will be detailed. Designed with the primary objective to reduce thermal radiation transport through TBC systems, the multiple layered structures consist of several highly reflective multiple layered stacks, with each stack used to reflect a targeted radiation wavelength range. Two ceramic materials with alternating high and low refractive indices are used in the stacks to provide multiple-beam interference. A broadband reflection of the required wavelength range is obtained using a sufficient number of stacks. In order to achieve an 80% reflectance to thermal radiation in the wavelength range 0.3–5.3μm, 12 stacks, each containing 12 layers, are needed, resulting in a total thickness of 44.9μm. Using a one dimensional heat transfer model, the steady state heat transfer through the multiple layered TBC system is computed. Various coating configurations combining multiple layered stacks along with a single layer are evaluated in terms of the temperature profile in the TBC system. When compared with a base line single layered coating structure of the same thickness, it is estimated that the temperature on the metal surface can be reduced by as much as 90°C due to the use of multiple layered coating configurations. This reduction in metal surface temperature, however, diminishes with increasing the scattering coefficient of the coating and the total coating thickness. It is also apparent that using a multiple layered structure throughout the coating thickness may not offer the best thermal insulation; rather, placing multiple layered stacks on top of a single layer can provide a more efficient approach to reducing the heat transport of the TBC system.

High Temperature Radiation Heat Transfer Performance of Thermal Barrier Coatings With Multiple Layered Structures

2008 ◽  
Author(s):  
Xiao Huang
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Thermal Barrier Coatings ◽  
Wavelength Range ◽  
Coating Thickness ◽  
Single Layer ◽  
Layered Structures ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Layered Coating

Meeting the demands for ever increasing operating temperatures in gas turbines requires concurrent development in cooling technologies, new generations of superalloys, and thermal barrier coatings (TBCs) with increased insulation capability. In the case of the latter, considerable research continues to focus on new coating material compositions, alloying/doping existing yttria stabilized zirconia ceramics, and the development of improved coating microstructures. The advent of the EB-PVD coating process has made it possible to consider the creation of multiple layered coating structures to meet specific performance requirements. In this paper, the advantages of layered structures are first reviewed in terms of their functions in impeding thermal conduction (via phonons) and thermal radiation (via photons). Subsequently, the design and performance of new multiple layered coating structures based on multiple layered stacks will be detailed. Designed with the primary objective to reduce thermal radiation transport through TBC systems, the multiple layered structures consist of several highly reflective multiple layered stacks, with each stack used to reflect a targeted radiation wavelength range. Two ceramic materials with alternating high and low refractive indices are used in the stacks to provide multiple-beam interference. A broadband reflection of the required wavelength range is obtained using a sufficient number of stacks. In order to achieve 80% reflectance to thermal radiation in the wavelength range of 0.3 ∼ 5.3 μm, 12 stacks, each containing 12 layers, are needed, resulting in a total thickness of 44.9 μm. Using a one dimensional heat transfer model, steady state heat transfer through the multiple layered TBC system is computed. Various coating configurations combining multiple layered stacks along with a single layer are evaluated in terms of the temperature profile in the TBC system. When compared to a baseline single layered coating structure of the same thickness, it is estimated that the temperature on the metal surface can be reduced by as much as 90°C due to the use of multiple layered coating configurations. This reduction in metal surface temperature, however, diminishes with increasing scattering coefficient of the coating and total coating thickness. It is also apparent that using a multiple layered structure throughout the coating thickness may not offer the best thermal insulation; rather, placing multiple layered stacks on top of a single layer can provide a more efficient approach to reduce the heat transport of the TBC system.

Running-in behaviour of thermal barrier coatings in the combustion chamber of a diesel engine

2019 ◽  
Vol 234 (1) ◽  
pp. 172-182 ◽  
Author(s):  
Anders Thibblin ◽  
Siamak Kianzad ◽  
Stefan Jonsson ◽  
Ulf Olofsson
Keyword(s):  
Heat Flux ◽  
Diesel Engine ◽  
Thermal Barrier Coatings ◽  
Yttria Stabilized Zirconia ◽  
Thermal Barrier ◽  
Heavy Duty ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Heavy Duty Diesel

Thermal barrier coatings have the potential to improve the fuel efficiency of heavy-duty diesel engines by reducing heat losses. A method for in-situ measurement of heat flux from the combustion chamber of a heavy-duty diesel engine has been developed and was used to study the running-in behaviour of different thermal barrier coating materials and types of microstructures. The in-situ measurements show that the initial heat flux was reduced by up to 4.7% for all investigated thermal barrier coatings compared to a steel reference, except for an yttria-stabilized zirconia coating with sealed pores that had an increase of 12.0% in heat flux. Gd2Zr2O7 had the lowest initial value for heat flux. However, running-in shows the lowest values for yttria-stabilized zirconia after 2–3 h. Potential spallation problems were observed for Gd2Zr2O7 and La2Zr2O7.

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