TY - GEN A1 - Somhorst, Joop A1 - Oevermann, Michael A1 - Bovo, Mirko A1 - Denbratt, Ingemar T1 - Evaluation of thermal barrier coatings and surface roughness in a single-cylinder light-duty diesel engine T2 - International Journal of Engine Research N2 - 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. KW - Engine KW - efficiency KW - emissions KW - Thermal barrier coating KW - TBC KW - surface roughness KW - MLR KW - regression KW - data model Y1 - 2019 U6 - https://doi.org/10.1177/1468087419875837 SN - 1468-0874 SN - 2041-3149 VL - 22(2021) SP - 890 EP - 910 ER - TY - GEN A1 - Somhorst, Joop A1 - Uczak De Goes, Wellington A1 - Oevermann, Michael A1 - Bovo, Mirko T1 - Experimental Evaluation of Novel Thermal Barrier Coatings in a Single Cylinder Light Duty Diesel Engine T2 - SAE Technical Papers N2 - The objective of this investigation was to improve the thermal properties of plasma sprayed thermal barrier coatings (TBC) for internal combustion engines. There is a need for further reduction of thermal conductivity and volumetric heat capacity and the negative effects on heat loss and combustion phasing of surface roughness and permeable porosity, typical for plasma sprayed coatings, should be minimized. Four measures for improvement of TBC properties were evaluated: i) modification of the coating's microstructure by using a novel suspension plasma spraying method, ii) application of gadolinium-zirconate, a novel ceramic material with low thermal conductivity, iii) polishing of the coating to achieve low surface roughness, and iv) sealing of the porous coating surface with a polysilazane. Six coating variants with different combinations of the selected measures were applied on the piston crown and evaluated in a single cylinder light duty diesel engine. The experimental data was modeled with multiple linear regression to obtain confidence intervals for the measurement results and to correct the data for variations of surface roughness, combustion phasing and compression ratio for the different pistons. The main tool for evaluation of the coating properties was cylinder pressure analysis, providing the apparent rate of heat release, indicated efficiency, wall heat loss, and exhaust loss. The new TBC microstructure from suspension plasma spraying in combination with the use of gadolinium-zirconate showed promising results with respect to indicated efficiency and heat loss reduction. Y1 - 2019 U6 - https://doi.org/10.4271/2019-24-0062 SN - 2688-3627 SN - 0148-7191 ER - TY - GEN A1 - Somhorst, Joop A1 - Oevermann, Michael A1 - Bovo, Mirko A1 - Denbratt, Ingemar T1 - A Method to Evaluate the Compression Ratio in IC Engines with Porous Thermal Barrier Coatings T2 - SAE Technical Papers N2 - The compression ratio is an important engine design parameter. It determines to a large extend engine properties like the achievable efficiency, the heat losses from the combustion chamber and the exhaust losses. The same properties are affected by insulation of the combustion chamber. It is therefore especially important to know the compression ratio when doing experiments with thermal barrier coatings (TBC). In case of porous TBCs, the standard methods to measure the compression ratio can give wrong results. When measuring the compression ratio by volume, using a liquid, it is uncertain if the liquid fills the total porous volume of the coating. And for a thermodynamic compression ratio estimation, a model for the heat losses is needed, which is not available when doing experiments with insulation. The subject of this paper is the evaluation of an alternative method to assess the compression ratio. It is based on motored cylinder pressure data like other thermodynamic methods but does not need a model for the heat losses. The validation and application of the method is done with data from experiments involving two types of porous TBCs, performed on a light duty single cylinder diesel engine. The results indicate that the proposed method accurately predicts the compression ratio for porous thermal barrier coatings. KW - Combustion chambers KW - Combustion and combustion processes KW - Coatings, colorants, and finishes KW - Insulation Y1 - 2018 U6 - https://doi.org/10.4271/2018-01-1778 SN - 2688-3627 SN - 0148-7191 ER -