Impact of a Yttria-Stabilized Zirconia Thermal Barrier Coating on HCCI Engine Combustion, Emissions, and Efficiency

Abstract

In-cylinder surface temperature has significant impacts on the thermo-kinetics governing the Homogeneous Charge Compression Ignition (HCCI) process. Thermal Barrier Coatings (TBCs) enable selective manipulation of combustion chamber surface temperature profiles throughout a fired cycle. In this way, TBCs enable a dynamic surface temperature swing, which prevents charge heating during intake while minimizing heat rejection during combustion. This preserves volumetric efficiency while fostering more complete combustion and reducing emissions. This study investigates the effect of a Yttria-Stabilized Zirconia (YSZ) coating on Low Temperature Combustion (LTC) engine combustion, efficiency, and emissions. This is an initial step in a systematic effort to engineer coatings best suited for LTC concepts. A YSZ coating was applied to the top of the aluminum piston using a powder Air Plasma Spray process, Final thickness of the coatings was approximately 150 microns. The coated piston was subsequently evaluated in the single-cylinder HCCI engine with exhaust re-induction. Engine tests indicated significant advancement of the autoignition point and reduced combustion durations with the YSZ coating. Hydrocarbon and carbon monoxide emissions were reduced, thereby increasing combustion efficiency. The combination of higher combustion efficiency and decreased heat loss during combustion produced tangible improvements in thermal efficiency. When the effects of combustion advance were removed, the overall improvements in emissions and efficiency were lower, but still significant. Overall, the results encourage continued efforts to devise novel coatings for LTC.

Experimental investigation of the relationship between thermal barrier coating structured porosity and homogeneous charge compression ignition engine combustion

“…The former is the result of faster reactions in the wall-affected zone and the latter is the result of reduced heat losses close to top dead center (TDC) that lead to increased peak-pressure and expansion work. This hypothesis has already been proven in a previous study, 13 which focused on the impact of a dense yttria-stabilized zirconia (YSZ) coating on an HCCI engine.…”

“…Recent studies utilizing an APS YSZ TBC within an LTC engine found modest reductions in emissions and increases in both combustion and thermal efficiency. 13 The ability to structure coating porosity into IPBs within TBCs enables a reduction of thermal conductivity, possibly leading to further emissions and thermal efficiency improvements. The overarching goal of this investigation is to set up a systematic experimental study utilizing three different YSZ coatings with IPBs, or structured porosity (YSZ-SP), and generate firm guidance regarding the preferred features of YSZ-SP coatings for HCCI applications.…”

“…The total residual mass is predicted using the state estimation method. 13,29 Measurements of exhaust pressure are obtained with a cooled Kistler 4045A pressure sensor in the exhaust runner. Air-tofuel ratio is determined using an ETAS ES630.1 lambda module with a Bosch LSU 4.9 wideband lambda sensor.…”

“…Surface temperature characteristics for uncoated metal combustion chamber walls, traditional thick coatings and thin ''temperature swing'' coatings. 13 there is a chemical reaction in the plasma jet, while APS sprays simply melt the injected ceramic powder. An advantage of the SPPS process is that it creates smaller splat sizes, enabling the creation of smaller, homogeneously distributed porosity.…”

Experimental Investigation of Thermal Barrier (8YSZ-MGO-TIO2) Coated Piston used in Diesel Engine

“…Banka et al (2017) based on his thermal analysis with creating different sizes of hole on yttria-stabilized zirconia thermal coated piston surfaces, predicted that the highest temperature distribution occurred in the maximum size of hole present in the coated piston crown. Powell et al (2017) investigated the effect of low temperature combustion engine performance and emission characteristics with coated yttria-stabilized zirconia piston. Thirunavukkarasu et al (2016) reported that the effect of MgO-ZrO2 and Al2O3-13%TiO2 thermal barrier coating on the piston crown with using methanol as a blend fuel in an engine.…”