NOVEL THERMAL BARRIER COATINGS FOR GASOLINE SPARK IGNITION ENGINES

Currently spark ignition (SI) engines dominate the light vehicle market, and over 80 million light vehicle engines are made worldwide. However, such SI engines experience exceptionally poor efficiency at low to medium loads and speeds, and this makes it difficult to meet new fuel efficiency standards expected to be imposed in many locations around the world. Furthermore, the insufficient wall temperatures during the tail of the combustion process in the internal combustion (IC) engines will lead to emissions of unburned hydrocarbons (UBHC),and carbon monoxide (CO) in the engine exhaust, raising environmental concerns. Therefore, there is a significant push by vehicle original equipment manufacturers to find effective solutions to improved IC engine efficiency while simultaneously reducing emissions. One way to address the economic and environmental challenge of SI engines is to adopt thermal barrier coatings (TBCs). With the application of TBCs, the heat loss to the piston and the cylinder head firedeck can be substantially reduced, leading to higher temperatures in the combustion chamber, which will increase the thermal efficiency of the engine work cycle. The increased coating surface temperatures will also improve the chances for oxidation of the charge emanating from the top-land crevices, thereby reducing emission of UBHC and ,CO. The hotter exhaust also aid NOx reduction after treatment. In prior collaborative work, the SST/CUICAR team has demonstrated up to 3% increase in thermodynamic efficiency in homogeneous charge compression ignition (HCCI) engines using a yttria-stabilized zirconia TBC deposited by the unique Solution Precursor Plasma Spray (SPPS) process. In this project, the SST/CUICAR team is proposing to use the learned knowledge to develop a new SPPS TBC suitable for SI engines, with the goal of further improving engine efficiency and mitigating exhaust gas emissions. The SST/CUICAR team will select a promising TBC candidate material based on the properties required specifically in the SI engines. The unique solution precursor plasma spray (SPPS) process, the core technology of SST, will be utilized and extensively optimized to deposit a thin, smooth and durable TBC on piston crowns, based on iterations on low cost motorcycle engines tests. The CUICAR team will simultaneously set up a 4-cylinder engine test cell, and firstly run uncoated pistons to gather baseline data. Later, with the coated pistons provided by SST, the CUICAR team will perform the same tests using the same conditions in the RPM- load space to demonstrate improved engine efficiency and reduced exhaust emissions.SI engines dominate the 230-million unit internal combustion engine market worldwide, and the projected engine efficiency achieved by this SPPS TBC technology will bring significant economic benefits to US consumers, US manufacturers and positive environmental impact. The technological advantage of more efficient IC engines also strengthens the competitiveness of US engine manufacturers in the global market, which will result in new high-paying domestic jobs.