Modelling on structural integrity of ceramic coated piston crown for a compressed natural gas direct injection engine

摘要

High temperature and pressure produced in an engine of compressed natural gas with a direct injection (CNGDI) system may lead to high thermal stresses. By insulating the piston crown using a thermal barrier coating (TBC) such as ceramic-based yttria partially stabilised zirconia (YPSZ), the heat transfer of the piston might be reduced and lead to an improvement of piston durability. Hence, in this research, YPSZ coating was utilised to compare the uncoated with the conventional tin-coated piston. A detailed finite element analysis (FEA) was carried out to determine the location of stress localisation via stress distribution profiles. In short, it was observed that stresses were concentrated mainly at the piston crown area, particularly above the pin holes and the edge of the exhaust valve clearance. It was noted that the YPSZ/NiCrAl-coated piston crown exhibited uniform stress distribution compared to the uncoated one.