DEVELOPING A MODEL TO DETERMINE THERMAL BOUNDARY CONDITIONS ON PISTON-CYLINDER OF 4-STROKE DIRECT-INJECTION DIESEL ENGINES

Nowadays, thermal boundary conditions on piston-cylinder surfaces can be determined experimentally or based on the synthesis of experience from previous studies. However, the experimental method is too complicated, the remaining method has low reliability and does not ensure energy balance in the piston-cylinder group. Therefore, the author proposes a model combining thermal cycle calculation software, the thermal boundary condition calculation module "BCOPC" designed by the author and FEM simulation software to determine equivalent thermal boundary conditions on piston-cylinder surfaces. The model uses algorithms to model the relative motion between the details in the piston-cylinder group and establishes an uninterrupted heat transfer relationship between the working medium - piston - piston ring - cylinder - coolant. The model is applied to calculate the thermal boundary conditions on the piston-cylinder surfaces of Paxman185, D80, 4Ch9.5/11 engines. The energy balance results in the piston-cylinder group with the largest relative deviation of 3.9% when calculating for the Paxman185 engine. Thus, the model can be used to determine the thermal boundary conditions on the piston-cylinder surfaces of 4-stroke direct-injection diesel engines.