FEM analysis of the opposed-piston aircraft engine block

Abstract

Abstract An important aspect of aircraft engine design is weight minimization. However, excessive weight reduction may reduce mechanical strength of the engine. This is especially important for aero-engines due to consequences of engine failure in flight. The article presents the results of the FEM opposed-piston diesel engine block model tests. The tested engine is a PZL-100 two-stroke three-cylinder aircraft engine with two crankshafts and six pistons. Air is supplied via a mechanical compressor and a turbocharger. Stress in the engine block is induced by the operating process of the engine block. The pressure in the combustion chamber of the analyzed engine is 13 MPa. The pistons in one of the cylinders are then near their TDC, the deflection angle of the connecting rods is small so almost the entire piston force is transferred to the crankshafts and then to the main bearing supports. This results in the occurence of a tensile force for the engine block applied in the bolt holes of the shaft supports. The calculation results are presented as stress and displacement distributions on the surface and selected block sections. The maximum values on the outer surfaces of the block occurred in the area of the compressor attached to the block and reached 39 MPa. Maximum stresses were, however, observed inside the block on the air and exhaust flow separators between the cylinder liners. The stress value on the outlet side reached 44 MPa.