A high compression ratio is an effective means for improving the thermal efficiency of an internal combustion engines. However, a high compression ratio leads to a rapid rise in the combustion pressure, as it causes a high impulse force. The impulse force generates vibrations and noise by spreading in the engine. Therefore, reducing the vibration of the combustion (which increases as the compression ratio increases) can improve the thermal efficiency while using the same technology.
We are conducting model-based research on technologies for reducing combustion vibration by applying a granular damper to a piston. To efficiently reduce the vibration, we suppress it directly with the piston, i.e., the source of the vibration. Thus, the damping effect is maximized within a minimized countermeasure range. The damping system is a piston equipped with an additively manufactured particle damper (AMPD), with porous voids (lattice structure) and can be manufactured using methods such as laser beam powder bed fusion (LPBF). For the installation of the AMPD, we propose an optimal design structure that enhances productivity and is able to achieve the same or better effect even if the other damping materials are reduced.
In this paper, we describe the design method for the vibration damping lattice piston and construction of a prediction method using the discretized element method for vibration damping by the AMPD. The pistons are manufactured using LPBF or casting. In addition, we consider the results of regarding the vibration and noise characteristics when changing the type of particles the AMPD.