Simulation Method for Geartrain NVH Assessment and Optimization

Geartrain-related noise has become a more dominant noise concern mainly due to the increasing demand for high-pressure injection systems. Engine geartrain noise is mainly caused by torque fluctuations of the crankshaft and the injection system, both leading to tooth impacts between the gears of the geartrain. Gear impacts can generate dominant NVH problems due to the high frequency content of the gear impact forces, although their amplitudes are much lower than those of the combustion forces. If the natural frequencies of the surrounding structure are met, an intensive radiation of the surrounding structure is caused.

FEV has developed a simulation method for the analysis of geartrain dynamics aimed at identifying and optimizing potential noise sources. This simulation method is an essential tool for the development process of a technical product. It realizes a minimum effort to set up the model at reduced calculation time. Since the method is based on a combination of Finite Element analysis (FEA) and Multi-Body System Analysis (MBA), two simulation models need to be constructed. The FEA model is used to investigate the vibration behavior of the geartrain and its individual components, whereas the MBA model simulates the dynamics of the geartrain.

The article summarizes the experience gathered in several projects with modern diesel engines. The applied simulation method will be described; assessment techniques and their results will be explained.