四缸柴油机机体NVH性能改进

Study of NVH performance improvement for a four-cylinder diesel engine body

为降低发动机辐射噪声,采用数值计算方法对某四缸柴油机机体的振动声学性能进行分析与改进设计.以有限元理论为指导,划分发动机有限元模型,建立整机的多体动力学模型以及声学模型.通过多体动力学和流体力学计算发动机动力学载荷,通过结构动力学计算机体的振动响应,通过声学计算预测机体的表面辐射噪声,并实验验证计算结果.根据计算得到的机体振动与声学特性,确定影响机体(NVH)性能的关键频率,有针对性的对机体进行低噪声优化设计.在改进模型的基础上重新建立发动机多体动力学模型,计算改进后机体的振动与声学性能.结果表明,通过优化设计,机体的辐射声功率级降低0.9dBA.

Numerical methods were used to improve a four-cylinder engine body vibro-acoustic performance. Based on finite element theory, the engine body finite element model, multi-body dynamics model and acoustic model were established. Multi-body dynamics and fluid mechanics were used to calculate the engine dynamic load. Structural dynamics was used to calculate the engine body dynamic response. Acous- tic method was used to calculate the engine body acoustic performance. All the calculated results were vali- dated by experiments. Based on those results, the critical frequency of engine body was found. Hence, the engine body was redesigned to avoid resonance. After improvement, the NVH performance of engine body was recalculated. The results showed that, the radiated sound power level was reduced 0. 9 dBA through optimized design.