Analysis of vibration transmission characteristics in lightweight auxiliary equipment isolation system

Modern permanent magnet marine auxiliary equipment is lighter and more compact with equal power output. Traditional vibration assessment indices cannot accurately evaluate its vibration performance. This paper presents a targeted vibration transmission analysis method, laying a theoretical framework for vibration evaluation of lightweight marine equipment.

To achieve this objective, a multi-step research framework was adopted. First, the power machinery and its vibration isolator were simplified into a single-degree-of-freedom (SDOF) system mounted on an elastic foundation. The equivalent parameters of the mass-spring-damper model were determined based on the equipment's mass characteristics and the impedance properties of the isolator. Under the conditions of constant installation frequency and unchanged input impedance of the elastic foundation, the system's dynamic equations were formulated to reveal the underlying mechanism governing the relationship between equipment mass and vibration transmission characteristics. Second, power flow analysis was employed as the primary metric for evaluating vibration energy transmission. Mathematical derivations were performed to establish the quantitative relationships between the equipment mass and both the foot vibration acceleration level and the vibration power flow transmitted to the base. Furthermore, numerical simulations and case validations were conducted using two types of base structures with different impedance characteristics: a simply supported rectangular plate (1 m × 1 m × 2 mm) and a typical marine bench base (with specific dimensions, such as a top plate area of 0.62 m × 0.43 m). Finite element analysis (FEA) was performed to compute the input velocity impedance and output power within the frequency range of 10–1 000 Hz, thereby verifying the theoretical derivations. Finally, a bench test was conducted using an IRG 32-125 centrifugal pump, to which additional masses were added to create three configurations with different masses (41.5, 71.5, 111.5 kg), each paired with BE-series vibration isolators. Acceleration sensors and force hammer excitation were used to collect vibration data, and the power flow was calculated using the four-pole parameter method to validate the theoretical and simulation results.

The results consistently demonstrated several key patterns. Under the conditions of constant installation frequency and base impedance, a reduction in equipment mass led to an increase in the foot vibration acceleration level while enhancing the overall vibration isolation performance. Specifically, at the first-order resonance frequency, the peak active power flow transmitted to the base increased with decreasing mass – showing gains of 5.97 and 20 dB corresponding to 50% and 90% mass reductions, respectively. Similarly, the foot vibration acceleration showed a significant upward trend: it increased by 1.97 times for a 50% mass reduction and by 9.98 times for a 90% reduction. Meanwhile, the acceleration level drop (i.e., the difference between the foot acceleration level and the base acceleration level) also increased with decreasing mass, indicating improved vibration isolation performance. The bench test results aligned with the theoretical and simulation outcomes. For the three mass configurations, the foot acceleration levels were 163.07, 153.36, and 144.63 dB respectively, while the corresponding acceleration level drops were 43.36, 30.75, and 25.30 dB. These findings confirmed the trend of improved isolation performance with reduced mass. Additionally, the power flow at the lower end of the vibration isolator increased as the equipment mass decreased, further validating the theoretical relationship between equipment mass and vibration energy transmission proposed in this study.

This study explores vibration transmission of lightweight auxiliary equipment with fixed installation frequency and base impedance. Equipment mass is key to the peak power flow at the base’s first natural frequency, showing an inverse correlation: lower mass brings markedly higher peak power flow. Although reduced mass increases foot vibration acceleration, it enhances vibration isolation with larger acceleration attenuation. Compared with the traditional foot acceleration level, power flow based on energy transmission is a more rational index to evaluate the acoustic performance of lightweight permanent magnet auxiliary equipment. In engineering, the acceleration criteria can be properly relaxed, and power flow evaluation helps maximize the benefits of lightweight design. This work offers theoretical support for vibration isolation design and performance assessment, advancing the application of such equipment in vehicles.