渔船主机尾气余热制冷发生器围壁破裂分析及对策

Analysis and countermeasure on broken enclosure bulkhead of main engine exhaust residual heat refrigeration generator of fishing vessel

为了达到节能环保的目的,在渔船上安装主机尾气余热制冷装置,实现主机排出的废气再利用。在运行过程中制冷设备的发生器围壁容易产生裂纹,需要分析该裂纹产生的原因并给出解决方法。应用CFD流体分析软件对进入发生器的烟气速度和压力进行分析,结果显示烟气速度和压力对围壁几乎没有影响。然后,进行了发生器结构的固有模态分析,通过增加围壁厚度的方法改变结构形式,从而改变该结构的固有频率,直至该结构频段与原结构频段无重叠部分。由于该厚度避开了会产生共振的频率范围,选用新的围壁厚度为3mm不锈钢板替换原来1.5mm不锈钢板制作设备的新围壁。在设备结构设计时,特别是小载荷流体运动的结构,应分析结构固有频率,避免其与流体运动产生激励频率重叠,导致发生共振,对结构造成破坏。

In order to achieve the goal of energy conservation and environmental protection,the main engine exhaust residual heat refrigeration unit was installed on the fishing vessel for reuse of the exhaust from the main engine.During the operation,cracks occurred in the generator enclosure bulkhead of the refrigeration equipment.It is necessary to analyze the cause of the cracks and give the solution.CFD fluid analysis software was used to analyze the smoke velocity and pressure of the generator.The results showed that the smoke velocity and pressure had little effect on the enclosure bulkhead.Then the inherent modal of the generator structure was analyzed,and the structure form was changed by increasing the thickness of the enclosure bulkhead,so as to change the natural frequency of the structure until there is no overlap between the structural frequency band and the original structural frequency band.Since the thickness avoids the frequency range that causes resonance,a new stainless steel plate with enclosure bulkhead thickness of 3 mm is selected to replace the original one of 1.5 mm for making a new enclosure bulkhead for the equipment.In the design of equipment structure,especially the structure of small load fluid motion,the natural frequency of the structure should be analyzed to avoid its overlap with excitation frequency of the fluid motion,causing resonance and damage to the structure.