飞机典型结构件的声疲劳实验研究

飞机典型结构件为蒙皮、框和长桁组成的双向双加筋的九格壁板结构.利用高声强行波管系统,以典型试件中心格的第一阶频率为中心、1/3倍频程为带宽的窄带随机谱激励,再现壁板结构的声疲劳破坏方式.通过原始状态的典型试件的两次预试验,发现了原典型结构件的设计缺陷.采用三种方式对原结构框的两端进行了支持加强,得到各种支持状态下的声疲劳破坏形式.     

Electro-Flocculation Mechanism of Physical Water Treatment for the Mitigation of Mineral Fouling in Heat Exchangers

Abstract

The objective of the present study was to investigate the mechanism of a physical water treatment (PWT) technology used to mitigate mineral fouling in a heat exchanger. The PWT method tested utilized a solenoid coil to produce induced electric fields in a feed pipe prior to the heat exchanger. Fouling experiments were conducted using well water circulated through a laboratory cooling tower over 270 h with no blowdown, and fouling resistances were determined over time. Compared with the fouling resistance for the baseline case, those obtained with the PWT technology showed high efficacy for maintaining a low fouling resistance value. Samples of circulating well water were collected and analyzed using a laser particle counter over time. After 4 days of operation, the total number of particles was approximately 1 million per cc for the untreated case, whereas the case with PWT produced 3.5 million per cc. The present data on the particle counting provide empirical support for the bulk-precipitation hypothesis for the mechanism of PWT generally and electro-flocculation mechanism for solenoid coil techniques in particular.