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现有的水轮机空化在线监测系统大多信号频带窄、仅有单通道且无板上信号处理,造成系统的检测精度比较低且不利于空化空间定位和在线检测。文中提出一种空化在线监测系统,系统的分析频段从1Hz到500kHz,扩大了研究频段,便于提高空化检测的精度;系统具有8个通道,提高了检测的空间分辨力,系统板载 TI公司数字信号处理器的特点提高了空化信号处理能力并压缩了数据量。在水轮机空化模型试验中采用了该系统。研究发现,随着空化系数减小,加速度信号和声信号的均方根总体均逐渐增大。所以,加速度信号和声信号都可以用来检测空化,其中声信号检测更加可靠。同时,发现在空化初生附近,声信号中高频成分能量百分比达到一个很显著的极值,这对于空化初生检测是很有益的。
Existing turbine cavitation on-line monitoring system mostly narrow signal band, only a single channel and no onboard signal processing, resulting in the detection accuracy of the system is relatively low and is not conducive to cavitation space positioning and online testing. In this paper, a kind of on-line monitoring system for cavitation is proposed. The analysis frequency range of the system is from 1Hz to 500kHz, and the research frequency range is expanded to improve the accuracy of cavitation detection. The system has 8 channels to improve the spatial resolution of detection. The onboard TI The company’s digital signal processor features enhance the signal processing capabilities of cavitation and reduce the amount of data. The system was used in turbine cavitation model tests. The study found that, with the decrease of cavitation coefficient, the root mean square of acceleration signal and acoustic signal are gradually increased. Therefore, the acceleration signal and the sound signal can be used to detect cavitation, in which the sound signal detection is more reliable. At the same time, it is found that the energy percentage of high-frequency components of acoustic signals reaches a very significant extremum near cavitational primary, which is very useful for primary cavitation testing.