摘要
采用多分辨分析方法研究了浆态床中压力脉动时序信号的定量特征,借以从这类信号中提取气泡运动参数——气含率.具体做法是:确定压力脉动信号功率谱图上的主频,同时通过小波变换将压力脉动信号分解成不同分辨率下的低频和高频信号,据此确定对应主频的小波主尺度,并对该尺度上的信号的间歇行为以局部间歇性值(localintermittencymeasure,LIM)定量表征;选取合适的阈值后,对LIM二值化可得床层中的局部气含率.与压降法测得的平均气含率值比较表明,根据LIM分析方法计算得到的气含率与压降法实测气含率相一致,这也表明反应器内气泡的发生是导致浆态床压力脉动的主要因素.本文提出的方法提供了一种适用于高温、高压场合下测取床层气含率的简便、实用方法.
In this work, a multi-resolution analysis method was used to quantitatively characterize the fluctuating pressure signals generated in a slurry bed, and thereby to evaluate the local gas hold-up values. The method was implemented by following three major steps. （1） by wavelet transform, the pressure signals were decomposed into different scales with different resolutions; （2） by FFT the prime frequency was determined from the power spectral density function （PSDF） diagram of the pressure fluctuation signals; （3） the major scale corresponding to the prime frequency was then used to reconstruct and map the denoised data of the original signals into a frame of local intermittency measure （LIM） at a dominant resolution. It was demonstrated that the intermittent passage of bubbles at a local position of the bed is related to changes in the LIM values. By choosing a proper threshold value for the LIM distribution, the gas hold-up was estimated at four radial locations and hence the area averaged gas hold- up was obtained. A comparison of the gas hold-up values obtained by means of the LIM analysis and the conventional bed could be pressure drop method showed good attributed to the bubble motions. agreement, This work indicating that the larger fluctuations in the presented a simple method for gas hold-up determination in slurry beds operated under high temperature and/or pressure conditions.
出处
《化工学报》
EI
CAS
CSCD
北大核心
2006年第9期2099-2104,共6页
CIESC Journal
基金
国家重点基础研究发展计划项目(2004CB217604).~~
关键词
多分辨分析
小波变换
浆态床
气含率
multi-resolution analysis
wavelet transform
slurry bed
gas hold-up
