基于多重分形的离心压缩机出口动态压力非线性特征研究及其在喘振识别中的应用

以800 kW离心压缩机系统的工作状态从平稳到喘振阶段的出口动态压力为分析对象,从多重分形角度研究了多重分形谱参数与出口动态压力之间的关系,着重研究了系统在喘振状态表现出的复杂非线性特征。通过控制系统出口防喘振阀的开度得到离心压缩机在不同工况下的出口动态压力。研究系统出口动态压力的结构函数在不同权重因子下的尺度特征和多重分形谱参数与离心压缩机出口动态压力的关系。研究结果显示,系统稳态时,动态压力结构函数的曲线线性特征较为明显,而随着系统从过渡状态进入喘振时,表现出明显的非线性和多重分形特征。从多重分形谱的形状可以看出,当离心压缩机在稳态时,多重分形谱的宽度Δα最小,接近于零。随着系统进入喘振状态,宽度明显增加,而且在过渡过程时Δα的变化量较大,系统的不稳定性增加。从出口动态压力的多重分形谱参数的变化可以看出,多重分形谱参数在离心压缩机的过渡状态均出现了突变特征,参数Δα、αmax和Δf(α)随着系统从稳态进入失稳时增大,但参数αmin和f(αmax)则反方向变化,并且参数Δα、αmin、αmax的突变最为明显,这些特征可以作为系统进入过渡过程的判断依据。参数Δα、αmin、αmax在喘振时的波动量远大于稳态时的波动量,表明在喘振时动态压力的分布不如稳态时均匀。参数f(αmin)在喘振初期出现了短暂的峰值平台,说明此阶段的动态压力峰值出现的概率最大,而且Δf(α)的峰值也出现在喘振初期,这一特征可以用于初始喘振预测。研究结果能够为离心压缩机初始喘振的识别和预测提供新的依据,并可进一步用于压缩机喘振的主动控制中。

Nonlinear characteristics of centrifugal compressor outlet dynamic pressure based on multifractal and their application in surge identification

Taking the outlet dynamic pressure of a 800 kW centrifugal compressor system from steady state to surge stage as the analysis object,the relationship between multifractal spectrum parameters and outlet dynamic pressure was studied from the perspective of multifractal.The complex nonlinear characteristics of the system in surge state were emphatically studied.Firstly,the outlet dynamic pressure of centrifugal compressor was obtained by controlling the opening of anti-surge valve at the outlet of the system.Then,the scale characteristics of the structure function of the system outlet dynamic pressure under different weight factors were studied.Finally,the relationship between multifractal spectrum parameters and the outlet dynamic pressure of centrifugal compressor was studied.The study results showedthatlinear feature of dynamic pressure structure function is obvious in steady state,but obvious nonlinear and multifractal characteristics appear when the system enters surge from transition state;when the centrifugal compressor is in steady state,the width Δα of multifractal spectrum is the smallest and close to zero;as the system enters the surge state,the width Δα increases obviously,and the change of Δα is larger during the transition process,and the instability of the system increases;parameters of multifractal spectrum have mutation characteristics in the transition state of centrifugal compressor,parameters Δα,αmax and Δf(α)increase with the system from steady state to instability,but parametersαminand f(αmax)change in the opposite direction,and abrupt changes of parameters Δα,αmin and αmax are the most obvious,this feature can be used as the judging basis for the system to enter the transition process;the fluctuation of parameters Δα,αmin and αmax in surge is much larger than that in steady state,so the distribution of dynamic pressure in surge is less uniform than that in steady state;the short peak value platform of parameter f(αmin)appears in the initial stage of surge,so the probability of dynamic pressure peak appearing at this stage is the largest,and the peak value of Δf(α)also appears in the initial stage of surge,it can be used to predict initial surge;the study results can provide a new basis for recognizing and predicting initial surge of centrifugal compressor,and be further used in the active control of compressor surge.