离心风机系统节能改造效益测算的数学模型

结合离心一次风机的调节原理,采用线性简化的方法,建立离心风机系统节能改造效益测算的数学模型,并采用该模型对某电厂一次风机改造前的试验数据进行分析。经理论和数据分析可知,变频改造前,低负荷下的风量与负荷近似成线性关系,低负荷下的电机功率又与风量近似成线性关系,而变频改造后,低负荷下的功率与风量成三次方关系,故变频改造具有较大的节能效益。利用数学模型进一步推导出了风机变频运行时旋转暖风器的节能公式,公式表明:在不同负荷下,旋转式暖风器的节电能力与风量成三次方关系;由定性分析可知,风机工频运行时旋转暖风器的节能效果比变频运行时差。基于该模型测算,某机组一次风机变频改造收益103.4万/年,投资回收期为2.46年;旋转暖风器比固定式暖风器多收益1.092万/年,增量投资回收期为2.755年。对离心一次风机系统节能改造建立的数学模型可供离心泵类、送风机等灵活性改造参考。

Mathematical Model of Benefits Calculation of Energy-saving Retrofitting for Centrifugal Fan System

Abstract:Based on regulating principle of primary centrifugal fan,mathematical model of benefits calculation of energy-saving retrofitting for centrifugal fan system is established using linear simplification.The fan performance test data of a power plant before retrofitting is analyzed by using this model.The analysis indicates that before frequency conversion retrofitting,the air flux at low load is approximately linear with respect to the load ,and the motor power input is also nearly linear with respect to the air flux.After frequency conversion retrofitting,the relationship between motor power input and air flux,however,becomes non-linear (third-order).Using frequency conversion technology,then a large energy-saving benefits are determined.The energy-saving formula is further deduced for the rotary air-heater under variable frequency operation .The formula shows that the power saving capability of rotary air-heater and the air flux are third-order related.Qualitative analysis shows that for application of rotary air-heater,energy-saving benefits under varying frequency operation is better than that under power frequency operation.Based on this mathematical model,it is estimated for a power plant that the profit of frequency conversion retrofitting of primary centrifugal fans is 1.034 million/year and the investement recovery period is 2.46 years.And the incremental profit of rotary air-heaters against fixed air-heaters is 10.92 thousand/year and the incremental investment recovery period is 2.755 years.The mathematical model based on primary centrifugal fan system retrofitting can be referenced for flexible retrofitting of centrifugal pump and secondary centrifugal fan system.