管道泵作透平飞逸过渡过程内流特性分析

Analysis of internal flow characteristics during runaway transition of inline pump turbine as turbine

相比与常规离心泵作透平,管道泵作透平时,尾水管采用了特殊的肘型弯管结构,使得内部流动产生畸变流。尤其在发生飞逸过渡过程时,因转速从额定转速迅速增大至飞逸转速,将产生巨大的离心力,造成危险的飞逸工况。为探究管道泵作透平时飞逸过渡过程中内部流动特性,应用了Fortran语言对CFX进行二次开发,基于RANS方程和SST k-ω模型,利用开发后的CFX软件对管道泵作透平进行了飞逸过渡过程的数值模拟,预测了管道泵作透平飞逸过渡过程中的转速、流量和扭矩变化。并结合涡量分布和Q准则方法,对管道泵作透平飞逸过度过程旋涡分布进行了研究。研究结果表明:具有特殊结构管道泵在透平工况飞逸过渡过程中最终达到的飞逸转速Nfea并不是固定不变的,而是在平均飞逸转速线上下波动,其中平均飞逸转速值Nave=3584 rev/min,为额定工况的1.23倍;流量Q先增大,后减小在Q_(ave)=14.7 kg/s上下波动;扭矩T一直下降至零,并在零线上下发生震荡;研究表明旋涡主要发生在工作面及尾缘部分。该研究揭示了管道泵作透平时飞逸过渡过程的内流特性,为管道泵的安全稳定运行提供了参考。

Compared with conventional centrifugal pump as turbine and the inline pump as turbine,the draft tube adopts special elbow pipe structure,which makes the internal flow produce distortion flow.Especially in the process of runaway transition,because the speed increases rapidly from rated speed to runaway speed,it will produce huge centrifugal force,which will cause dangerous runaway condition.In order to study the internal flow characteristics of the inline pump during the runaway transition process,the second development of CFX is carried out by FORTRAN language.Based on the RANS equation and SST k-ωmodel,the developed CFX software is used to simulate the runa way transition process of the inline pump,and the changes of the speed,flow rate and torque during the transition process are pr edicted.Combined with the method of vorticity distribution and Q criterion,the vortex distribution in the process of turbine runa way is studied.The results show that the final runaway speed N fea of the inline pump with special structure is not fixed but fluctuates on the average runaway speed line,in which the average runaway speed value Nave=3584 rev/min is 1.23 times of the rat ed working condition.The flow rate Q increases first,then decreases to the fluctuation value about Qave=14.7 kg/s.Torque T i s lowered to zero and oscillates near the zero line.The results show that the vortex mainly occurs in the working face and the ta il edge of the inline pump.The research reveals the internal flow characteristics of the inline pump during the runaway transition,and provides a reference for the safe and stable operation of the inline pump.