科创中国

在某汽轮机除湿级的空心静叶上设计了不同的热蒸汽喷射缝,应用两相均质混合模型和湿蒸汽平衡相变模型,对具有缝隙的叶栅流场进行了全三维定常的数值计算.引入炯参数的方法进行能量转化过程的经济性评估.结果表明:尾缘喷射热蒸汽时,同一喷射流量下,缝隙宽度越大,炯有效效率越高.同时,在较大缝隙宽度下,有一个最佳的喷射流量,此时的炯有效效率最高.压力面中部喷射热蒸汽时,在喷射流量比小于6%下,各方案的[火用]有效效率均比无热蒸汽喷射的原型要高.同一喷射流量下,顺主流喷射且缝隙宽度越大,其[火用]有效效率越高.

抽汽压损是一种不明显的热力损失,使蒸汽的作功能力下降、热经济性降低.假定抽汽口的压力不变,加热器端差不变,分析抽汽压损变化对热力系统的影响.根据抽汽压损的理论分析和热力系统汽水分布方程建立抽汽压损对回热系统抽汽系数影响的数学模型,并结合炯平衡原理和小扰动理论建立抽汽压损对炯损分布的影响的数学模型.以某电厂N1000-25/600/600机组热力系统为例,在TRL工况下,定量计算热力系统炯损变化情况.根据定量计算结果定性分析了抽汽压损对热力系统的影响.

Majority of non-Newtonian fluids are pseudoplastic with shear-thinning property,which means that the viscosity will be different in different parts of the stirred tank.In such mixing process,it is difficult to predict accurately the power consumption and mean shear rate for designing novel impeller.Metzner-Otto method is a widely accepted method to solve these questions in mixing non-Newtonian fluids.As a result,Metzner-Otto constant will become a key factor to achieve an optimum way of economical mixing.In this paper,taking glycerine and xanthan gum solutions as research system,the power consumption,stirred by the impeller composed of perturbed six-bent-bladed turbine(6PBT)with differently geometrical characteristics in a cylindrical vessel,is studied by means of computational fluid dynamics(CFD).The flow is modeled as laminar and a multiple reference frame(MRF)approach is used to solve the discretized equations of motion.In order to determine the capability of CFD to forecast the flow process,the torque test experiment is used to measure the glycerine solution power consumption.The rheological properties of the xanthan gum solutions are determined by a Brookfield rheometer.It is observed that the power consumption predicted by numerical simulation agrees well with those measured using torque experiment method in stirring glycerine solution,which validate the numerical model.Metzner-Otto constant is almost not correlated with the flow behavior index of pseudoplastic fluids.This paper establishes the complete correlations of power constant and Metzner-Otto constant with impeller geometrical characteristics through linear regression analysis,which provides the valuable instructions and references for accurately predicting the power consumption and mean shear rate of pseudoplastic fluids in laminar flow,comparatively.