炉膛内空气射流初值依赖性及非线性分析

Analysis of Initial Value Dependence and Nonlinearity of Air Jet in Furnace

为研究炉膛内空气射流的初值依赖性及其非线性,以某塔式燃煤锅炉为研究对象,分别建立了简化的二维CFD数值模型和三维冷态切圆射流实验模型,运用数值模拟与实验相结合的方法探讨了炉膛内流动的非线性特性,并提出了新的喷嘴启动方式——顺序启动。结果表明:即使几何结构和边界条件完全对称,其流场也有可能是非对称的,随着雷诺数的增大,内部流动依次经历稳定定态解、周期振荡解和混沌解;当布置1对喷嘴时,流动表现出明显的多解特性,在一定雷诺数范围内,采用顺序启动方式可以控制唯一结果,实现流动的精准控制;只有当监测点的速度相轨迹图为定常吸引子或极限环吸引子时,流动才会表现出对喷嘴开启顺序的初值依赖性;经过实验验证,按一定顺序启动4个角的喷嘴,可以控制流场的唯一结果,即实现了精准控制。

In order to study the initial value dependence and nonlinearity of air jet in furnace,a simplified two-dimensional CFD numerical model and a three-dimensional cold tangential jet experimental model were established respectively for a tower coal-fired boiler.The nonlinear characteristics of flow in the furnace were discussed by combining numerical simulation with experiment,and a new nozzle startup mode-"sequential startup"was proposed.Results show that even if the geometric structure and boundary conditions are completely symmetric,the flow field may also be asymmetric.With the increase of Reynolds number,the internal flow undergoes stable steady state solution,periodic oscillation solution and chaotic solution in turn.When arranging a pair of nozzles,the flow shows obvious multi solution characteristics.Within a certain Reynolds number range,the only result can be controlled by"sequential startup"to achieve accurate flow control.Only when the velocity phase diagram of the monitoring point is a steady attractor or a limit cycle attractor,will the flow show an initial value dependence on the opening sequence of the nozzle.After experimental verification,starting the nozzles at four corners in a certain sequence can control the only result of the flow field,that is,precise control is realized.