联合进汽阀内部流场三维数值模拟及阀碟受力分析

Numerical Simulation of Flow Characteristics and Forces on Valve Disc for a Combined Inlet Valve

针对联合进汽阀流道内因湍流、旋涡产生压损,进而降低汽轮机组经济性这一问题,建立由两个主汽阀E、F及左侧次大调节阀B、中间最小调节阀A、右侧最大调节阀C构成的某进口联合进汽阀的三维数值模型,并进行不同工况模拟计算。主要研究阀C和阀B全开时,阀内流动特性、各阀压损以及阀碟各表面受力随阀A开度增大而变化的情况。研究发现,在小开度下,阀A迎风侧为贴附阀碟流,并且阀座迎风侧存在大旋涡,随着阀A开度的增大整体流场趋于平稳,迎风侧和背风侧流体转变为两股射流,阀碟内腔中的低速流体区仅位于阀座喉部及以上区域,但阀碟内腔会出现小旋涡。随着阀A开度的增大,阀A压损逐渐较减小,阀B和阀C压损基本维持不变,主汽阀E和F压损随阀A开度增大而继续增大。阀A阀碟所受纵向力在阀A开度小于80%时随开度增大而减小,在开度大于80%时则相反。阀B阀碟和阀C阀碟所受纵向力基本不随阀A开度的变化而变化。阀A阀碟、阀B阀碟和阀C阀碟的横向受力随阀A开度的增大而增大。

The turbulence and vortex inside combined inlet valve flow passage may easily induce pressure loss, and then lead to adverse effects on the efficiency of steam turbine units. To study the above mentioned problems, a three-dimensional numerical model of an combined inlet valve is constructed. The combined inlet valve system consists of two main steam valves, the largest valve C on the right, the second size valve B on the left and the minimum valve A in the middle. The variations of the flow characteristics inside the valves, the pressure loss of the valves and the force distribution on the valve disc surfaces with the increase of valve A opening are investigated when valve B and valve C are fully opened. It is found that fluid attaches to valve disc at the windward side of annular channel, and there exists maelstrom at seat windward side when valve A is slightly opened. The whole flow field tends to be steadier with the increase in opening of valve A. Two jet flows appear at the windward side and leeward side, and the low-speed fluid in the valve disc lumen area locates in or above the valve seat throat with small vortex inside the valve disc lumen. With the increase in opening of valve A, pressure loss of valve A decreases gradually, pressure losses of valve B and valve C are nearly unchanged, and pressure losses of the main steam valve E and F continue to increase. The longitudinal force imposed on disc of valve A decreases with its opening when the opening is less than 80%, and it is opposite when the opening is greater than 80%. The increase in opening of valve A has no effect on longitudinal forces imposed on discs of valve B and valve C. The lateral force on disc of valve A increases with the increase in opening of valve A, while the lateral forces on discs of valve B has no and valve C continue to increase with the increase in opening of valve A.