350MW超临界机组可调式蒸汽喷射器工业供热性能数值模拟研究及试验验证

Numerical Simulation and Test Verification on Industrial Heating Performance of Adjustable Steam Ejector in 350MW Supercritical Unit

为解决“以热定电”传统运行模式下燃煤热电联产机组在中、低负荷运行时,工业供热量不足、蒸汽参数不达标等问题,某350 MW热电联产机组引进了世界首套应用于超临界机组的增汽机工业供热系统。利用计算流体力学软件,对该系统的核心部件可调式蒸汽喷射器进行三维数值模拟,在模拟结果经现场试验试验验证其可靠性后,分析了不同工作参数(工作蒸汽压力、引射蒸汽压力和背压)和结构参数(面积比)对其工作性能(引射系数和出口流量)和调节能力产生的影响。结果表明:临界背压决定其在变工况时的调节能力,随面积比的增大而减小;通过改变结构参数,可以削弱工作参数对其性能产生的影响,拓宽增汽系统的适用范围,利于热电解耦;扩压室段二次激波的产生会使其引射系数减小,系统经济性降低。

In order to solve such problems as insufficient industrial heat supply and substandard steam parameters when coal-fired cogeneration units operate at medium and low loads under the traditional operation mode of"power determined by heat",the world’s first industrial steam incremental supply system,which had been applied to supercritical unit,was introduced into a 350 MW CHP unit. Based on the field test data,this study employs computational fluid dynamics software to carry out three-dimensional numerical simulation of the adjustable steam ejector,which is core to the system. We further analyze the influences of different operating parameters including operating steam pressure,ejector steam pressure and back pressure,and structure parameters like area ratio,on its performance such as entrainment ratio and outlet flow,and adjustability. The results show that critical back pressure determines its adjustability at off-design conditions and decreases with the increase of area ratio. By changing the structure parameters,the influence of the operating parameters on its performance can be weakened. A broader application of the steam increment system is conducive to the thermoelectric decoupling. The second shock wave in the diffuser chamber will reduce its ejection coefficient and lower the economic efficiency of the system.