定功率下轴封系统对机组热经济性的影响

摘要

汽轮机轴封系统是火电厂热力系统的重要组成部分,轴封系统漏汽的大小对机组的热经济性有直接的影响.基于热经济状态方程,利用矩阵分析的思路,根据轴封系统漏汽的来源不同,分别建立了定功率条件下高压缸漏汽和中低压缸漏汽对机组热经济性影响的定量数学模型.利用微分理论,得出了轴封蒸汽流量变化时主蒸汽流量和轴封漏汽量的依变关系.以某300 MW火电机组为例,针对其典型工况,分别计算高压缸漏汽和中低压缸漏汽变化对机组热经济性的影响.结果表明：高压缸轴封漏汽对机组热经济性影响较大.%Shaft seal system is an important component in the thermodynamic system of thermal power plant,where the steam leakage directly impacts the thermal economy of the unit.Based on the thermal economic state equation,making use of the idea of matrix analysis and considering different sources where the steam leaks out,mathematical models have been derived for quantitative analysis of the influence of steam leakage from HP and MP/LP cylinder on the unit thermal economy under conditions of constant power output.The relation between main steam flow and gland leakage has been deduced based on differential theory.Taking a 300 MW thermal power unit as an example,relevant calculations were carried out so as to analyze the influence of steam leakage respectively from HP and MP/LP cylinder on the unit thermal economy under typical working conditions.Results show that the steam leakage from HP cylinder plays a more important role in influencing the thermal economy of the unit.