超临界350 MW机组低压缸切缸技术冷却蒸汽热力分析

Thermodynamic analysis of LP cylinder cooling steam of a supercritical 350 MW unit

针对超临界350 MW机组低压缸切缸技术冷却蒸汽的设计问题,基于汽轮机的热力设计计算方法,通过对不同冷却条件工况下以及正常运行工况下低压缸通流各级叶片出口温度分布进行详细的计算及分析,得到其与冷却蒸汽量和蒸汽温度的关系。结果表明:在切缸运行工况下,末级叶片处于鼓风状态,此时低压缸排汽温度基本与冷却蒸汽流量和冷却蒸汽温度呈线性变化趋势,与冷却蒸汽流量负相关,与冷却蒸汽温度正相关,因此合理设置冷却蒸汽流量和温度可以有效控制末两级叶片的出口温度。本文从理论分析角度为机组切缸后低压缸冷却蒸汽的设计提供依据,为机组切缸提供相应的安全理论支撑。

In view of the design problem of cooling steam in low pressure (LP) cylinder cutting technology of supercritical 350 MW units, by using the thermodynamic design calculation method of steam turbine, the temperature distribution at outlet of each stage blades of the low pressure cylinder under different cooling conditions and normal operation conditions was calculated in detail, and the relationship between the outlet temperature of low pressure cylinder with the cooling steam volume and steam temperature was obtained. The results show that, the final stage blade is in the state of blowing, and the exhaust temperature of the low pressure cylinder is linear with the cooling steam flow rate and the cooling steam temperature. It is negatively related to the cooling steam flow rate and positively correlated with the cooling steam temperature. Therefore, the outlet temperature of the last two stage blades can be effectively controlled by setting the cooling steam flow rate and temperature reasonably. This paper provides theoretical basis for design of the cooling steam of low pressure cylinder when the low pressure cylinderis is resected of the unit, and also provides the corresponding safety theoretical support for cylinder cutting.