冷端系统协同工作下的凝汽器性能数值计算

Numerical Calculation of Condenser Performance Considering Cooperative Operation of Cold-end System

基于汽轮机冷端系统内部协同工作的实际情况,探讨了准确确定凝汽器压力的数值研究方法。以某600MW机组低压凝汽器及其配套的水环式真空泵为研究对象,采用数值计算的方法模拟凝汽器在不同冷却水温下的工作性能,确定了冷却水温变化引起的水环式真空泵抽吸能力的变化;计算了凝汽器抽气口至水环式真空泵入口抽气管道内的流动压损;在考虑冷却水温对凝汽器与水环式真空泵性能影响以及抽气管道流动压损影响的情况下,实施了与凝汽器实际运行情况相符的确定凝汽器压力的数值研究方法。研究结果表明:抽气管道流动压损对凝汽器压力的影响较小,在凝汽器压力确定的过程中可以忽略;真空泵变工况对凝汽器压力的影响较大,当真空泵工作水温低于设计工况下的工作水温,忽略真空泵变工况的影响将会使确定出的凝汽器压力偏高;反之,则确定出的凝汽器压力偏低;而且工作水温高于设计工况越远,确定出的凝汽器压力偏差值越大。以文中的研究对象为例,当真空泵工作水温高于设计工况20℃,考虑真空泵变工况与否确定出的凝汽器压力相差达到213Pa。

Based on the actual situation of cold-end system of steam turbine, a numerical method for accurately determining condenser pressure was discussed. One low pressure condenser of 600MW power unit and its water ring vacuum pump was taken as the research object. The performance of the condenser was numerical simulated under the different cooling water temperatures. The change of pumping capacity of water ring vacuum pump caused by varying cooling water temperature was determined. The flow pressure loss between the condenser suction port to the water ring vacuum pump was calculated. In accordance with the actual operation of the condenser, a numerical method for determining the pressure of the condenser was carried out under considering the influence of cooling water temperature on the performance of condenser and water ring vacuum pump and the flow loss of suction pipe. The research results showed that the influence of flow loss of suction pipe on the pressure of the condenser is very small. It can be ignored in the process of determining the pressure of condenser. The off-design condition of vacuum pump has great influence on condenser pressure. When the temperature of water working in the vacuum pump is lower than under the design condition of the vacuum pump, the pressure of condenser determined from the numerical method would be greater than ignoring the influence of the off-design condition of the vacuum pump. On the other hand,the pressure of condensers would be lower. The higher the temperature of working water is than the design condition, the greater the pressure deviation of the condenser is determined. Taking the research object as an example. When the temperature of working water of the vacuum pump is higher than the design condition of 20℃, the difference of condenser pressure is 213Pa considering the off-design condition or not.