660 MW超临界机组凝汽器（型号N-36600）在循环水系统调试过程中，出现噪声、水侧液位波动等异常现象，液位最大波动幅度达400 mm，现场通过逐步关小凝汽器回水阀门，提高凝汽器冷却管内压力，当进口水室压力达到0.106 MPa时，凝汽器水侧的噪声、液位波动等现象消失。结合空化初生理论分析，认为凝汽器内部发生了空化。标准与工程经验中确定虹吸利用高度时，基于水的饱和蒸汽压力，通常要求凝汽器最高点冷却管压力不低于20 kPa（绝压），而有关试验研究表明：清水的饱和蒸汽压力比空化初生压力低得多，即清水的绝对压力高于相应温度下的饱和蒸汽压力时，仍然可能发生空化，空化初生与水中的气态微核有直接关系。因此，在循环水系统水力计算中，虹吸利用高度的确定应充分考虑空化初生压力的影响，留出余量。并给出了处理建议，通过加高脱硫曝气池溢流堰的堰顶标高，提高凝汽器冷却管末端压力，是消除凝汽器空化现象最为经济合理的解决方案，有助于分析类似问题。

The abnormal phenomenon of noise and undulating water level in condenser water side occurred during the commissioning of circulating water system of 660 MW super-critical unit condenser (type: N-36600),and the maximum fluctuation reached 400 mm.The tests in field showed that when the outlet valves of condenser water side were shut off to increase the pressure in tubes as the pressure of inlet water chamber reached 0.106 MPaG,the abnormal phenomenon disappeared.Based on the theories of cavitation inception,cavitation formation was concluded.In the calculation of siphonate height,the pressure of tubes in the top layer of condenser should not be less than 20 kPa abs dute according to the standards,while it is based on the vapor pressure of water.Per the related experiments and studies,the vapor pressure of water is much lower than incipient cavitation pressure.It means that even the absolute pressure of water is higher than the saturated vapor pressure with the corresponding temperature,cavitation may still occur.There is a direct relation between incipient cavitation and gas nucleus.Therefore,the effects of incipient cavitation pressure should be taken into full consideration for the confirmation of siphonate height in the hydraulic calculation of circulating water system.Increasing the elevation of overflow weir in flue-gas desulphurization basin is the most reasonable solution for condenser cavitation,which is informative for the similar problems.

TK264.1+1