汽轮机低负荷工况胀差分析及对策

汽轮机胀差是汽轮机运行时的重要监视参数,它反映了汽轮机转子和汽缸热膨胀量的相对关系。在启动和停机过程中,如汽轮机以及发电机试验较多或者出现故障,要求汽轮机长时间保持定速空负荷或低负荷运转时,或抽汽凝汽式机组由于热、电负荷要求,维持高供热量低发电量时,汽轮机胀差就会出现负值。通常喷嘴出口至动叶入口的轴向间隙要比动叶出口至喷嘴入口的轴向间隙小,更容易发生超限现象,因此胀差负值比正值更加危险。当胀差超过警戒值时,如没有控制汽轮机胀差的有效措施,只能打闸停机。针对上述现象的原因和对策进行了探讨,并提出了一种行之有效的解决办法。

Analysis and Countermeasure on Differential Expansion of Steam Turbine Under Low-Load Condition

The differential expansion is a very important monitor parameter during the operation of steam turbine. It reflects relative relationship of heat expansion between the rotor of the steam turbine and the cylinder. In the process of starting and stopping, if there are a lot of experiments or something wrong with the steam turbine or the generator, the steam turbine needs working for a long time at a constant speed under zero- load or low- load condition, it will cause negative value of differential expansion. There is the same situation while keeping high heat supply and low generating amount according to heat and electricity load requirement in an extraction - condensing turbine. Generally the axial clearance between the exit of the jet and the entry of the movable vane is smaller than that between the exit of the movable vane and the entry of the jet, which results easily in exceeding the limit, so a negative value of the differential expansion is more dangerous than a positive one. If the differential expansion is beyond the guard- line and no effective measures are taken to control the differential expansion, the only way is to switch off and stop the turbine. The cause of the phenomenon was discussed, and an effective method to solve the problem was presented.