What are the effects of excessively high and low vacuum levels on turbine startup?
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Question: What are the effects of excessively high and low vacuum levels on the startup of a steam turbine? I hope fellow sailors will not hesitate to share their advice; thank you all~~! !
This issue can be viewed in the following way: 1. First, the degree of vacuum is related to the work done—what is its impact? 2. Excessively high vacuum level – causes sealing issues? 3. Vacuum level deviation – Is there a problem with the operation? 4. Vacuum level deviation – Is there a problem with the equipment?
At the start of operation, the vacuum level does not need to be very high; maintaining a certain level of vacuum is necessary for proper warming up. This is because when the vacuum level is low, there is more steam in the cylinders, which helps to ensure even heating of the cylinders and rotor. Too high a vacuum means, first, that it takes longer to evacuate the air, and second, there is less steam in the cylinder, which hinders warming up. Generally, a vacuum level of 60-66 kPa is sufficient; for hot-starting, a higher value around 80 is acceptable. Creating an excessively high vacuum takes a long time and is not conducive to warming up. Excessively high vacuum can easily cause water erosion of the last stages of the blades. When the vacuum level is low, the steam intake must be higher compared to when the vacuum level is high (at the same rotational speed). This also helps to accelerate the warming up process. The higher the vacuum level in a turbine, the greater the total enthalpy drop of a unit amount of steam within the turbine. When the amount of work that needs to be done by the turbine remains constant, the total amount of steam required input decreases. Conversely, when the vacuum level drops and the total enthalpy drop per unit of steam decreases, more steam needs to be inputted in order to maintain the same amount of work output. ）
The vacuum level in the turbine is too high, requiring increased power consumption for circulation
Too low a vacuum level during operation is not conducive to efficient operation, as it results in high steam consumption； Moreover, high exhaust temperature increases the load on the low-pressure cylinder, as well as the temperature of the rotor bearings