[Q&A Question 114] 2017.04.24
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【Q&A Question 114】April 24, 2017: What is the impact of too low steam temperature on the operation of a turbine? The reference answer can be seen after responding; points will be awarded for identifying the key points. (Unless otherwise specified, all questions and answers are based on hydrogenation units.) If the steam temperature is too low, below the designed value, it increases the reaction degree of the blades, resulting in an increase in axial force. As the temperature drops, the temperature drop at the steam point decreases; consequently, the absolute velocity of the steam decreases, and the direction of its relative velocity changes, thereby generating a reactive force on the blades. To maintain constant output, more steam must be used, which affects economic operation. Additionally, a lower steam temperature leads to higher temperatures in the subsequent blades, causing water erosion and shortening their service life. Scoring criteria: 2 Wealth points for incorrect attempts; 3–8 points for *incomplete* answers. 10 Wealth points for correct answers, provided with a detailed explanation; 15–20 Wealth points if the answer is correct but lacks sufficient details. Please score according to these criteria. 2017 Q&A Summary Thread (updates starting now) http://bbs.hcbbs.com/thread-1657793-1-1.html 2017 Daily Question Summary Thread (updates starting now) http://bbs.hcbbs.com/thread-1657794-1-1.html 2016 Q&A Summary Thread (updates completed) http://bbs.hcbbs.com/thread-1597792-1-1.html Petrochemical Sector – “Creative Ideas for Energy Savings” campaign (sponsors sought; highest returns ever) http://bbs.hcbbs.com/thread-1666758-1-1.html Sponsors are being sought for this campaign; those interested may contact the event organizer. Petrochemical deep processing version – the event to share pictures of chemical equipment has started! A vast amount of wealth, as well as HChuan coins, are waiting for you to claim them. http://bbs.hcbbs.com/thread-1760733-1-1.html Notice regarding the collection of chemical engineering technical materials in the \"Petroleum and Chemicals Section\": http://bbs.hcbbs.com/thread-1614796-1-1.html (Source: HChuan Chemical Engineering Forum)
If the steam temperature is too low, it tends to contain water
Steam contains water, which can cause corrosion of the components in turbine equipment and shorten their service life
Lower temperature results in lower steam pressure. 1. The generator output needs to be reduced ； 2. While maintaining the rated load, the main steam flow rate increases compared to before ； 3. Increased steam humidity at the trailing blades reduces their service life ； 4. If the main steam temperature drops sharply by 50 degrees, it is a sign of water hammer.
1. When maintaining the rated load and the main steam flow rate increases compared to before, it will cause overload of the final-stage blades. 2. An increase in steam humidity at the trailing edge of the blades reduces their service life. 3. The reaction degree at each stage of the turbine increases, axial thrust rises, and bearing temperatures go up. 4. High-temperature components experience significant thermal stress and thermal deformation. 5. If the main steam temperature drops by 50 degrees suddenly, it is a sign of water hammer, which is extremely dangerous.
Water hammer affects the lifespan of turbines and reduces their efficiency
The turbine has low efficiency; liquid in the casing may damage the impeller, and there is significant vibration in the casing
A steam temperature lower than the design value increases the blade reaction degree, thereby increasing the axial thrust. Operating at too low a temperature increases steam consumption and affects economic efficiency. Furthermore, a decrease in steam temperature will cause water erosion of the blades in the latter stages of a condensing steam turbine, thereby reducing its service life
If the steam temperature is too low, below the design value, it will increase the blade reaction degree, resulting in an increase in axial force. As the decrease in temperature leads to a reduced drop in the steam point temperature, the absolute velocity of the steam decreases; meanwhile, the direction of its relative velocity changes, resulting in a reactive force acting on the timing plate. If the output is to be maintained unchanged, more steam must be used, which affects efficient operation. Furthermore, a decrease in steam temperature will lead to an increase in the temperature of the blades behind them, causing water erosion of the blades and shortening their service life.
1. The final stage blades may be overloaded. 2. Increased steam humidity at the final stage blades, leading to erosion by water droplets on the moving blades of the furniture. 3. The degree of reactivity at all levels increases. 4. High-risk components experience significant thermal stress and thermal deformation. 5. Water hammer is possible.