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1. What is the normal range for the exhaust temperature of the low-pressure cylinder of a steam turbine? The inlet temperature of the low-pressure cylinder of a turbine is usually the saturation temperature of steam or slightly higher than that temperature; the specific value depends on the pressure of the steam, as in a saturated state, the pressure of the steam directly determines its corresponding saturation temperature. For example, in a typical steam power cycle, the inlet pressure of the low-pressure turbine stage may range from 0.005 MPa to 0.03 MPa, with the corresponding saturated temperature falling within the range of approximately 40°C to 120°C. However, in practice, to ensure efficiency and prevent wet steam from damaging the blades, the steam entering the turbine is usually kept at a certain degree of superheat, that is, about 50–80°C above the saturation temperature, to ensure that the steam is in a dry state. As for the exhaust temperature of the low-pressure cylinder, it is influenced by the operating conditions of the condenser. Ideally, the condenser is able to condense the steam into water, and in such cases the exhaust temperature is close to the temperature of the cooling water used in the condenser, usually ranging between 30°C and 40°C. However, in practice this temperature can vary due to various factors. II. What are the reasons for the high exhaust temperature of the low-pressure cylinder of the steam turbine? The main reasons for the high exhaust temperature in the low-pressure cylinder of a turbine include, but are not limited to, the following: 1. Insufficient steam flow: During startup, due to low steam flow, the enthalpy drop of the steam after throttling is reduced, which weakens the steam’s ability to do work in the low-pressure cylinder; as a result, the steam that is not fully converted into mechanical energy is discharged at a higher temperature. 2. Blowing loss: At low flow rates, the friction between the steam and the last stage blades of the low-pressure turbine, along with the \"blowing effect\" caused by the steam flow, results in additional heat generation, thereby raising the exhaust temperature. 3. Low vacuum level: An insufficient vacuum level in the condenser means that steam does not condense effectively during the condensation process, and it is unable to remove effectively the residual heat generated after work is done in the low-pressure cylinder, resulting in an increase in the exhaust steam temperature. 4. Shaft seal issue: An excessively high steam supply temperature for the shaft seal of the low-pressure cylinder, or abnormal operation of the shaft seal system, can directly heat the low-pressure cylinder, thereby affecting the exhaust steam temperature. 5. Jamming in the sliding pin system: Jamming in the sliding pin system of the low-pressure cylinder restricts the free expansion of the cylinder, which can lead to localized overheating, including an increase in temperature in the exhaust area. 6. Too rapid load increase: A quick increase in load can cause a sharp change in steam flow, and if the cooling system cannot adapt quickly enough, it may lead to an increase in exhaust temperature. 7. Circulating water system failures: Problems with the circulating water system, such as insufficient flow rate, excessively high water temperature, low pressure of the spray water, or clogged nozzles, can all affect the condensation process, thereby increasing the exhaust steam temperature. 8. Jet water system failure: The jet water system is used to increase the vacuum in the condenser; if it does not function properly, it can indirectly lead to an increase in the exhaust steam temperature. 9. System leakage: Leakage in the vacuum system or air leakage from the shaft seals can introduce non-condensable gases, reducing vacuum efficiency, affecting steam condensation, and raising the exhaust steam temperature. 10. Other heat exchange system failures: Such as abnormalities in the low-pressure heater air system or issues with the extraction steam reheat system, can affect the operating conditions of the low-pressure cylinder and lead to abnormal exhaust steam temperatures. For the above reasons, corresponding maintenance and adjustment measures are usually required, such as checking and repairing the vacuum system, adjusting the parameters of the circulating water system, checking and cleaning the nozzle filters, and controlling the rate of load increase, in order to ensure the safe and efficient operation of the turbine. III. Why is the exhaust temperature of the low-pressure cylinder of a steam turbine not allowed to exceed 121°C? The exhaust temperature of the low-pressure cylinder of a steam turbine must not exceed 121°C, for several key reasons: 1. To ensure the safety of the equipment: When the exhaust temperature of the low-pressure cylinder is too high, it can lead to increased thermal expansion of the low-pressure cylinder and its associated components such as the cylinders and rotor. This results in changes in the clearance between the various components of the turbine, causing increased vibration. Over time, this can damage the equipment, leading to serious issues such as cylinder deformation and friction between moving and stationary parts. 2. Avoid condenser failures: Excessively high exhaust steam temperatures increase the temperature difference within the condenser, which can lead to leaks at the joints of the copper tubes in the condenser due to increased thermal stress. Circulating water may then enter the steam system, compromising the purity of the condensate and potentially causing corrosion issues, thereby severely affecting heat exchange efficiency and the safe operation of the unit. 3. Maintaining vacuum level: Excessively high exhaust steam temperature reduces the vacuum level in the condenser, as it is more difficult for high-temperature steam to condense; this in turn worsens the exhaust steam temperature, creating a vicious cycle. A decrease in vacuum level directly affects the output and efficiency of the turbine. 4. Preventing degradation of material properties: Long-term operation at high temperatures may exceed the temperature limits specified for the materials, leading to metal fatigue and accelerated creep, which affects the mechanical properties and service life of the materials. 5. Stability of control systems: Excessively high temperatures can also affect the stability and reliability of control systems and protection systems, leading to issues such as false readings from sensors and improper operation of protection devices. Therefore, 121°C is set as a warning value to ensure that the turbine can operate safely and stably under various operating conditions, and to allow timely action to prevent potential equipment damage and operational failures. Once the exhaust temperature approaches or exceeds this limit, it is usually necessary to conduct an immediate inspection and take appropriate measures to reduce the temperature; if needed, the system should be shut down for inspection in order to identify and resolve any faults.