【Mechanical Equipment Technology Exchange Edition】Mechanical Equipment 【Daily Question】20190927
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Question: What are the characteristics of twin-spool speed stages? There are no answers provided for this series of posts; fellow netizens are free to share their own opinions – just reply with what you understand. Replies earn rewards ranging from 5 to 15 points; all forum members are welcome to participate actively and support the development of the forum! ! ! Chemical Equipment and Machinery
The use of double-row speed stages in the regulation stage offers the following advantages: 1. Under the same conditions of steam parameters and turbine power, it allows for a reduction in the number of turbine stages, simplifying the structure, with little difference in the unit’s power output. 2. Since the steam pressure and temperature drop significantly after the double-row speed stages, the high-pressure and high-temperature sections downstream of the control stage are shortened, which allows for the saving of a certain amount of precious metal material both in the turbine and the rotor, thereby reducing the cost of the steam turbine. 3. Since the pressure drops significantly after the steam passes through the double-row speed stages, the high-pressure shaft seal design can be simplified and air leakage losses can be reduced. It should be noted that in the two-row speed stage, due to the large drop in thermal enthalpy, the steam flow velocity is very high; as a result, the residual velocity of the steam exiting the second row of blades is high, and much of the kinetic energy is not utilized, leading to low efficiency.
To increase the enthalpy drop in the regulating stage, the residual velocity at the exit of the first row of rotor blades is utilized to reduce residual velocity losses; thereafter, the steam stream exiting those rotor blades changes direction due to the guide vanes fixed on the cylinder, and then enters the second row of rotor blades to continue doing work. At this point, a stage that has one row of nozzles but two rows of moving blades on the first-stage impeller is called a double-row velocity stage.
The use of a double-row speed stage can increase the enthalpy drop in the regulating stage of the turbine, reduce the number of pressure stages, decrease the axial size of the turbine, and save materials, but its efficiency is lower.
The use of double-row speed stages in the regulation stage offers the following advantages: 1. Under the same conditions of steam parameters and turbine power, it allows for a reduction in the number of turbine stages, simplifying the structure, with little difference in the unit’s power output. 2. Since the steam pressure and temperature drop significantly after the double-row speed stages, the high-pressure and high-temperature sections downstream of the control stage are shortened, which allows for the saving of a certain amount of precious metal material both in the turbine and the rotor, thereby reducing the cost of the steam turbine. 3. Since the pressure drops significantly after the steam passes through the double-row speed stages, the high-pressure shaft seal design can be simplified and air leakage losses can be reduced. It should be noted that in the two-row speed stage, due to the large drop in thermal enthalpy, the steam flow velocity is very high; as a result, the residual velocity of the steam exiting the second row of blades is high, and much of the kinetic energy is not utilized, leading to low efficiency.
The use of speed stages allows for an increase in the enthalpy drop in the turbine’s regulating stages, reduces the number of pressure stages, and saves high-temperature resistant premium materials; however, the efficiency is lower.
The use of double-row speed stages in the regulation stage offers the following advantages: 1. Under the same conditions of steam parameters and turbine power, it allows for a reduction in the number of turbine stages, simplifying the structure, with little difference in the unit’s power output. 2. Since the steam pressure and temperature drop significantly after the double-row speed stages, the high-pressure and high-temperature sections downstream of the control stage are shortened, which allows for the saving of a certain amount of precious metal material both in the turbine and the rotor, thereby reducing the cost of the steam turbine. 3. Since the pressure drops significantly after the steam passes through the double-row speed stages, the high-pressure shaft seal design can be simplified and air leakage losses can be reduced. It should be noted that in the two-row speed stage, due to the large drop in thermal enthalpy, the steam flow velocity is very high; as a result, the residual velocity of the steam exiting the second row of blades is high, and much of the kinetic energy is not utilized, leading to low efficiency.
The use of speed stages allows for an increase in the enthalpy drop in the turbine’s regulating stages, reduces the number of pressure stages, and saves high-temperature resistant premium materials; however, the efficiency is lower.
The use of speed stages allows for an increase in the enthalpy drop in the turbine’s control stages, reduces the number of pressure stages, and saves high-temperature resistant premium materials; however, the efficiency is lower. The control stage of 100MW turbines uses a double-row speed stage, while those of 125MW, 200MW, and 300MW turbines use a single-row control stage
The use of double-row speed stages in the regulation stage offers the following advantages: 1. Under the same conditions of steam parameters and turbine power, it allows for a reduction in the number of turbine stages, simplifying the structure, with little difference in the unit’s power output. 2. Since the steam pressure and temperature drop significantly after the double-row speed stages, the high-pressure and high-temperature sections downstream of the control stage are shortened, which allows for the saving of a certain amount of precious metal material both in the turbine and the rotor, thereby reducing the cost of the steam turbine. 3. Since the pressure drops significantly after the steam passes through the double-row speed stages, the high-pressure shaft seal design can be simplified and air leakage losses can be reduced. It should be noted that in the two-row speed stage, due to the large drop in thermal enthalpy, the steam flow velocity is very high; as a result, the residual velocity of the steam exiting the second row of blades is high, and much of the kinetic energy is not utilized, leading to low efficiency.
To increase the enthalpy drop in the regulating stage, the residual velocity at the exit of the first row of rotor blades is utilized to reduce residual velocity losses; thereafter, the steam stream exiting those rotor blades changes direction due to the guide vanes fixed on the cylinder, and then enters the second row of rotor blades to continue doing work. At this point, a stage that has one row of nozzles but two rows of moving blades on the first-stage impeller is called a double-row velocity stage.