What are the functions of the balance drum and the regulating stage in a steam turbine?

When a turbine is regulated using nozzles, the inlet area of the first stage changes in response to load variations; therefore, the first stage of such a turbine is commonly referred to as the regulating stage. 5 J. K* g6 f: K" w9 X+ o1 s The speed stage of a turbine is also known as the regulating stage; in multi-stage turbines, it refers to the first stage that performs work. Since the steam ejected from the nozzles of the turbine’s regulation stage is steam from the turbine that has been depressurized and expanded through these nozzles, it possesses a very high flow velocity at this point. To a large extent, the work done by the steam on the impellers of the control stage is achieved through the impact of this high velocity steam flow; therefore, the control stage was referred to as a velocity stage from an early stage. It is still more convenient to refer to them by their control stages. 7 E1 K: }# H’ n3 Y” The inlet blade of the control stage experiences temperatures, velocities, and pressures that are much higher than those in the subsequent pressure stages. Moreover, when the turbine adjusts the amount of steam supplied, sequence valves are typically used for this purpose; as a result, the control stage receives only a partial supply of steam (in fact, even when all the control valves of the turbine are open, the control stage still receives only a partial supply of steam, rather than full-flow steam). Unlike all the other pressure stages, which receive full-flow steam, the control stage is directly involved in regulating the turbine’s power output, which is why it is often referred to as a control stage. Since it has the highest steam inlet temperature, greatest pressure, high steam velocity, and partial steam injection among all stages of the turbine, the operating conditions in the regulating stage are more severe than those in other pressure stages. Moreover, the regulating stage has a strong capacity for performance. Therefore, in terms of appearance, the diameter of the impeller in the regulating stage is larger than that of the impellers in the subsequent ordinary pressure stages. The blades and blade roots of the regulating stage are also designed to be thick, in order to withstand the harsh working conditions. This must be the difference between the regulating stage and the pressure stage. : ` E) C% F8 W8 i+ U I saw it elsewhere too; hope it helps you

Reply to 2# 525h: Thank you so much! I now understand the function of the turbine regulation stage; may I also ask about the function of the balance drum?

The balance piston is used to balance axial forces

Balance drums generally utilize the principle of throttling and pressure reduction based on a labyrinth design; that is, a balance drum is installed on the final rotor to throttle and reduce pressure from the inside outward, and the pressure difference is used to generate a force that counteracts the axial force, thereby balancing it.

The balance piston of a turbine is used to balance axial forces.