Purpose and types of steam turbines
A steam turbine is a turbine in which steam is the circulating agent
The prototype of the steam turbine was Heron's pump. It is an engine (heat engine) that uses the thermal energy of steam, usually produced in a steam boiler or steam generator, to generate mechanical energy transmitted by a shaft to another machine, such as an electric generator.
A steam turbine is a rotary heat engine. It processes the thermal energy of steam, which enters the turbine from the boiler for mechanical work.
Since a heat turbine consists of various successive stages, turbine energy calculations are reduced to calculating the individual stages. The total turbine power is the sum of the powers of the individual stages. A turbine stage consists of a stationary steering ring permanently connected to the casing and a rotor ring connected to a rotating shaft. In the working wheel, the enthalpy of the agent is converted into its kinetic energy, and in the impulse rim, the exchange of kinetic energy is converted into mechanical energy. In general, the enthalpy of the agent is converted into mechanical energy.
A turbine is a complex technical device. For commissioning, a full range of services is required: installation of a steam turbine, adjustment, testing, conducting pilot tests, and commissioning of the unit. During installation, the foundation is laid, the necessary pipes are laid, the turbine is installed and steam is supplied, as well as connected to the electrical network.
Varieties
Depending on the steam movement vector, turbines are:
- radial;
- axial.
In the first, the steam flow is directed perpendicular to the axis. The blade apparatus is located parallel to the rotating axis.
In axial type machines, steam moves along the rotating axis. This type of steam turbine is widely used.
Steam turbines are:
- single-casing;
- two-casing;
- three-casing;
- multi-casing.
Inside the turbine, a double energy conversion occurs:
- When steam expands, the thermal energy of the steam is converted into the kinetic energy of the steam flow (this occurs mainly in stationary intermolecular channels),
- In the intermolecular channels of the rotor, the kinetic energy is converted into mechanical work.
The turbine blade system consists of stationary blade rims (blades and casing) and rotating rims (rotor).
In the blade apparatus, some of them are stationary during operation. They are called nozzle blades. They serve the purpose of providing additional acceleration to the steam flow. Blades that are in the rotation cycle are called working blades.
The steam turbine is reliably protected from air penetration from the outside. This is achieved by using various seals, which receive steam in small quantities.
If the turbine rotation speed exceeds the standard values, the steam supply can be turned off using the safety regulator, which is located on the front section of the shaft.
By the state of the thermodynamic factor, turbines are:
- for superheated steam with subcritical pressure,
- for superheated steam with supercritical pressure,
- for saturated steam (used in nuclear power plants).
By angular velocity, there are:
- turbines with normal speed (50 or 60 Hz),
- turbines with half speed (25 Hz or 30 Hz),
- high-speed turbines with gear transmission.
By purpose, turbines are:
- for driving electric generators,
- for driving working machines (pumps, compressors, etc.),
- for setting in motion transport means (ships, etc.).
Turbine with energy-saving properties
Is an excellent replacement for reducing devices. The turbine design allows the use of saturated steam, as well as steam with significant differences or the so-called "crumpled".
Such equipment can be two-crown single-stage for quick acceleration and stop of the rotor. The use of such a steam turbine is simple: start and stop is carried out using a button, and the operation of the unit is regulated by automation.
Turbines up to 1000 kW
Such equipment is used to utilize excess steam energy, which makes the conservation of electrical energy effective. When using this technology, steam is obtained not by throttling (a similar method is used in boiler houses), but by expansion, as a result of which additional energy is created, electricity and heat are produced.