The steam turbine is one of the oldest and most widely used traditional mobile technology. These turbines drive countless motors and generate electricity in many factories around the world. Steam turbines have been in use for over 120 years, as their equivalent steam engines are being replaced due to higher efficiency and lower costs. For large units, steam turbine capacity can range from 20 kW to hundreds of megawatts (MW).
Steam turbines are commonly used in the direct-drive configuration to generate most of the mechanical energy using the least amount of steam in a compact drive configuration. The ability to change or adjust the speed is also important for steam turbines. Today, steam turbines are widely used in a variety of mechanical drive and generator applications with a global production capacity of nearly 1 million (megawatts).
The steam turbine rotor is a rotating part with wheels and blades attached. Blades are components that receive energy from the steam.
A steam turbine operates on the Rankine cycle. It works in the following way:
During the working, the steam hits the first row of blades with great pressure, which can create torque in a small area of the surface. The steam pulse causes the rotor to rotate. However, as the vapor phase of the turbine progresses, the vapor loses its pressure and energy, so it must increase the level. Because of this, the size of the leaves increases with each step.
As the steam exits the turbine, its temperature decreases, and most of the pressure increase disappear. There is also a pressure drop in the diaphragm, which is the part between the outer wall and the inner mesh. The diaphragm directs the steam diaphragm towards the rotating blades.
Types of Steam Turbines
The steam turbines have the following types:
The main type of steam turbine is the condensing turbine, which uses for driving large applications that exceed a certain power range (for example, as a very difficult indicator, above 8 MW).
These steam turbines directly suck one or more condensers and maintain a vacuum when the steam turbine is empty. A row of tubes containing steam cooling water flushes with water (liquid) in the condenser.
When cold water sends steam to the condenser (turbine outlet) near the atmosphere, a vacuum creates in the condenser. Since a small amount of air enters the system when the pressure is below atmospheric pressure, relatively small compressors are often used to remove minor gases from the condenser. Non-liquefied gases can contain air, small quantities of corrosion products due to the reaction of water and iron, and hydrogen.
This turbine compaction process provides maximum mechanical strength and efficiency in steam supply. However, the output of dense steam turbines is very sensitive to ambient temperature. The hive steam turbine is expensive, cumbersome, complex, and unsuitable for mechanical applications.
Steam turbines, especially for small and medium-sized engines, lose steam around the rows of blades and at the end of the seal. Air can enter the system when one end is at low pressure, such as a dense turbine. The strength of the loss was less than expected.
2) Back-pressure Turbine
Another type of steam turbine is the back pressure turbine, which is the most suitable equipment for mechanical applications such as compressors or pump drives. The term pressure refers to a turbine that emits steam at a higher pressure than the atmosphere. The discharge pressure is usually determined by the specific use of steam on the system. Low-pressure turbines often use in small and large low pressure (LP) applications such as heating systems, and higher pressures often use when supplying steam to industrial processes.
Industrial processes often involve further expansion of smaller mechanical drives, using small steam turbines for long-term continuous operation of rotating equipment (e.g., oil pumps, lubricants).
When steam uses at the right pressure instead of expanding into the vacuum in the condenser, significant power generation capacity is lost. The steam is discharged to the steam distribution system with a size of 10 bar (bar). About half the power can sacrifice when the steam inlet is 50 bar and 420 ° C (small and medium-sized conventional steam turbines).
3) Extraction Turbine
The extraction turbine has one or more nozzles in its chamber to absorb part of the steam at certain medium pressure. The resulting steam can use for process purposes. Depending on the design of the turbine, the extracted pressure may or may not be automatically adjusted.
The removal of regulated air improves the flow rate through the turbine to create greater mechanical strength depending on the operating conditions. In some specialized steam turbines; different extraction points may consider. Each extraction point is under different pressure related to different temperatures that require heating services; (or other services) in the factory.