What is the main purpose of using low pressure turbine and high pressure turbine in a steam power plant?

The high pressure turbine is designed to efficiently extract work out of the high pressure steam as it initially enters the main propulsion turbines. The low pressure turbine is designed to efficiently extract work out of steam which is exhausting out of the high pressure turbine at a lower pressure.

Why high pressure steam is used in turbine?

A high pressure and high temperature steam from the boiler outlet needs a high pressure turbine for its expansion. In turbine, as this high pressure steam is used to drive the turbine blades, it looses it energy and gets converted to low pressure steam.

Why low pressure turbine is bigger than high pressure turbine?

As the high pressure steam comes out of the high pressure turbine losing its pressure to rotate the blades, its specific volume increases (Pressure decreases). So in order to handle fluid with high specific volume, low pressure turbine is made bigger in size.

What is the function of low pressure turbine?

The Low Pressure Turbine (LPT) is uniquely designed to provide high aerodynamic efficiency in low pressure ratio operation, to recover exhaust energy whilst minimising back pressure.

Why do we use economiser?

An economizer is a mechanical device used to reduce energy consumption. Economizers recycle energy produced within a system or leverage environmental temperature differences to achieve efficiency improvements.

Why LP turbine is double flow?

In a double flow rotor, the blades in each half face opposite ways, so that the axial forces negate each other but the tangential forces act together. This design of rotor is also called two-flow, double-axial-flow, or double-exhaust. This arrangement is common in low-pressure casings of a compound turbine.

What is low pressure turbine rotor?

The low pressure rotors, consisting of a series of alloy steel discs shrunk on a shaft and keyed in position, are machined from alloy steels forgings. Low pressure (LP) steam turbine disc cracking caused by stress corrosion is experienced worldwide in rotors used in both nuclear and fossil fuel power plants.

What is the pressure of a low pressure steam turbine?

In the low-pressure turbine the steam continuously expands from point E to F. The exhausted steam then condenses in the condenser and it is at a pressure well below atmospheric (absolute pressure of 0.008 MPa).

What is the function of economiser in power plant?

Function of economiser in thermal power plant is to recover some of the heat from the heat carried away in the flue gases up the chimney and utilize for heating the feed water to the boiler.

Why superheated steam is used in steam turbines?

Superheated steam is preferred over saturated steam because it can release a lot of its internal energy for work and remain above the liquid’s water vapor point (at a given pressure within the turbine/piston engine). Droplets of liquid that are formed can result in pitting of turbine blades.

Why are low pressure steam turbines bigger than high pressure turbines?

As the high pressure steam comes out of the high pressure turbine losing its pressure to rotate the blades, its specific volume increases (Pressure decreases). So in order to handle fluid with high specific volume, low pressure turbine is made bigger in size. It is true for the same mass of steam flow from high and low pressure turbine.

What is the quality of steam in a wind turbine?

The steam is in a partially condensed state (point F), typically of a quality near 90\%. High pressure and low pressure stages of the turbine are usually on the same shaft to drive a common generator, but they have separate cases.

What is the function of steam turbine and generator?

High pressure and low pressure stages of the turbine are usually on the same shaft to drive a common generator, but they have separate cases. The main generator produces electrical power, which is supplied to the electrical grid. Schema of a steam turbine of a typical 3000MWth PWR.

What is the difference between HPT and LPLP turbine?

LP turbines however work under low pressures and can also extract work from higher pressure medium. But due to higher pressure fluids, the turbine blades and the casing will be damaged heavily. Hence, a high pressure fluid is firstly passed over HPT and then over LPT.