GAS TURBINE
POWER PLANT:
A gas turbine, also called
a combustion turbine, is a type of internal combustion engine. It has an
upstream rotating compressor coupled to a downstream turbine,
and a combustion chamber in-between.
Energy is added
to the gas stream in the combustor, where fuel is mixed with air and ignited.
In the high pressure environment of the combustor, combustion of the fuel
increases the temperature. The products of the combustion are
forced into the turbine section. There, the high velocity
and volume
of the gas flow is directed through a nozzle over the
turbine's blades, spinning the turbine which powers the compressor and, for
some turbines, drives their mechanical output. The energy given up to the
turbine comes from the reduction in the temperature and pressure of the exhaust
gas.
COMBINED POWER
CYCLES:
In electric power generation a combined
cycle is an assembly of heat engines that work in tandem off the same
source of heat, converting it into mechanical energy, which in turn usually
drives electrical generators. The principle is
that the exhaust of one heat engine is used as the heat source for another,
thus extracting more useful energy from the heat, increasing the system's
overall efficiency. This works because heat engines are only able to use a
portion of the energy their fuel generates (usually less than 50%).
The remaining heat (e.g., hot
exhaust fumes) from combustion is generally wasted. Combining two or more
thermodynamic cycles results in improved overall efficiency, reducing fuel
costs. In stationary power plants, a successful, common combination is the Brayton cycle
(in the form of a turbine burning natural gas
or synthesis gas
from coal)
and the Rankine cycle (in the form of a steam power
plant). Multiple stage turbine or steam cylinders are also common.
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