GE Oil & Gas. Heavy duty gas turbine monitoring & protection

GE Oil & Gas, 1631 Bently Parkway South, Minden, 2015. — 48 p.A gas turbine is an internal combustion rotary engine that converts
fuel into mechanical output power to drive equipment such as
electric generators, pumps, and compressors. Gas turbines are
widely used in the power generation and the oil and gas industry in
production, midstream and downstream applications.
A typical gas turbine contains three main sections: the compressor,
the combustor, and the turbine. The compressor is connected to the
turbine by the same rotor.
The basic functions of the three sections are: 1. Compressor – Compresses the incoming atmosphere to a
high pressure into the combustion area.2. Combustion area – Mixes a fuel with the compressed
atmospheric air and burns the air - fuel mixture and produces
high-pressure, high-velocity gas that passes through
the turbine section.3. Turbine (Expander) – Extracts the energy from the highpressure,
high-velocity gas flowing from the combustion
chamber. The extracted energy is converted to a mechanical
output resulting in the rotation of the turbine rotor.
The mechanical output of the turbine rotor is used to drive the
driven machine directly or sometimes through a gear box. The
mechanical output also drives the compressor section of the gas
turbine which brings in high-pressure air to mix with the fuel for
combustion to continue the cycle over again. Roughly 50 percent
(ranging from 40 to 80 percent) of the power generated by the
turbine section is consumed by the compressor.
External power is required to get the compressor section rotating
before the combustion section and turbine section can perform
their tasks. The startup of a gas turbine is often accomplished
with an external starting mechanism such as an electric motor or
hydraulic motor, which is temporarily applied to initially turn the
gas turbine rotor. The gas turbine (compressor and turbine) rotor
is accelerated to approximately 20 to 25 percent of rated speed
before the combustor is fired. Then an additional 40 to 60 percent
of the rated speed is necessary for the gas turbine to fully start
and become self-sustaining. This cranking of the gas turbine is also
held for a period of a few minutes to purge the gas turbine of any
possible unwanted gases that may be in the turbine.
A wide variety of fuel types can be used, such as natural gas,
diesel oil, residual oils, crude oil, syngas from refineries, and the
gasification of solid fuels such as coal and other organic matter.
The fuel type governs the need for any fuel treatment skids, and
the combustor design needs to also be matched to the fuel type for
proper combustion.
The formal name of the thermodynamic process is as the
Brayton Cycle. This cycle can be broken down into three individual
thermodynamic processes know as isentropic compression,
isobaric (constant pressure) combustion, and isentropic expansion.
The gas turbine is a fairly complex system operating at high
speeds and high temperatures that place significant demands
on the direct mechanical system and support systems. As such,
the gas turbine can benefit from protection and condition
monitoring systems to identify problematic conditions, avoid
significant machine damage, and enable planned maintenance
to be performed.