How a gas turbine works
An industrial gas turbine is a rotating engine that burns fuel in a continuous flow of air. It has three main sections.
- Compressor. Draws in air and squeezes it to a higher pressure.
- Combustor. Fuel is injected and burned in the compressed air, raising its temperature sharply.
- Turbine. The hot, high-pressure gas expands through turbine blades, spinning the shaft. Part of the shaft power runs the compressor, and the rest is the useful output.
The useful output either turns a generator, or drives a mechanical load such as a pipeline compressor or a large pump. Despite the name, “gas” in the turbine refers to the working gas flowing through, not necessarily to natural gas fuel. Many units burn natural gas, and some can burn liquid fuels. This is different from the on-site gas generation equipment discussed under industrial gas generators, which produces gases such as nitrogen or oxygen.
Where they are used
Common roles include:
- Electric power generation, both for utilities and for large industrial sites.
- Combined heat and power (cogeneration). The exhaust is still very hot, so it can be used to make steam or hot water. Using this heat is related to waste heat recovery, and it is one reason the overall fuel use of a site can be lower than when electricity and heat are made separately.
- Combined-cycle plants, where exhaust heat makes steam for a steam turbine as well.
- Mechanical drive, in oil and gas facilities for compressors and pumps.
- Offshore and remote locations, where compact power is valued.
Some designs are derived from aircraft engines and are light and quick to start. Others are heavy-duty industrial frames built for long, steady operation.
Selection considerations
A turbine is a major investment, and the selection involves specialists. The general questions include:
- Required output and duty. Is it for continuous operation, peaking duty with frequent starts, or standby? Frequent starts and stops usually wear turbines faster than steady running.
- Heat needs. If there is a steady use for the exhaust heat, a cogeneration arrangement may suit. Without one, smaller engine-driven units might be worth comparing; see the notes on prime power generators.
- Fuel supply. Availability, pressure and quality of the fuel. Fuel contaminants can damage hot parts.
- Site conditions. Output generally falls when ambient air is hot or when the site is at high altitude, because the air is less dense.
- Emissions rules. Local limits often require specific combustion technology or exhaust treatment.
- Noise, space and ventilation. Turbines are loud, need large volumes of air and need clearance for maintenance.
- Support and parts. Long-term service arrangements and availability of spares matter as much as the purchase.
- Electrical connection. Grid interconnection, protection and the switchgear involved need to be designed with the generator.
Maintenance at a general level
Gas turbines run at very high temperatures and speeds, so their maintenance is planned, documented and usually guided by the manufacturer’s schedule. Typical themes are:
- Inlet air. Filters keep dirt out of the compressor. Fouling lowers performance, and cleaning is part of routine care.
- Condition monitoring. Operators watch vibration, temperatures, pressures and performance trends, with methods similar to vibration analysis for other rotating equipment.
- Lubrication systems. Oil quality, filters and bearings need regular checks.
- Combustion and hot section inspections. Periodic inspections look at combustors and turbine blades. Intervals are often counted in operating hours and number of starts rather than calendar time.
- Fuel system. Nozzles, filters and valves need attention.
- Controls and protection. Sensors, trip systems and fire protection must be tested.
- Major overhauls. Large parts may be sent for specialist repair or replaced.
Because outages are expensive, many owners plan critical spares and schedule work during planned shutdowns.
Safety
Gas turbines involve high-pressure fuel, very hot surfaces, rotating equipment and hazardous electrical connections. Operation and maintenance should be left to trained and certified personnel working with the manufacturer’s procedures, energy isolation methods and local regulations. This article is general information, not engineering advice.