Methods To Increase Power
The power output of a Brayton engine can be improved in the following manners:
- Reheat, wherein the working fluid—in most cases air—expands through a series of turbines, then is passed through a second combustion chamber before expanding to ambient pressure through a final set of turbines. This has the advantage of increasing the power output possible for a given compression ratio without exceeding any metallurgical constraints (typically about 1000 °C). The use of an afterburner for jet aircraft engines can also be referred to as "reheat"; it is a different process in that the reheated air is expanded through a thrust nozzle rather than a turbine. The metallurgical constraints are somewhat alleviated, enabling much higher reheat temperatures (about 2000 °C). Reheat is most often used to improve the specific power (per throughput of air), and is usually associated with a drop in efficiency, this effect is especially pronounced in afterburners due to the extreme amounts of extra fuel used.
- Overspray, wherein, after a first compressor stage, water is injected into the compressor, thus increasing the mass-flow inside the compressor, increasing the turbine output power significantly and reducing compressor outlet temperatures. In a second compressor stage the water is completely converted to a gas form, offering some intercooling via its latent heat of vaporization.
Read more about this topic: Brayton Cycle
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