Braytoncykler

Braytoncykler, or Brayton cycles in English, are thermodynamic cycles used to model the operation of gas-turbine and jet engines. The cycle describes a steady-flow process in which the working fluid is compressed, heated at roughly constant pressure, expanded through a turbine, and then returned to the compressor. In an open Brayton cycle the working fluid (typically air) enters from the environment and exhausts back to it, while in a closed Brayton cycle the fluid circulates in a sealed loop and heat is exchanged with external sources.

Variants of the Brayton cycle include intercooling, reheating, and regeneration, which modify the sequence and conditions of compression and expansion to improve efficiency or power output. Gas-turbine power plants often employ open cycles, whereas closed cycles are used in specialized applications and where heat sources are external to the working fluid. Intercooling reduces the work required by the compressor, reheating increases turbine work, and regeneration uses exhaust heat to preheat the incoming air, reducing fuel consumption.

History and naming: The cycle is named after George Brayton, an American inventor who studied constant-pressure combustion engines in the 1870s. The Brayton cycle has since become a standard theoretical model for modern gas turbines and jet propulsion, even though practical devices introduce irreversibilities and non-idealities that differentiate real performance from the ideal model.

Efficiency and practical use: In the ideal Brayton cycle with a perfect gas and isentropic compression and expansion, thermal efficiency increases with the pressure ratio. A common expression for the ideal case is η ≈ 1 − (P1/P2)^{(γ−1)/γ}, where γ is the specific-heat ratio (about 1.4 for air). Real cycles are limited by material temperature limits, component efficiencies, and losses, but the Brayton cycle remains foundational for designing and analyzing contemporary gas-turbine and jet-engine systems, including combined-cycle plants that reuse exhaust heat to generate additional power.