Brayton Cycle Efficiency Calculator

The Brayton cycle is the idealized thermodynamic cycle that models gas turbines and jet engines, consisting of adiabatic compression, constant-pressure heat addition (combustion), adiabatic expansion (through the turbine), and constant-pressure heat rejection.

η = 1 − (1/rp)^((γ−1)/γ), where rp is the pressure ratio (compressor outlet pressure divided by inlet pressure) and γ is the heat capacity ratio of the working gas.

Pressure ratio rp is the ratio of the pressure at the compressor's outlet to the pressure at its inlet, a key design parameter for gas turbines that directly determines the ideal Brayton cycle efficiency.

In the idealized Brayton cycle, the temperature ratio across each adiabatic process is fixed entirely by the pressure ratio (via the adiabatic relation), so the efficiency formula reduces to depend only on rp and γ, though a higher peak temperature does increase the actual work output per cycle even though it doesn't change the ideal efficiency ratio.

Modern industrial gas turbines and jet engines commonly operate with pressure ratios from about 15 up to 40 or higher, giving high ideal Brayton efficiency, though real turbines achieve less due to compressor and turbine inefficiencies and other losses.

The Otto and Diesel cycles model piston (reciprocating) engines with intermittent combustion, while the Brayton cycle models continuous-flow turbomachinery (compressor-combustor-turbine), with fluid continuously flowing through the system rather than being compressed and expanded in a single cylinder.

A combined-cycle plant pairs a Brayton cycle gas turbine with a Rankine cycle steam turbine, using the gas turbine's hot exhaust to boil water and drive a second turbine, capturing energy that would otherwise be wasted and achieving significantly higher overall efficiency than either cycle alone.

In the idealized cycle, no, ideal efficiency depends only on pressure ratio and γ. In practice, higher turbine inlet temperature increases the actual net work output per unit of airflow, which is why advances in high-temperature turbine blade materials and cooling are a major focus of real gas turbine engineering.

At a pressure ratio of 15, the ideal Brayton cycle efficiency is about 53.9%, rising further at higher pressure ratios used in modern high-performance turbines, real achieved efficiency is lower due to component losses.

Yes, it describes the thermodynamics of industrial gas turbines used for electricity generation (standalone or in combined-cycle plants), as well as some auxiliary power units and marine propulsion systems.