Brayton Cycle

Ideal cycle for gas turbines. Open cycle. Named after George Brayton.

The cycle is converted to a close cycle using a heat exchanger (aka. heat recovery steam generator).

Processes

1 → 2: isentropic compression (compressor) 2 → 3: constant-pressure heat addition (combustor) 3 → 4: isentropic expansion (turbine) 4 → 1: constant-pressure heat rejection

Pressure Ratio

$$r_p = \frac{P_2}{P_1}$$

Efficiency

$$\eta = 1 - \frac{1}{r_p^{1 - \frac{1}{k}}}$$

Back-Work Ratio

$$BWR = \frac{W_\text{comp}}{W_\text{turb}} = \frac{W_\text{in}}{W_\text{out}}$$