Imagine a Brayton cycle where heat is added at constant volume instead of constant pressure. We want to develop a mathematical formula for its thermal efficiency. This formula should involve factors like the pressure ratio $($rp$),$ the specific heat ratio $(\backslash$gamma $),$ and a new term called the combustor temperature ratio $(\backslash$psi $),$ which represents the ratio of temperatures T$3$ and T$2$ across the combustor.