Flameless combustion is a novel technique developed to reduce the emissions to ultra-low level with enhanced thermal efficiency. This technique is extensively studied for various fuels and different phases of fuels. This technique is far well developed to operate at atmospheric pressure. However, its achievement at high pressure is most challenging since it involves many constraints. Reaction zone distribution in flameless combustion is in direct relation with ignition delay of the reactants. Ignition delay is in direct and inverse relation with dilution and operating pressure respectively. Hence, more dilution is required to achieve the flameless combustion at high pressure. With increased operating pressure of the combustor, the level of the dilution also needs to be increased. Therefore an attempt is made to address this issue. The present numerical study is aimed to predict suitable flow conditions to achieve flameless combustion at high pressure. In this study a combustor is developed to study the role of dilution and operating pressure on reaction distribution. A swirl-based combustor is used in this study and partial external dilution is provided at inlet of the combustor. Swirl flow pattern in the combustor creates recirculation and improves the dilution ratio. The present combustor is operating in the pressure range of 1 to 5 atm.