With an increase in global need of fossil fuels and considering the fact that they are non renewable, it is necessary to investigate the optimization of their industrial applications. Vast application of combustion process in industry raises the need for the optimization of combustion systems. To achieve this goal and maximize the performance of combustion process, reducing the fuel consumption and minimizing the pollution are needed. In this study, a three-dimensional model is used for numerical simulation of combustion process with methane gas. Effects of increasing the amount of inlet air and air temperature as preheating on the parameters of combustion process are investigated. And the results of this study are shown in the presented diagrams.