Adiabatic flame temperature is pretty straightforward to calculate if you know he feed composition the air.composition and the air to fuel ratio (amount of excess air) and the preheat temperature of the fuel and the air.  You can do the calculation by have the heating value of each of the feed component but it is easier to simulate it in a Gibbs reactor with a simulator like Hysys.  If you don't have a simulator and you have heat of combustion at 25C  and Cp. 1) heat/cool fuel and air to 25 C and the heat of combustion at 25 C calculate Cp of flue gas (CO2, H20, N2 and Excess O2" add he heat to cool feed to 25C plus heat if combustion to the flue gas to heat it to the "adiabatic flame temperature".  If you change the composition of the fuel or the amount of excess air or you dope the air with O2 or a contaminant like N2 the adiabatic flame temperature will change.  If you give me more details I may have a spreadsheet that will do the calc for you.  But it is easier to use a simulation tool like Hysys..

The adiabatic flame temperature depends upon feed ratio and the preheat temperature of the fuel and the air.  The maximum adiabatic flame temperature for a given fuel and oxidizer combination occurs with a stoichiometric mixture (correct proportions such that all fuel and all oxidizer are consumed). The amount of excess air can be tailored as part of the design to control the adiabatic flame temperature. The considerable distance between present temperatures in a gas turbine engine and the maximum adiabatic flame temperature at stoichiometric conditions is shown in attached figure, based on a compressor exit temperature of  922 K.