A Study On Reaction Conditions And Characteristics Of Mild Combustion Of Gas Turbine Combustor Application

Mild combustion is a promising low NOx combustion mode for next generation gas turbine combustor for its low flame temperature caused by preheated and low oxygen concentrated air. Combining experimental model and numerical model, thermodynamic and flow conditions, and combustion characteristics of mild combustion are explored, the purpose of which is to better understand the reaction conditions of mild combustion, expand the operation range and provide technical support for the design of mild combustion gas turbine combustor.The ideal model is to implement mild combustion after quick mixing of flue gas and fuel/air. Experimental model and numerical model are set up. This research set up an experimental model by uncoupling the mixing process:a first section of the setup generates flue gas, which mixes quickly with fuel/air in a mixing section, and then mild combustion occurs in a second section. Numerical model is set up using chemical reactor network. It is found that flue gas and fuel/air mix well in the experimental setup, which validates the feasibility of the experimental model approach.By numerical approach, the implement conditions of mild combustion in gas turbine combustor is determined. The flue gas mixing ratio affects mild combustion operation range by changing the temperature of mixture. Ignition delay time decreases while the mixing ratio increases. It is found that mild combustion is of wide fuel flexibility and load flexibility, which reflects the feasibility of mild combustion of gas turbine combustor application.Using experimental model and numerical model, mild combustion operation range in experimental setup is determined. Mild combustion conditions are:mixing ratio larger than 1, mixture temperature higher than 1200K, and oxygen concentration less than 13%. The ignition delay time is mainly affected by the temperature of the mixture of flue gas and fuel/air. Damkohler number is induced to analyze the flow conditions which relates flow characteristic time and chemical characteristic time.Finally, mild combustion characteristics in the experimental setup is explored. The flame of mild combustion is distributed in a large space, flame luminosity as well as OH intensity is very low. Mild combustion can suppress NO emission. The flame stability is quite high, because temperature of the mixture is higher than its ignition temperature, and no specific flame stability mechanism is required.The present study determined the reaction conditions of mild combustion of gas turbine combustor application. The phenomenon and combustion characteristics of mild combustion is better understood.