Influence of Fuel Jet Momentum on Characteristics of a Reverse-Cross Flow Combustor

The current work is aimed towards development of high thermal intensity, low emission combustor for gas turbine engines. Employing discrete and direct injection of air and fuel in a combustion chamber and has been demonstrated to result in low pollutant emissions (NO_x, CO, UHC). From our previous investigations, we found that the reverse-cross flow configuration, where air is injected from the exit end and fuel is injected in the cross flow of the injected air, results in favorable combustion and emission characteristics. Though the air jet is the dominant jet, the fuel jet can also influence the flow field, mixing and the combustion behavior inside the combustor, which is the subject of the current investigation. Here we investigate a high thermal intensity combustor relevant to gas turbine engines (at equivalence ratio of 0.8, the combustor operates at thermal intensity of 39 MW/m³-atm and heat load of 6.25 kW). Natural gas is used as the fuel and two different fuel injection diameters of 1 mm and 2 mm are investigated. This result in significantly higher (four times) fuel jet momentum from the smaller fuel injection port as compared to the larger port. From computational fluid dynamics (CFD) studies, it is observed that for the case with higher fuel jet momentum, the fuel jet deflects the air jet such that the flow pattern is significantly altered as compared to the case with lower fuel jet momentum. OH* chemiluminescece images show that the reaction zone location is significantly affected with high momentum fuel jet. NO_x is reduced whereas CO is increased with higher momentum fuel jet.