Experimental Investigation of a Multiplex Fuel Injector Module with Discrete Jet Swirlers for Low Emission Combustors

A low-NOx emissions combustor concept has been demonstrated in flame-tube tests. A lean-direct injection (LDI) concept was used where the fuel is injected directly into the flame zone and the overall equivalence ratio of the mixture is lean. The LDI concept described in this report is a multiplex fuel injector module containing multipoint fuel injection tips and multi-burning zones. The injector module comprises 25 equally spaced injection tips within a 76 by 76 mm area that fits into the flame-tube duct. The air swirlers were made from a concave plate on the axis of the fuel injector using drilled holes at an angle to the axis of the fuel injector. The NOx levels were quite low and are greater than 70 percent lower than the 1996 ICAO standard. At an inlet temperature of 810 K, inlet pressure of 2760 kPa, pressure drop of 4 percent and a flame temperature of 1900 K with JP8 fuel, the NOx emission index was 9. The 25-point injector module exhibited the most uniform radial distribution of fuel-air mixture and NOx emissions in the flame tube when compared to other multipoint injection devices. A correlation is developed relating the NOx emissions to inlet temperature, inlet pressure, equivalence ratio and pressure drop.