Unique, stabilized flame in fuel injectors created by ignitor-booster system

A new airfoil-shaped fuel injector with an ignitor-booster system, was designed for the 8-Foot High-Temperature Tunnel (8-FT HTT) at NASA Langley Research Center. This fuel injector was developed so that it could be used as an uncooled injector in high-pressure, oxygen-enriched air. This effort required the development of new technology in fuel injector design. A high-velocity, vortex stabilizer injector was developed. The development and tests conducted in a simple fan-driven apparatus are explained for the injectors at atmospheric pressure. Similar tests at high pressure were carried out in the Combustor Heated Test Facility (CHTF) with air and with oxygen enriched air. The ignition of the fuel injector array is a quasi-stable ignition scheme. The stabilizing concept was obtained through tests validated with the computational fluid dynamics (CFD) code FLUENT. A large sonic jet of methane is extremely difficult to ignite. A pilot burner added to the flow at an equivalence ratio of 3 generates H2, CO, and H20. These products are very hot at 3000°R; the reaction of the CO and H2 enables the stability of the near sonic methane air flame. The combination of pilot and near sonic jet flames yields a large, vigorous stable flame that is ideal for igniting the large fuel injector array. The results helped the design engineers of the 8-FT HTT to define the correct diameter of fuel orifices of injectors and fuel and air velocities. A final three-dimensional case using FLUENT was the simulation of the combustion processes of both the ignitor and fuel injectors to examine the size of the flame and its effect on the fuel injectors and liners of the 8-FT HTT. In conclusion, the present study helps the designers of the airfoil fuel injector and the 8-FT HTT ignitor to predict and verify the high performance and reliability of successful ignition of the tunnel.