Researchers: Prof. Ann Karagozian, Prof. Owen Smith Former Researchers: Mark Mitchell (grad), Ari Majamaki (grad), Thomas Selerland (grad), Olivier Delabroy (grad), Tim Gerk (grad), Robert Lobbia (undergrad), Lydia Treviño (undergrad), Dr. Lance Smith (postdoc) Research Supported By: NASA and The Office of Naval Reseach

	Layout of lobed injector showing gap through which fuel is injected.

This project involves modeling, design, construction, and testing of a unique lobed injector/burner. The shape of the burner is designed to generate a large degree of streamwise vorticity with low a pressure drop. This results in very rapid mixing of the fuel, which is introduced through the slot, and the surrounding air. Near the injector exit strain rates can be made high enough to suppress combustion, so that burning occurs further downstream in a partially premixed mode. This is seen to result in lower formation rates of thermal NO_x and products of incomplete combustion.

Both low speed as well as transonic mixing experiments utilized acetone planar laser-induced fluorescence (PLIF) from which mixedness, scalar dissipation rates, and strain rates have been extracted. A combustion tunnel was used to study ignition delay and emissions reduction using the lobed fuel injector. Numerical simulation of a component of the mixing and reacting flow problem, the strained fuel strip, has also been completed.

Recent work in this project has involoved transonic wind tunnel testing of lobed injectors. PLIF was again used to image slices of the flow at specific locations downstream of the injector. The images have been processed and scalar dissipation and strain rates have been measured at various Mach numbers. In coordination with these experimental tests numerical simulations (using vortex elements) were performed showing some striking similarities.

Mixing evolution due to lobed fuel injector seen here in these images taken at different downstream locations from the exit of the lobed injector (injectant illuminated via acetone PLIF).		The four injectors tested, starting from upper left going clockwise the injectors are: square, half-circle rectangular, flat, and sine wave. Fuel is passed through the centers of the injectors.

Images of the injectant from the square wave lobed injector, situated at different downstream locations, as determined from: (top row) acetone PLIF experiments with the "actual" lobed injector shape, (middle row) computations of the flow or vorticity distrubution with the actual lobed injector shape as the input, and (bottom row) computations of the flow or vorticity distribution with the lobed injector shape that would be formed by an "ideal" EDM wire cut fabrication.

Photo of the fixture used for testing the lobed injector at the UCLA/A2I2 Trisonic Wind Tunnel in El Segundo, CA.

Publications:

1. Effects of Passive Fuel-Air Mixing and Emissions Control via Lobed Injectors, Mitchell, M.G., Smith, O.I., and Karagozian, A.R., AIAA Journal, Vol. 42, No. 1, pp.61-69, January, 2004.
   
   
2. Passive Mixing Control via Lobed Injectors in High Speed Flow, Majamaki, A. J., Smith, O. I., and Karagozian, A. R, AIAA Journal, Vol. 41, No. 4, pp. 623-632, April 2003.
   
   
3. Effects of Passive Fuel-Air Mixing Control on Burner Emissions via Lobed Fuel Injectors, Mitchell, M. G., Smith, O. I., and Karagozian, A. R., AIAA Paper No. 99-2400, 35^th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, June, 1999.
   
   
4. Numerical Simulation of Reactive Flows Associated with a Lobed Fuel Injector, Selerland, T. and Karagozian, A. R., Paper 97F-108, Western States Section/The Combustion Institute Fall Meeting, October, 1997.
   
   
5. Ignition, Burning, and Extinction of a Strained Fuel Strip with Complex Kinetics, T. Selerland and A.R. Karagozian, Combustion Science and Technology 131, No. 1-6, p. 251, 1998.
   
   
6. Burner Emissions Associated with Lobed and Non-Lobed Fuel Injectors, M.G. Mitchell, L.L. Smith, A.R. Karagozian, and O.I. Smith, 27^th Symposium (Intl.) on Combustion, 1998.
   
   
7. Numerical Simulations of a Lobed Fuel Injector, J. H. Strickland, T. Selerland, and A. R. Karagozian, The Physics of Fluids, Vol. 10, No. 11, pp. 2950-2964, 1998.
   
   
8. Emissions Measurements from a Lobed Fuel-Injector/Burner, M.G. Mitchell, L.L. Smith, A.R. Karagozian, and O.I. Smith, Paper AIAA 98-0802, AIAA 36^th Aerospace Sciences Meeting, Reno. NV, January 12-15, 1998.
   
   
9. Mixing Enhancement in a Lobed Injector, L.L. Smith, A.J. Majamaki, I.T. Lam, O. Delabroy, A.R. Karagozian, F.E. Marble, and O.I. Smith, The Physics of Fluids 9, pp. 667-678, March, 1997.
   
   
10. Ignition Delay Associated with Strained Fuel Layers, T. J. Gerk and A. R. Karagozian, 26^th Symposium (International) on Combustion, pp. 1095-1102, 1996