Dynamics of Transient Fuel Injection, Mixing, and Auto-Ignition
The transient behavior of auto-ignition under turbulent fuel injection is of great importance for several engineering applications, including diesel and HCCI engines and scramjets. Understanding auto-ignition also is required for situations where such events are undesired (e.g. gas turbines, SI engines) and could lead to a catastrophic failure. Autoignition in turbulent environments is a complex phenomenon, where the chemical time scales responsible for ignition are on the same order as the fluid mechanic time scales and thus both chemical kinetics and turbulence play a major role in the events that lead to ignition and flame stabilization.
We are currently investigating auto-ignition using advanced optical and laser-based diagnostics in canonical configurations to isolate the relative roles of flow turbulence, turbulent mixing, and reaction chemistry on auto-ignition processes of turbulent fuel jets injected into a high-temperature, vitiated oxidizer stream.
Below we show a schematic of the OSU auto-ignition burner (AIB) and video of the transient operation. Each "burst" is less than 50 ms and we collect more than 1000 individual sequences at each operating condition.
We have examined the role of mixing rate fluctuations on auto-igntion. Below is a sample image sequence of time-resolved mixture fraction, temperature, and OH* (representing the onset of combustion) in a Re = 40,000 DME fuel jet issuing into a T = 1330 K coflow. Each image sequence corresponds to approximately 5 ms of real time.
Results show that for the current fuels and thermodynamic conditions, auto-igntion occurs in very lean regions with low values of scalar dissipation rate [1, 2]
 Papageorge, M., Arndt, C.M., Fuest, F., Meier, W., Sutton, J.A., “High-Speed Mixture Fraction and Temperature Imaging of Pulsed, Turbulent Fuel Jets Auto-Igniting in Vitiated Co-Flows,” Experiments in Fluids, 2014, 55(7), 1763.
 Arndt, C.M., Papageorge, M., Fuest, F., Sutton, J.A., Meier, W., Aigner, W., "The Role of Temperature, Mixture Fraction, and Scalar Dissipation Rate on Transient Methane Injection and Auto-Ignition in a Jet-in-Hot-Coflow Burner", Combustion and Flame, 2016, 167, 60-71.
 Saksena R., Sutton, J.A., "Transient and Steady-State Behavior of Auto-Igniting Propane and Dimethyl Ether Fuel Jets in High-Temperature Vitiated Coflows", accepted, Proceedings of the Combustion Institute
 Arndt, C.M, Papageorge, M., Fuest, F., Sutton, J.A., Meier, W., "Experimental Investigation of the Auto-Ignition of a Transient Propane Jet-In-Hot-Coflow", accepted, Proceedings of the Combustion Institute