Discipline: Technology and Engineering
Subcategory: Civil/Mechanical/Manufacturing Engineering
David Alexander IV - Tuskegee University
Co-Author(s): Leavohn Lewis, Tuskegee University, Tuskegee Alabama; Javis Howard, Tuskegee University, Tuskegee, Alabama
High-speed flow mixing has great importance in the scramjet combustor. Despite its simple geometry, a scramjet engine experiences a rather complex flow-field. The incoming flow is supersonic and is subjected to multiple shock terrains within the engine before it reaches the combustor where the fuel is injected. The fuel jet injected needs effective and quick mixing for an efficient combustion process. Moreover, the very small convective time scale associated with the airflow demands efficient fuel injection techniques. The injected fuel should mix with the incoming air within a fraction of a second for an efficient combustion process and heat release. For improved and controlled mixing at high speed, we have developed an active scheme. The resonance enhanced microactuator (REM) nozzle system developed can steadily inject a fluid through four micro-nozzles of 400 ?m diameter positioned around a 1 mm nozzle through which the high frequency, pulsed supersonic jet flows out. This configuration has the potential to aid mixing at a high speed. The REM nozzle design is composed of 4 major elements. An under expanded source jet that enters a constricted cavity with nozzle through which the pulsed high frequency micro-jets exit, and four micro-nozzles integrated surrounding a 1 mm nozzle through which a steady jet exits [1-3].
In this study, the REM-nozzle uses a high frequency pulsed micro-jet in a frequency range of 13-21 kHz that produces compressible vortices in the flow-field in the same frequency range. High speed microschlieren imaging is used to understand the flow-field quantitatively and qualitatively. Flow-field images acquired using a 64-kHz frame rate with corresponding time signatures were used to obtain the Mach disc oscillations of source jet and the velocity at which the vortex evolves downstream. The Mach disc oscillation is measured at an average frequency of 12.82 kHz with a velocity of 4.52 m/s, while the pulsed flow vortices propagated at an average velocity of 212.10 m/s. A qualitative analysis of the flow structures, using microschlieren imaging, displayed the mixing characteristics. The vortices produced by the pulsing jet expanded the interfacial area between the fluid and actuation stream which signifies the improved mixing at high speed.
. J.T. Solomon., C. Nayak., K. Cairnes, D. Alexander, M. Jones, ‘Resonance Enhanced Microactuator Nozzles for high-speed flow mixing’, AIAA Aviation Forum, Colorado, 2017-4308.
. J.T. Solomon., C. Nayak., K. Cairnes, D. Alexander, M. Jones, Higgins., ‘High-Speed Flow Mixing Using High-frequency Microactuators ‘, AIAA, Scitech Forum Grapevine, TX 1885- 2017.
. J.T. Solomon, J., Caines, K., Nayak, C., Jones, M., and Alexander, D. 2017, ‘Design and Characterization of Nozzle Injection Assemblies Integrated High Frequency Microactuators,’ AIAA Journal under review submitted Aug. 19, 2017.Not Submitted
Funder Acknowledgement(s): Funder Acknowledgement: Funding was provided by NSF/ HBCU-UP grant to John Solomon
Faculty Advisor: Dr. John Solomon, firstname.lastname@example.org
Role: In this research, I designed one of the two actuator nozzles tested for the high speed mixing studies. Performed the characterization study on the REM nozzle. Designed and conducted experiments to acquire, process and analyze data. Assisted in setting up the flow diagnostics laboratory at Tuskegee University. Designed the apparatus set up for the actuator nozzle and a component of the microschlieren system.