Discipline: Technology and Engineering
Subcategory: Physics (not Nanoscience)
Leavohn Lewis - Tuskegee University
Co-Author(s): David Alexander IV, Tuskegee University; Javis Howard, Tuskegee University
This research aims at improved mixing of fluids for high speed applications, such as fuel and air mixing in a scramjet engine to enhance the efficiency and economy of such systems. To achieve this, the research group at Tuskegee University has designed and developed a prototype of the resonance enhanced micro-actuator nozzles (REM-nozzles) integrated with high frequency actuators. Theses REM-nozzles can inject a steady fluid, such as fuel, surrounded by supersonic pulsing micro-actuators (micro-jets) pulsing at 13-21kHz. The REM nozzle design is composed of four major elements. An under expanded source jet from a 1.5mm nozzle flows into a constricted cavity with a 1 mm nozzle, through which the pulsed high frequency jet flows out surrounding four 0.4mm nozzles, through which steady mixing fluid is injected [1&2].
To understand the flow fields of the prototype REM nozzles, a micro-Schlieren imaging system was developed to capture the flow characteristics of nitrogen and compressed air. This micro-Schlieren system uses lens and knife edges in order to refract light, and a high speed camera to capture the high speed flows from the REM nozzles. A customized LED was used with the camera for time resolved images. Also, data from the flowfield are captured in multiple ways, such as LabVIEW for Fast Fourier Transform (FFT) analysis, and MATLAB for background subtraction.
This abstract report studies on mixing of a fluid with a steady supersonic actuation jet in comparison to an unsteady pulsing jet. The microschlieren images shows that the compressed air injected from REM nozzle at 10 psi has a cone shaped plume envelope. At the center of this plume a steady jet is being injected at a rate of 65 psi. Pulsed supersonic jet also experimented at the center of the plume for mixing studies at the same pressure. Images indicate qualitative evidence of entrainment both in steady and unsteady actuation. However, unlike the steady jet mixture, the pulsing jet creates vortices at higher frequency rate that expand the interfacial area between the nitrogen and air due to the entrainment of the air by the vortices generated.
More detailed analysis on how a REM nozzle could improve mixing of fluids through pulsing will be presented in the conference.
References:
[1]. Solomon, J., Nayak, C., Alexander, Caines, K., Higgins, F., and Jones, M., 2017, ‘High-Speed Flow Mixing Using High Frequency Pulsed Microactuators,’ AIAA SciTech Forum, 2017.
[2]. Solomon, J., Nayak, C., Alexander, Caines, K., and Jones, M., 2017, ‘Design and Characterization of Nozzle Injection Assemblies Integrated High-frequency Microactuators,’ Submitted to AIAA Journal and under review, 2017.
[3] Solomon, J, Alexander, J, J. Howard, Lewis, L and C. Nayak Temporal Flow Characteristics of High-Frequency Supersonic Actuators Integrated in REM-Nozzle Assembly, to be presented in ICTACEM conference at IIT Kharagpur, India, Dec 2017.
Not SubmittedFunder Acknowledgement(s): Funding was provided by NSF/ HBCU-UP grant to Dr. John Solomon.
Faculty Advisor: Dr. John Solomon, JSolomon@tuskegee.edu
Role: The microschlieren images shows that the compressed air injected from REM nozzle at 10 psi has a cone shaped plume envelope. At the center of this plume a steady jet is injected at a rate of 65 psi. The pulsed supersonic jet was also experimented at the center of the plume with the same pressure. Images indicate qualitative evidence of entrainment both in steady and unsteady actuation. However, unlike the steady jet mixture, the pulsing jet creates vortices at higher frequency rate that expand the interfacial area between the mixture due to the entrainment caused by the vortices generated.