Parametric experimental studies on mixing characteristics within a low area ratio rectangular supersonic gaseous ejector

Karthick, SK and Rao, Srisha MV and Jagadeesh, G and Reddy, KPJ (2016) Parametric experimental studies on mixing characteristics within a low area ratio rectangular supersonic gaseous ejector. In: PHYSICS OF FLUIDS, 28 (7).

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Abstract

We use the rectangular gaseous supersonic ejector as a platform to study the mixing characteristics of a confined supersonic jet. The entrainment ratio (ER) of the ejector, the non-mixed length (L-NM), and potential core length (L-PC) of the primary supersonic jet are measures to characterize mixing within the supersonic ejector. Experiments are carried out on a low area ratio rectangular supersonic ejector with air as the working fluid in both primary and secondary flows. The design Mach number of the nozzle (MPD = 1.5-3.0) and primary flow stagnation pressure (P-op = 4.89-9.89 bars) are the parameters that are varied during experimentation. Wall static pressure measurements are carried out to understand the performance of the ejector as well as to estimate the L-NM (the spatial resolution is limited by the placement of pressure transducers). Well-resolved flow images (with a spatial resolution of 50 mu m/pixel and temporal resolution of 1.25 ms) obtained through Planar Laser Mie Scattering (PLMS) show the flow dynamics within the ejector with clarity. The primary flow and secondary flow are seeded separately with acetone that makes the L-NM and L-PC clearly visible in the flow images. These parameters are extracted from the flow images using in-house image processing routines. A significant development in this work is the definition of new scaling parameters within the ejector. L-NM, non-dimensionalized with respect to the fully expanded jet height hJ, is found to be a linear function of the Mach number ratio (Mach number ratio is defined as the ratio of design Mach number (MPD) and fully expanded Mach number (MPJ) of the primary jet). This definition also provides a clear demarcation of under-expanded and over-expanded regimes of operation according to M-PD/M-PJ] > 1 and M-PD/M-PJ] < 1, respectively. It is observed that the ER increased in over-expanded mode (to 120%) and decreased in under-expanded mode (to 68%). Similarly, L-NM decreased (to 21.8%) in over-expanded mode and increased (to 20.4%) in under-expanded mode. Lengthening of L-PC by 139% and a reduction of 50% in shock cell spacing have also been observed for specific flow conditions. The details regarding experimentation, analysis, and discussions are described in this article. Published by AIP Publishing.

Item Type:	Journal Article
Publication:	PHYSICS OF FLUIDS
Additional Information:	Copy right for this article belongs to the AMER INST PHYSICS, 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA
Department/Centre:	Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Date Deposited:	22 Oct 2016 09:09
Last Modified:	22 Oct 2016 09:09
URI:	http://eprints.iisc.ac.in/id/eprint/54981

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