Flow characteristics of sub- and supersonic jets issued from orifice and notched orifice nozzles, and application to ejector

Abstract

The flow characteristics of sub-and supersonic under-expanded jets issued from circular nozzles have been studied well; however, this does not apply to sub-and supersonic jets from an orifice nozzle. In this study, the flow characteristics of sub-and supersonic jets issued from an orifice or notched special orifice nozzle are examined experimentally based on the results of a visualized flow pattern by the Schlieren method and the measurements of velocity distribution by a thin supersonic Pitot tube. That is, the effects of the nozzle shape on the flow characteristics such as the decay of the jet centerline velocity, velocity distribution at the cross section, increment of the jet-width and-flow rate to the downstream are examined experimentally. Results indicate that the jet issued from the notched orifice nozzle with a rectangular notch demonstrates excellent entrainment performance. In addition, to improve the performance of a cylindrical ejector, the application of the results is examined.

Flow Characteristics of Two-Dimensional Supersonic Under-Expanded Coanda-Reattached Jet

“…The minimum of the negative value and maximum of P w /P 0 increase with P 0 , and are almost the same at P 0 ≥ 0.4 MPa. This is because increasing the velocity owing to the increase in P 0 hinders the jet from entraining the surrounding fluid [12], jet flows penetrates. The numerical analysis reflected the experimental well, particularly when P 0 ≥ 0.3 MPa, that is, when P 0 is large.…”

“…Zaman [8] examined the flow characteristics of sub-and supersonic jets from special nozzles, whereas Shakouchi [12] studied those from an orifice nozzle.…”

Passive flow control of jets

“…The flow contracts suddenly at the nozzle exit and the velocity vector heads inward. The flow characteristics of a circular jet can be controlled by an orifice nozzle with a contraction area ratio (Shakouchi et al, 2008) or notched orifice nozzle (Shakouchi at al., 2009(Shakouchi at al., , 2011(Shakouchi at al., , 2019. Figure 6 shows the velocity distribution, u/u m and u'/u m , of the jet issued from an orifice nozzle measured by hot wire anemometry.…”

“…The flow characteristics of a supersonic under-expanded free jet issued from a circular (Murakami, et al, 2000) or orifice nozzle (Shakouchi et al, 2019), especially the effect of the contraction area ratio, was examined. Figure 22 shows the orifice nozzle (Ori-n) with a contraction area ratio (CR) = (d o /d i ) 2 = 0.13.…”

“…In this paper, the flow control of jets is examined with the flow characteristics, control methods, and some examples of practical applications. In particular, the effects of the nozzle shape (Fiedler, 1998), the tab, rib, and vortex generator (Samimy et al, 1993, Carletti et al, 1996, Zaman et al, 1999, Miyakoshi et al, 2003, Ito et al, 2018, and the orifice or notched nozzle (Shakouchi et al, 2008(Shakouchi et al, , 2009(Shakouchi et al, , 2011(Shakouchi et al, , 2019, on the characteristics of jet flows including supersonic jet, and suppression of the high speed jet noise by the chevron nozzle (Gutmark, 2006, Munday et al, 2013 are examined. Furthermore, some examples of active flow control (Kral, 2000), for example, using an intelligent nozzle , Kasagi, 2006 are also examined.…”