Characteristics of cold-flow modes and gas concentration distributions behind a novel unconfined nozzle

Abstract

This study utilized a novel Tai-Chi swirl generator (TCSG) to modulate the cold-flow behaviour behind a conventional/pure-jet nozzle. This TCSG significantly increased the air-CO₂ mixing efficiency. The TCSG was installed at the exit of the pure-jet nozzle so as to transform the axial momentum into tangential momentum. The turbulence intensity increased when the flow passed through the TCSG. Laser-light sheet and smoke-wire flow visualization schemes were utilized to explore the modulated flow characteristics behind the TCSG. The flow patterns were categorized into five modes: jet flow, recirculation bubble, deflected flow, unstable flow, and turbulent flow modes. The vortex-shedding frequency behind the pure-jet nozzle increased as the Reynolds number of the annular jet (Re_a) increased. However, the vortex-shedding frequency behind the bluff disc controller and TCSG decreased as Re_a increased. The mixing efficiency of air and CO₂ in each characteristic mode was determined by measuring the concentration of CO₂ released from the nozzle centre. The highest mixing efficiency occurred in the unstable flow mode.

Keywords

Tai-Chi swirl generator flow characteristics gas concentration

Get full access to this article

View all access options for this article.

References

Reynolds

W. C.

Parekh

D. E.

Juvet

P. J. D.

Lee

M. J. D.

Bifurcating and blooming jets. Ann. Rev. Fluid Mech., 2003, 35, 295–315.

Gutmark

E. J.

Grinstein

F. F.

Flow control with noncircular jets. Ann. Rev. Fluid Mech., 1999, 31, 239–272.

Nathan

G. J.

Luxton

R. E.

Centreline mixing characteristics of jets from nine differently shaped nozzles. Exp. Fluids, 2000, 28, 93–94.

Zheng

Q. P.

Jasuja

A. K.

Lefebvre

A. H.

Structure of airblast sprays under high ambient pressure conditions. Trans. ASME, J. Engng Gas Turbines Power, 1997, 119, 512–518.

Carmody

Establishment of the wake behind a disk. J. Basic Engng, 1964, 86, 869–882.

Davies

T. W.

Beer

J. M.

Flow in the wake of bluff-body flame stabilizers. In: Proceedings of the 13th International Symposium on Combustion, Salt Lake City, Utah, 23–29 August, 1971, 631–638.

Durao

D. F. G.

Whitelaw

J. H.

Velocity characteristics of the flow in the near wake of a disk. J. Fluid Mech., 1978, 86, 369–385.

Schefer

R. W.

Namazian

Kelly

Velocity measurement in turbulent bluff-body stabilized flows. AIAA J., 1994, 32, 1844–1851.

Rose

W. G.

A swirling round turbulent jet 1-mean-flow measurements. J. Appl. Mech., 1962, 29, 615–625.

10.

Hartnett

J. P.

Eckert

E. R. G.

Experiment study of the velocity and temperature distribution in a high velocity vortex type flow. Trans. ASME, Part I: J. Fluids Engng, 1957, 79, 751–757.

11.

Hübner

A. W.

Tummers

M. J.

Hanjalić

van der Meer

T. H.

Experiments on a rotating-pipe swirl burner. Exp. Thermal Fluid Sci., 2003, 27(4), 481–489.

12.

Chigier

N. A.

Beer

J. M.

Velocity and static pressure distributions in swirling air jets issuing from annular and divergent nozzles. Trans. ASME, Part I: J. Fluids Engng, 1964, 86, 788–798.

13.

Cheng

R. K.

Velocity and scalar characteristics of premixed turbulent flames stabilized by weak swirl. Combust. Flame, 1995, 101(1–2), 1–14.

14.

Al-Abdeli

Y. M.

Masri

A. R.

Recirculation and flowfield regimes of unconfined non-reacting swirling flows. Exp. Thermal Fluid Sci., 2003, 27(5), 655–665.

15.

Kerr

N. M.

Fraser

Swirl part 1: effect on axisymmetrical turbulent jets. J. Inst. Fuel, 1965, 38, 519–526.

16.

Guttenfelder

W. A.

Renfro

M. W.

Laurendeau

N. M.

King

G. B.

Gore

J. P.

Hydroxyl time series and recirculation in turbulent nonpremixed swirling flames. Combust. Flame, 2006, 147(1–2), 11–21.

17.

Huang

R. F.

Tsai

F. C.

Observations of swirling flows behind circular discs. AIAA J., 2001, 39(6), 1106–1112.

18.

San

K. C.

Hsu

H. J.

Characteristics of flow and flame behavior behind rifled/unrifled nozzles. Trans. ASME, J. Engng Gas Turbines Power, 2009, 131, 1–12.

19.

Mueller

T. J.

Flow visualization by direct injection. Fluid mechanics measurements, second edition ( Goldstein

R. J.

) 2000, 367–450Taylor & Francis, Washington, District of Columbia).

20.

Flagan

R. C.

Seinfeld

J. H.

Fundamentals of air pollution engineering, 1988 (Prentice Hall, Englewood Cliffs, New Jersey295–307.

21.

von Dyke

An album of fluid motion, 1982, p. 60Parabolic Press, Stanford, California).

22.

Huang

R. F.

Yen

S. C.

Axisymmetric swirling vortical wakes modulated by a control disc. AIAA J., 2003, 41(5), 888–896.