An experimental study of the under-expanded swirling jet with secondary coaxial stream

Lee, K. H.; Setoguchi, Toshiaki; Matsuo, Shigeru; Kim, Heuy Dong

doi:10.1007/s00193-004-0239-0

Cited by 4 publications

(5 citation statements)

References 23 publications

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“…For velocity ratios less than around U 2 (0)/U 0 ≈ 0.7, increasing S w causes a reduction in the critical expansion angle, thereby increasing the range of parameter values for which stagnation occurs. This is expected and consistent with the findings of Lee et al [2]. However, an unexpected result is that for velocity ratios close to 1, increasing S w reduces the range of parameter values for which stagnation occurs.…”

Section: B Stagnation Regionsupporting

confidence: 92%

“…As is discussed by Lee et al [2], flows with large swirl numbers have the tendency to form a region of slowly moving recirculation. Here, we use our simple model to characterise the onset and size of this region by approximating it as a stagnant zone with zero velocity, as described earlier.…”

Section: B Stagnation Regionmentioning

confidence: 89%

“…(U 2 = 0), then the respective Bernoulli's equation no longer holds downstream of that point. The latter modelling assumption is based on the observation that if the swirl intensity in the core region is sufficiently large, a slow-moving recirculation region can form along the pipe axis, as shown by Lee et al [2]. A similar recirculation region has been observed for non-swirling flows if the flow is very non-uniform, or if the pipe expansion angle is too large [35].…”

Section: Core Plugmentioning

confidence: 92%

“…There are many industrial applications where swirl is added to jet flows and annular flows to improve performance. Most commonly, swirl is used in combustion chambers to increase fuel mixing rates and to stabilise the flame [1,2]. There have also been studies which indicate that swirl can be used to improve plasma jet cutting performance [3], to increase the efficiency of a jet pump [4], and to reduce flow separation in diffusers [5].…”

Section: Introductionmentioning

confidence: 99%

“…In the case of annular flows, Lee et al [2] studied the effect of swirl on the characteristics of an unconfined co-axial annular flow. In their experiments, both the core flow and the annular flow had swirl components, not necessarily in the same direction.…”

Section: Introductionmentioning

confidence: 99%

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The effect of inner swirl on confined co-axial flow

Benham¹,

Hewitt²,

Please³

et al. 2018

Preprint

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We study the problem of mixing between core and annular flow in a pipe, examining the effect of a swirling core flow. Such flows are important across a range of applications, including jet pumps, combustion chambers and aerospace engineering. Previous studies show that swirl can increase shear layer growth rates and, in the case of confining walls, reduce flow separation. However, the effect of swirl on pressure loss in a confined flow is uncertain. To address this, we develop a simplified model that approximates the axial flow profile as a linear shear layer separating uniform-velocity core and annular streams. The azimuthal flow profile is approximated as a solid body rotation within the core region, and a parabolic mixing profile within the shear layer. This model shows good agreement with computational turbulence modelling, whilst its simplicity and low computational cost make it ideal for benchmark predictions and design purposes. Using this model, we confirm that a swirling core is useful for increasing shear layer growth rates, but find that it is detrimental to pressure recovery. This has important implications for the design of diffusers that incorporate swirling flows. We use the model to describe the slow recirculation region that can form along the pipe axis for sufficiently large swirl, by approximating it as a stagnant zone with zero velocity. The criteria for the development of such a region are established in terms of the pipe expansion angle and inflow velocity profile.

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Section: B Stagnation Regionsupporting

confidence: 92%

Section: B Stagnation Regionmentioning

confidence: 89%