Experimental study on mixing enhancement by petal nozzle in supersonic flow

Srikrishnan, A R; Kurian, Job; Sriramulu, V.

doi:10.2514/3.24006

Cited by 30 publications

(8 citation statements)

References 10 publications

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“…Novel supersonic nozzles with complex exit geometries are excellent passive techniques to enhance jet mixing rate [1,2,3,4]. Enhancement of mixing at supersonic speeds becomes particularly important after extensive research has conclusively shown that compressibility effects reduce growth rate of mixing layers [5,6].…”

Section: Introductionmentioning

confidence: 99%

“…[7], and the effectiveness of passive techniques that use geometrical modifications at the trailing edge of the nozzle was described. Lobes proceeding from the throat to exit of the nozzle that alternately deeply penetrate the core supersonic flow at the lobe trough and expand at the lobe crest are the characteristic of lobed supersonic nozzles [4,3]. Large streamwise vorticity generated by such convoluted nozzle structure was shown to have increased the mixing and entrainment rate greatly.…”

Section: Introductionmentioning

confidence: 99%

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Comparative studies on supersonic free jets from nozzles of complex geometry

Rao

Asano

Saito

2016

Applied Thermal Engineering

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Experimental and numerical studies are conducted to compare free jets from different supersonic nozzles for mixing enhancement. A conical nozzle of Mach 1.80 is the reference. Three complex nozzles are a beveled nozzle, a nozzle with six chevrons and a six lobed ESTS nozzle [1]. All nozzles have the same throat diameter and designed average exit Mach number. The studies are conducted at NPR=6, using acetone PLIF, centerline pitot pressure measurements and 3D RANS simulations. A novel method of decomposing PLIF images based on intensity histogram and then recomposing after applying selective gains to emphasize the growth of shear layers is discussed. PLIF images are processed to extract the growth rate of jet width which indicates the rate of mixing. The ESTS lobed nozzle shows the highest enhancement of mixing (430%) followed by chevron (222%) and the beveled nozzle with a moderate (138%). The numerical simulations are validated and agree well with experimental results. ESTS lobed nozzle is found to produce widespread streamwise vortices compared to clustered vortices of the chevron nozzle. The mechanism of streamwise vorticity production from ESTS nozzle is clarified for the first time in this study.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comparative studies on supersonic free jets from nozzles of complex geometry

Rao

Asano

Saito

2016

Applied Thermal Engineering

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“…In addition, the increase in contact surface is obtained in far regions where gradients and entrainment rate are lower. Therefore, more advanced solutions could derive from new design configurations of the primary nozzle, e.g., annular primary nozzle [19], petal nozzles [20] and multiple nozzles [21]. This last solution basically consists in a partition of the primary mass flow rate that is redirected through many smaller nozzles, whose sizes and positions must be carefully designed.…”

Section: S116mentioning

confidence: 99%

Constructal design of the mixing zone inside a supersonic ejector

Grazzini¹,

Mazzelli

Milazzo³

2016

IJHT

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Supersonic ejectors can be used in heat powered chillers to transfer mechanical energy between the motive and the inverse cycle. Within the ejector, momentum is exchanged between a high speed flow produced by a primary nozzle and a slow current coming from the chiller evaporator. Due to the supersonic regime of the primary flow, the mixing of the two streams causes significant loss and impairs the system efficiency. Up to now, second law efficiency of ejector chillers is quite low and optimization is highly needed. The fluid dynamics of the whole ejector involves turbulent mixing, shock trains and complex wall flow, requiring CFD analyses for an adequate description. However, in order to attempt an optimization, mathematically workable models are advantageous. An analytical scheme that captures the basic features of the turbulent mixing zone is discussed here in view of a Constructal design of an ejector chiller.

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“…Recently, Srikrishnan et al 9 obtained experimental data on pressure drop for conical and lobed nozzles for isothermal mixing. The present study is an experimental investigation of the enhancement of thermal mixing by a radially lobed petal nozzle in coaxial supersonic jets.…”

Section: Introductionmentioning

confidence: 99%

Enhancement of thermal mixing in coaxial supersonic jets

Srikrishnan

Kurian

Sriramulu

1996

Journal of Propulsion and Power

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An experimental study was conducted to investigate the thermal mixing of a hot, supersonic, primary jet of combustion gases with a coflowing secondary jet of air at ambient temperature. The Mach numbers of the two jets were 1.2 and 1.7, respectively. To enhance the mixing, the core (primary) jet was admitted through a three-dimensional, radially lobed nozzle, referred to as the petal nozzle. The uniformity of stagnation temperature in the flowfield was used to characterize the extent of mixing between the jets. The effect of confinement on the mixing was also investigated. The mixing performance of the lobed nozzle and the associated loss in stagnation pressure were compared with those for a conventional conical nozzle. The study confirms the efficacy of the radially lobed nozzle in thermal and momentum mixing of supersonic jets and highlights its potential in supersonic combustion systems. Nomenclature T = stagnation temperature, °C fji = momentum flux, N/m 2 cr = standard deviation

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Experimental study on mixing enhancement by petal nozzle in supersonic flow

Cited by 30 publications

References 10 publications

Comparative studies on supersonic free jets from nozzles of complex geometry

Comparative studies on supersonic free jets from nozzles of complex geometry

Constructal design of the mixing zone inside a supersonic ejector

Enhancement of thermal mixing in coaxial supersonic jets

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