LES for Turbulent Duct Flow with Surface Mass Injection

Kim, Bohoon; Na, Yang; Lee, Changjin

doi:10.5139/jksas.2010.39.3.232

Cited by 3 publications

(2 citation statements)

References 10 publications

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“…This process might be related to the reaction traces that leave on the hybrid rocket experiment [1][2][3][4][5] . The structures represent more active reaction than surrounding area, and their shape is usually aligned in azimuthal direction.…”

Section: Pressure Fieldsmentioning

confidence: 99%

“…[1][2][3] The appearance of these peculiar cell patterns may be thought of as a realization of the inherent flow instability. And, it is very likely that the formation of cell structures is, to some extent, originated from the modification of boundary layer characteristics of an entering oxidizer flow caused by a blowing effect mainly taking place in the vicinity of the wall during the regression process.…”

Section: Introductionmentioning

confidence: 99%

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The Effect of a Block on Flow Oscillations near the Fuel Surface with Wall Blowing

Koo¹,

Mon²,

Lee³

2012

48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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The stability and combustion behavior in hybrid rockets are significantly affected by the formation of vortex and their interactions. Experimental results also show that the change in the flow conditions prior to entering the fuel grain can also alter behaviors of regression rate and pressure fluctuations. This study focuses on effect of vorticity interactions on the combustion behaviors by controlling the vortex formation in the pre-chamber. In this regard, an annular-shape obstacle located in front of mass-injection part was used in combustion tests. A numerical calculation with LES was done to simulate the evolution of flow interactions including vortex dynamics and pressure oscillations in the cylindrical configuration. It is found that flow structure is changed in that momentum and fluctuation are increased near wall, and an additional layer of vorticity is created due to the obstacle which interacts with near-wall vortices generated by mass blowing. Also due to mass injection through the wall, a number of positive azimuthal vorticity spots are created that effectively squeeze mainstream flow toward the wall.

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Section: Pressure Fieldsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Effect of a Block on Flow Oscillations near the Fuel Surface with Wall Blowing

Koo¹,

Mon²,

Lee³

2012

48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

View full text Add to dashboard Cite

show abstract

LES for Turbulent Duct Flow with Surface Mass Injection and Vortex Shedding

Mon¹,

Koo²,

Lee³

2012

Journal of the Korean Society for Aeronautical & Space Scie

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Hybrid rocket shows interesting characteristics of complicated mixing layers developed by interactions between turbulent oxidizer flow and mass flow from surface due to fuel vaporization. In this study, compressible LES with a ring structure attached at the entrance of the combustor are performed. According to one recent report, adding a ring structure in the middle of the combustor helps increasing regression rate. From the numerical results, it is seen that vortex structures near the wall becomes stronger due to the interaction with surface mass injection, and the local heat flux increases due to the vortices. This phenomenon is obviously related to the generation of dimple structures which are seen in the number of experiments. Also, the ring structure at the entrance induces strong vortex flow which enhances heat transfer to the wall surface and mixing between fuel and oxidizer as well as reaction efficiency.

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Vortex sheddings and Pressure Oscillations in Hybrid Rocket Combustion

Park¹,

Shin²,

Lee

2013

Journal of the Korean Society for Aeronautical & Space Scie

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The similarity in internal flow of solid and hybrid rocket suggests that hybrid rocket combustion can be susceptible to instability due to vortex sheddings and their interaction. This study focuses on the evolution of interaction of vortex generated in pre-chamber with other types of vortex in the combustor and the change of combustion characteristics. Baseline and other results tested with disks show that there are five different frequency bands appeared in spectral domain. These include a frequency with thermal lag of solid fuel, vortex shedding due to obstacles such as forward, backward facing step and wall vortices near surface. The comparison of frequency behavior in the cases with disk 1 and 3 reveals that vortex shedding generated in pre-chamber can interact with other types of vortex shedding at a certain condition. The frequency of Helmholtz mode is one of candidates resulting to a resonance when it was excited by other types of oscillation even if this mode was not discernable in baseline test. This selective mechanism of resonance may explain the reason why non-linear combustion instability occurs in hybrid rocket combustion.

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LES for Turbulent Duct Flow with Surface Mass Injection

Cited by 3 publications

References 10 publications

The Effect of a Block on Flow Oscillations near the Fuel Surface with Wall Blowing

The Effect of a Block on Flow Oscillations near the Fuel Surface with Wall Blowing

LES for Turbulent Duct Flow with Surface Mass Injection and Vortex Shedding

Vortex sheddings and Pressure Oscillations in Hybrid Rocket Combustion

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