How the Nozzle Geometry Impacts Vortex Breakdown in Compressible Swirling-Jet Flows

Luginsland, Tobias

doi:10.2514/1.j053843

Cited by 16 publications

(16 citation statements)

References 50 publications

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“…The trend of Mix A is obvious when the sulfur rank of TESPD is taken into account: the sulfur bridge in TESPD consists of app. 90% of S2 11, 12 , which means that it is a rather pure material compared to a mixture as TESPT. Therefore, the fillerpolymer coupling reaction rate of Mix A will be the same at isothermal measurement conditions.…”

Section: Filler-polymer Coupling Rate After Mixingmentioning

confidence: 99%

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The Origin of Marching Modulus of Silica-Filled Tire Tread Compounds

Jin

Noordermeer

Dierkes

et al. 2019

Rubber Chemistry and Technology

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Silica-reinforced S-SBR/BR tire tread compounds often show characteristic vulcanization profiles that do not exhibit a distinct maximum in the cure curve nor a plateau profile within acceptable time scales (marching modulus). In such a situation, it is difficult to determine the optimum curing time, and as a consequence, the physical properties of the rubber compounds may vary. Previous studies stated that the curing behavior of silica-filled rubber compounds is related to the degree of filler dispersion, the silanization, and the filler–polymer coupling reaction, as well as to the donation of free sulfur from the silane coupling agent. Such results imply that these are the key factors for minimization of the marching modulus. Various silane coupling agents with different sulfur ranks and functionalities were mixed at varied silanization temperatures. The correlation between these factors and their effect on the marching modulus intensity (MMI) were investigated. The MMI was monitored by measuring the vulcanization rheograms using a rubber process analyzer at small (approximately 7%) and large (approximately 42%) strains to discriminate the effects of filler–filler and filler–polymer interactions on the marching modulus of the silica-filled rubber compounds. Both factors have an intricate influence on the marching modulus, determined by the degree of filler–filler interaction and the coupling agent.

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Section: Filler-polymer Coupling Rate After Mixingmentioning

confidence: 99%

“…However, TESPT is a mixture of silanes with various sulfur ranks from S2 to S10. 12 The longer sulfur bridges can donate active sulfur 11,13 ; this sulfur can in turn activate other silane molecules. This result agrees well with the results shown here.…”

Section: Filler-polymer Coupling Rate After Mixingmentioning

confidence: 99%

The Origin of Marching Modulus of Silica-Filled Tire Tread Compounds

Jin

Noordermeer

Dierkes

et al. 2019

Rubber Chemistry and Technology

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“…For the activation of silica-rubber coupling, curatives such as elemental sulfur and accelerators play an important role in the silane-rubber reaction. [76][77][78] It is well known that silane-rubber coupling takes place during the vulcanization process. In the presence of elemental sulfur, the poly-sulfide of the silane is activated due to the insertion of elemental sulfur into the poly-sulfide of the silane.…”

Section: Silane-rubber Coupling Reactions 2451 Crosslinking Reactimentioning

confidence: 99%

Reactive processing of silica-reinforced tire rubber

Mihara¹

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“…The inflow plane outside of the nozzle acts therefore as a solid wall as in the investigations of Liang and Maxworthy [8] and Billant et al [5], who performed experiments in a large water tank, as well as in those of Facciolo et al [9] and Oberleithner et al [4], who attached a plate to the nozzle end. For the case of a nozzle at rest [5,9,4] the position of the solid wall relative to the nozzle end section (or, in other words, the intrusion depth of the nozzle into the tank,) is of minor importance and generally affects the entrainment of ambient fluid only locally (for an extensive discussion see Luginsland [37]). For the rotating nozzle, the intrusion depth may be of importance due to the developing boundary layer at the outer nozzle wall.…”

Section: Setup Differences For the Rotating Nozzle And The Nozzle At mentioning

confidence: 99%

Impact of rotating and fixed nozzles on vortex breakdown in compressible swirling jet flows

Luginsland

Gallaire

Kleiser

2016

European Journal of Mechanics - B/Fluids

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a b s t r a c tVortex breakdown of swirling, round jet flows is investigated in the compressible, subsonic regime by means of Direct Numerical Simulation (DNS). This is achieved by solving the compressible Navier-Stokes equations on a cylindrical grid using high-order spatial and temporal discretization schemes. TheReynolds number is Re = ρ The integral swirl number at the inflow is S int = 0.85. The parameters are chosen properly so as to make comparisons with existing experiments at lower Mach numbers possible while still enabling a study of compressible and baroclinic effects. Different from previous numerical investigations, a nozzle immersed in the fluid is included in the computational domain and is modelled as an isothermal no-slip wall, either rotating with the mean azimuthal flow direction or kept at rest. The present investigation aims to clarify the role played by the nozzle wall motion for the vortex breakdown of the swirling jet. We study the nozzle flow as well as the swirling jet flow simultaneously, a novelty for numerical investigations of vortex breakdown in swirling jets. Depending on the nozzle wall motion, the flow differs significantly upstream of the vortex breakdown: for the rotating nozzle, the flow inside the nozzle is purely laminar and the azimuthal boundary layer at the outer nozzle wall gives rise to the axisymmetric mode n = 0 and a single-helix type instability with azimuthal wave number n = 1. With the nozzle at rest, a transitional flow is observed within the nozzle where a helical instability with azimuthal wave number n = 12 dominates, growing in the boundary layer at the nozzle wall. For both nozzle setups, the helical instabilities observed for the nozzle flow interact with the developing vortex breakdown and the conical shear-layer downstream of the nozzle. For the nozzle at rest, this interaction results in a vortex breakdown configuration which is shifted in the upstream direction and which has a smaller radial and streamwise extent compared to the rotating nozzle case and the recirculation intensity is higher. The dominant frequency is highly influenced by the flow upstream of the vortex breakdown and is substantially higher for the nozzle at rest. Although the nozzle flow field differs for the two configurations and therefore alters the vortex breakdown downstream, a single-helix type instability n = 1 governing the vortex breakdown is found for both cases. This provides strong evidence for the robustness of the instability mechanisms leading to vortex breakdown.

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How the Nozzle Geometry Impacts Vortex Breakdown in Compressible Swirling-Jet Flows

Cited by 16 publications

References 50 publications

The Origin of Marching Modulus of Silica-Filled Tire Tread Compounds

The Origin of Marching Modulus of Silica-Filled Tire Tread Compounds

Reactive processing of silica-reinforced tire rubber

Impact of rotating and fixed nozzles on vortex breakdown in compressible swirling jet flows

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