Sea-level transitioning dual bell nozzles

Stark, Ralf; Génin, Chloe

doi:10.1007/s12567-017-0154-8

Cited by 7 publications

(3 citation statements)

References 32 publications

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“…Schneider et al [41] suggest to use a combination of chamber mixture ratio as well as the cooling fluid mass flow rate to control the dual-bell mode transition. To avoid the additional risk due to mode transition during flight, it is also possible to perform transition before lift-off allowing for a potential payload gain of still 219 kg, according to [45].…”

Section: Introductionmentioning

confidence: 99%

Investigation of the base flow of a generic space launcher with dual-bell nozzle

Scharnowski

Kähler

2020

CEAS Space J

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The typical afterbody flow of a space launcher is characterized by a strong interaction of the engine’s exhaust jet and the separated shear layer emerging from the main body. This interaction is further complicated by strong changes in the spatial and temporal behavior of the afterbody flow during the atmospheric ascent of a launcher. Theoretically, a dual-bell nozzle not only allows for a gain in payload compared to standard single-bell nozzles, but also it alters the wake flow topology due to the two nozzle modes. To predict the benefits as well as the additional risks, the afterbody flow of a generic space launcher model equipped with a cold-flow dual-bell nozzle is investigated in detail. The flow was analyzed for sub-, trans- and supersonic Mach numbers ranging from 0.3 to 2.9 for a variety of nozzle pressure ratios. Particle image velocimetry measurements and schlieren measurements with high repetition rate were performed to determine the dynamics of the separated shear layer, the nozzle jet and their interaction. It is shown that the reattachment length of the base flow decreases with increasing nozzle pressure ratio. Furthermore, the nozzle pressure ratio at which the dual-bell nozzle switches from sea-level mode to altitude mode is reduced by $$15\%$$ 15 % with high subsonic outer flow and by as much as $$65\%$$ 65 % for an outer flow at a Mach number of 1.6. Even for a constant nozzle pressure ratio, the nozzle flow topology depends on the Mach number of the outer flow.

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Section: Introductionmentioning

confidence: 99%

Investigation of the base flow of a generic space launcher with dual-bell nozzle

Scharnowski

Kähler

2020

CEAS Space J

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“…The nozzle of the first stage engine of a launch vehicle due to its fixed geometric expansion ratio, operates in off-design modes during most of the active flight trajectory in the rarefied atmosphere, resulting in losses of thrust of up to 7-9% due to under-expansion of the jet flow [1]. One way to reduce these losses and increase the efficiency of a rocket engine at altitude is to increase the expansion area ratio of the nozzle with a nozzle attachment [2][3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

The Impact of Streamwise Steps and Cavities Geometry on Supersonic Turbulent Boundary Layer

Ch’ng

Teryaev

Sidhu

et al. 2020

CFDL

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In some cases, the nozzle of a rocket engine could deform during manufacturing or testing, flare up and distort during operation in such a way that periodically repeating structures of depressions and protrusions form on the wall surface. Complex configurations of roughness topologies have been experimentally observed to form due to this fluid-structure interaction and have been known to distort the boundary layer and increase local drag and heat transfer. A numerical experiment was carried out using ANSYS FLUENT to assess the effects of geometry (streamwise wavelengths ? and length-to-depth ratios (L/D)) of discrete roughness topologies in the form of steps and cavities on flow field distortions and resulting total drag. It was found that cavity L/D ratios of 19.8 – 23.1 and 12.8 – 15.5 yielded the highest drag coefficients. The flow fields over these periodic arrays exhibited closed and a combination of closed cavity type features, and it can be concluded that the flow phenomena associated with separation caused by forward facing steps in closed cavity type topologies contributed the most to the total drag. L/D ratios of 6.3 – 8.4 exhibited the lowest drag coefficient. The lower drag coefficient is due to the modification of the turbulent boundary layer by the trapped coherent vortical structure within the cavities. Pressure forces become more dominant as the surface wavelength is decreased. For all cases, there was a pronounced increase in the boundary layer thickness after each successive cavity.

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“…Due to the altitude adaption a larger area ration and thus an increased expansion of the flow can be achieved at altitude mode compared to a classical rocket engine improving the overall performance. The dual-bell flow behavior, e.g., the transition behavior, the arising side loads, and the payload gain, has experimentally, e.g., by Stark et al [11], and numerically, e.g., by Schneider and Genin [9], been investigated proving the functionality of the adaptive nozzle concept. More recently, Loosen et al [7], investigated the aerodynamic integration of the dualbell nozzle into the launcher's architecture and the influence of the outer flow onto the dual-bell nozzle flow for a generic planar space launcher configuration.…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of the Turbulent Wake for a Generic Space Launcher with a Dual-Bell Nozzle

Loosen

Meinke

Schröder

2020

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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The turbulent wake of an axisymmetric generic space launcher equipped with a dual-bell nozzle is simulated at transonic ($$Ma_\infty = 0.8$$ and $$Re_D = 4.3\cdot 10^5$$) and supersonic ($$Ma_\infty = 3$$ and $$Re_D = 1.2\cdot 10^6$$) freestream conditions, to investigate the influence of the dual-bell nozzle jet onto the wake flow and vice versa. In addition, flow control by means of four in circumferential direction equally distributed jets injecting air encountering the backflow in the recirculation region is utilized to determine if the coherence of the wake and consequently, the buffet loads can be reduced by flow control. The simulations are performed using a zonal RANS/LES approach. The time-resolved flow field data are analyzed by classical spectral analysis, two-point correlation analysis, and dynamic mode decomposition (DMD). At supersonic freestream conditions, the nozzle counter pressure is reduced by the expansion of the outer flow around the nozzle lip leading to a decreased transition nozzle pressure ratio. In the transonic configuration a spatio-temporal mode with an eigenvalue matching the characteristic buffet frequency of $$Sr_D=0.2$$ is extracted by the spectral and DMD analysis. The spatial shape of the detected mode describes an antisymmetric wave-like undulating motion of the shear layer inducing the low frequency dynamic buffet loads. By flow control this antisymmetric coherent motion is weakened leading to a reduction of the buffet loads on the nozzle fairing.

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Sea-level transitioning dual bell nozzles

Cited by 7 publications

References 32 publications

Investigation of the base flow of a generic space launcher with dual-bell nozzle

Investigation of the base flow of a generic space launcher with dual-bell nozzle

The Impact of Streamwise Steps and Cavities Geometry on Supersonic Turbulent Boundary Layer

Numerical Analysis of the Turbulent Wake for a Generic Space Launcher with a Dual-Bell Nozzle

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