Flow transition in dual bell nozzles

Nürnberger-Génin, Chloé; Stark, Ralf

doi:10.1007/s00193-008-0176-4

Cited by 37 publications

(31 citation statements)

References 5 publications

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“…At ¦rst, one can see weak oscillations at NPR = 137 for t < 95 s. At this NPR, wall pressure signals immediately after the junction were also characterized by strong amplitude oscillations. The ¦rst regime of oscillations can be attributed to the beginning of a sneak transition as mentioned in [9]. The second regime of oscillations, with a bigger amplitude between NPR = 120 and 140, is observed for t > 95 s; the apparent frequency is about 1 Hz.…”

Section: Nozzle Pressure Ratio Stabilizationmentioning

confidence: 83%

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Wall pressure and thrust of a dual bell nozzle in a cold gas facility

Reijasse

Coponet

Luyssen

et al. 2011

Progress in Propulsion Physics

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A dual-bell nozzle has been tested in the ONERA-R2Ch wind tunnel within the CNES PERSEUS program. The wall pressure distributions and the thrust for the two §ow regimes have been characterized in the nozzle pressure ratio (NPR) range from 51 up to 597. A hysteresis on the transition NPR between the two §ow regimes has been observed according to the evolution of NPR. The duration for the switch between the two §ow regimes is less than 10 ms. The hysteresis of about 20% on the NPR has also a direct e¨ect on the thrust. The total thrust of the dual-bell nozzle becomes higher than the thrust of the isolated base nozzle without extension for NPR > 1500. The hysteresis phenomenon has been modeled with the use of supersonic separation criteria and by making the assumption that incipient separation occurs immediately after the transition for increasing NPRs, while e¨ective separation occurs just before the transition for decreasing NPRs.

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Section: Nozzle Pressure Ratio Stabilizationmentioning

confidence: 83%

“…The e¨ect of the nozzle extension length on the NPR transition and the transition time was studied [9]. The appellation of the ¤sneak¥ transition (the phenomenon preceding the actual transition) was given in [9] but this phenomenon was previously characterized in [9] experimentally and in [10] numerically.…”

Section: Short Bibliographical Surveymentioning

confidence: 99%

Wall pressure and thrust of a dual bell nozzle in a cold gas facility

Reijasse

Coponet

Luyssen

et al. 2011

Progress in Propulsion Physics

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“…Given are the mean separation pressures p sep / p a as a function of the related wall Mach number M sep . The black line depicts the introduced criterion for turbulent separation equation (2). The separation pressures of configuration 1 follow the awaited trend.…”

Section: Resultsmentioning

confidence: 99%

“…Its sealevel to altitude operating mode transition and hence the related flight altitude of the launcher can be determined [2] using (1), where M ext is the wall Mach number of the dual bell extension…”

Section: Introductionmentioning

confidence: 99%

Flow separation in rocket nozzles under high altitude condition

Stark

Génin

2016

Shock Waves

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The knowledge of flow separation in rocket nozzles is crucial for rocket engine design and optimum performance. Typically, flow separation is studied under sealevel conditions. However, this disregards the change of the ambient density during ascent of a launcher. The ambient flow properties are an important factor concerning the design of altitude-adaptive rocket nozzles like the dual bell nozzle. For this reason an experimental study was carried out to study the influence of the ambient density on flow separation within conventional nozzles.

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“…Recent studies at DLR Lampoldshausen have indicated that as the nozzle pressure ratio (NPR) of the dual-bell approaches the transition value, the nozzle first approaches the phase of `sneak' transition [14][15] wherein the separation point begins to gradually move from the inflection point to the first point in the nozzle extension (i.e., in the region of negative pressure gradient, time duration t tr,1 ) after which it finally accelerates in the nozzle extension in a very short time interval (time duration t tr,2 ). The former transition time t tr,1 is found to be sensitive to the wall inflection design, local Reynolds number of operation and secondary-film cooling which modifies the width of the region of wall inflection [16,19,21].…”

mentioning

confidence: 99%

Effect of Ambient Pressure Fluctuations on the Dual-Bell Transition Behavior

Verma¹,

Stark²,

Haidn³

2012

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

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An experimental investigation was conducted to study the effect of ambient pressure fluctuations on dual-bell transition behavior. Back pressure fluctuations of frequency (f = 0.5, 1.0, 1.5, 2 and 3Hz) were artificially introduced inside the HASC using three magnetic valves. The dual-bell transition behavior is found to be very sensitive to P b fluctuations of magnitude > 20% which triggers a flip-flop phenomenon that is observed to continue as long as the fluctuations prevail. The tests show that for frequencies >2Hz, although significant fluctuations in P w in the nozzle extension can be felt, no full transition is achieved. This behavior too is not favorable as it can lead to a delay in transition. These preliminary test results suggest that the dual-bell nozzle can present problems in real-flight operation as the launcher experiences the buffeting phase of flight. The only solution therefore lies in increasing the DB stability corridor to a value greater than the magnitude of P b fluctuations (of 20%) so as to avoid the NPR range that will set the dual-bell into a flip-flop mode during buffeting.

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Flow transition in dual bell nozzles

Cited by 37 publications

References 5 publications

Wall pressure and thrust of a dual bell nozzle in a cold gas facility

Wall pressure and thrust of a dual bell nozzle in a cold gas facility

Flow separation in rocket nozzles under high altitude condition

Effect of Ambient Pressure Fluctuations on the Dual-Bell Transition Behavior

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