Acoustic characterisation of a rectangular rocket combustor with liquid oxygen and hydrogen propellants

Hardi, Justin; Oschwald, Michael; Dally, Bassam B.

doi:10.1177/0954410012437511

Cited by 10 publications

(9 citation statements)

References 10 publications

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“…An ideal design will offer free control of amplitude over a wide range of acoustic frequencies. But, as seen in the acoustic control systems of existing facilities 6 , this proves to be difficult. Designs must often sacrifice either control of frequency or amplitude in order to achieve high pressure amplitudes on the order of those manifested by LRE combustion instabilities.…”

Section: Acoustic Characterizationmentioning

confidence: 99%

Development of a Facility for Combustion Stability Experiments at Supercritical Pressure

Wegener

Leyva

Forliti

et al. 2014

52nd Aerospace Sciences Meeting

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Combustion instability in liquid rocket engines can have severe consequences including degraded performance, accelerated component wear, and potentially catastrophic failure. High-frequency instabilities, which are generally the most harmful in liquid rocket engines, can be driven by interactions between disturbances associated with transverse acoustic resonances and the combustion process. The combustion response to acoustic perturbation is a critical component of the instabililty mechanism, and is in general not well understood. The current paper describes an experimental facility at the Air Force Research Laboratory (AFRL) at Edwards Air Force Base that is intended to investigate the coupling between transverse acoustic resonances and single/multiple liquid rocket engine injector flames.Critical aspects of the facility will be described, including the capability to operate at supercritical pressures that are relevant to high-performance liquid rocket engines, accurately-controlled and cryogenically-conditioned propellants, and optical access to facilitate the use of advanced diagnostics. The transverse acoustic resonance is induced through the use of carefully-controlled piezoelectric sirens, allowing monochromatic excitation across a range of amplitudes at a number of discrete frequencies. The location of the flame within the acoustic resonance mode shape can also be varied through relative phase control of the two acoustic sources. The operating space of the facility, for oxygen and hydrogen operation, will be described. Preliminary nonreacting and reacting data will also be presented to demonstrate the quality of operation of this facility. It is anticipated that future results generated using this facility will provide both fundamental insight into the acoustic-flame interactions as well as provide a database useful for validating combustion instability models. NomenclatureA = area c = speed of sound 2 D 1 = inner injector inner diameter D 2 = inner injector outer diameter D 3 = outer injector inner diameter D 4 = outer injector outer diameter dt = time step f F = acoustic frequency m = waveguide flare constant p c = mean chamber pressure pʹ = acoustic pressure perturbation amplitude t = inner post thickness uʹ = acoustic velocity perturbation amplitude x = streamwise (longitudinal) coordinate axis y = spanwise (transverse) coordinate axis z = depthwise coordinate axis

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Section: Acoustic Characterizationmentioning

confidence: 99%

Development of a Facility for Combustion Stability Experiments at Supercritical Pressure

Wegener

Leyva

Forliti

et al. 2014

52nd Aerospace Sciences Meeting

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“…Increasing pressure perturbations may result when heat release oscillation frequencies equal resonant modes of the combustion chamber. Resonant chamber modes can be radial, tangential, longitudinal, or a mixture of the three, and are determined by geometric chamber dimensions [8,[17][18][19]. Acoustic pressure oscillations alone may have little direct effect on combustion processes.…”

Section: Physical Mechanismsmentioning

confidence: 99%

“…The VHAM uses a toothed wheel to periodically block gas flow through exhaust nozzles, creating high pressure amplitudes inside the combustion chamber. The tooth wheel exhaust nozzle technique is also employed in the MIC, BKH, and CRC designs for the same purpose [18,131]. With this method, the periodic nozzle imposes an acoustic boundary condition on the chamber wall, where the acoustic frequency is controlled by the wheel speed.…”

Section: Propellant Mixing and Stability Considerationmentioning

confidence: 99%

Multi-Phase Combustion and Transport Processes Under the Influence of Acoustic Excitation

Wegener¹

2014

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“…BKH 13 was designed to study flame-acoustic interaction under more representative injection conditions and higher operating pressures, up to 60 bar, than have previously been achieved with such devices using LOx/H 2 propellants. The combustor has a configuration similar to the MIC, also using the nozzle-modulation excitation technique to study transverse mode flame-acoustic interaction.…”

Section: Introductionmentioning

confidence: 99%

Coupling Behaviour of LOx/H2 Flames to Longitudinal and Transverse Acoustic Instabilities

Hardi¹,

Beinke²,

Oschwald³

et al. 2012

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

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A rectangular combustor with acoustic forcing was used to study flame-acoustic interaction under injection conditions which are representative of industrial rocket engines. Hot-fire tests using liquid oxygen and gaseous hydrogen were conducted at pressures of 40 and 60 bar, which are sub-and supercritical conditions respectively for oxygen. To our knowledge, acoustic forcing has never before been conducted at pressures this high in an oxygen-hydrogen system. Examined samples of hydroxyl-radical emission imaging, collected using a high-speed camera during periods of forced acoustic resonance, show significant response in the multi-injection element flame. Transverse acoustic velocity causes shortening of the flame, concentrating heat release near the injection plane. Fluctuating acoustic pressure causes in-phase fluctuation of the emission intensity. Based on these observations, a theorized flame-acoustic coupling mechanism is offered as an explanation for how naturally occurring high frequency combustion instabilities are sustained in real rocket engines. Nomenclature c = bulk sound speed in combustion chamber I = OH* emission intensity I' = fluctuating component of OH* emission intensity Ī = time averaged OH* emission intensity J = injection momentum flux ratio N = response factor ω = acoustic frequency p' = acoustic pressure amplitude P cc = combustion chamber pressure p 0 = eigenmode solution acoustic pressure distribution R = Rayleigh index ROF = oxidizer-to-fuel mixture ratio ρ = bulk density in combustion chamber u' = acoustic (particle) velocity VR = injection velocity ratio

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Acoustic characterisation of a rectangular rocket combustor with liquid oxygen and hydrogen propellants

Cited by 10 publications

References 10 publications

Development of a Facility for Combustion Stability Experiments at Supercritical Pressure

Development of a Facility for Combustion Stability Experiments at Supercritical Pressure

Multi-Phase Combustion and Transport Processes Under the Influence of Acoustic Excitation

Coupling Behaviour of LOx/H2 Flames to Longitudinal and Transverse Acoustic Instabilities

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