Interaction of LOX/GH2 Spray-Combustion with Acoustics

Knapp, Bernhard; Farago, Zoltan; Oschwald, Michael

doi:10.2514/6.2007-572

Cited by 10 publications

(7 citation statements)

References 1 publication

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“…Combustion instabilities can have severe consequences on the efficiency of the burner and can lead to its destruction. Such instabilities are still not fully understood and active research is currently dedicated to this field (see for example [46][47][48]). In these investigations, the amplitude of pressure oscillations never goes over 30% of the mean pressure.…”

Section: Case 3: Effect Of Pressurementioning

confidence: 99%

A non-premixed combustion model based on flame structure analysis at supercritical pressures

Lacaze

Oefelein

2012

Combustion and Flame

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a b s t r a c tThis work presents a study of non-premixed flames at supercritical-pressure conditions. Emphasis is placed on flame stability in liquid rocket engines fueled with liquid oxygen and gaseous hydrogen. The flame structure sensitivity to strain, pressure, temperature and real-fluid effects was investigated in detailed opposed-jet flames calculations. It is shown that the flame is very robust to strain, that the flamelet assumption is valid for the conditions of interest, and that real-fluid phenomena can have a significant impact on flame topology. At high-pressure supercritical conditions, small pressure or temperature variations can induce strong changes of thermodynamic properties across the flame. A substantial finding was also that the presence of water from combustion significantly increases the critical pressure of the mixture, but this does not lead to a saturated state where two-phase flow may be observed. The present study then shows that a single-phase real-fluid approach is relevant for supercritical hydrogen-oxygen combustion. Resultant observations are used to develop a flamelet model framework that combines detailed real-fluid thermodynamics with a tabulated chemistry approach. The governing equation for energy contains a compressible source term that models the flame. Through this approach, the solver is capable of capturing compressibility and strain-rate effects. Good agreements have been obtained with respect to detailed computations. Heat release sensitivity to strain and pressure variations is also recovered. Consequently, this approach can be used to study combustion stability in actual burners. The approach preserves the density gradient in the high-shear region between the liquid-oxygen jet and product rich flame region. The latter is a key requirement to properly simulate dense-fluid jet destabilization and mixing in practical devices.

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Section: Case 3: Effect Of Pressurementioning

confidence: 99%

A non-premixed combustion model based on flame structure analysis at supercritical pressures

Lacaze

Oefelein

2012

Combustion and Flame

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“…The addition of windows into such experimental combustors allows the application of high-speed flame emission imaging, which enables the distribution and phase of flame response to acoustic disturbances to be examined. Knapp et al 6 and Oschwald and Knapp 7 , for example, observed LOx/H 2 flame response in phase with acoustic pressure in the CRC combustor. The distribution of hydroxyl-radical (OH*) intensity fluctuation also reflected the acoustic pressure distribution, with high amplitude emission intensity fluctuations at the location corresponding to the acoustic pressure antinode.…”

Section: Introductionmentioning

confidence: 94%

“…The general definition of response factor, N, first used by Heidmann and Wieber 19 and given in Equation (5), is an indicator of the degree of gain in heat release resulting from the acoustic pressure fluctuation. A discretised version of this expression was used here, again substituting twodimensional OH* emission intensity for volumetric heat release rate, as given in Equation (6). The time-integrated…”

Section: B Response To Excitation Of the 1l Modementioning

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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“…The 1T mode pressure ¦eld reconstruction algorithm [24] was originally developed for the CRC (Common Research Chamber) research combustor [36]. The pressure oscillations are measured on the wall of a cylindrical combustion chamber.…”

Section: Pressure Field Reconstructionmentioning

confidence: 99%

Measuring the phase between fluctuating pressure and flame radiation intensity in a cylindrical combustion chamber

Gröning

Hardi

Suslov

et al. 2019

Progress in Propulsion Physics – Volume 11

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The energy transfer from the heat release of the combustion to the acoustic pressure oscillations is the driving element of combustion instabilities. This energy transfer is described by the Rayleigh criterion and depends on the phase shift between the pressure and heat release rate oscillations. A research rocket engine combustor, operated with the propellant combination hydrogen/oxygen, was equipped with dynamic pressure sensors and fibre optical probes to measure the flame radiation. This setup has been used for a phase shift analysis study which showed that unstable operation is characterized by a phase shift leading to an energy transfer from the heat release to the acoustic pressure oscillations.

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Interaction of LOX/GH2 Spray-Combustion with Acoustics

Cited by 10 publications

References 1 publication

A non-premixed combustion model based on flame structure analysis at supercritical pressures

A non-premixed combustion model based on flame structure analysis at supercritical pressures

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

Measuring the phase between fluctuating pressure and flame radiation intensity in a cylindrical combustion chamber

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