Combustion Response of Shear Coaxial Injectors to Transverse Combustion Instabilities

Gejji, Rohan; Lemcherfi, Aaron; Strelau, Ryan; Slabaugh, Carson D.; Anderson, William E.

doi:10.2514/6.2020-0424

Cited by 7 publications

(5 citation statements)

References 17 publications

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“…As a result, we observe higher intensities in the central flame compared to its neighbors. The dynamics of the central lifted flame for low amplitude periodic oscillations during intermittency and high amplitude periodic oscillations during thermoacoustic instability is discussed elaborately with the supporting schlieren images by Gejji et al [57].…”

Section: Spatial Analysis Of the Jet Flames And Their Coupled Interac...mentioning

confidence: 81%

“…6), we observe the presence of periodic transverse displacement of each jet flame during the periodic epochs of intermittency as the steep fronted shock wave sweeps through it. Therefore, we observe that each jet flame exhibits substantial asymmetric oscillations due to the asymmetric vortex shedding from the gaps between the neighboring injector recesses [57].…”

Section: Phase-averaged Flame Images During Periodic Epochs Of Interm...mentioning

confidence: 83%

“…Moreover, during thermoacoustic instability, the jet flames which are compact near the injector spread out at the downstream locations. Eventually, the propellants autoignite leading to higher heat release rate, well downstream of the injector [57].…”

Section: Phase-averaged Flame Images During Periodic Epochs Of Interm...mentioning

confidence: 99%

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Coupled interaction between acoustics and unsteady flame dynamics during the transition to thermoacoustic instability in a multi-element rocket combustor

Kasthuri,

Pawar,

Gejji

et al. 2021

Preprint

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Rocket engine combustors are prone to transverse instabilities that are characterized by large amplitude high frequency oscillations in the acoustic pressure and the heat release rate. In this work, we study the coupled interaction between the acoustic pressure and the CH* intensity (representative of heat release rate) oscillations in a 2D multi-element self-excited model rocket combustor during the transition from a stable state to thermoacoustic instability through intermittency. We show the emergence of synchronization between these oscillations from desynchronization through intermittent phase synchronization during the onset of thermoacoustic instability. We find substantial evidence that the intensities of the jet flames close to the end wall is higher than that observed near the center of the combustor as a result of its strong coupling to the local acoustic field. Using concepts from recurrence theory, we distinguish the type of synchronization between the acoustic pressure and the CH* intensity oscillations at the end wall and the center of the combustor during thermoacoustic instability. Analyzing the local CH* intensity oscillations, we observe that the longitudinally propagating jet flames experience substantial transverse displacement with flame merging effects during thermoacoustic instability. Furthermore, we differentiate the interaction of the jet flames with the shock wave during intermittency and thermoacoustic instability at both the end wall and the center of the combustor. We also discerned the change from stochastic to deterministic nature in the local CH* intensity oscillations during the transition to thermoacoustic instability. Our results demonstrate that only the first few transverse modes contribute to the generation of acoustic power from the reacting flow, in spite of the pressure oscillations featuring several harmonics. The insights gained from such coupled analysis during the transition from stable state to thermoacoustic instability can be leveraged to aid modeling efforts of thermoacoustic instability in rocket engines with multiple injectors.

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Section: Spatial Analysis Of the Jet Flames And Their Coupled Interac...mentioning

confidence: 81%

Section: Phase-averaged Flame Images During Periodic Epochs Of Interm...mentioning

confidence: 83%

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Coupled interaction between acoustics and unsteady flame dynamics during the transition to thermoacoustic instability in a multi-element rocket combustor

Kasthuri,

Pawar,

Gejji

et al. 2021

Preprint

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“…The design maintains similarities with several other rocket and gas turbine combustion experiments studied at Purdue University. 35,[37][38][39][40] VIPER-M was designed to promote self-excited, transverse instabilities while operating at a mean chamber pressure up to 825 kPa with an inlet air temperature up to 510 K. The multi-element configuration supports jet-stabilized combustion with flames anchored at the injector-exit plane (y ¼ 0), as labeled in Figure 1. This injector configuration is similar to the FLOX V R combustion experiments, which have been widely studied.…”

Section: Combustor Designmentioning

confidence: 99%

Injector-coupled transverse instabilities in a multi-element premixed combustor

Philo

Gejji

Slabaugh

2020

International Journal of Spray and Combustion Dynamics

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Combustion instabilities in a high-pressure, multi-element combustor are studied in order to understand the relationship between the chamber and injector dynamics. A linear array of seven injectors supplies premixed natural gas and air into a rectangular combustion chamber designed to promote high-frequency, transverse thermoacoustic instabilities. The effect of equivalence ratio on the combustion dynamics was investigated for two injector lengths, 62.5 and 125 mm. For all operating conditions, the 125 mm injectors promote high-amplitude instabilities of the fundamental transverse (1T) mode, which has a frequency of 1750–1850 Hz. Reducing the injector length significantly lowers the instability amplitudes for all operating conditions and, for lower equivalence ratio cases, excites an additional mode near 1550 Hz. The delineating feature controlling the growth of the instabilities in each injector configuration is the coupling with axial pressure fluctuations in the injectors that occur in response to the transverse modes in the chamber.

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“…The results indicated that combustion instability was associated with periodic vortex shedding. Subsequently, a seven-element (Pomeroy and Anderson, 2016;Popov and Sirignano, 2016) and a nine-element (Orth et al, 2018;Gejji et al, 2020) sub-scale rocket combustor was designed to boost self-excited transverse instabilities. Indepth numerical simulations (Tudisco et al, 2016;Harvazinski et al, 2019) based on the experimental setup were performed.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Tangential Combustion Instability Modes in a LOX/Kerosene Liquid Rocket Engine Based on OpenFOAM

Guo

Ren

et al. 2022

Front. Energy Res.

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Self-excited high frequency combustion instability (HFCI) of first-order tangential (1T) mode was observed in a staged-combustion LOX/Kerosene liquid rocket engine numerically. Two different kinds of 1T patterns, standing wave mode and traveling wave mode, were captured in the present work. In the nominal operation condition, the ratio of oxygen-to-fuel (O/F) was 2.5. Propellant was evenly distributed in all injectors and no HFCI occurred. The chamber pressure obtained from the numerical simulation and experiment showed a good agreement, which validated the numerical model. When the mass flow of fuel for two injectors was modified, severe HFCI occurred. The pressure wave node was located at a fixed diameter, showing a 1T standing wave mode. As the O/F was set 4.4 and the propellant distribution was completely uniform, the numerical result yielded a 1T wave node featured a spinning behavior, which was a traveling 1T wave mode. Once the HFCI arose, no matter what standing mode or spinning mode, the pressure and heat release oscillated totally in phase temporally and coupled spatially. The heat release from combustion was fed into the resonant acoustic mode. This was the thermoacoustic coupling process that maintained the HFCI.

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Combustion Response of Shear Coaxial Injectors to Transverse Combustion Instabilities

Cited by 7 publications

References 17 publications

Coupled interaction between acoustics and unsteady flame dynamics during the transition to thermoacoustic instability in a multi-element rocket combustor

Coupled interaction between acoustics and unsteady flame dynamics during the transition to thermoacoustic instability in a multi-element rocket combustor

Injector-coupled transverse instabilities in a multi-element premixed combustor

Analysis of Tangential Combustion Instability Modes in a LOX/Kerosene Liquid Rocket Engine Based on OpenFOAM

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