Visualization and analysis of the characteristics of transitional underexpanded jets

Yu, Jingzhou; Vuorinen, Ville; Kaario, Ossi; Sarjovaara, Teemu; Larmi, Martti

doi:10.1016/j.ijheatfluidflow.2013.05.015

Cited by 75 publications

(27 citation statements)

References 47 publications

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“…The near-nozzle shock structure and the strong compression effects were taken into account by using a bulk viscosity model in conjunction with a second-order filter that was activated at the location of the strong shocks. Vourinen et al [51] also showed that the Mach disk dimensions and shock structure were in very good agreement with the experimental observations of Yu et al [37,52] that included PLIF visualisation. Important mixing characteristics, e.g.…”

Section: Les Modellingsupporting

confidence: 70%

“…Computational studies of under-expanded jets have been performed using compressible Euler equations [38][39][40][41], Reynolds Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) methodologies [41][42][43][44][45][46][47][48][49][50][51][52], mainly for air jets or by assuming the injection of a passive scalar. Early studies were also conducted by analytical approaches and the method of characteristics [24,53].…”

Section: Literature Surveymentioning

confidence: 99%

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Large eddy simulation of highly turbulent under-expanded hydrogen and methane jets for gaseous-fuelled internal combustion engines

Hamzehloo¹,

Aleiferis²

2014

International Journal of Hydrogen Energy

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Burning hydrogen in conventional internal combustion (IC) engines is associated with zero carbon-based tailpipe exhaust emissions. In order to obtain high volumetric efficiency and eliminate abnormal combustion modes such as preignition and backfire, in-cylinder direct injection (DI) of hydrogen is considered preferable for a future generation of hydrogen IC engines. However, hydrogen's low density requires high injection pressures for fast hydrogen penetration and sufficient in-cylinder mixing. Such pressures lead to chocked flow conditions during the injection process which result in the formation of turbulent under-expanded hydrogen jets. In this context, fundamental understanding of the under-expansion process and turbulent mixing just after the nozzle exit is necessary for the successful design of an efficient hydrogen injection system and associated injection strategies. The current study used large-eddy simulation (LES) to investigate the characteristics of hydrogen under-expanded jets with different nozzle pressure ratios (NPR), namely 8.5, 10, 30 and 70. A test case of methane injection with NPR=8.5 was also simulated for direct comparison with the hydrogen jetting under the same NPR. The near-nozzle shock structure, the geometry of the Mach disk and reflected shock angle, as well as the turbulent shear layer were all captured in very good agreement with data available in the literature. Direct comparison between hydrogen and methane fuelling showed that the ratio of the specific heats had a noticeable effect on the near-nozzle shock structure and dimensions of the Mach disk. It was observed that with methane, mixing did not occur before the Mach disk, whereas with hydrogen high levels of momentum exchange and mixing appeared at the boundary of the jet. This was believed to be the effect of the high turbulence fluctuations at the nozzle exit of the hydrogen jet which triggered Gortler vortices. Generally, the primary mixing was observed to occur after the location of the Mach disk and particularly close to the jet boundaries where large-scale turbulence played a dominant role. It was also found that NPR had significant effect on the mixture's local fuel richness. Finally, it was noted that applying higher injection pressure did not essentially increase the penetration length of the hydrogen jets and that there could be an optimum NPR that would introduce more enhanced mixing whilst delivering sufficient fuel in less time. Such an optimum NPR could be in the region of 100 based on the geometry and observations of the current study.3

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Section: Les Modellingsupporting

confidence: 70%

Section: Literature Surveymentioning

confidence: 99%

Large eddy simulation of highly turbulent under-expanded hydrogen and methane jets for gaseous-fuelled internal combustion engines

Hamzehloo¹,

Aleiferis²

2014

International Journal of Hydrogen Energy

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“…3 that at time t 2 -t 6 , the explosion overpressure in the chamber was larger than 0.89 bar, indicating that the venting flow is chocked and underexpanded. The flame regime was a periodic alternation of expansion wave and compression wave, which was a typical appearance of an underexpanded free jet with shock diamonds (Yu, et al, 2013). Obviously, this flame regime during the dust explosion process at the elevated static activation overpressure of 3 bar was totally different with the results obtained in the literature for relatively small static activation overpressures (Copper, Fairweather, and Walker, 1986;Proust and Leprette, 2010;Taveau, 2010).…”

Section: Flame Behaviors and Pressure Characteristics During Venting mentioning

confidence: 56%

Flame behaviors and pressure characteristics of vented dust explosions at elevated static activation overpressures

Yan

Gao

2015

Journal of Loss Prevention in the Process Industries

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“…An experimental investigation was made by Voropayev et al [11] on the evolution of turbulent jets into a cylinder by using digital video recordings and particle image velocimetry (PIV) to map the flow structures, and the frequency of jet switching, mean flow, and turbulence characteristics were inferred. The work of Yu et al [12] investigated the flow structure and turbulent mixing of pulsed jets issuing from a circular nozzle by using acetone planar laser-induced fluorescence (PLIF) and interpreted different features of gaseous jets by monitoring axial and various radial cross-sections under different injection pressure conditions. Comprehensive experimental studies were conducted by Law and Herlina [13,14] on kinematic and scalar mixing characteristics of a turbulent circular wall jet with the nonintrusive laser imaging approach of combining PIV and PLIF, and the results show that the growth of the lateral length scale is five times that of the normal length scale.…”

Section: Introductionmentioning

confidence: 99%

Study on three-dimensional expansion characteristics of four wall combustion-gas jets in confined liquid space

2017

Acta Mech. Sin.

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To explore further the launch mechanism of the new underwater launching technology proposed in this paper, the expansion characteristics of four wall combustion-gas jets in confined liquid space must be studied firstly. The experimental device is designed, and the high-speed digital photographic system is adopted to obtain the expansion sequence processes of Taylor cavities formed by the four wall jets. Meanwhile, the influence of the injection pressure on the axial expansion property of the four wall jets is discussed. Based on the experiments, a three-dimensional unsteady mathematical model is established to simulate the turbulent flow process of the four wall jets expanding in liquid, and the temporal and spatial distribution laws of phase, pressure, temperature, and velocity and the evolution rules of vortices are illustrated in detail. Results show that, accompanied by the jets expanding downstream, the four wall combustion-gas jets get close to each other and achieve convergence eventually under induction of the interference effect between multiple jets. Meanwhile, the heads of the Taylor cavities separate from the observation chamber wall and offset to the central axis of the observation chamber with time going on. The numerical simulation results of the four wall combustion-gas jets coincide well with the experimental data.

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Visualization and analysis of the characteristics of transitional underexpanded jets

Cited by 75 publications

References 47 publications

Large eddy simulation of highly turbulent under-expanded hydrogen and methane jets for gaseous-fuelled internal combustion engines

Large eddy simulation of highly turbulent under-expanded hydrogen and methane jets for gaseous-fuelled internal combustion engines

Flame behaviors and pressure characteristics of vented dust explosions at elevated static activation overpressures

Study on three-dimensional expansion characteristics of four wall combustion-gas jets in confined liquid space

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