Large-eddy simulation on the effect of injection pressure and density on fuel jet mixing in gas engines

Vuorinen, Ville; Wehrfritz, Armin; Duwig, Christophe; Boersma, Bendiks Jan

doi:10.1016/j.fuel.2014.04.045

Cited by 48 publications

(53 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In further agreement with [40], the present LES study predicted the reflected shock (at the triple point) to be inclined ~28° against the nozzle centreline axis. The reflected shock angle for the methane test case (NPR=8.5) was measured to be ~28.5°, which in addition to the Mach disk height (H disk ≈1.9D) were in agreement with the recent work of Vuorinen et al [13,37] on a nozzle of 1.4 mm dimeter, NPR=8.5 and under-expanded nitrogen and methane jets. Similarly to the experimental observations of [40], it was also seen that hydrogen and air were mixing outside of the intercepting shock, before the Mach reflection.…”

Section: Model Validationsupporting

confidence: 88%

“…This means that not all of the incoming hydrogen passed through the Mach disk surface. For methane, similarly to [37], mixing did not occur before the Mach reflection. The mixing process at the boundary of the intercepting shock in underexpanded jets is discussed further later in the current paper.…”

Section: Model Validationmentioning

confidence: 88%

“…Recently large eddy simulation (LES) was employed to investigate under-expanded methane and nitrogen jets [13,35]. However, very limited experimental and computational studies are available in the literature on under-expanded hydrogen and methane jets and specifically with respect to applications in DI gaseous engines [36][37][38][39][40][41]. Recently, the authors of the present paper used LES to investigate the near-nozzle shock structure and mixing characteristics of highly under-expanded hydrogen and methane jets with NPR=8.5-70 issuing from a circular nozzle into a low ambient pressure (P ∞ ≈1 bar) [14,42].…”

Section: Present Contributionmentioning

confidence: 99%

“…For all simulations, an initial constant temperature of 295.4 K and 296 K was employed for the fuel and air containing volumes, respectively. Following practices in the literature [13,35,37] and also based on the discussion provided in [14], adiabatic slip boundary conditions were assigned to the nozzle and high-pressure tank boundaries. …”

Section: Simulation Setup and Validationmentioning

confidence: 99%

“…Since modelling transient compressible in-nozzle flows requires very small time steps (usually of the order of nanoseconds and mainly because of the existence of high density gradient inside the nozzle volume) the common practices in the literature is to omit it by applying an arbitrary pressure gradient inside the nozzle [13,37]. However, in the present LES study, the in-nozzle transient process was taken specifically into the account.…”

Section: Computational Setupmentioning

confidence: 99%

See 4 more Smart Citations

Gas dynamics and flow characteristics of highly turbulent under-expanded hydrogen and methane jets under various nozzle pressure ratios and ambient pressures

Hamzehloo

Aleiferis

2016

International Journal of Hydrogen Energy

View full text Add to dashboard Cite

The current study used large eddy simulations to investigate the sonic and mixing characteristics of turbulent under-expanded hydrogen and methane jets with various nozzle pressure ratios issued into various ambient pressures including elevated conditions relevant to applications in direct injection gaseous-fuelled internal combustion engines. Due to the relatively low density of most gaseous fuels such as hydrogen and methane, DI requires high injection pressures to achieve suitable mass flow rates for fast in-cylinder fuel delivery and rapid fuel-air mixing. Such pressures typically form an under-expanded fuel jet past the nozzle exit. Test cases of hydrogen injection with nozzle pressure ratio (NPR) of 10 issued into quiescent air with pressure P ∞ ≈1, 5 and 10 bar were simulated. Direct comparison between hydrogen and methane jets with NPR=8.5 and P ∞ ≈1 was also made. The effect of ambient pressure on features of transient development of the nearnozzle shock structure and tip vortices (vortex ring) was investigated. It was observed that at constant NPR, higher ambient pressure resulted in slightly faster formation of the Mach reflection and shorter Mach disk settlement time. Different mechanisms were observed between hydrogen and methane with regards to transient formation of their initial tip vortex rings. It was found that the initial transient tip vortices of hydrogen jets may also contribute to the flow instabilities at the boundary of the intercepting shock and, unlike for methane, promote fuel-air mixing before the Mach reflection. It was also shown that the nearnozzle shock structure was only affected by NPR regardless of the ambient pressure. Furthermore, no flow recirculation zone was found just downstream of the Mach disk, a finding comparable to all previous experimental investigations. Also, it was observed that a locally richer mixture was created for jets with higher NPR or with higher ambient pressure at constant NPR. Based on the results of the current study, correlations were proposed for the shock cell spacing and jet tip penetration of highly under-expanded jets issued from millimetre-size circular nozzles.

show abstract