Effect of Gas Density and Temperature on Air Entrainment in a Transient Diesel Spray

Cossali, Gianpietro; Gerla, A.; Coghe, A.; Brunello, G.

doi:10.4271/960862

Cited by 34 publications

(24 citation statements)

References 8 publications

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“…This effect of promoting pre-mixed combustion is more important at retarded SoI, since at earlier SoI values, the period of premixed combustion is very short. Late IVC extends also combustion duration in the region of early SoI, possibly due to the lower in-cylinder gas density, which inhibits the fuel-air mixing process, and consequently slows down the heat release during the diffusion-controlled combustion phase (Cossali et al, 1996). The observed prolongation in combustion duration is less important at most retarded SoI, and even at low IP, there is a shortening of the combustion period.…”

Section: Modelling Results With Advanced and Retarded Ivcmentioning

confidence: 96%

Improving pollutant emissions in diesel engines for heavy-duty transportation using retarded intake valve closing strategies

Benajes

Molina

Riesco

2008

Int.J Automot. Technol.

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A combined theoretical and experimental study has been carried out to determine the real potential of reducing pollutant emissions in a HD diesel engine by means of retarding the intake valve closing. The effects produced by this alteration of the basic operation cycle have been examined by a preliminary modelling study, and from the obtained results, a modified camshaft was manufactured with a delayed intake valve closing of 60 crank angle degrees. Single-cylinder engine tests were carried out with this modified camshaft, and the emissions and fuel consumption were recorded. The results showed that the retarded intake valve closing can enhance the premixed combustion phase, and thus simultaneously reduce soot and NOx emissions. Moreover, the combustion process attained is extremely tolerant to exhaust gas recirculation, and by adoption of this measure, Euro-5 emissions limits can be achieved at the tested conditions without after-treatment.

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Section: Modelling Results With Advanced and Retarded Ivcmentioning

confidence: 96%

Improving pollutant emissions in diesel engines for heavy-duty transportation using retarded intake valve closing strategies

Benajes

Molina

Riesco

2008

Int.J Automot. Technol.

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“…The experimental apparatus usually employed at CNR-TeMPE for unsteady spray optical diagnostics [5][6][7] was slightly modified for this study.…”

Section: Experimental Setup and Proceduresmentioning

confidence: 99%

Effects of Fuel Temperature and Ambient Pressure on a GDI Swirled Injector Spray

Araneo¹,

Coghe²,

Brunello³

et al. 2000

SAE Technical Paper Series

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The effects of fuel temperature on both the geometry and the droplet size and velocity of a GDI swirled injector spray were investigated by means of visualizations and PDA measurements. Isooctane was used as model fuel and was injected in a quiescent bomb at injection pressure of 7 MPa. Bomb pressure ranged from 40 kPa to 800 kPa with injector nozzle temperature ranging from 293 K to 393 K. A drastic change in spray geometry was observed when conditions above the vaporization curve were reached. The temperature increase has two macroscopic effects on the spray geometry: at the nozzle exit the liquid flash boiling strongly enlarges the spray angle, at a certain distance from the nozzle the air entrainment collapses the spray. Raising the fuel temperature up to flash boiling conditions causes a significant decrease of the average droplet size.

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“…Most of the efforts within this field have been devoted to the understanding of the mixing process between fuel and air, which governs Diesel combustion process. Experimental investigations have delivered spray tip penetration [6], [7], mixture fraction [7] and local velocity measurements [8] [9], which have led to the general conclusion that the mixing process of a Diesel spray is rather similar to that of a gas jet at similar mass momentum and fuel/air density ratio conditions [10]. On the other hand, knowledge on the interaction between mixing process and flame development is a more open topic, where some questions are still unresolved.…”

Section: Introductionmentioning

confidence: 99%

“…Keeping the previous framework in mind, some still unknown issues on the evolution of Diesel sprays can be identified, which mainly have to do with the spray flow development. The latter topic has been deeply analysed in terms of spray tip penetration and, to a much lower extent, with local velocity measurements [8], [9], [16]. However, except for the classical work by Kobayashi [17] using shadowgraph visualization and a more recent one by Farrell [16] using PIV, most of such studies have been usually carried out under inert spray conditions.…”

Section: Introductionmentioning

confidence: 99%

A study on the interaction between local flow and flame structure for mixing-controlled Diesel sprays

García-Oliver

Malbec

Toda

et al. 2017

Combustion and Flame

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A detailed study on the spray local flow and flame structure has been performed by means of PIV and laser-sheet LIF techniques under Diesel spray conditions. Operating conditions were based on Engine Combustion Network recommendations. A consistent comparison of inert and reacting axial velocity fields has produced quantitative information on the effect of heat release on the local flow. Local axial velocity has been shown to increase 50 to 60% compared to the inert case, while the combustion-induced radial expansion of the spray has been quantified in terms of a 0.9 to 2.1 mm radius increase. As a result, the drop in entrainment rate has been quantified around 25% compared to the inert case. Streamline analysis also hints at a reduced entrainment under reacting conditions. A 1D spray model under reacting condition has been used, which confirms the modifications obtained in the main flow metrics when moving from inert to reacting conditions. When comparing the flow evolution with the flame structure, little effect of chemical activity on the spray flow upstream the lift-off length has been evidenced, in spite of the presence of formaldehyde in such regions. Only downstream of the lift-off length, as defined by OH LIF, has a strong change in flow pattern been observed as a result of combustion-induced heat release.

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Effect of Gas Density and Temperature on Air Entrainment in a Transient Diesel Spray

Cited by 34 publications

References 8 publications

Improving pollutant emissions in diesel engines for heavy-duty transportation using retarded intake valve closing strategies

Improving pollutant emissions in diesel engines for heavy-duty transportation using retarded intake valve closing strategies

Effects of Fuel Temperature and Ambient Pressure on a GDI Swirled Injector Spray

A study on the interaction between local flow and flame structure for mixing-controlled Diesel sprays

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