On the Effect of Ambient Turbulence and Thermodynamic Conditions on Fuel Spray Development for Direct-Injection Spark-Ignition Engines

Aleiferis, P.G.; Romunde, Z. R. van; Larson, Gordon P.; Lawes, M.; Sheppard, C. G. W.

doi:10.1007/s10494-015-9605-5

Cited by 9 publications

(4 citation statements)

References 39 publications

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“…An integral length scale represents an average of all turbulent scales in the flow, but with the larger energy containing eddies governing mainly its magnitude. Data on in-cylinder integral length scales carry great significance in understanding fundamental phenomena like airflow effects on initial flame kernel wrinkling and the turbulent flame speeds of various fuels [17,18], as well as fuel atomisation during high-pressure in-cylinder injection processes [19], especially under low-load engine operation.…”

Section: Introductionmentioning

confidence: 99%

Integral Length Scales and Time Scales of Turbulence in an Optical Spark-Ignition Engine

Aleiferis

Behringer

Malcolm

2016

Flow Turbulence Combust

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In-cylinder air flow structures are known to play a major role in mixture preparation and flame development in spark-ignition engines. In this paper both LDV and PIV measurements were undertaken in an optical spark-ignition at 1500 RPM, 0.5 bar inlet plenum pressure. One of the primary PIV planes was vertical, cutting through the centrally located spark plug (tumble plane) inside the pentroof at ignition timing. The other plane was horizontal inside the pentroof 1 mm below the spark plug. LDV was conducted 1 mm below the spark plug on a line from inlet to exhaust but also on a lower line 14 mm below the spark plug. In-cylinder PIV data at specific crank angles in the intake and compression strokes were also analysed on the central tumble plane and on a horizontal plane 14 mm below the spark plug. The combination of both techniques allowed high spatial and temporal resolution as the two data sets complemented each other to provide details of mean flow and turbulence characteristics on different levels, aiming ultimately for quantification of integral time scales and length scales. LDV cycle-resolved analysis distinguished between the classic approach of using the time integral of the autocorrelation function to obtain the integral time scale and a high-frequency cut-off analysis to obtain high-and low-frequency fluctuations about an in-cycle mean.3

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Section: Introductionmentioning

confidence: 99%

Integral Length Scales and Time Scales of Turbulence in an Optical Spark-Ignition Engine

Aleiferis

Behringer

Malcolm

2016

Flow Turbulence Combust

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“…1. The flow velocity is less than that in direct-injection studies Aleiferis et al (2015), and is much lower than the ambient velocity in diesel engines Xuan et al (2019). Air enters through a diffuser section followed by a flow conditioner consisting of six 0.5 mm thick, 100 micron mesh screens to break up eddies and uniformly distribute the flow across the CPFC.…”

Section: Methodsmentioning

confidence: 95%

“…In that case, as ignition occurs from near piston top center up to 10 • later resulting in the maximum cylinder pressure for a cycle observed being 36% higher than lowest cycle. Experimentally, Aleiferis et al (2015) studied the impact of ambient flow field on the spray under non-and flash boiling sprays and noted large impact for flash boiling cases. To provide some measure of turbulence they report mean and RMS spray images results though focus on discussion of ensemble average behaviors.…”

Section: Introductionmentioning

confidence: 99%

Representative Phenomena of Cyclic Turbulent Combustion in High-Pressure Fuel Sprays

Parker

Agrawal

Bittle

2023

Flow Turbulence Combust

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Cyclic variations in conventional diesel combustion engines can lead to large differences in engine out emissions even at steady operation. This study uses an optically accessible constant-pressure flow chamber to acquire fuel injections in quick succession to analyze mixing, auto-ignition, and combustion of diesel-surrogate n-heptane using multiple high-speed optical diagnostics. Prior studies have utilized fewer injections and/or they rely on analysis of ensemble average behavior. These approaches do not yield information on injection-to-injection variation or provide confidence in utilizing individual injection measurements for high-fidelity computational fluid dynamics(CFD) model validation. In this study, a large set of 500 injections is used to obtain global parameters including liquid length, vapor penetration length, ignition delay time, and lift-off length. Results for multiple injections are presented to illustrate large injection to injection variations. Potential sources for these variations are analyzed to conclude localized, small scale turbulence and rate of injection variations as the likely sources. Then, a statistical method based on z-scores is proposed and implemented to identify instantaneous injections that best represent the bulk data-set of jet boundaries measured independently by three different diagnostics. This synthesis of statistics-guided screening of data set and ensemble-average analysis offers higher confidence for CFD model validation relying upon both a representative single and average injection results.

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“…Additionally, due to stratified charge, the progressive charge cooling is realised which contributes to the utilisation of higher compression ratio without the risk of engine knock. Under such circumstances, the thermal efficiency is significantly increased [6].…”

Section: Introductionmentioning

confidence: 99%

Computational Fluid Dynamics (CFD) Modelling of Mixture Formation in Gasoline Direct Injection (GDI) Engine

Amedorme

Apodi

2019

JERR

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Automotive engine faces stringent regulations on emission with improved fuel consumption. As such, the Gasoline Direct Injection (GDI) engines which have the potential to meet these requirements are being improved on especially the mixture formation to the burning of the mixture. In GDI, late injection compared with early injection scheme generates charge stratification which contributes to the optimised fuel consumption and combustion. As a result, this strategy in GDI engines is considered to be promising with increasing research focus. This paper aims at evaluating the computational fluids dynamics (CFD) modelling of two-phase transient injection process in generic GDI engines with the late injection to study the features of fuel atomisation process, injection velocity and its influence on turbulence. The commercial CFD code Star CCM+ was used to perform this simulation due to its advanced polyhedral mesh technology and the user-friendly interface. Transient liquid and gas flow inside the combustion chamber was simulated using the Eulerian multiphase segregated flow model with k-epsilon turbulence. The contour plots show that during the injection period turbulence for each phase was independent of the spray shape predicted to be asymmetric under non-vaporisation conditions. In addition, increasing injection velocity of liquid fuel causes stronger turbulence for the liquid phase. The results also show that the variation of turbulence for gas-phase is mainly centred in the region of the inlet during the injection process and non-homogenous turbulent characteristics were observed for the late injection with the volume fraction of the liquid phase also seen to be asymmetric.

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On the Effect of Ambient Turbulence and Thermodynamic Conditions on Fuel Spray Development for Direct-Injection Spark-Ignition Engines

Cited by 9 publications

References 39 publications

Integral Length Scales and Time Scales of Turbulence in an Optical Spark-Ignition Engine

Integral Length Scales and Time Scales of Turbulence in an Optical Spark-Ignition Engine

Representative Phenomena of Cyclic Turbulent Combustion in High-Pressure Fuel Sprays

Computational Fluid Dynamics (CFD) Modelling of Mixture Formation in Gasoline Direct Injection (GDI) Engine

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