Combustion Visualization, Performance, and CFD Modeling of a Pre-Chamber Turbulent Jet Ignition System in a Rapid Compression Machine

Gentz, Gerald; Thelen, Bryce; Litke, Paul J.; Hoke, John; Toulson, Elisa

doi:10.4271/2015-01-0779

Cited by 74 publications

(37 citation statements)

References 20 publications

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“…The difference in the operating pressure may cause disparities in the ignition mechanism. The works on RCM did not consider the intake and expansion process of the piston engine [13][14][15] that could substantially affect the residual gas scavenging and fuel/air charge distribution inside the PC, gas exchange between PC and MC, as well as emission formations from the PC. Some studies on optical engines provided insights into the general combustion characteristics of the PCC.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous Negative PLIF and OH* Chemiluminescence Imaging of the Gas Exchange and Flame Jet from a Narrow Throat Pre-Chamber

Tang¹,

Sampath²,

Marquez³

et al. 2020

SAE Technical Paper Series

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Pre-chamber combustion (PCC) is a promising engine combustion concept capable of extending the lean limit at part load. The engine experiments in the literature showed that the PCC could achieve higher engine thermal efficiency and much lower NOx emission than the spark-ignition engine. Improved understanding of the detailed flow and combustion physics of PCC is important for optimizing the PCC combustion. In this study, we investigated the gas exchange and flame jet from a narrow throat pre-chamber (PC) by only fueling the PC with methane in an optical engine. Simultaneous negative acetone planar laser-induced fluorescence (PLIF) imaging and OH* chemiluminescence imaging were applied to visualize the PC jet and flame jet from the PC, respectively. Results indicate a delay of the PC gas exchange relative to the built-up of the pressure difference (△P) between PC and the main chamber (MC). This should be due to the gas inertia inside the PC and the resistance of the PC nozzle. The PC jet can be either continuous or intermittent depending on the △P and pressure fluctuation amplitude. Distinct PC jet with low speed is witnessed after 15° CA ATDC, which could account for the postcombustion of the PCC engine in the literature. The probability distribution analysis of the PLIF and OH* images presents a much longer penetration length of the PC jet than that of the flame jet. This means that the flame jet resides in an atmosphere of the unburned gas mixture from the PC when it appears in the MC. The flame jet and PC jet show longer penetration length and become more stable with the enriching of the prechamber charge from lean to stoichiometric. However, the overall PC jet characteristics regarding the penetration length and probability distribution become less sensitive to the PC global excess air ratio (λ) when the PC charge is close to stoichiometry.

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Section: Introductionmentioning

confidence: 99%

Simultaneous Negative PLIF and OH* Chemiluminescence Imaging of the Gas Exchange and Flame Jet from a Narrow Throat Pre-Chamber

Tang¹,

Sampath²,

Marquez³

et al. 2020

SAE Technical Paper Series

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“…1,2 A variety of systems have been proposed for ignition of lean premixed methane/air, for example, by means of Diesel pilots, 3–7 laser ignition, 8 as well as by turbulent jets issuing from scavenged or un-scavenged pre-chambers. 9–21 Among all these techniques, un-scavenged pre-chambers are particularly attractive due to their low cost and engineering simplicity.…”

Section: Introductionmentioning

confidence: 99%

Characterization of combustion in a gas engine ignited using a small un-scavenged pre-chamber

Wright

Schiliro

et al. 2018

International Journal of Engine Research

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Prechamber ignition technology receives increasing attention due to its considerable improvement on engine combustion efficiency and stability. However, fundamental knowledge concerning flame propagation inside the pre-chamber and jet formation in the main chamber is still quite scarce. In this study, a small (<0.5% VTDC) un-scavenged pre-chamber was tested in a medium size gas engine with pressure transducers installed in both pre- and main chamber. Three-dimensional computational reactive fluid dynamics Reynolds-averaged Navier–Stokes simulations were carried out using a level-set combustion model –G-equation – towards improved understanding of the combustion processes occurring inside the pre and main chamber. The characteristics of the turbulence and the flame at locations just ahead of the propagating turbulent flame front were recorded and analysed by means of the well-known Borghi–Peters diagram. The results revealed that the characteristics of the flame inside the pre-chamber differed greatly from those inside the main chamber due to considerably reduced turbulent length scales. In addition, a wide range of turbulence intensity and length scales are covered throughout the combustion event, presenting a significant challenge to modelling of flame–turbulence interaction. Various turbulent flame speed ( ST) closures widely used in internal combustion engine simulation were therefore assessed and the ranges of their respective model constants explored. A correlation for ST is subsequently proposed by blending two formulations of Gülder developed for small and large scale turbulence, respectively, and compared to the well-known Peters correlation. With appropriate model constants, both successfully reproduce the pre and main chamber combustion for the reference case in terms of evolutions of cylinder pressure, heat release rate and pressure difference between pre and main chamber. Following successful calibration of the reference operating condition, variations in engine speed, load, spark timing and lambda were calculated using both correlations, demonstrating encouraging predictive capabilities of the proposed modelling strategy.

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“…The RCM combustion cylinder optical head assembly is shown in Figure 1. A more illustrative picture of the RCM as well as a detailed description can be found in the study of Gentz et al 24,28 During experiments, the combustion chamber was filled with a homogeneous charge of air and fuel at the desired stoichiometry condition. Two Kistler pressure transducers were used to measure the prechamber and main chamber pressures, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…Further details of the RCM experimental setup can be found in the study of Gentz and colleagues. 24,25,35…”

Section: Methodsmentioning

confidence: 99%

Large eddy simulation of a homogeneously charged turbulent jet ignition system

Gholamisheeri

Givler

Toulson

2017

International Journal of Engine Research

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Transient jet ignition of a homogeneous methane air mixture in a turbulent jet ignition system is studied computationally using a large eddy simulation turbulence model. The jet discharges from a prechamber into a main combustion chamber via one or more orifice(s) and provides a distributed ignition source in turbulent jet ignition. The effect of orifice size and stoichiometry is studied numerically using the Converge computational fluid dynamics code. A reduced kinetic mechanism is used for combustion along with a Smagorinsky sub-model for turbulence modeling. The computed pressure traces are compared with experimental measurements through rapid compression machine tests. Computational fluid dynamics results are in acceptable agreement with the experimental data during compression and the early stage of combustion; however, an over-prediction of peak pressure was reported. Peak pressure error is in the range of 0.1%-4% for Reynolds-averaged Navier-Stokes simulation estimation compared to the experimental measurements. This error is a function of mixture stoichiometry and unburned gas temperature. The error calculation showed that with the large eddy simulation model, 1% and 12% improvements in peak pressure and burn rate estimations, respectively, were achieved compared to Reynolds-averaged Navier-Stokes results. The reduced large eddy simulation error relative to the Reynolds-averaged Navier-Stokes simulations were considered to be in the acceptable range; however, further improvements could be achieved through validation and testing of additional turbulence models. In addition, computational fluid dynamics temperature contours for various nozzle orifices and air-fuel ratios are compared to achieve deeper insight into the turbulent jet ignition combustion process in the rapid compression machine combustion cylinder. The numerical iso-surface temperature contours were obtained which enabled three-dimensional views of the flame propagation, the jet discharge, ignition and extinction events. The heat release process and regeneration of mid-range temperature iso-surfaces (1200 K) were not visible through the experimental images.

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Combustion Visualization, Performance, and CFD Modeling of a Pre-Chamber Turbulent Jet Ignition System in a Rapid Compression Machine

Cited by 74 publications

References 20 publications

Simultaneous Negative PLIF and OH* Chemiluminescence Imaging of the Gas Exchange and Flame Jet from a Narrow Throat Pre-Chamber

Simultaneous Negative PLIF and OH* Chemiluminescence Imaging of the Gas Exchange and Flame Jet from a Narrow Throat Pre-Chamber

Characterization of combustion in a gas engine ignited using a small un-scavenged pre-chamber

Large eddy simulation of a homogeneously charged turbulent jet ignition system

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