Comparative Study of Ignition Systems for Lean Burn Gas Engines in an Optically Accessible Rapid Compression Expansion Machine

Schlatter, Stéphanie; Schneider, Bruno; Wright, Yuri M.; Boulouchos, Konstantinos

doi:10.4271/2013-24-0112

Cited by 36 publications

(20 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Despite these complications, and of course the fact that the high pressure and temperature in an engine make the flame quicker and thinner and ignition times shorter, the present results highlight some details of the jet ignition process that are relevant and were not available previously, and that warrant further investigation with both simulation [24,25] and experiment. Direct comparisons of this ignition mechanism with the dual-fuel (pilot ignition) system are also available [26] and they can be supplemented with the present results. The Large-Eddy Simulations may also be improved with better correlations for flame speed [27] if engine conditions are targeted.…”

Section: Further Discussionmentioning

confidence: 97%

See 1 more Smart Citation

Fundamental Aspects of Jet Ignition for Natural Gas Engines

Mastorakos

Allison

Giusti

et al. 2017

SAE Int. J. Engines

Self Cite

View full text Add to dashboard Cite

Large-bore natural gas engines may use pre-chamber ignition. Despite extensive research in engine environments, the exact nature of the jet, as it exits the pre-chamber orifice, is not thoroughly understood and this leads to uncertainty in the design of such systems. In this work, a specially-designed rig comprising a quartz pre-chamber fit with an orifice and a turbulent flowing mixture outside the pre-chamber was used to study the pre-chamber flame, the jet, and the subsequent premixed flame initiation mechanism by OH* and CH* chemiluminescence. Ethylene and methane were used. The experimental results are supplemented by LES and 0D modelling, providing insights into the mass flow rate evolution at the orifice and into the nature of the fluid there. Both LES and experiment suggest that for large orifice diameters, the flow that exits the orifice is composed of a column of hot products surrounded by an annulus of unburnt pre-chamber fluid. At the interface between these layers, a cylindrical reaction zone is formed that propagates in the main chamber in the axial direction assisted by convection in the jet, but with limited propagation in the cross-stream direction. For small orifice diameters, this cylinder is too thin, and the stretch rates are too high, for a vigorous reaction zone to escape the pre-chamber, making the subsequent ignition more difficult. The methane jet flame is much weaker than the one from ethylene, consistent with the lower flame speed of methane that suggests curvature-induced quenching at the nozzle and by turbulent stretch further downstream. The velocity of the jet is too high for the ambient turbulence to influence the jet, although the latter will affect the probability of initiating the main premixed flame. The experimental and modelling results are consistent with ongoing Direct Numerical Simulations at ETH Zurich.

show abstract

Section: Further Discussionmentioning

confidence: 97%

“…Studies in rapid compression machine (RCM) have also been conducted [4][5][6]. Gentz et al [4] studied the effect of nozzle diameter as well as the number of orifices.…”

Section: Introductionmentioning

confidence: 99%

Fundamental Aspects of Jet Ignition for Natural Gas Engines

Mastorakos

Allison

Giusti

et al. 2017

SAE Int. J. Engines

Self Cite

View full text Add to dashboard Cite

show abstract

“…The RCEM is a generic free-floating piston test rig (bore: 84 mm, variable stroke: 120 -249 mm) with optical accessibility through piston and cylinder head windows. A brief description of the machine and its operation principle is provided here, while further descriptions are available in [20,32,33].…”

Section: Rapid Compression-expansion Machinementioning

confidence: 99%

Optical Investigation of Sooting Propensity of n-Dodecane Pilot/Lean-Premixed Methane Dual-Fuel Combustion in a Rapid Compression-Expansion Machine

Srna¹,

Bruneaux²,

Rotz³

et al. 2018

SAE Int. J. Engines

Self Cite

View full text Add to dashboard Cite

The sooting propensity of dual-fuel combustion with n-dodecane pilot injection in a lean-premixed methane-air charge has been investigated using an optically accessible Rapid Compression-Expansion Machine to achieve engine relevant pressure and temperature conditions at start of pilot injection. A Diesel injector with a 100 µm single-hole coaxial nozzle, mounted at the cylinder periphery, has been employed to admit the pilot fuel.The aim of this study was to enhance the fundamental understanding of soot formation and oxidation processes of n-dodecane in presence of methane in the air charge by parametric variation of methane equivalence ratio, charge temperature and pilot fuel injection duration. The influence of methane on ignition delay and flame extent of the pilot fuel jet has been determined by simultaneous OH* chemiluminescence and Schlieren imaging. The sooting behavior of the flame has been characterized using the 2D-DBI imaging methodology. The apparent soot black-body temperature has been measured 1D-resolved along the injector axis by applying an imaging spectrograph.Addition of methane into the air charge considerably prolongs the ignition delay with an increasing effect under less reactive conditions and with higher methane equivalence ratios. Therefore, the influence of methane on the formation of soot is two-fold: in case of short pilot injection, the presence of methane was found to decrease the soot formation due to the leaner pilot fuel mixture at time of ignition. For longer pilot fuel injections, methane enhances the soot production by decreasing oxygen availability and introducing additional carbon. In all cases, methane strongly defers the oxidation of soot due to the lower availability of oxygen.

show abstract

“…In a RCEM, part of the expansion stroke of the piston can be also analyzed, and most of the engine parameters can be calculated, such as the heat release rate or the combustion efficiency. In this facility both homogeneous and heterogeneous (direct injection) mixtures can be tested, as well as new combustion modes such as the dual fuel technology [27] or LTC [28].…”

Section: Rcemmentioning

confidence: 99%