Experimental and Numerical Investigation of the Engine Operational Conditions’ Influences on a Small Un-Scavenged Pre-Chamber’s Behavior

Xu, Guiqing; Wright, Yuri M.; Kyrtatos, Panagiotis; Bardis, Konstantinos; Schiliro, Michele; Boulouchos, Konstantinos

doi:10.4271/2017-24-0094

Cited by 16 publications

(9 citation statements)

References 32 publications

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“…In addition, jet impingement on the piston or walls may affect the downstream motion of the reaction zone into the pre-chamber fluid jet, hence affecting overall ignition success by large-scale transport effects. 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.…”

Section: Further Discussionmentioning

confidence: 58%

Fundamental Aspects of Jet Ignition for Natural Gas Engines

Mastorakos

Allison

Giusti

et al. 2017

SAE Int. J. Engines

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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.

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Section: Further Discussionmentioning

confidence: 58%

Fundamental Aspects of Jet Ignition for Natural Gas Engines

Mastorakos

Allison

Giusti

et al. 2017

SAE Int. J. Engines

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“…Nowadays, prechamber gas engine technology is commercially established in larger stationary engines where engines in the 10-MW class with two-stage turbocharging technology achieve peak brake thermal efficiencies of around 50%. 25,26 Prechamber systems have also found their way to high-performance race engines 27,28 and recently gained increasing interest in the research and technology community in terms of numerical modeling in different fidelity levels, 29–35 in fundamental experiments 36–39 or in the implementation to engines. 23,27,40,41…”

Section: Introductionmentioning

confidence: 99%

Efficient light-duty engine using turbulent jet ignition of lean methane mixtures

Soltic

Hilfiker

Hänggi

2019

International Journal of Engine Research

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Diesel engines use diffusion-controlled combustion of a high-reactivity fuel and offer high efficiencies because they combine lean combustion with a high compression ratio. For low-reactivity fuels such as gasoline or natural gas, premixed combustion is used, which leads to lower efficiency levels as usually stoichiometric combustion is combined with lower compression ratios. Trying to apply diesel-like process parameters to low-reactivity fuels inevitably leads to problems with classical spark ignition systems as they are not able to establish robust flame propagation for such hard-to-ignite conditions. One possibility to enable fast combustion for diluted mixtures at high pressure levels is to establish ignition in a prechamber and ignite the charge of the main combustion chamber using the turbulent jets exiting the prechamber. In this study, the experimental results of a prechamber-equipped four-cylinder natural gas engine with 2 L displacement are discussed in detail. In the majority of the engine map, auxiliary fueling is used in the prechamber and a global air–fuel equivalence ratio λ is set to 1.7. At full load, a λ of 1.5 is applied without auxiliary prechamber fueling. The experiments show that such a setup is able to achieve brake efficiency levels of above 45% while maintaining peak brake mean effective pressure levels above 20 bar. At high load conditions, cylinder pressure levels at ignition timing achieve more than 80 bar and cylinder peak pressures of around 180 bars occur. The technology proved to enable robust and very fast combustion at comparably low NOx levels. A remaining challenge for the on-road use of such a technology is the reduction of the methane emissions at lean conditions.

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“…The magnitude and timing of the peak pressure difference are of prime significance, as the former relates to the reactive jet exit timing and the latter to the jet momentum and penetration. 24,26,69 For the FM-v1 and FM-v12 there is no available prechamber experimental pressure measurement and, therefore, the one from the CFD has to be used. As can be seen in Figure 10(a), the evolution of the pressure difference is predicted well for all the prechambers apart from FM-v12.…”

Section: Prechamber Combustionmentioning

confidence: 99%

“…Numerical simulations of TJI included 3-D Reynolds Averaged Navier Stokes (RANS) simulations, 21–28 Large Eddy Simulations (LES), 29–31 and more recently Direct Numerical Simulations (DNS). 32–34 Zero/quasi-dimensional models have also been developed for prechamber gas engines and vary to the degree that the relevant physics are included.…”

Section: Introductionmentioning

confidence: 99%

Development and validation of a novel quasi-dimensional combustion model for un-scavenged prechamber gas engines with numerical simulations and engine experiments

Bardis

Kyrtatos²,

et al. 2020

International Journal of Engine Research

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Lean-burn gas engines equipped with an un-scavenged prechamber have proven to reduce nitrogen oxides (NOx) emissions and fuel consumption, while mitigating combustion cycle-to-cycle fluctuations and unburned hydrocarbon (UHC) emissions. However, the performance of a prechamber gas engine is largely dependent on the prechamber design, which has to be optimised for the particular main chamber geometry and the foreseen engine operating conditions. Optimisation of such complex engine components relies partly on computationally efficient simulation tools, such as quasi and zero-dimensional models, since extensive experimental investigations can be costly and time-consuming. This article presents a newly developed quasi-dimensional (Q-D) combustion model for un-scavenged prechamber gas engines, which is motivated by the need for reliable low order models to optimise the principle design parameters of the prechamber. Our fundamental aim is to enhance the predictability and robustness of the proposed model with the inclusion of the following: (i) Formal derivation of the combustion and flow submodels via reduction of the corresponding three-dimensional models. (ii) Individual validation of the various submodels. (iii) Combined use of numerical simulations and experiments for the model validation. The resulting model shows very good agreement with the numerical simulations and the experiments from two different engines with various prechamber geometries using a set of fixed calibration parameters.

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Experimental and Numerical Investigation of the Engine Operational Conditions’ Influences on a Small Un-Scavenged Pre-Chamber’s Behavior

Cited by 16 publications

References 32 publications

Fundamental Aspects of Jet Ignition for Natural Gas Engines

Fundamental Aspects of Jet Ignition for Natural Gas Engines

Efficient light-duty engine using turbulent jet ignition of lean methane mixtures

Development and validation of a novel quasi-dimensional combustion model for un-scavenged prechamber gas engines with numerical simulations and engine experiments

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