Numerical Simulations of Pre-Chamber Combustion in an Optically Accessible RCEM

Bolla, Michele; Shapiro, Evgeniy; Tiney, Nick; Kyrtatos, Panagiotis; Kotzagianni, Maria; Boulouchos, Konstantinos

doi:10.4271/2019-01-0224

Cited by 18 publications

(10 citation statements)

References 33 publications

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“…Note that for the set of pre-chambers and injection cases presented in this study, no direct comparison of OH* chemiluminescence has been made and hence it is difficult to ascertain this behaviour. However in a similar study performed for a different set of conditions for PC-A [30], the degree of asymmetry has been observed to be similar between the experiment and the simulation. Figure 16 shows the comparison of jet exit times with the experimental data with variable threshold for flame exit point.…”

Section: Combustion Processsupporting

confidence: 61%

Experimental and Numerical Analysis of Pre-Chamber Combustion Systems for Lean Burn Gas Engines

Shapiro

Tiney

Kyrtatos

et al. 2019

SAE Technical Paper Series

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The current trend in automobiles is towards electrical vehicles, but for the most part these vehicles still require an internal combustion engine to provide additional range and flexibility. These engines are under stringent emissions regulations, in particular, for the reduction of CO2. Gas engines which run lean burn combustion systems provide a viable route to these emission reductions, however designing these engines to provide sustainable and controlled combustion under lean conditions at λ=2.0 is challenging. To address this challenge, it is possible to use a scavenged Pre-Chamber Ignition (PCI) system which can deliver favorable conditions for ignition close to the spark plug. The lean charge in the main combustion chamber is then ignited by flame jets emanating from the prechamber nozzles. Accurate prediction of flame kernel development and propagation is essential for the analysis of PCI systems. A modelling approach is proposed based on the Dynamic Discrete Particle Ignition Kernel model coupled with the G-equation combustion model. The model is validated for an air/methane academic benchmark. The approach is then applied to the investigation of performance of three pre-chamber designs developed within Horizon 2020 GASON project in conjunction with the experimental investigation of these pre-chambers mounted on Rapid Compression Expansion Machine (RCEM). The investigated prechamber designs vary with respect to the tangential nozzle angle and volume. The study focusses on a lean limit of the proposed system's operation with the main charge at λ=2.0 and a variation of prechamber design and scavenging level. The comparison of the simulation results with the experimental observations demonstrates good accuracy of the developed model. In addition, the combined experimental and modelling provides insights into the effect of prechamber geometry on potential performance.

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Section: Combustion Processsupporting

confidence: 61%

Experimental and Numerical Analysis of Pre-Chamber Combustion Systems for Lean Burn Gas Engines

Shapiro

Tiney

Kyrtatos

et al. 2019

SAE Technical Paper Series

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Section: Introductionmentioning

confidence: 99%

“…On the other hand, based on the Large Eddy Simulation (LES) framework, MZ-WSR, 27 Flamelet Generated Manifold (FGM), 28 ECFM-3Z, 29 Weller combustion model, 30 and Thickened Flame Model 20 were used. Bolla et al 28 performed simulations of an active pre-chamber mounted in a rapid compression-expansion machine. The LES FGM model slightly under-estimated the peak pressure but aligned the time of the first jet exit and jet penetration against the experimental data.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of a fueled pre-chamber spark-ignition natural gas engine

Kim

Scarcelli

Som

et al. 2021

International Journal of Engine Research

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Pre-chamber spark-ignition (PCSI) is a leading advanced ignition concept for internal combustion engines with the potential to enable diesel-like efficiency in medium-duty/heavy-duty (MD/HD) natural gas (NG) engines. By leveraging distributed ignition sources from multiple turbulent jets, the PCSI technology can deliver extremely short combustion duration in ultra-lean mixtures and significantly improve the engine thermal efficiency. However, in the automotive industry there is a lack of adequate science base and predictive simulation tools required for commercial development of PCSI engines. In this study, Reynolds-Average Navier-Stokes simulations are carried out to describe the combustion process in lean-burn NG engines, focusing on the combustion modeling approach. Two combustion models, multi-zone well-stirred reactor (MZ-WSR) and G-equation, are used to simulate the combustion process in an MD NG engine equipped with a fueled-PCSI system for four operating conditions close to the lean operating limit. A skeletal chemical mechanism and a laminar flame speed tabulation are used to compute the combustion accurately. Simulation results are compared with experimental data regarding measured cylinder pressure, heat release rate, and combustion duration. By dividing the PCSI combustion process into four distinct phases, the difference between the two models’ results for each phase is analyzed in detail. The MZ-WSR model overestimates the combustion duration for early flame kernel growth in the pre-chamber due to the lack of a specific formulation to take turbulence-chemistry interaction into account. Despite the prolonged combustion duration and low pressure built-up inside the pre-chamber, the model matches the combustion rate in the main-chamber. In contrast, the G-equation model delivers good agreements for the pre-chamber combustion and turbulent jet-driven combustion processes. However, the model starts to underestimate the combustion rate in the main-chamber, especially under ultra-lean mixture conditions. Finally, improvements are needed for both models to simulate the later combustion stage that occurred in the near-wall regions.

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“…The effective ratio describing the spark location governs the flame dynamics in the pre-chamber. Bolla et al (2019) simulated an automotivesized scavenged pre-chamber mounted at the head of a rapid compression-expansion machine using RANS and LES. It is shown that the tilted nozzle of the pre-chamber orifice generates a swirl flow inside the pre-chamber.…”

Section: Introductionmentioning

confidence: 99%

CFD Optimization of the Pre-Chamber Geometry for a Gasoline Spark Ignition Engine

Bakir

Yadav

et al. 2021

Front. Mech. Eng.

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In the present paper, an efficient optimization method based on Bayesian updating strategy is developed for the design of a spark-ignition engine equipped with pre-chamber. 3D computational fluid dynamics (CFD) simulation coupled with strategies including design of experiment, genetic algorithm, and machine learning methods is used to optimize the pre-chamber with desired combustion phasing. The optimization process starts from a design of experiment matrix of 11 design parameters, which are used to analytically characterize the pre-chamber geometry and set up the 3D combustion CFD. Taking CA50 as the single objective, the CFD results are then used to train the machine learning models. Different machine learning models are evaluated based on their Root Mean Square Error. Five machine learning models from five different categories are selected for second round evaluation. The trained machine learning model is used in the genetic algorithm optimization, which yields the optimized configuration and is again justified by CFD. The new CFD results based on the optimized design are added into the database to further refine the machine learning model. After 24 iterations for each selected machine learning models, the medium Gaussian support vector machine model is identified as the best method for the present application. Iterations using the medium Gaussian support vector machine model continue until a satisfactory result is achieved. Detailed combustion analysis is conducted to investigate the physical mechanism about how the design of pre-chamber influences the engine's performance. It is found that larger volume of the upper part of the pre-chamber results in stronger jet flow and turbulent intensity which further accelerates the flame propagation inside the pre-chamber, dominating the contrary effects from reduced pressure and temperature. Regression analysis shows that the radius of the pre-chamber is the most influential design parameter. The current work not only sheds light on the optimization of engine design, but also has demonstrated a general strategy applicable to the purpose of arbitrary engine optimization and mechanical system design.

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Numerical Simulations of Pre-Chamber Combustion in an Optically Accessible RCEM

Cited by 18 publications

References 33 publications

Experimental and Numerical Analysis of Pre-Chamber Combustion Systems for Lean Burn Gas Engines

Experimental and Numerical Analysis of Pre-Chamber Combustion Systems for Lean Burn Gas Engines

Numerical investigation of a fueled pre-chamber spark-ignition natural gas engine

CFD Optimization of the Pre-Chamber Geometry for a Gasoline Spark Ignition Engine

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