Experimental study of the ignition of lean methane/air mixtures using inductive and NRPD ignition systems in the pre-chamber and turbulent jet ignition in the main chamber

Turbulent jet ignition technology can significantly improve lean combustion stability and suppress engine knocking. However, the narrow jet channel between the pre-chamber and the main chamber leads to some difficulties in heat exchange, which significantly affects combustion performance and mechanical component lifetime. To clarify the effect of temperature conditions on combustion evolutions of turbulent jet ignition, direct numerical simulations with detailed chemical kinetics were employed under engine-relevant conditions. The flame propagation in the pre-chamber and the early-stage turbulent jet ignition in the main chamber were investigated. The results show that depending on temperature conditions, two types of flame configuration can be identified in the main chamber, i.e., the normal turbulent jet flame propagation and the spherical flame propagation, and the latter is closely associated with pressure wave disturbance. Under low-temperature conditions, the cold jet stoichiometric mixtures and the vortexes induced by the jet flow determine the early-stage flame development in the main chamber. Under intermediate temperature conditions, pre-flame heat release and leading pressure waves are induced in the jet channel, which can be regarded as a transition of different combustion modes. Whereas under high-temperature conditions, irregular auto-ignition events start to occur, and spherical flame fronts are induced in the main chamber, behaving faster flame propagation.

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Experiments and modeling of a dual-mode, turbulent jet ignition engine

International Journal of Engine Research ◽

10.1177/1468087419875880 ◽

2019 ◽

Vol 21 (6) ◽

pp. 966-986 ◽

Cited By ~ 3

Author(s):

Sedigheh Tolou ◽

Harold Schock

Keyword(s):

Experimental Data ◽

Thermal Efficiency ◽

Internal Combustion Engines ◽

Peak Pressure ◽

Operating Conditions ◽

Turbulent Jet ◽

Engine Fuel ◽

Main Chamber ◽

Dual Mode ◽

Ignition System

The dual-mode, turbulent jet ignition system is a promising combustion technology to achieve high diesel-like thermal efficiency at medium to high loads and potentially exceed diesel efficiency at low-load operating conditions. The dual-mode, turbulent jet ignition systems to date proved a high level of improvement in thermal efficiency compared to conventional internal combustion engines. However, some questions were still unanswered. The most frequent question regarded power requirements for delivering air to the pre-chamber of a dual-mode, turbulent jet ignition system. In addition, there was no study available to predict the expected efficiency of a dual-mode, turbulent jet ignition engine in a multi-cylinder configuration. This study, for the first time, predicts the ancillary work requirement to operate the dual-mode, turbulent jet ignition system. It also presents a novel, reduced order, and physics-based model of the dual-mode, turbulent jet ignition engine with a pre-chamber valve assembly. The developed model was calibrated based on experimental data from the Prototype II dual-mode, turbulent jet ignition engine. The simulation results were in good agreement with the experimental data. The validity of the model was observed based on the standard metric of the coefficient of determination as well as comparison plots for in-cylinder pressures. Numerical predictions were compared to experiments for three metrics of main chamber combustion: gross indicated mean effective pressure, main chamber peak pressure, and main chamber phasing for the peak pressure. Predictions were within 5% of experimental data, with one exception of 6%. In addition, the absolute root mean square errors of in-cylinder pressures for both pre- and main-combustion chambers were below 0.35. The calibrated model was further studied to introduce a predictive and generalized model for dual-mode, turbulent jet ignition engines. Such a model can project engine behavior in a multi-cylinder configuration over the entire engine fuel map.

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Numerical Simulation of Ignition Mechanism in the Main Chamber of Turbulent Jet Ignition System

Volume 2: Emissions Control Systems; Instrumentation, Controls, and Hybrids; Numerical Simulation; Engine Design and Mechanical Development ◽

10.1115/icef2018-9587 ◽

2018 ◽

Cited By ~ 5

Author(s):

Matias Muller ◽

Corbin Freeman ◽

Peng Zhao ◽

Haiwen Ge

Keyword(s):

Turbulent Flame ◽

Chemical Kinetic ◽

Turbulent Jet ◽

Michigan State University ◽

State University ◽

Main Chamber ◽

Turbulent Flame Speed ◽

Ignition Mechanism ◽

Inlet Conditions ◽

Kinetic Effects

The ignition mechanism of a lean premixed CHVair mixture by a hot turbulent jet issued from the pre-chamber combustion is investigated using 3D combustion CFD. The turbulent jet ignition experiments conducted in the rapid compression machine (RCM) at Michigan State University (MSU) were simulated. A full simulation was carried out first using RANS model for validation, the results of which were then taken as the boundary condition for the detailed simulations using both RANS and LES. To isolate the thermal and chemical kinetic effects from the hot jet, two different inlet conditions of the chamber were considered: inert case (including thermal effects only) and reactive case (accounting for both thermal and chemical kinetic effects). It is found that the chemical kinetic effects are important for the ignition in the main chamber. Comparison of OH and HRR (heat release rate) computed by RANS and LES shows that RANS predicts slightly faster combustion, which implies higher predicted turbulent flame speed. Correlations between vorticity, mixing field, and temperature field are observed, which indicate that the flow dynamics strongly influence the mixing process near the flame front, and consequently affect flame propagation.

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