Future gasoline engine ignition: A review on advanced concepts

Abstract

To meet the future requirements of fuel economy and exhaust emissions, high-efficiency gasoline engines tend to employ diluted combustion concepts along with intensified charge motion and stratified mixtures. Securing the ignition of such mixtures over the full engine operation range is challenging, because of the lowered mixture reactivity and increased discrepancy of stoichiometry. In recent years, increasing research efforts have been spending on innovations of ignition technologies to tackle the challenges. In this paper, the directions of ignition improvement are highlighted based on the fundamental understanding of the ignition mechanisms. The working principles of the primary types of advanced ignition systems are introduced; and relevant engine and combustion vessel test results are reviewed. The ignition systems are categorized as: (1) high-energy spark ignition, (2) pulsed nanosecond discharge ignition, (3) radio-frequency plasma ignition, (4) laser-induced plasma ignition, and (5) pre-chamber ignition. The advanced ignition systems are commented, regarding the ignition effectiveness and the implementation challenges, according to the literatures and the extensive empirical work at the authors’ laboratory.

Investigations on spark pre-chamber ignition and subsequent turbulent jet main chamber ignition in a novel optically accessible test rig

“…3 Lean burn engines generally require a higher energy to ignite the air-fuel mixture; this process takes longer and requires a wider spread of the ignition source. 10 Most of the advantages of turbulent jet ignition relate to the air-fuel mixture flammability while maintaining combustion quality and repeatability. 10,11 The mechanisms of turbulent jet ignition involve a complex interaction between chemical reactions and turbulent mixing that determines the ignition propensity, timing and location.…”

“…10 Most of the advantages of turbulent jet ignition relate to the air-fuel mixture flammability while maintaining combustion quality and repeatability. 10,11 The mechanisms of turbulent jet ignition involve a complex interaction between chemical reactions and turbulent mixing that determines the ignition propensity, timing and location. 12–14 Figure 1 shows a schematic representing the single ignition location of a spark-ignited combustion chamber (left) in comparison to the wide spread multiple ignition locations created by a turbulent hot jet (right).…”

Effect of Ignition Energy and Hydrogen Addition on Laminar Flame Speed, Ignition Delay Time, and Flame Rising Time of Lean Methane/Air Mixtures

“…Burning the lean natural gas/air mixtures is a promising method for enhancing the thermal efficiency of spark ignition (SI) engines through an increase in the specific heat ratio [7] and the reduction in heat-transfer losses due to its lower combustion temperature together with a decrease in the pumping loss for the wide-opening throttle [5,8]. However, methane has a slower flame propagation that may cause misfire [8][9][10], high cycle-to-cycle variation, and emission of unburned hydrocarbon [1,11]. The slower development of flame kernel and thus the longer explosion duration interfere with an optimal combustion phasing [10] in SI engines, limiting the full potential of lean combustion.…”

“…However, methane has a slower flame propagation that may cause misfire [8][9][10], high cycle-to-cycle variation, and emission of unburned hydrocarbon [1,11]. The slower development of flame kernel and thus the longer explosion duration interfere with an optimal combustion phasing [10] in SI engines, limiting the full potential of lean combustion. How to accelerate the flame kernel propagation and the explosion duration of lean natural gas is thus crucial to the further development of high thermal efficiency and low-emission SI engines.…”

Fuel consumption and emission reduction of marine lean-burn gas engine employing a hybrid propulsion concept

“…By supplying a large quantity of turbulent hot gas to the combustion chamber, the pre-chamber ignites even a highly diluted mixture. 9,10…”