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Turbulent Jet Ignition is an advanced spark-initiated pre-chamber combustion system for otherwise standard spark ignition engines. Combustion in the main chamber is initiated by jets of partially combusted (reacting) pre-chamber products which provide a high energy ignition source. The resultant widely distributed ignition sites allow relatively small flame travel distances enabling short combustion durations and high burn rates. Demonstrated benefits include ultra-lean operation (λ≻2) at part load and high-load knock improvement near stoichiometric conditions. Although previous results of this combustion system have been very promising, the main hurdle of this system has been the need for a dual-fuel system, with liquid gasoline used in the main combustion chamber and small fractions of gaseous propane in the pre-chamber.

Turbulent Jet Ignition is an advanced spark-initiated pre-chamber combustion system for otherwise standard spark ignition engines. Combustion in the main chamber is initiated by jets of partially combusted (reacting) pre-chamber products which provide a high energy ignition source. The resultant widely distributed ignition sites allow relatively small flame travel distances enabling short combustion durations and high burn rates. Demonstrated benefits include ultra lean operation (λ≻2) at part load and high load knock limit extension. Previous jet ignition experimental results have highlighted high thermal efficiencies, high load capability and near-zero engine-out NOx emissions in a standard contemporary engine platform. Although previous results of this system have been very promising, the main hurdle has been the need for a dual fuel system, with liquid gasoline used in the main combustion chamber and small fractions of gaseous propane in the pre-chamber.

Turbulent Jet Ignition is an advanced spark initiated pre-chamber combustion system for otherwise standard spark ignition engines found in current passenger vehicles. This next generation pre-chamber design simply replaces the spark plug in a conventional spark ignition engine. Turbulent Jet Ignition enables very fast burn rates due to the ignition system producing multiple, widely distributed ignition sites, which consume the main charge rapidly. This high energy ignition results from the partially combusted (reacting) pre-chamber products initiating combustion in the main chamber. The distributed ignition sites enable relatively small flame travel distances enabling short combustion durations and high burn rates. Multiple benefits include extending the knock limit and initiating combustion in very dilute mixtures (excess air and or EGR), with dilution levels being comparable to other low temperature combustion technologies (HCCI), without the complex control drawbacks.

A study of the fundamental design characteristics of SI engine inlet ports is presented. The work involved the parameterisation of inlet port design features to enable a simplified description of the fundamental form of a port to be made. A parametrically controlled CAD model was then created to enable variations in port geometry to be generated quickly and surface meshes created for CFD analysis. CFD analysis and Design of Experiments were employed to establish the relationship between design parameters and port flow characteristics. Correlation of the CFD results was established via the use of a number of rapid prototype port models, tested on a flow bench. To aid interpretation of the data, a computer emulation of the results with a Graphical User Interface (GUI) was produced using MATLAB software. The resultant GUI is available for use as a tool to highlight the effects of key design parameters during the concept and optimisation stages of inlet port design.

Turbulent Jet Ignition is an advanced spark initiated pre-chamber combustion system for otherwise standard spark ignition engines found in current passenger vehicles. This next generation pre-chamber design simply replaces the spark plug in a conventional spark ignition engine. Turbulent Jet Ignition enables very fast burn rates due to the ignition system producing multiple, widely distributed ignition sites, which consume the main charge rapidly. This high energy ignition results from the partially combusted (reacting) pre-chamber products initiating combustion in the main chamber. The distributed ignition sites enable relatively small flame travel distances enabling short combustion durations and high burn rates. Multiple benefits include extending the knock limit and initiating combustion in very dilute mixtures (excess air and/or EGR), with dilution levels being comparable to other low temperature combustion technologies (HCCI), without the complex control drawbacks.

This work was concerned with evaluation of the performance and emissions of potential future biofuels during advanced spark ignition engine operation. The fuels prepared included three variants of gasoline, three gasoline-ethanol blends and a gasoline-butanol fuel altogether covering a range of oxygen mass concentrations and octane numbers to identify key influencing parameters. The combustion of the fuels was evaluated in a turbocharged multi-cylinder direct fuel injection research engine equipped with a standard three-way catalyst and an external EGR circuit that allowed use of either cooled or non-cooled EGR. The engine operating effects studied at both part and boosted high load conditions included fuel injection timing and pressure, excess air tolerance, EGR tolerance and spark retard limits. A number of blends were also mapped at suitable sites across the European drive cycle under downsized engine conditions.

The current energy climate has created a push toward reducing consumption of fossil fuels and lowering emissions output in power generation applications. Combined with the desire for a more distributed energy grid, there is currently a need for small displacement, high efficiency engines for use in stationary power generation. An enabling technology for achieving high efficiencies with spark ignited engines for such applications is the use of jet ignition which enables ultra-lean (λ > ~1.6) combustion via air dilution. This paper provides a comprehensive review of the development of a 390cc, high efficiency single cylinder natural gas-fueled jet ignition engine operating ultra-lean. The engine was developed as part of the Department of Energy’s Advanced Research Projects Agency–Energy (DOE ARPA-E) GENSETS program. Design choices for minimizing friction are highlighted as well as test results showing further friction reduction through downspeeding.

Turbulent Jet Ignition is an advanced spark-initiated pre-chamber combustion system for otherwise standard spark ignition engines. Combustion in the main chamber is initiated by jets of partially combusted (reacting) pre-chamber products which provide a high energy ignition source. The resultant widely distributed ignition sites allow relatively small flame travel distances enabling short combustion durations and high burn rates. Demonstrated benefits include ultra lean operation (λ≻2) at part load and high load knock improvement. This study compared the knock limit of conventional spark ignition and pre-chamber jet ignition combustion with reducing fuel quality in a modern PFI engine platform. Seven PRF blends ranging from 93-60 octane were experimentally tested in a stoichiometric normally aspirated single-cylinder research engine at 1500 rev/min and ~WOT (98 kPa MAP).

This work was concerned with increasing the attainable load during gasoline controlled auto-ignition combustion in a multi-cylinder direct fuel injection research engine. To extend the peak output under naturally aspirated conditions it proved favourable to combine internal and external exhaust gas recirculation under stoichiometric fuelled conditions. During turbocharged high load operation it was beneficial in terms of fuel economy to dilute the charge with a combination of internally re-circulated exhaust gases and excess air. Replacing a proportion of these diluents with externally re-circulated burned gases appeared to facilitate lower emissions of HC and CO. The highest load generated via boost was limited by increasing peak in-cylinder pressure and falling gas exchange efficiency. Regardless, the use of boost increased the load at which CAI could be invoked without lean NOx after-treatment.

With an increasing global awareness of the need to conserve fuel resources and reduce carbon dioxide emissions, the automotive sector has been seeking gains in engine efficiency. One such method for achieving these gains on a spark ignition (SI) engine platform is through lean burn operation. Ultra-lean operation (λ>2) has demonstrated the ability to increase thermal efficiency and significantly reduce emissions of nitrogen oxides (NOx) due primarily to lower mean gas temperatures. Turbulent Jet Ignition (TJI), a pre-chamber-based combustion system, is a technology that enables ultra-lean operation. TJI is also an effective knock mitigation system due to the distributed nature of main chamber ignition, resulting in rapid burn rates. Pre-chamber combustors such as that utilized in TJI have been studied extensively for decades, but the interaction of the combustion events between the two chambers is not well understood.

Progressively more stringent efficiency and emissions regulations for internal combustion engines have led to growing interest in advanced combustion concepts for spark ignition engines. MAHLE Jet Ignition® (MJI) is one such concept which enables ultra-lean (λ > ~1.6) combustion via air dilution. This pre-chamber-based combustion system has demonstrated highly efficient lean operation, producing efficiencies competitive with those of advanced compression ignition concepts. Compared to a traditional spark ignition engine, the additional degrees of freedom associated with Jet Ignition introduce further complexity when optimizing the system for peak efficiency throughout the engine map. The relationship between operating condition and the lambda at which peak efficiency occurs for a Jet Ignition engine has been presented in prior work by the authors.

The work was concerned with applying cooled EGR for improved high load fuel economy and reduced pollutant emissions in a turbocharged gasoline engine. While the thermodynamic benefits of EGR were clear, challenges remain to bring the technique to market. A comparison of pre and post compressor EGR supply indicated that post-compressor routing allowed higher compressor efficiencies to be maintained and hence reduced compressor work as the mass flow of EGR was increased. However, with this post-compressor routing, attaining sufficient EGR rate was not possible over the required operating map. Furthermore, at higher engine speeds where the pre-turbine exhaust pressure was greater than the intake plenum pressure, the timing of peak in-cylinder pressure was not as readily advanced towards the optimum.

Increasingly stringent global fuel economy and carbon dioxide (CO2) legislation for light duty passenger cars has created an interest in unconventional operating modes. One such mode in spark ignition (SI) gasoline engines is lean combustion. While lean operation in SI engines has previously demonstrated the ability to reduce fuel consumption, the degree of enleanment capability of the system is limited by increasingly unstable combustion in the lean region, particularly for homogeneous lean approaches. MAHLE Jet Ignition® (MJI) is a pre-chamber-based combustion system that extends this lean limit beyond the capabilities of modern SI engines by increasing the ignition energy present in the system. This allows the engine to exploit the benefits of homogeneous ultra-lean (λ > ∼1.6) combustion, namely reduced fuel consumption and reduced emissions of nitrogen oxides (NOx). Pre-chamber combustors such as that utilized in MJI have been studied extensively for decades.

Alternative combustion modes for spark ignition engines, such as homogeneous lean combustion, have been extensively researched in transportation and large stationary power applications due to their inherent emissions and fuel efficiency benefits. However, these types of approaches have not been explored for small engines (≤ 30 kW), as the various applications for these engines have historically had significantly different market demands and less stringent emissions requirements. However, going forward, small engines will need to incorporate new technologies to meet increasingly stringent regulatory guidelines. One such technology is jet ignition, enables lean combustion via air dilution through the use of a pre-chamber combustor.

The work was concerned with visualisation of the charge homogeneity and cyclic variations within the planar fuel field near the spark plug in an optical spark ignition engine fitted with an outwardly opening central direct fuel injector. Specifically, the project examined the effects of fuel type and injection settings, with the overall view to understanding some of the key mechanisms previously identified as leading to particulate formation in such engines. The three fuels studied included a baseline iso-octane, which was directly compared to two gasoline fuels containing 10% and 85% volume of ethanol respectively. The engine was a bespoke single cylinder with Bowditch style optical access through a flat piston crown. Charge stratification was studied over a wide spectrum of injection timings using the Planar Laser Induced Fluorescence (PLIF) technique, with additional variation in charge temperature due to injection also estimated when viable using a two-line PLIF approach.

Increasingly stringent US fuel economy regulation has emphasized the need for automotive engines to achieve greater levels of efficiency. Lean operation in spark ignition engines has demonstrated the ability to increase thermal efficiency, but this is typically accompanied by increased nitrogen oxides (NOx) emissions. Ultra-lean operation (λ > 2), however, has demonstrated increased thermal efficiency and the potential for significant reductions in NOx. Turbulent Jet Ignition (TJI) enables ultra-lean operation by utilizing radical turbulent jets emerging from a pre-chamber combustor as the ignition source for main chamber combustion in a spark ignition engine. This study seeks to better understand the interaction between the pre-chamber and main chamber combustion events, specifically the effect that particular TJI design parameters have on this interaction.

In spark ignited engines, thermal efficiency is strongly influenced by the quality of the combustion process as initiated by the ignition system. Jet Ignition is a combustion concept that utilizes a small pre-chamber to produce reactive jets which distribute ignition energy throughout the main combustion chamber. This distributed ignition energy can be leveraged to induce ignition in traditionally difficult-to-ignite regimes, such as in highly dilute mixtures. Highly dilute jet ignition combustion has been proven to produce thermal efficiencies significantly higher than those of conventional spark ignition combustion. To fully exploit the efficiency potential of active jet ignition, multiple aspects of the engine architecture and peripheral systems must be adjusted. Efficiency sensitivities to compression ratio, boost system, and intake port design have been explored extensively.

Internal combustion engines currently face increasing regulatory reform which has motivated investigation of alternative combustion modes, particularly for spark ignition engines. Fuel economy regulations, among others, are presently driving the need for technological advances in the automotive sector. Stationary power generation is facing emissions standards that will be increasingly difficult to achieve with combustion-based current practices, particularly in the case of nitrogen oxides (NOx). Ultra-lean (λ > ~1.6; air-fuel ratio > 23:1) combustion via air dilution is one such combustion mode that provides the benefits of reduced fuel consumption and reduced NOx emissions. Jet ignition is a pre-chamber-based combustion system that enables enleanment beyond what is achievable with traditional spark ignition engines. Previous studies of MAHLE’s Jet Ignition® concept have primarily focused on light-duty gasoline engines.