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Abstract Deep learning (DL)-based approaches enable unprecedented control paradigms for propulsion systems, utilizing recent advances in high-performance computing infrastructure connected to modern vehicles. These approaches can be employed to optimize diesel aftertreatment control systems targeting the reduction of emissions. The optimization of the Trapped Soot Load (TSL) reduction in the Diesel Particulate Filter (DPF) is such an example. As part of the diesel aftertreatment system, the DPF stores the soot particles resulting from the combustion process in the engine. Periodically, the stored soot is oxidized during a DPF regeneration event. The efficiency of such a regeneration influences the fuel economy, and potentially the service interval of the vehicle. The quality of a regeneration depends on the operating conditions of the DPF, the engine, and the ability to complete the regeneration event.

Abstract The cold crank-start stage, including the first three engine cycles, is responsible for a significant amount of the cold-start phase emissions in a Gasoline Direct Injection (GDI) engine. The engine crank-start is highly transient due to substantial engine speed changes, Manifold Absolute Pressure (MAP) dynamics, and in-cylinder temperatures. Combustion characteristics change depending on control inputs variations, including throttle angle and spark timing. Fuel injection strategy, timing, and vaporization dynamics are other parameters causing cold-start first cycles analysis to be more complex. Hybrid Electric Vehicles (HEVs) provide elevated cranking speed, enabling technologies such as cam phasing to adjust the valve timing and throttling, and increased fuel injection pressure from the first firings.

Abstract The hydrocarbons constituting the heavy tail of gasoline are key contributors to particulate matter (PM) emissions from spark-ignition (SI) engines. They are predominantly aromatic and, to a significant degree, bicyclic aromatic. For example, above a boiling point of 400°F, the content of bicyclic compounds in the United States (US) summer E10 regular-grade gasoline exceeds 50%v. Various gasoline parameters, such as the PM Index, Particulate Evaluation Index (PEI), Particulate and Soot Correlation Equation (PASCE), or Threshold Sooting Index (TSI), have been proposed as predictors of PM emissions from SI engines. In particular, the PM Index, whose value is dominated by the content of heavy aromatics and which, so far, has yielded the most predictive PM emissions models, appears to be the best metric to achieve this objective.

Abstract Quantifying exhaust gas composition and temperature in vehicles with internal combustion engines (ICEs) is crucial to understanding and reducing emissions during transient engine operation. This is particularly important before the catalytic converter system lights off (i.e., during cold start). Most commercially available gas analyzers and temperature sensors are far too slow to measure these quantities on the timescale of individual cylinder-firing events, thus faster sensors are needed. A two-color mid-infrared (MIR) laser absorption spectroscopy (LAS) sensor for gas temperature and carbon monoxide (CO) mole fraction was developed and applied to address this technology gap. Two quantum cascade lasers (QCLs) were fiber coupled into one single-mode fiber to facilitate optical access in the test vehicle exhaust. The QCLs were time-multiplexed in order to scan across two CO absorption transitions near 2013 and 2060 cm–1 at 15 kHz.

Abstract The 2010 Environmental Protection Agency (EPA) Emission Standard for heavy-duty engines required 0.2 g/bhp-hr over certification cycles (cold and hot Federal Test Procedure [FTP]), and the California Air Resources Board (CARB) standards require 0.02 g/bhp-hr for the same cycles leading to a 90% reduction of overall oxides of nitrogen (NOx) emissions. Similar reductions may be considered by the EPA through its Cleaner Trucks Initiative program. In this article, aftertreatment system components consisting of a diesel oxidation catalyst (DOC); a selective catalytic reduction (SCR) catalyst on a diesel particulate filter (DPF), or SCR-F; a second DOC (DOC2); and a SCR along with two urea injectors have been analyzed, which could be part of an aftertreatment system that can achieve the 0.02 g/bhp-hr standard.

Abstract Heavy-duty (HD) diesel engines are the primary propulsion systems in use within the transportation sector and are subjected to stringent oxides of nitrogen (NOx) and particulate matter (PM) emission regulations. The objective of this study is to develop a robust calibration technique to optimize HD diesel engine for performance and emissions to meet current and future emissions standards during certification and real-world operations. In recent years, California - Air Resources Board (C-ARB) has initiated many studies to assess the technology road maps to achieve Ultra-Low NOx emissions for HD diesel applications [1]. Subsequently, there is also a major push for the complex real-world driving emissions as the confirmatory and certification testing procedure in Europe and Asia through the UN-ECE and ISO standards.

Abstract Stratified lean combustion has proven to be a promising approach for further increasing the thermal efficiency of gasoline direct injection engines in low load conditions. In this work, a new injection strategy for stratified operation mode is introduced. A side and a central-mounted solenoid multi-hole injector are simultaneously operated in a single-cylinder engine. Thermodynamic investigations show that this concept leads to improved stability, faster combustion, reduced particle number emissions, and lower fuel consumption levels compared to using only one injector. Experiments at an optical engine and three-dimensional computational fluid dynamics (CFD) simulations explain the improvements by a more compact mixture and reduced piston wetting with two injectors. Finally, the application of external EGR in combination with the above concept allows NOx emissions to be effectively kept at a low level while maintaining a stable operation.

Abstract Realizing the potential of the gasoline direct injection (GDI) concept lies in effectively stratifying the charge at different engine operating conditions. This is generally obtained by properly directing the air and fuel through carefully oriented intake port(s) and fuel spray and appropriately changing injection parameters. However, robust methods of charge stratification are essential to extend the lean operating range, particularly in small GDI engines. In this work, a novel piston shape was developed for a 200 cm3, single-cylinder, four-stroke gasoline engine to attain charge stratification. Stratification of charge is achieved even when the fuel was injected early in the intake stroke by a specially shaped wedge on the piston crown that produced twin vortices during compression and physically separated the charge into two sides in the combustion chamber.

Abstract Emission Control has always been a major concern in each and every field. An increase in emissions leads to climate change, global warming, and even various diseases. The transportation system is responsible for around 30% of emission production, of which 70% of the total atmospheric burden comes from automobiles. Recently developed emission-free electric vehicles have positively affected the levels of impurity in the environment, yet the remaining Internal Combustion Engine (ICE) vehicles on the road have been left with unchecked emissions. Traditional Catalytic Converters are widely used to reduce the emissions of vehicles. It works on the principle of converting hazardous gases emitted from the engine to less harmful carbon dioxide (CO2), nitrogen (N2), and water (H2O). It is integrated with the exhaust of the engine. High efficiency and better emission control catalytic converters are still major milestones to achieve for automotive industries.

Abstract Mankind’s quest for clean alternative energy sources pushes the boundaries of science and technology every passing day. Increasing environmental and human health concerns caused by conventional fuels underscores the importance of identifying an energy source which is sustainable in terms of production, emissions, and wide application. Hythane (hydrogen-methane gas) is a contender for applications ranging from transportation and combined heating-power generation to cooking. In land transportation, the use of gaseous hythane for internal combustion engines shows better performance, enhanced combustion, and lower emission than conventional liquid hydrocarbon fuels. The use of liquefied Natural Gas (NG) and hydrogen in aircraft and ships is a steppingstone to more the wide-scale use of hythane in air, sea, and rail transportation sectors which could lower emissions and operating costs.

Abstract Particulate matter (PM) indices—those linking PM emissions from gasoline engines to the composition and properties of the fuel—have been a topic of significant study over the last decade. It has long been known that fuel composition has a significant impact on particulate emissions from gasoline engines. Since gasoline direct injection (GDI) engines have become the market-leading technology, this has become more significant because the evaporative behavior of fuel increases in importance. Several PM indices have been developed to provide metrics describing this behavior and correlating PM emissions. In this article, 16 different PM indices are identified and collected—to the authors’ knowledge, all of the indices are available at the time of writing. The indices are reviewed and discussed in the context of the information required to calculate them, as well as their utility.

Abstract Natural gas (NG) can be compressed to a high pressure of around 200 bar for use in engines and other applications. Compressed natural gas (CNG) contains 87–92% methane (CH4) and has a low carbon-to-hydrogen ratio compared to other hydrocarbon (HC) fuels. Due to this, it can potentially reduce carbon dioxide (CO2) emissions by more than 20% compared to conventional fuels like diesel or gasoline. This makes CNG one of the most environmentally friendly fuels for internal combustion engines (ICEs). To improve the thermal efficiency of ICEs, higher compression ratios (CRs) and leaner combustion are essential. Since CNG is a gaseous fuel, it has several advantages over liquid fuels due to its favorable physical and chemical properties. A few of these advantages are minimal fuel evaporation issues, a low-carbon content in the fuel composition and a high-octane number. The CNG high-octane number allows for a high CR, resulting in higher thermal efficiency and lower emissions.

Abstract Evaluating the effects of deposits formed in existing engines on their performance is essential, particularly for gasoline direct injection (GDI) engines, wherein such deposits can be even more problematic. Furthermore, it has been suggested that some gasoline detergent additives (GDAs) may increase combustion chamber deposit (CCD) formation. However, there is a lack of data available regarding CCD formation in GDI engines, and there are no systematic investigations of the effects of the relationship between detergent additives and CCD formation on the GDI engines operation. Thus, the aim of this article was to critically review the existing literature on the effects of the deposit buildup associated with GDAs on the knocking performance, emissions, and operational properties of GDI engines. Surveyed studies showed that, GDI engines produce higher amounts of CCDs compared with port fuel injection (PFI) engines.

Abstract The long-term use of conventional liquid energy sources for internal combustion (IC) engines has its own negative ramifications on the health of living beings and the ecosystem at large. The search for solutions to overcome these implications brings us to one of the domains of research called alternative fuels. Alternative fuels may be used to enrich or fully substitute conventional fuels. In this review, a literature study on the enrichment of a primary fuel using hydroxy gas (HOH) produced from the electrolysis of water is discussed. The experimental evidence shows that HOH induction between 5 and 10 liters per minute (lpm) enhances the results of performance parameters coupled with a decrease in emission levels except for the oxides of nitrogen (NOx). However, this shortfall is nullified using techniques such as exhaust gas recirculation (EGR) and water injection.

Abstract The design of the modern aftertreatment system to meet Real Driving Emissions (RDE) regulations is a significant challenge faced by manufacturers today. This is because testing vehicles under RDE conditions is both time consuming and expensive. In this study, we quantify the effect of real driving conditions on vehicle performance (efficiency and emissions) using a system model comprised of vehicle and aftertreatment subsystems, built using the commercial simulation software GT-SUITE. The developed system model will allow manufacturers to predict vehicle performance and prospective emissions under real driving conditions early in the development cycle and to ensure compliance with current and future regulations. The engine used in this study is a 2.0 L turbocharged diesel engine, while the aftertreatment system consists of a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and a selective catalytic reduction (SCR).

Abstract To reduce particulate emissions, the use of particulate filters in diesel engines is meanwhile state of the art, while the integration of such systems in gasoline engines is now also necessary in order to comply with today’s regulations. Over its lifetime, a gasoline particulate filter (GPF) collects ash components of fuel, lubrication oil, and materials originating from the catalytic coating and from engine abrasion. In the development and application process, synthetic ashing from GPFs is challenging. The ash of the lubrication oil can be increased in various ways, like oil-doped fuel, a separate oil burner, or changes in the piston-cylinder system of the engine. However, these methods show major disadvantages.

Abstract Gasoline particulate filters (GPFs) are important aftertreatment components that enable gasoline direct injection (GDI) engines to meet European Union (EU) 6 and China 6 particulate number emissions regulations for nonvolatile particles greater than 23 nm in diameter. GPFs are rapidly becoming an integral part of the modern GDI aftertreatment system. The Active Exhaust Tuning (EXTUN) Valve is a butterfly valve placed in the tailpipe of an exhaust system that can be electronically positioned to control exhaust noise levels (decibels) under various vehicle operating conditions. This device is positioned downstream of the GPF, and variations in the tuning valve position can impact exhaust backpressures, making it difficult to monitor soot/ash accumulation or detect damage/removal of the GPF substrate. The purpose of this work is to present a unique example of subsystem control and diagnostic architecture for an exhaust system combining GPF and EXTUN.

Abstract This scientific publication presents the application of artificial intelligence (AI) techniques as a virtual sensor for tailpipe emissions of CO, NOx, and HC in a high-performance vehicle. The study aims to address critical challenges faced in real industrial applications, including signal alignment and signal dynamics management. A comprehensive pre-processing pipeline is proposed to tackle these issues, and a light gradient-boosting machine (LightGBM) model is employed to estimate emissions during real driving cycles. The research compares two modeling approaches: one involving a unique “direct model” and another using a “two-stage model” which leverages distinct models for the engine and the aftertreatment. The findings suggest that the direct model strikes the best balance between simplicity and accuracy.

Abstract Swirl is known to have impact on the combustion process and the engine emission performance. Generally the swirl flows are generated on engines by e.g. helical or tangential intake ports. However, such features of intake ports constrict the airflow, resulting in raising pumping losses and thus higher fuel consumption. This article introduces a further possibility to generate and regulate the swirl flow by injecting air directly into the intake ports using Vortex Generating Jets (VGJs). The effect of air injection was studied by means of experimental investigations regarding swirl generation and flow rate improvement. The optimization of VGJ diameters, positions as well as injection airflow rate was carried out with respect to energy efficiency of swirl generation.

Abstract While the hot debate keeps going about whether the internal combustion engine (ICE) will die or not, the ICE community never stopped improving the technologies that improve the fuel economy and reduce harmful emissions. Focusing on the emissions and the control system, this article reviewed the latest improvement and advances of related technologies. By firstly introducing the noteworthy emissions from ICE, this work then summarized the evolution of the related emission regulations on both light-duty and high-duty vehicles in a few major market regions. The key technologies that applied or are still under development for both carbon dioxide (CO2), nitrogen oxides (NOx), and particulate matter (PM)/particle number (PN) emissions control were reviewed in detail. Lastly, the foreseeable regulations limits and the potential challenges were discussed briefly.