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Increasingly stringent tailpipe emissions regulations have prompted renewed interest in catalyst heating technology – where an integrated device supplies supplemental heat to accelerate catalyst ‘light-off’. Bosch and Boysen, following a collaborative multi-year effort, have developed a Rapid Catalyst Heating System (RCH) for gasoline-fueled applications. The RCH system provides upwards of 25 kW of thermal power, greatly enhancing catalyst performance and robustness. Additional benefits include reduction of precious metal loading (versus a ‘PGM-only’ approach) and avoidance of near-engine catalyst placement (limiting the need for enrichment strategies). The following paper provides a technical overview of the Bosch/Boysen (BOB) Rapid Catalyst Heating system – including a detailed review of the system’s architecture, key performance characteristics, and the associated impact on vehicle-level emissions.

This study focuses on evaluation of various fuels within a conventional gasoline internal combustion engine (ICE) vehicle and the implementation of advanced emissions reduction technology. It shows the robustness of the implemented technology packages for achieving ultra-low tailpipe emissions to different market fuels and demonstrates the potential of future GHG neutral powertrains enabled by drop-in lower carbon fuels (LCF). An ultra-low emission (ULE) sedan vehicle was set up using state-of-the-art engine technology, with advanced vehicle control and exhaust gas aftertreatment system including a prototype rapid catalyst heating (RCH) unit. Currently regulated criteria pollutant emission species were measured at both engine-out and tailpipe locations. Vehicle was run on three different drive cycles at the chassis dynamometer: two standard cycles (WLTC and TfL) at 20°C, and a real driving emission (RDE) cycle at -7°C.

Rapid compression machines can be used to measure a fuel’s ignition delay time and develop an understanding of its resistance to autoignition. Continuing developments in engine design demand higher octane fuels that are resistant to autoignition. Substituted phenols are members of the aromatic hydrocarbon family, and aromatics like toluene are often added to pump-grade gasoline to increase the fuel octane number. Previous numerical and experimental studies have found that substituted phenols included at additive levels in gasoline surrogates, such as the toluene reference fuel in this study, may have a lengthening effect on the ignition delay time of the base fuel they are added to.

Since its implementation, exhaust gas recirculation has proven to be a reliable technique to control NOx emissions by lowering combustion temperature. Dilution with exhaust gas recirculation, whether in internal combustion engines or sequential-staged gas turbine combustors, affects flame reactivity and stability, which are related to the heat release rate and engine power. Another way to control emissions is to use hydrogen as a carbon-free alternative fuel, which is considered a milestone in the energy-decarbonization journey. However, the high reactivity of hydrogen is one of its hurdles and understanding this effect on laminar burning velocity is important. Flame propagation and burning velocity control the mixture reactivity and exothermicity and are related to abnormal combustion phenomena, such as flashback and knock. Therefore, understanding the effect of exhaust gas addition on the laminar burning velocity of hydrogen/air mixtures is imperative for engine design.

Aromatics have long been used in pump-grade gasoline to inhibit engine knock and enhance a fuel’s octane number, therefore this study focuses on how the addition of aromatics at 2% by mole affects the ignition characteristics of a Toluene Reference Fuel (TRF). The additives investigated in this study are the substituted phenols p-cresol and 2,6-xylenol. In addition to fuel composition, exhaust gas recirculation dilution can be used to lower the combustion temperature and consequently lengthen the ignition delay time of a given fuel-air mixture. This study replicated exhaust gas recirculation dilution by using N2, as it was inert and did not interfere with reactions between the fuel and oxidizer. Determination of whether the similar structures of p-cresol and 2,6-xylenol result in different autoignition inhibiting characteristics was performed on a rapid compression machine.

Autoignition delay times of two full blend gasoline fuels (high and low RON) were explored in a rapid compression machine. CO2 dilution by mass was introduced at 0%, 15%, and 30% levels with the O2:N2 mole ratio fixed at 1:3.76. This dilution strategy is used to represent exhaust gas recirculation (EGR) substitution in spark ignition (SI) engines by using CO2 as a surrogate for major EGR constituents(N2, CO2, H2O). Experiments were conducted over the temperature range of 650K-900K and at 10 bar and 20 bar compressed pressure conditions for equivalence ratios of (Φ =) 0.6-1.3. The full blend fuels were admitted directly into the combustion chamber for mixture preparation using the direct test chamber (DTC) approach. CO2 addition retarded the autoignition times for the fuels studied here. The retarding effect of the CO2 dilution was more pronounced in the NTC region when compared to the lower and higher temperature range.

Surface coatings are one of the most widely used routes to enhance the tribological properties of cylinder kits due to effective sealing capability with low friction coefficient and high wear resistance. In the current study, we have conducted the surface texture characterization of the coating on piston skirts and evaluated the impact of a novel Abradable Powder Coating (APC) on cylinder-kit performance in comparison to stock pistons. The surface texture and characteristic properties varying across the piston skirt are obtained and analyzed via a 3D optical profiler and OmniSurf3D software. The engine operating conditions are found through a combination of measurements, testing, and a calibrated GT-Power model. The variable surface properties along with other dimensions, thermodynamic attributes, flow characteristics and material properties are used to build a model in CASE (Cylinder-kit Analysis System for Engines)- PISTON for both an APC coated piston and a stock piston.

Cylinder-kit tribology has been a significant focus in developing internal combustion engines of lower emission, reduced friction and oil consumption, and higher efficiency. This work addresses the impact of ring-groove geometry on oil (liquid oil and oil vapor) transport and combustion gas flow in the cylinder kit, using a dynamic three-dimensional multiphase modeling methodology during the four-stroke cycle of a piston engine. The ring and groove geometry, along with the temperature and pressure conditions at the interface between piston and liner, trigger the oil and gas (combustion gases and oil vapor) transport. A study of the second ring dynamics is presented to investigate the effect of negative ring twist on the three-dimensional fluid flow physics. The oil (liquid oil and oil vapor) transport and combustion gas flow processes through the piston ring pack for the twisted and untwisted geometry configurations are compared.

Mixture formation and combustion dynamics are the primary contributors to the performance and emission characteristics of direct-injected spark ignition (SI) engines. This requires assessing the benefits and tradeoffs of the design and control factors that influence mixing and the subsequent combustion event. In this study, Taguchi's L18 orthogonal array design of experiment (DoE) methodology has been applied to assess contributions and tradeoffs of varied compression ratio, piston bowl design, intake port tumble design, injector spray pattern, injection timing, injection pressure, exhaust gas recirculation (EGR) rate, and intake valve closing timing in a single-cylinder boosted gasoline direct injection (GDI) SI engine. This multiparameter study has been carried out across three speed-load conditions representative of typical automotive application operating ranges.

Rapid Compression Machines (RCM) offer the ability to easily change the compression ratio and the pressure/mixture composition/temperature to gather ignition delay data at various engine relevant conditions. Therefore, RCMs with optical access to the combustion chamber can provide an effective way to analyze macroscopic spray characteristics needed to understand the spray injection process and for spray model development, validation and calibration at conditions that are suitable for engines. Fuel surrogates can help control fuel parameters, develop models for spray and combustion, and perform laser diagnostics with known fluorescence characteristics. This study quantifies and evaluates the macroscopic spray characteristics of multicomponent gasoline surrogates in comparison to their gasoline counterparts, under gasoline direct injection (GDI) engine conditions.

In this work autoignition delay times of two multi-component surrogates (high and low RON) were experimentally compared with their target full blend gasoline fuels. The study was conducted in a rapid compression machine (RCM) test facility and a direct test chamber (DTC) charge preparation approach was used for mixture preparation. Experiments were carried over the temperature range of 650K-900K and at 10 bar and 20 bar compressed pressure conditions for equivalence ratios of (Φ =) 0.6-1.3. Dilution in the reactant mixture was varied from 0% to 30% CO2 (by mass), with the O2:N2 mole ratio fixed at 1:3.76. This dilution strategy emulates exhaust gas recirculation (EGR) substitution in spark ignition (SI) engines. The multicomponent surrogate captured the reactivity trends of the gasoline-air mixtures reasonably well in comparison to the single component (iso-octane) surrogate.

Particulate matter emissions from internal combustion engines have become an increasingly important area of focus for development teams in recent years. This is due to greater regulatory scrutiny on vehicles globally, and especially on particulate emissions. The chemical composition and bulk physical properties of the fuel have been shown to influence the particulate number emissions characteristics. Although some predictive models have been proposed, the causality of specific properties or constituents has not been demonstrated due to the co-linearity of the variables considered in previous studies. In this work, fuels were formulated to capture the expected variation in three key properties of United States (US) market gasoline fuels. Specifically, total aromatics, volatility, and particulate matter index (PMI) were varied across market extremes within regulatory limits--while holding other properties constant.

Studies have shown that fuel quality plays an important role in engine-out emissions. The wide variation in composition and properties of gasoline fuels available in the market can lead to discrepancies between the expected emission levels as per set regulations and actual on-road measurements. This study compares engine-out gaseous and particulate emission results between 5 US market fuels, 5 certification fuels and one street-legal race fuel. The market fuels were acquired from different terminals in Michigan. Tests were performed on a 4-cylinder 2.3 L turbocharged direct injection spark-ignited engine. The tests covered a wide range of steady-state operating conditions including load, injection timing and engine speed sweeps. Transient load steps were also performed under warm and cold engine conditions.

Charge dilution is widely considered as one of the leading strategies to realize further improvement in thermal efficiency from current generation spark ignition engines. While dilution with excess air (lean burn operation) provides substantial thermal efficiency benefits, drastically diminished NOx conversion efficiency of the widely used three-way-catalyst (TWC) during off-stoichiometric/lean burn operation makes the lean combustion rather impractical, especially for automotive applications. A more viable alternative to lean operation is the dilution with EGR. The problem with EGR dilution has been the substantially lower dilution tolerance limit with EGR and a consequent drop in thermal efficiency compared to excess air/lean operation. This is particularly applicable to the pre-chamber jet ignition technologies with considerably higher lean burn capabilities but much lower EGR tolerance due to the presence of a high fraction of residuals inside the pre-chamber.

High-pressure gasoline injection can improve combustion efficiency and lower engine-out emissions; however, the spray characteristics of high-pressure gasoline (>500 bar) are not well known. Effects of different injector nozzle geometry on high-pressure gasoline sprays were studied using a constant volume chamber. Five nozzles with controlled internal flow features including differences in nozzle inlet rounding, conicity, and outlet diameter were investigated. Reference grade gasoline was injected at fuel pressures of 300, 600, 900, 1200, and 1500 bar. The chamber pressure was varied using nitrogen at ambient temperature and pressures of 1, 5, 10, and 20 bar. Spray development was recorded using diffuse backlit shadowgraph imaging methods.

Understanding cylinder-kit tribology is pivotal to durability, emission management, reduced oil consumption, and efficiency of the internal combustion engine. This work addresses the understanding of the fundamental aspects of oil transport and combustion gas flow in the cylinder kit, using simulation tools and high-performance computing. A dynamic three-dimensional multi-phase, multi-component modeling methodology is demonstrated to study cylinder-kit assembly tribology during the four-stroke cycle of a piston engine. The percentage of oil and gas transported through different regions of the piston ring pack is predicted, and the mechanisms behind this transport are analyzed. The velocity field shows substantial circumferential flow in the piston ring pack, leading to blowback into the combustion chamber during the expansion stroke.

Continuous efforts to improve thermal efficiency and reduce exhaust emissions of internal combustion engines have resulted in development of various solutions towards improved lean burn ignition systems in spark ignition engines. The Dual Mode, Turbulent Jet Ignition (DM-TJI) system is one of the leading technologies in that regard which offers higher thermal efficiency and reduced NOx emissions due to its ability to operate with very lean or highly dilute mixtures. Compared to other pre-chamber ignition technologies, the DM-TJI system has the distinct capability to work with a very high level of EGR dilution (up to ~40%). Thus, this system enables the use of a three-way catalyst (TWC). Auxiliary air supply for pre-chamber purge allows this system to work with such high EGR dilution rate. This work presents the results of experimental investigation carried out with a Dual Mode, Turbulent Jet Ignition (DM-TJI) optical engine equipped with a cooled EGR system.

Deep learning based approaches for object detection are heavily dependent on the nature of data used for training, especially for vehicles driving in cluttered urban environments. Consequently, the performance of Convolutional Neural Network (CNN) architectures designed and trained using data captured under clear weather and favorable conditions, could degrade rather significantly when tested under cloudy and rainy conditions. This naturally becomes a major safety issue for emerging autonomous vehicle platforms relying on CNN based object detection methods. Furthermore, despite a noticeable progress in the development of advanced visual deraining algorithms, they still have inherent limitations for improving the performance of state-of-the-art object detection. In this paper, we address this problem area by make the following contributions.

Over the years, many studies have examined the natural gas flame characteristics with either CO2, H2O, or N2 dilution in order to investigate the exhaust gas recirculation (EGR) effect on the performance of natural gas vehicles. However, studies analyzing the actual EGR concentration are very scarce. In the present study, spherically expanding flames were employed to investigate the EGR effect on the laminar flame speed (LFS) and the burned gas Markstein length (Lb) of premixed CH4/air flames at 373 K and 3 bar. The EGR mixture was imitated with a mixture of 9.50% CO2 + 19.01% H2O + 71.49% N2 by mole. EGR ratios of 0%, 5%, 10%, and 15% were tested. Experimental results show that LFS values are lowered by 20-23%, 38-43% and 53-54% due to 5%, 10% and 15% EGR, respectively. Additionally, it was observed that Lb values slightly increase at high equivalence and EGR ratios, where CH4 flames are more stable and more stretched.

Previous studies have shown that several facility dependent factors can influence ignition delay times measured in a rapid compression machine. Compression ratio variation represents one such aspect of many facility-to facility differences in RCMs, and can have a major impact on measured ignition delay times due to changes in surface-area-to-volume ratio, initial conditions and compression duration even when the same compressed conditions are maintained. In this study, iso-octane, which exhibits two stage ignition delay and has a pronounced negative temperature coefficient (NTC) region, is used to investigate the effects of changing compression ratio on ignition delay. Resulting trends are also compared to previous results obtained with ethanol, which has very different combustion properties. Experiments were carried out for rich mixtures (ϕ = 1.3) of iso-octane and air over a compressed temperature range of 675-900 K at 20 bar compressed pressure.