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Technical Paper

In-Cylinder Flow Measurements in a Transparent Spark Ignition Engine

2019-08-15
2019-24-0099
Flame development, combustion efficiency and emissions of a gasoline direct injection engine are strongly related with mixture preparation. Consequently, it is important to investigate the flow field and turbulence quantities at the parts of the thermodynamic cycle in which mixture preparation occurs. Flow field measurements were obtained by using 2D digital Particle Image Velocimetry technique in a 475cc optical single – cylinder GDI spark ignition engine. The results include phase averaged velocity fields at 1000 and 1500 RPM with 100% and 25% throttle position. These sets of measurements were conducted for cold flow conditions at three different planes including the tumble plane and the swirl plane. The flow was recorded at various crank angles between -340° and -20° before the combustion top dead center (BTDC) with an increment of 40°. The spatial averaged TKE (Turbulent Kinetic Energy) was calculated along with the TR (Tumble Ratio).
Technical Paper

Experimental and Numerical Analysis of Latest Generation Diesel Aftertreatment Systems

2019-08-15
2019-24-0142
A comprehensive experimental and numerical analysis of two state-of-the-art diesel AfterTreatment Systems (ATS) for automotive applications is presented in this work. Both systems, designed to fulfill Euro 6 emissions regulations standards, consist of a closed-coupled Diesel Oxidation Catalyst (DOC) followed by a Selective Catalytic Reduction (SCR) catalyst coated on a Diesel Particulate Filter (DPF), also known as SCR on Filter (SCRoF). While the two systems feature the same Urea Water Solution (UWS) injector, major differences could be observed in the UWS mixing device, which is placed upstream of the SCRoF, whose design represents a crucial challenge due to the severe flow uniformity and compact packaging requirements.
Technical Paper

A novel 1D co-simulation framework for the prediction of tailpipe emissions under different IC engine operating conditions.

2019-08-15
2019-24-0147
The prediction of the pollutants emitted by internal combustion engines during driving cycles has been a challenge since the introduction of the emission regulation legislation. During the last decade, along with the more tightening limits and increased public concern about the matter of air quality, the possibility of simulating various driving tests with cost effective computing facilities has become a key feature for modern simulation codes. Many 1D simulation tools are available on the market, offering real time models capable of achieving the simulation of any driving cycle in limited time frames. These approaches are based on the extreme simplification of the engine geometry and on the adoption of engine maps, which, for any engine operating condition, give the engine output in terms of power, or torque, and of exhaust gas composition.
Technical Paper

Reactivity Analysis and Modeling of NOx purification Considering Reactions on Cu active sites and Brønsted acid sites in a Cu-chabazite SCR catalyst

2019-08-15
2019-24-0150
In this study, the NOx purification reactivity of a Cu-chabazite SCR catalyst was analyzed over a wide temperature range based on the NH3-SCR mechanism considering Cu redox reactions and reactions on a Brønsted acid site. It was revealed that the De-NOx reactions on the active site of Cu proceeded in different paths at lower and higher temperatures. This means that the rate-limiting step of SCR reactions was changed as each temperature. The reaction rate of NOx purification on a Cu site less than 200 °C was determined by the reaction rate of oxidation of Cu sites. On the other hand, the NH3 adsorption on Cu sites played a dominant role in NOx purification at temperature range higher than 300°C. Moreover, it was also observed that the Cu reaction site took different states at low and high temperatures during the NOx purification and was estimated that the valence state of a Cu site was changed as the temperature increased.
Technical Paper

Analysis of the emission conversion performance of gasoline particulate filters and four-way catalysts over lifetime

2019-08-15
2019-24-0156
Gasoline particulate filters (GPF) recently entered the market, and are already regarded a state-of-the-art solution for gasoline exhaust aftertreatment systems to enable EU6d-TEMP fulfilment and beyond. Due to their rapid market introduction, extensive field experience with GPFs is not yet available. Especially for four-way catalytic converters, the prognosis of the emission conversion performance over lifetime poses an ambitious challenge, which significantly influences future catalyst diagnosis calibrations. In the first part of the paper, experimental GPF ash loading results are presented. Since most of the ash accumulated in the filter results from the combustion of lubricating oil additives, a burner test bench with a purpose-designed oil injection system was chosen for the investigations. The analysis of the backpressure results show that, contrary to high soot loadings, the ash load has a relatively low impact on engine performance and fuel consumption.
Technical Paper

Pressure drop of particulate filters and correlation with the deposited soot for heavy-duty engines

2019-08-15
2019-24-0151
Particulate filters are a widely used emission control device on heavy-duty diesel engines. The accumulation of particulate matter, mostly consisting of soot, inside the filter results in increased filter pressure-drop (backpressure). This increased backpressure has been used by the on-board control systems as trigger for regeneration procedures, which aim to actively oxidize the accumulated soot. However, it is known that passive soot oxidation during normal operation affects the correlation between backpressure and the deposited soot mass in filter. Therefore, the backpressure alone cannot be a reliable trigger for regeneration. In this work we highlight operating conditions with very poor correlation between backpressure and accumulated soot mass in filter and evaluate the possible root causes. Experiments with several heavy-duty diesel engines and particulate filters were conducted on engine test bench.
Technical Paper

Analysis of TWC operation characteristics in a Euro6 gasoline light duty vehicle

2019-08-15
2019-24-0162
A Euro6 gasoline light duty vehicle has been tested at the engine dynamometer and the emissions have been analyzed upstream and downstream the Three-Way-Catalyst (TWC) during the WLTP cycle. Catalyst simulations have been used for assessing the processes inside the catalytic converter using a reaction scheme based on 19 brutto reactions (Direct oxidation and reduction, selective catalytic re-ductions with CO, C3H6 and H2, steam reforming, water-gas shift and bulk Ceria as well as surface Ce-ria reactions). The reactions have been parametrized in order to best approximate the measurements. Based on the reactions taken into account, the real vehicle emissions can be predicted with good accu-racy. The simulations show that the cycle emissions are comprising mainly by the cold start contribution as well as discrete emission break-through events during transients.
Technical Paper

Heat Transfer characterization of Catalytic Converter Substrates during Warm-up

2019-08-15
2019-24-0163
The transient heat transfer behavior of a real size automotive catalytic reactor has been simulated with OpenFOAM in 1D. The model takes into consideration the gas-solid convective heat transfer, axial wall conduction and heat capacity effects in the solid phase, but also the chemical reactions of CO and C3H6 oxidations, based on simplified Arrhenius and Langmuir-Hinshelwood approaches. The associated parameters have been chosen based on the tuning of experimental data. The impact of different initial catalytic converter temperatures, inlet flow temperatures and inlet flow rates have been quantified, even in terms of overall cumulative emissions. . A dimensional analysis is proposed and dimensionless temperature difference and space-time coordinate are defined. Using this suitably modified coordinates, for the case of negligible axial solid conduction, computed solid temperature at the reactor outlet lay on the typical S-curve.
Technical Paper

The Szorenyi Three-Chamber Rotary Engine concept

2019-08-15
2019-24-0168
Currently automotive engines are reciprocating or Wankel rotary engine types. Reciprocating engines are bulky, heavy and complex, mainly due to the intake and exhaust valves and their associated cam-­‐train. Wankel engines are rev limited due to the large eccentric load on the crankshaft, and have poor sealing of the apex seals leading to poor economy and undesirable emission gases. The Rotary Engine Development Agency (REDA) has designed a three­‐chamber rotary internal combustion engine concept using its patented Szorenyi Curve. It is an evolution of the four chamber engine design which was the subject of SAE Technical Paper 2017-­‐01-­‐2413 and SAE publication ‘So You Want to Design Engines: UAV Propulsion Systems’. This paper on the three­‐chamber engine concept includes an analysis of the major issues affecting the Wankel engine.
Technical Paper

Direct performance comparison between conventional and integrated exhaust manifold (IEM) design

2019-08-15
2019-24-0180
Integrated Exhaust Manifold (IEM) technology has recently become of interest in production engine design as a technical response to increasing specific power output and stricter limits on engine emission. Indeed, the added cooling effect of exhaust runners integrated in the cylinder head allows for a significant reduction in fuel enrichment and consequent CO and HC emissions. Furthermore, IEM can result in overall weight and cost savings due to the exclusion of a conventional exhaust manifold. The IEM implementation offers considerable challenges to the design of the engine cylinder head, which is an already highly loaded and function-dense component. The integration of the exhaust runners in the cylinder head leads to a radical increase of the surface exposed to high thermal loads. In order to prevent thermal failure, the runners need to be enveloped in a coolant jacket.
Technical Paper

A simple approach for the estimation of the exhaust noise source at the valves

2019-08-15
2019-24-0174
Exhaust noise emission is the result of the propagation of pressure perturbations along the exhaust line. Such perturbations are primarily originated by the discharge of hot, high-speed gases through the exhaust valves. These gases do not simply displace the gases present in the exhaust port but compress them, giving rise to the perturbation mentioned above. Therefore, any attempt at the prediction of exhaust noise is based on the knowledge of the instantaneous mass flow rate across the exhaust valves. However, this magnitude is not readily accessible to measurements, and it is thus imperative to use predictive models. It is apparent that, while information on the instantaneous mass flow through the exhaust valves may be obtained from well-validated commercial gas-dynamic codes, the data required is not always available or fully defined at the time of starting the design of an exhaust line.
Technical Paper

Hybrid Powertrain Calibration Techniques

2019-08-15
2019-24-0196
Meeting the particle (PN) emissions limits in dynamic vehicle test sequences needs specific attention on each power variation event occurring in the internal combustion engine (ICE). Such transients arise from engine start onwards along the entire test drive. In hybrid systems, there is one further source for transient ICE response: each power shift between E-motor (EM) and ICE introduces gas flow variations with subsequent temperature response in the ICE and in the engine aftertreatment system (EAS). This bears consequences for engine out emissions as well as for the EAS efficiency and even for the durability of a catalytic converter. As system calibration engineers must decide on numerous actuator parameters, their decisions, finally, are crucial for meeting legislative limits under the boundary conditions given by the ICE’s hybrid and drive environment.
Technical Paper

Selection of Three Way Catalyst Converter for CNG engine to meet BSVI Emission Norms

2019-08-15
2019-24-0044
Compressed natural gas (CNG) is a substitution of alternative fuel for automotive application with significant environmental advantages as it is the only fuel cheaper than gasoline or diesel, comparatively lower air pollution emissions, lesser CO2 emissions. Stringent regulations have been adopted to curb the menace of vehicular pollution. In order to meet the stringent regulations catalytic convertor using noble metals proved to a boon in vehicular industry. Noble metals are highly active for removal of methane as a pollutant. However, their expensiveness, deterioration with time can generate even more toxic volatile pollutants. The paper related to developing of a new gas engines with high energy efficiency and meeting future emission standards. It is necessary to develop complex exhaust gas after treatment systems to treat the toxic components efficiently when the engine runs on stoichiometric and lean mixtures.
Technical Paper

Experimental High Temperature Analysis of a Low-Pressure Diesel Spray for DPF Regeneration

2019-08-15
2019-24-0035
In the current automotive scenario, particulate filter technology is mandatory in order to attain emission limits in terms of particulate matter for Diesel engines. Despite DPF is often considered a mature technology, significant issues can derive from the use of the engine fuel injectors to introduce in the exhaust pipe the fuel needed to light on the particulate matter in the filter during its regeneration, primarily the lubricant oil dilution with fuel a consequence of significant spray impact on the cylinder liner. As an alternative, the fuel required to start regeneration can be introduced in the exhaust pipe by an auxiliary low pressure injector spraying in the hot exhaust gas stream. In this conditions, the spray evolution and its possible interaction with the surrounding gas stream are relevant in order to better identify the overall layout of the system, so to have the fuel vaporized at the DPF inlet section.
Technical Paper

Development of a dedicated CNG three-way catalyst model in 1-D simulation platforms

2019-08-15
2019-24-0074
A growing interest in heavy-duty engines powered with CNG dictated by stringent regulations in terms of emissions, has made it essential to study a specific Three-Way Catalyst (TWC). Oxygen storage phenomena characterize catalytic converter efficiency under real world driving operating conditions and, consequently, during strong dynamics in Air-to-Fuel (A/F) ratio. A numerical “quasi-steady” model has been set-up to simulate the chemical process inside the reactor. A dedicated experimental campaign has been performed in order to evaluate the catalyst response to a defined lambda variation pattern of the engine exhaust stream, thus providing the data necessary for the numerical model validation. In fact, goal of the present research activity was to investigate the effect of very fast composition transitions of the engine exhaust typical of the mentioned driving conditions (including fuel cutoffs etc.) on the catalyst performance and on related emissions at the tailpipe.
Technical Paper

Multidimensional Modeling of SCR Systems via the Lattice Boltzmann Method

2019-08-15
2019-24-0048
In this paper, we deploy a novel, multidimensional approach to simulate SCR reactors across physical scales. For the first time, a full 3D Lattice Boltzmann (LB) solver is developed, able to accurately capture the fluid dynamic phenomena taking place inside SCR reactors, as well as the catalytic conversion of NOx. The influence of engine load on exhaust gas mass flow rate and catalytic converter activity is taken into account. The proposed approach is computationally light and the results prove the reliability and versatility of the LB Method for the simulation of the complex phenomena that take place inside the aftertreatment devices.
Technical Paper

Chemical and Physical Characterization of Organic Particulate Matter from Last Generation Exhaust Aftertreatment System of Medium Duty Diesel Engine

2019-08-15
2019-24-0053
Particulate Matter from Euro 6 Medium Duty diesel engine was analyzed from engine-out, downstream of particulate filter (DPF), and up to the exit of a selective catalytic reactor (SCR) to characterize its chemical and physical nature. Particular attention was devoted to the analysis of particles down to 23 nm. An array of chemical, physical and spectroscopic techniques (Gas chromatography coupled with mass spectrometry (GC-MS), mobility analyzer, UV-visible absorption and fluorescence spectroscopy) was applied for characterizing the organic particulate matter (PM, constituted of polycyclic aromatic hydrocarbons (PAH), heavy aromatic compounds, soot) in the exhaust. The engine was operated at “full-load” (100% of the total power, representing the best performance of the engine operation) condition, and at different engine speeds. Results showed that the DPF efficiency was greater than 96% in the reduction of the sub 23 nm particles across the speeds range.
Technical Paper

Experimental and Computational Investigation of Particle Filtration Mechanisms in Partially Damaged DPFs

2019-08-15
2019-24-0149
Since September 2018 new threshold limits are applied in the European Union for On-Board Diagnosis (OBD) of particulate mass (PM) leakage. OBD systems are obliged to detect exhaust system malfunctions that account to 2.5 times higher PM emissions compared to the type approval limit. Often the malfunction is located in the Diesel Particulate Filter (DPF), which might suffer substrate crack or melting during harsh regeneration events. In addition, DPF systems have become a tampering target, usually to avoid the high cost of replacement or lower fuel consumption. In this context, understanding the filtration mechanisms in partially damaged DPFs can facilitate the assessment of their environmental effects and the design of exhaust systems with efficient OBD functionality. Two common types of DPF failure are included in this study, namely partial rear plug removal and internal crack development due to uncontrolled regeneration with excessive soot loading.
Technical Paper

Fuel Consumption and Pollutant Emission Optimization at Part and Full Load of a High-Performance V12 SI Engine by a 1D Model

2019-08-15
2019-24-0080
Modern internal combustion engines show complex architectures in order to improve their performance in terms of brake torque and fuel consumption. Concerning naturally-aspirated engines, the arrangement of intake and exhaust systems is crucial to get the prescribed target. An optimization of the intake port geometry, together with the selection of a proper valve timing, allow to improve the cylinder filling and hence the performance. This possibility is enhanced by a variable valve timing, even more with unphased intake and exhaust controls. The identification of an optimal calibration strategy at test bench usually requires long and expensive experimental activities. Focusing on these aspects, numerical tools can help to support engine calibration, especially in the early design phases. In the present work, a 12-cylinder naturally aspirated spark ignition engine is investigated. In a preliminary stage, the engine is experimentally tested under full load operation.
Technical Paper

Experimental investigations on engine-out emissions sensitivity to fuel injection pressure of a high-performance DISI single cylinder engine

2019-08-15
2019-24-0169
In recent times complying with increasingly stringent emission regulations has become ever more challenging. While an efficient after-treatment system that includes gasoline particulate filter enables compliance with legislation requirements, lowering engine-out emissions by improving combustion system has to be considered as a crucial advantage not only in regard to pollutants emission control, but also performance. In this respect, high-performance enabling contents such as relatively large displacement, flow-capacity oriented intake ports and a limited stroke-to-bore ratio have significant drawbacks on the charge motion quality and as direct consequence on mixture formation and homogeneity.
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