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Technical Paper

Analysis of the Impact of the WLTP Procedure on CO2 Emissions of Passenger Cars

2019-10-07
2019-24-0240
Until 2017 in Europe the Type Approval (TA) procedure for light duty vehicles for the determination of pollutant emissions and fuel consumption was based on the New European Driving Cycle (NEDC), a test cycle performed on a chassis dynamometer. However several studies highlighted significant discrepancies in terms of CO2 emissions between the TA test and the real world, due to the limited representativeness of the test procedure. Therefore, the European authorities decided to introduce a new, up-to date, test procedure capable to closer represent real world driving conditions, called Worldwide Harmonized Light Vehicles Test Procedure (WLTP). This work aims to analyze the effects of the new WLTP on vehicle CO2 emissions through both experimental and simulation investigations on two different Euro 5 vehicles, a petrol and a diesel car, representatives of average European passenger cars.
Technical Paper

The Effect of Post Injection Coupled with Extremely High Injection Pressure on Combustion Process and Emission Formation in an Off-Road Diesel Engine: A Numerical and Experimental Investigation

2019-09-09
2019-24-0092
In this paper, a numerical and experimental assessment of post injection potential for soot emissions mitigation in an off-road diesel engine is presented, with the aim of supporting hardware selection and engine calibration processes. As a case study, a prototype off-road 3.4 liters 4-cylinder diesel engine developed by Kohler Engines was selected. In order to explore the possibility to comply with Stage V emission standards without a dedicated aftertreatment for NOx, the engine was equipped with a low pressure cooled Exhaust Gas Recirculation (EGR), allowing high EGR rates (above 30%) even at high load. To enable the exploitation of such high EGR rates with acceptable soot penalties, a two-stage turbocharger and an extremely high-pressure fuel injection system (up to 3000 bar) were adopted. Moreover, post injections events were also exploited to further mitigate soot emissions with acceptable Brake Specific Fuel Consumption (BSFC) penalties.
Technical Paper

Experimental and Numerical Analysis of Latest Generation Diesel Aftertreatment Systems

2019-09-09
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 or SCRF). 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

Assessment through Numerical Simulation of the Impact of a 48 V Electric Supercharger on Performance and CO2 Emissions of a Gasoline Passenger Car

2019-04-02
2019-01-1284
The demanding CO2 emission targets are fostering the development of downsized, turbocharged and electrified engines. In this context, the need for high boost level at low engine speed requires the exploration of dual stage boosting systems. At the same time, the increased electrification level of the vehicles enables the usage of electrified boosting systems aiming to exploit the opportunities of high levels of electric power and energy available on-board. The aim of this work is therefore to evaluate, through numerical simulation, the impact of a 48 V electric supercharger (eSC) on vehicle performance and fuel consumption over different transients. The virtual test rig employed for the analysis integrates a 1D CFD fast running engine model representative of a 1.5 L state-of-the-art gasoline engine featuring an eSC in series with the main turbocharger, a dual voltage electric network (12 V + 48 V), a six-speed manual transmission and a vehicle representative of a B-SUV segment car.
Technical Paper

Calculating Heavy-Duty Truck Energy and Fuel Consumption Using Correlation Formulas Derived From VECTO Simulations

2019-04-02
2019-01-1278
The Vehicle Energy Consumption calculation Tool (VECTO) is used in Europe for calculating standardised energy consumption and CO2 emissions from Heavy-Duty Trucks (HDTs) for certification purposes. The tool requires detailed vehicle technical specifications and a series of component efficiency maps, which are difficult to retrieve for those that are outside of the manufacturing industry. In the context of quantifying HDT CO2 emissions, the Joint Research Centre (JRC) of the European Commission received VECTO simulation data of the 2016 vehicle fleet from the vehicle manufacturers. In previous work, this simulation data has been normalised to compensate for differences and issues in the quality of the input data used to run the simulations. This work, which is a continuation of the previous exercise, focuses on the deeper meaning of the data received to understand the factors contributing to energy and fuel consumption.
Technical Paper

Application of Genetic Algorithm for the Calibration of the Kinetic Scheme of a Diesel Oxidation Catalyst Model

2018-09-10
2018-01-1762
In this work, a methodology for building and calibrating the kinetic scheme for the 1D CFD model of a zone-coated automotive Diesel Oxidation Catalyst (DOC) by means of a Genetic Algorithm (GA) approach is presented. The methodology consists of a preliminary experimental activity followed by a modelling, optimization and validation process. The tested aftertreatment component presents zone coating, with the front brick side covered with Zeolites in order to ensure hydrocarbons trapping at low temperature, and Platinum Group Metal (PGM), while the rear brick side presents an alumina washcoat with a different PGM loading. Reactor scale samples representative of each coating zone were tested on a Synthetic Gas Bench (SGB), to fully characterize the component’s behavior in terms of Light-off and hydrocarbons (HC) storage for a wide range of inlet feed compositions and temperatures, representative of engine-out conditions.
Technical Paper

Application of Adjoint Methods on Drag Reduction of Current Production Cars

2018-05-30
2018-37-0016
Automotive manufacturers are facing stronger and stronger pressure to optimize all aspects related to fuel consumption of cars, and aerodynamic drag makes no exception, due to increasing government enforcing rules for the reduction of the emissions and the increasing influence of aerodynamic performance on fuel consumption with WLTC and RDE driving cycles. Nowadays, CFD simulation is a common tool across automotive industries for the assessment and the optimization of vehicle resistance in the design phase. The full power of these numerical methods of studying many design variants in advance of experimental testing, however, can be fully exploited when coupled with optimization techniques, always keeping into account constraints and aesthetical demands. On the other hand, a massive use of CFD optimization can lead to unaffordable computational efforts or a limitation of the design exploration space.
Technical Paper

Performance and Emission Comparison between a Conventional Euro VI Diesel Engine and an Optimized PCCI Version and Effect of EGR Cooler Fouling on PCCI Combustion

2018-04-03
2018-01-0221
Premixed charge compression ignition (PCCI) is an advanced combustion mode that has the aim of simultaneously reducing particulate matter and nitrogen oxide exhaust emissions, compared with conventional diesel combustion, thanks to a partially premixed charge and low temperature combustion. In this work, PCCI combustion has been implemented by means of an early single-injection strategy and large amounts of recirculated exhaust gas. Starting from a commercial Euro VI on-road engine, the engine hardware has been modified to optimize PCCI operations. This has involved adopting a smaller turbo group, a new combustion chamber and injectors, and a dedicated high-pressure exhaust gas recirculation system. The results, in terms of engine performance and exhaust emissions, under steady-state operation conditions, are presented in this work, where the original Euro VI calibration of the conventional engine has been compared with the PCCI calibration of the optimized hardware engine.
Technical Paper

Development through Simulation of a Turbocharged 2-Stroke G.D.I. Engine Focused on a Range-Extender Application

2017-11-05
2017-32-0121
An original 2-stroke prototype engine, equipped with an electronically controlled gasoline direct-injection apparatus, has been tested over the last few years, and the performances of these tests have been compared with those obtained using a commercial crankcase-scavenged 2-stroke engine. Very satisfactory results have been obtained, as far as fuel consumption and unburned hydrocarbons in the exhaust gas are concerned. Large reductions in fuel consumption and in unburned hydrocarbons have been made possible, because the injection timing causes all the injected gasoline to remain in the combustion chamber, and thus to take part in the combustion process. Moreover, a force-feed lubrication system, like those usually exploited in mass-produced 4-stroke engines, has been employed, because of the presence of an external pump. In fact, it is no longer necessary to add oil to the gasoline in the engine, as the gasoline does not pass through the crankcase volume.
Technical Paper

A Fully Physical Correlation for Low Pressure EGR Control Linearization

2017-09-04
2017-24-0011
Nowadays stringent emission regulations are pushing towards new air management strategies like LP-EGR and HP/LP mix both for passenger car and heavy duty applications, increasing the engine control complexity. Within a project in collaboration between Kohler Engines EMEA, Politecnico di Torino, Ricardo and Denso to exploit the potential of EGR-Only technologies, a 3.4 liters KDI 3404 was equipped with a two stage turbocharging system, an extremely high pressure FIS and a low pressure EGR system. The LP-EGR system works in a closed loop control with an intake oxygen sensor actuating two valves: an EGR valve placed downstream of the EGR cooler that regulates the flow area of the bypass between the exhaust line and the intake line, and an exhaust flap to generate enough backpressure to recirculate the needed EGR rate to cut the NOx emission without a specific aftertreatment device.
Technical Paper

Numerical Analysis on the Potential of Different Variable Valve Actuation Strategies on a Light Duty Diesel Engine for Improving Exhaust System Warm Up

2017-09-04
2017-24-0024
The need for achieving a fast warm up of the exhaust system has raised in the recent years a growing interest in the adoption of Variable Valve Actuation (VVA) technology for automotive diesel engines. As a matter of fact, different measures can be adopted through VVA to accelerate the warm up of the exhaust system, such as using hot internal Exhaust Gas Recirculation (iEGR) to heat the intake charge, especially at part load, or adopting early Exhaust Valve Opening (eEVO) timing during the expansion stroke, so to increase the exhaust gas temperature during blowdown. In this paper a simulation study is presented evaluating the impact of VVA on the exhaust temperature of a modern light duty 4-cylinder diesel engine, 1.6 liters, equipped with a Variable Geometry Turbine (VGT).
Technical Paper

Zero Dimensional Models for EGR Mass-Rate and EGR Unbalance Estimation in Diesel Engines

2017-09-04
2017-24-0070
A precise estimation of the recirculated exhaust gas rate and oxygen concentration as well as a predictive evaluation of the possible EGR unbalance among cylinders are of paramount importance, especially if non-conventional combustion modes, which require high EGR flow-rates, are implemented. In the present paper, starting from the equation related to convergent nozzles, the EGR mass flow-rate is modeled considering the pressure and the temperature upstream of the EGR control valve, as well as the pressure downstream of it. The restricted flow-area at the valve-seat passage and the discharge coefficient are carefully assessed as functions of the valve lift. Other models were fitted using parameters describing the engine working conditions as inputs, following a semi-physical and a purely statistical approach. The resulting models are then applied to estimate EGR rates to both conventional and non-conventional combustion conditions.
Technical Paper

Catalytic Activity of Nanostructured Ceria-Based Materials Prepared by Different Synthesis Conditions

2017-09-04
2017-24-0145
In this work, several nanostructured ceria-based catalysts were prepared by the hydrothermal technique varying two synthesis parameters (namely, temperature and pH). Then, cerias with different shapes (i.e., cubes, rods, combination of them, other polyhedra) and structural properties were obtained. The prepared materials were tested for the CO oxidation and soot oxidation efficiency. The results have shown that, for the CO oxidation, activities depend on the surface properties of the catalysts. Conversely, for the soot oxidation, the most effective catalysts exhibit better soot-catalyst contact conditions.
Journal Article

Development of a K-k-∊ Phenomenological Model to Predict In-Cylinder Turbulence

2017-03-28
2017-01-0542
The turbulent flow field inside the cylinder plays a major role in spark ignition (SI) engines. Multiple phenomena that occur during the high pressure part of the engine cycle, such as early flame kernel development, flame propagation and gas-to-wall heat transfer, are influenced by in-cylinder turbulence. Turbulence inside the cylinder is primarily generated via high shear flows that occur during the intake process, via high velocity injection sprays and by the destruction of macro-scale motions produced by tumbling and/or swirling structures close to top dead center (TDC) . Understanding such complex flow phenomena typically requires detailed 3D-CFD simulations. Such calculations are computationally very expensive and are typically carried out for a limited number of operating conditions. On the other hand, quasi-dimensional simulations, which provide a limited description of the in-cylinder processes, are computationally inexpensive.
Technical Paper

A Possible Adaptive Wing Apparatus for New UAV Configurations

2015-09-15
2015-01-2463
The problem of wing shape modification under loads in order to enhance the aircraft performance and control is continuously improving by researchers. This requirement is in contrast to the airworthiness regulations that constraint stiffness and stress of the structure in order to maintain structural integrity under operative flight conditions. The lifting surface modification is more stringent in those cases, such as UAV configurations, where the installed power is limited but the variety of operative scenario is wider than in conventional aircraft. A possible solution for adaptive wing configuration can be found in the VENTURAS Project idea. The VENTURAS Project is a funded project with the aim of improve the wind turbine efficiency by means of introducing a twisting capability for the blade sections according to the best situation in any wind condition. The blade structure is composed by two parts: 1) internal supporting element, 2) external deformable envelope.
Technical Paper

Nonlinear Slender Beam-Wise Schemes for Structural Behavior of Flexible UAS Wings

2015-09-15
2015-01-2462
The innovative highly flexible wings made of extremely light structures, yet still capable of carrying a considerable amount of non- structural weights, requires significant effort in structural simulations. The complexity involved in such design demands for simplified mathematical tools based on appropriate nonlinear structural schemes combined with reduced order models capable of predicting accurately their aero-structural behaviour. The model presented in this paper is based on a consistent nonlinear beam-wise scheme, capable of simulating the unconventional aeroelastic behaviour of flexible composite wings. The partial differential equations describing the wing dynamics are expanded up to the third order and can be used to explore the effect of static deflection imposed by external trim, the effect of gust loads and the one of nonlinear aerodynamic stall.
Journal Article

Offline and Real-Time Optimization of EGR Rate and Injection Timing in Diesel Engines

2015-09-06
2015-24-2426
New methodologies have been developed to optimize EGR rate and injection timing in diesel engines, with the aim of minimizing fuel consumption (FC) and NOx engine-out emissions. The approach entails the application of a recently developed control-oriented engine model, which includes the simulation of the heat release rate, of the in-cylinder pressure and brake torque, as well as of the NOx emission levels. The engine model was coupled with a C-class vehicle model, in order to derive the engine speed and torque demand for several driving cycles, including the NEDC, FTP, AUDC, ARDC and AMDC. The optimization process was based on the minimization of a target function, which takes into account FC and NOx emission levels. The selected control variables of the problem are the injection timing of the main pulse and the position of the EGR valve, which have been considered as the most influential engine parameters on both fuel consumption and NOx emissions.
Technical Paper

Experimental Investigation on Early and Late Intake Valve Closures for Knock Mitigation through Miller Cycle in a Downsized Turbocharged Engine

2015-04-14
2015-01-0760
The application of Miller cycle through Late Intake Valve Closure (LIVC) or Early Intake Valve Closure (EIVC) for knock mitigation at high load on a turbocharged downsized spark ignition engine was experimentally investigated. By reducing the effective compression ratio due to a shorter compression stroke and hence achieving lower charge temperatures inside the cylinder, significant mitigation of knock tendency could be obtained. As a consequence, the spark advance retard could be substantially decreased and the enrichment of the mixture could significantly be reduced, thus obtaining impressive efficiency improvements. In this research, both EIVC and LIVC strategies have been examined aiming to achieve possible improvements for knock mitigation and after some preliminary investigations confirmed LIVC being more effective than EIVC for this goal, the latter was discarded and the research activities were focused on LIVC only.
Technical Paper

Design the City Vehicle XAM using CFD Analysis

2015-04-14
2015-01-1533
XAM is a two-seat city vehicle prototype developed at the Politecnico di Torino, equipped with a hybrid propulsion system to obtain low consumptions and reduced environmental impact. The design of this vehicle was guided by the requirements of weight reduction and aerodynamic optimization of the body, aimed at obtaining a reduction of resistance while guarantying roominess. The basic shape of the vehicle corresponding to the requirements of style, ergonomics and structure were deeply studied through CFD simulation in order to assess its aerodynamic performance (considering the vehicle as a whole or the influence of the various details and of their changes separately). The most critical areas of the body (underfloor, tail, spoiler, mirrors, A-pillar) were analyzed creating dedicated refinement volumes.
Technical Paper

A Methodology to Mimic Cycle to Cycle Variations and to Predict Knock Occurrence through Numerical Simulation

2014-04-01
2014-01-1070
In this paper a novel approach to mimic through numerical simulation Cycle-to-Cycle Variations (CCV) of the combustion process of Spark Ignition (SI) engines is described. The proposed methodology allows to reproduce the variability in combustion which is responsible for knock occurrence and thus to replicate the stochastic behavior of this abnormal combustion phenomenon. On the basis of the analysis of a comprehensive database of experimental data collected on a typical European downsized and turbocharged SI engine, the proposed approach was demonstrated to be capable to replicate in the simulation process the same percentage of knocking cycles experimentally measured in light-knock conditions, after a proper calibration of the Kinetics-Fit (KF), a new phenomenological knock model which was recently developed by Gamma Technologies.
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