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Technical Paper

A Modal-Geometrical Selection Criterion for Master Nodes Applied to Engine Components

2011-04-12
2011-01-0498
Usually, both an experimental modal analysis or a numerical modal analysis performed on reduced model present the problem of master nodes selection. A methodology based on the experience is normally used or computationally heavy criterion can be applied. In that paper, the Modal-Geometrical Selection Criterion (MoGeSeC) is applied to a crankshaft, both for an EMA (experimental modal analysis) and for a reduction procedure. Then the results are compared with other literature criteria. As far as the EMA is concerned, the nodes suggested by MoGeSeC and other criteria are used for identification of the component. The connection conditions between components are origin of uncertainty but in that case the comparison is done for each methodology in the same conditions. In that way MoGeSeC proves to be a very quick and accurate method because the nodes it selects depicts very well the dynamic behavior of the components.
Journal Article

Computational Analysis of Internal and External EGR Strategies Combined with Miller Cycle Concept for a Two Stage Turbocharged Medium Speed Marine Diesel Engine

2011-04-12
2011-01-1142
In this work different internal and external EGR strategies, combined with extreme Miller cycles, were analyzed by means of a one-dimensional CFD simulation code for a Wärtsilä 6-cylinder, 4-strokes, medium-speed marine diesel engine, to evaluate their potential in order to reach the IMO Tier 3 NOx emissions target. By means of extreme Miller cycles, with Early Intake Valve Closures (up to 100 crank angle degrees before BDC), a shorter compression stroke and lower charge temperatures inside the cylinder can be achieved and thanks to the cooler combustion process, the NOx-specific emissions can be effectively reduced. EIVC strategies can also be combined with reductions of the scavenging period (valve overlap) to increase the amount of exhaust gases in the combustion chamber. However, the remarkably high boost pressure levels needed for such extreme Miller cycles, require mandatorily the use of two-stage turbocharging systems.
Journal Article

Model Based Engine Control Development and Hardware-in-the-Loop Testing for the EcoCAR Advanced Vehicle Competition

2011-04-12
2011-01-1297
When developing a new engine control strategy, some of the important issues are cost, resource minimization, and quality improvement. This paper outlines how a model based approach was used to develop an engine control strategy for an Extended Range Electric Vehicle (EREV). The outlined approach allowed the development team to minimize the required number of experiments and to complete much of the control development and calibration before implementing the control strategy in the vehicle. It will be shown how models of different fidelity, from map-based models, to mean value models, to 1-D gas dynamics models were generated and used to develop the engine control system. The application of real time capable models for Hardware-in-the-Loop testing will also be shown.
Technical Paper

Integrated CAD/CAE Functional Design for Engine Components and Assembly

2011-04-12
2011-01-1071
In the present paper, starting from a first attempt design of engine components, a CAD/CAE integrated approach for designing engine is proposed. As first step, some typological quantities are setting in order to define the designed engine, for example the number of cylinders, displacements, thermodynamic cycle and geometrical constraints. Using literature approach and tailored design methodologies, the developed software provides the geometric parameters of the main engine components: crankshaft, piston, wrist pin, connecting rod, bedplate, engine block, cylinder head, bearings, valvetrain. Form the geometrical parameters, the developed software, using 3D CAD parametric models, defines a first functional model of each component and of their mutual interactions. Then a numerical analysis can be evaluated and it provides important feedback result for design targets. In the paper the particular case of a crank mechanism model is presented.
Journal Article

Impact on Performance, Emissions and Thermal Behavior of a New Integrated Exhaust Manifold Cylinder Head Euro 6 Diesel Engine

2013-09-08
2013-24-0128
The integration of the exhaust manifold in the engine cylinder head has received considerable attention in recent years for automotive gasoline engines, due to the proven benefits in: engine weight diminution, cost saving, reduced power enrichment, quicker engine and aftertreatment warm-up, improved packaging and simplification of the turbocharger installation. This design practice is still largely unknown in diesel engines because of the greater difficulties, caused by the more complex cylinder head layout, and the expected lower benefits, due to the absence of high-load enrichment. However, the need for improved engine thermomanagement and a quicker catalytic converter warm-up in efficient Euro 6 diesel engines is posing new challenges that an integrated exhaust manifold architecture could effectively address. A recently developed General Motors 1.6L Euro 6 diesel engine has been modified so that the intake and exhaust manifolds are integrated in the cylinder head.
Journal Article

Assessment of a New Quasi-Dimensional Multizone Combustion Model for the Spray and Soot Formation Analysis in an Optical Single Cylinder Diesel Engine

2013-09-08
2013-24-0044
An innovative quasi-dimensional multizone combustion model for the spray formation, combustion and emission formation analysis in DI diesel engines was assessed and applied to an optical single cylinder engine. The model, which has been recently presented by the authors, integrates a predictive non stationary 1D spray model developed by the Sandia National Laboratory, with a diagnostic multizone thermodynamic model. The 1D spray model is capable of predicting the equivalence ratio of the fuel during the mixing process, as well as the spray penetration. The multizone approach is based on the application of the mass and energy conservation laws to several homogeneous zones identified in the combustion chamber. A specific submodel is also implemented to simulate the dilution of the burned gases. Soot formation is modeled by an expression which derives from Kitamura et al.'s results, in which an explicit dependence on the local equivalence ratio is considered.
Technical Paper

Effects of Different Geometries of the Cylinder Head on the Combustion Characteristics of a VVA Gasoline Engine

2013-09-08
2013-24-0057
Two different modifications of the baseline cylinder head configuration have been designed and experimentally tested on a MultiAir turbocharged gasoline engine, in order to address the issue of the poor in-cylinder turbulence levels which are typical of the Early-Intake-Valve-Closing (EIVC) strategies which are adopted in Variable Valve Actuation systems at part load to reduce pumping losses. The first layout promotes turbulence by increasing the tumble motion at low valve lifts, while the second one allows the addition of a swirl vortex to the main tumble structure. The aim for both designs was to achieve a proper flame propagation speed at both part and full load. The experimental activity was initially focused on the part load analysis under high dilution of the mixture with internal EGR, which can allow significant further reductions in terms of pumping losses but, on the other hand, tends to adversely affect combustion stability and to increase cycle-to-cycle variations.
Technical Paper

Energy Consumption in ICE Lubricating Gear Pumps

2010-10-25
2010-01-2146
Scope of this work is the analysis of the energy consumed by lubricating gear pumps for automotive applications during a driving cycle. This paper presents the lumped parameter simulation model of gerotor lubricating pumps and the comparison between numerical outcomes and experimental results. The model evaluates the power required to drive the pump and the cumulative energy consumed in the driving cycle. The influence of temperature variations on leakage flows, viscous friction torque and lubricating circuit permeability is taken into account. The simulation model has been validated by means of a test rig for hydraulic pumps able to reproduce the typical speed, temperature and load profiles during a NEDC driving cycle. Experimental tests, performed on a crankshaft mounted pump for diesel engines, have confirmed a good matching with the simulation model predictions in terms of instantaneous quantities and overall energy consumption.
Journal Article

Cfd Diagnostic Methodology for the Assessment of Mixture Formation Quality in GDI Engines

2011-09-11
2011-24-0151
The fuel injection plays a crucial role in determining the mixture formation process in Gasoline Direct Injection (GDI) engines. Pollutant emissions, and soot emissions in particular, as well as phenomena affecting engine reliability, such as oil dilution and injector coking, are deeply influenced by the injection system features, such as injector geometric characteristics (such as injector type, injector position and targeting within the combustion chamber) and operating characteristics (such as injection pressure, injection phasing, etc.). In this paper, a new CFD methodology is presented, allowing a preliminary assessment of the mixture formation quality in terms of expected soot emissions, oil dilution and injector coking risks for different injection systems (such as for instance multihole or swirl injectors) and different injection strategies, from the early stages of a new engine design.
Technical Paper

Diagnostics of Mixing Process Dynamics, Combustion and Emissions in a Euro V Diesel Engine

2011-09-11
2011-24-0018
An innovative approach to the study of combustion and emission formation in modern diesel engines has been applied to a EURO V diesel engine equipped with an indirect-acting piezo injection system. The model is based on the joint use of a predictive non-stationary 1D spray model, which has recently been presented by Musculus and Kattke, and a diagnostic multizone thermodynamic model developed by the authors. The combustion chamber content has been split into homogeneous zones, to which mass and energy conservation laws have been applied: an unburned gas zone, made up of air, EGR and residual gas, several fuel/unburned gas mixture zones, premixed combustion burned gas zones and diffusive combustion burned gas zones. The 1D spray model enables the mixing process dynamics of the different fuel parcels with the unburned gas to be estimated for each injection pulse; therefore, the equivalent ratio time-history of each mixture zone can be estimated.
Journal Article

Use of an Innovative Predictive Heat Release Model Combined to a 1D Fluid-Dynamic Model for the Simulation of a Heavy Duty Diesel Engine

2013-09-08
2013-24-0012
An innovative 0D predictive combustion model for the simulation of the HRR (heat release rate) in DI diesel engines was assessed and implemented in a 1D fluid-dynamic commercial code for the simulation of a Fiat heavy duty diesel engine equipped with a Variable Geometry Turbocharger system, in the frame of the CORE (CO2 reduction for long distance transport) Collaborative Project of the European Community, VII FP. The 0D combustion approach starts from the calculation of the injection rate profile on the basis of the injected fuel quantities and on the injection parameters, such as the start of injection and the energizing time, taking the injector opening and closure delays into account. The injection rate profile in turn allows the released chemical energy to be estimated. The approach assumes that HRR is proportional to the energy associated with the accumulated fuel mass in the combustion chamber.
Journal Article

Modelling and Simulation of Brake Booster Vacuum Pumps

2013-05-15
2013-01-9016
Aim of this work is the development of a lumped parameters simulation model of single-vane vacuum pumps for pneumatically actuated brake boosters. Kinematic and fluid-dynamic models are integrated in a simulation environment to create a tool aimed at evaluating the vacuum pump performance and at guiding the designer during the prototype development. The paper describes extensively the mathematical model, the time domain simulation and experimental analyses performed on a camshaft mounted unit. Great emphasis is placed on the evaluation of the geometric quantities of the control volumes into which the vacuum pump has been divided. For each control volume the mass and energy conservation equations lead to the determination of the instantaneous pressure. The volume of each variable chamber and the respective angular derivative are calculated as function of the shaft position starting from the stator track profile supplied as a generic closed polyline.
Journal Article

Analysis of Combustion and Emissions in a EURO V Diesel Engine by Means of a Refined Quasi-Dimensional Multizone Diagnostic Model

2012-04-16
2012-01-1066
A quasi-dimensional multizone combustion model, that was previously developed by the authors, has been refined and applied for the analysis of combustion and emission formation in a EURO V diesel engine equipped with a piezo indirect-acting injection system. The model is based on the integration of the predictive non-stationary variable-profile 1D spray model recently presented by Musculus and Kattke, with a diagnostic multizone thermodynamic model specifically developed by the authors. The multizone approach has been developed starting from the Dec conceptual scheme, and is based on the identification of several homogeneous zones in the combustion chamber, to which mass and energy conservation laws have been applied: an unburned gas zone, made up of air, EGR (Exhaust Gas Recirculation) and residual gas, several fuel/unburned gas mixture zones, premixed combustion burned gas zones and diffusive combustion burned gas zones.
Technical Paper

Real-Time Predictive Modeling of Combustion and NOx Formation in Diesel Engines Under Transient Conditions

2012-04-16
2012-01-0899
The present work has the aim of developing a fast approach for the predictive calculation of in-cylinder combustion temperatures and NOx formation in diesel engines, under steady state and transient conditions. The model has been tested on a PC, and found to require very little computational time, thus suggesting it could be implemented in the ECU (Engine Control Unit) of engines for model-based control tasks. The method starts with the low-throughput predictive combustion model that was previously developed by the authors, which allows the predictive estimation of the heat-release rate and of the in-cylinder pressure trace to be made on the basis of the injection parameters and of a few quantities measured by the ECU, such as the intake manifold pressure and temperature.
Technical Paper

Numerical and Experimental Analysis of Mixture Formation and Performance in a Direct Injection CNG Engine

2012-04-16
2012-01-0401
This paper presents the results of part of the research activity carried out by the Politecnico di Torino and AVL List GmbH as part of the European Community InGAS Collaborative Project. The work was aimed at developing a combustion system for a mono-fuel turbocharged CNG engine, with specific focus on performance, fuel economy and emissions. A numerical and experimental analysis of the jet development and mixture formation in an optically accessible, single cylinder engine is presented in the paper. The experimental investigations were performed at the AVL laboratories by means of the planar laser-induced fluorescence technique, and revealed a cycle-to-cycle jet shape variability that depended, amongst others, on the injector characteristics and in-cylinder backpressure. Moreover, the mixing mechanism had to be optimized over a wide range of operating conditions, under both stratified lean and homogeneous stoichiometric modes.
Journal Article

A Feed-Forward Approach for the Real-Time Estimation and Control of MFB50 and SOI In Diesel Engines

2014-05-05
2014-01-9046
Feed-forward low-throughput models have been developed to predict MFB50 and to control SOI in order to achieve a specific MFB50 target for diesel engines. The models have been assessed on a GMPT-E Euro 5 diesel engine, installed at the dynamic test bench at ICEAL-PT (Internal Combustion Engine Advanced Laboratory at the Politecnico di Torino) and applied to both steady state and transient engine operating conditions. MFB50 indicates the crank angle at which 50% of the fuel mass fraction has burned, and is currently used extensively in control algorithms to optimize combustion phasing in diesel engines in real-time. MFB50 is generally used in closed-loop combustion control applications, where it is calculated by the engine control unit, cycle-by-cycle and cylinder by-cylinder, on the basis of the measured in-cylinder pressure trace, and is adjusted in order to reduce the fuel consumption, combustion noise and engine-out emissions.
Technical Paper

Development of an Improved Fractal Model for the Simulation of Turbulent Flame Propagation in SI Engines

2005-09-11
2005-24-082
The necessity for further reductions of in-cylinder pollutant formation and the opportunity to minimize engine development and testing times highlight the need of engine thermodynamic cycle simulation tools that are able to accurately predict the effects of fuel, design and operating variables on engine performance. In order to set up reliable codes for indicated cycle simulation in SI engines, an accurate prediction of heat release is required, which, in turn, involves the evaluation of in-cylinder turbulence generation and flame-turbulence interaction. This is generally pursued by the application of a combustion fractal model coupled with semi-empirical correlations of available geometrical and thermodynamical mass-averaged quantities. However, the currently available correlations generally show an unsatisfactory capability to predict the effects of flame-turbulence interaction on burning speed under the overall flame propagation interval.
Technical Paper

Optimization of a Light Aircraft Spark-Ignition Engine

2006-08-30
2006-01-2420
The aim of this study was to find a convenient set-up for an innovative engine dedicated to light aircraft through a numerical one-dimensional simulation. Six different engine layouts were analyzed in order to find the highest power/weight ratio and the least voluminous configuration. The first was a four cylinder, four stroke, horizontally opposed, naturally aspirated, water cooled engine with 16 valves that delivered 75 kW (∼100 bhp) at 2400 rpm for an estimated weight of 65 kg. A gearbox was also used in the naturally aspirated model to decrease the displacement, the weight and the overall dimensions. The other solutions involved these two engines in a turbocharged layout in order to gain a further downsizing. The supercharging was obtained through a centrifugal compressor driven by an exhaust-gas driven turbine, which also allows the power to be restored at cruising altitude.
Technical Paper

The Potential of Electric Exhaust Gas Turbocharging for HD Diesel Engines

2006-04-03
2006-01-0437
The potential of an electric assisted turbocharger for a heavy-duty diesel engine has been analyzed in this work, in order to evaluate the turbo-lag reductions and the fuel consumption savings that could be obtained in an urban bus for different operating conditions. The aim of the research project was to replace the current variable geometry turbine with a fixed geometry turbine, connecting an electric machine which can be operated both as an electric motor and as an electric generator to the turbo shaft. The electric motor can be used to speed up the turbocharger during the acceleration transients and reduce the turbo-lag, while the generator can be used to recover the excess exhaust energy when the engine is operated near the rated speed, in order to produce electrical power that can be used to drive engine auxiliaries. In this way the engine efficiency can be improved and a kind of “electric turbocompounding” can be obtained.
Technical Paper

Performance of Combination Particulate/Gaseous Contaminant Air Filters in the Highway and Street Traffic Environment

2007-04-16
2007-01-1425
Automotive cabin filters of the “combo” type are intended to remove both aerosols and gaseous contaminants from air entering the climate control system. We analyze the performance of two filters of this type, using published values for the concentration of gaseous contaminants found in highway and street traffic. Using existing expressions for the performance of activated carbons, including the effects of contaminant concentration, flow rate and carbon bed depth, we calculate retentivity and breakthrough time for benzene and carbon tetrachloride at street-level concentrations. The calculated factors are compared to published test data on similar filters.
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