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Technical Paper

Thermo-Mechanical Analysis of a Cast Iron Exhaust Manifold: a Comparison Between the Traditional and a New Methodology

2010-04-12
2010-01-0498
Thermo-structural analysis of components is usually carried out by means of two FE models, one that solves the thermal problem and one that, using the results of the thermal model, computes strains and stresses. The interaction between the two models is based on the superposition principle, but it means that the mutual effects and the non-linearities between the two physical problems are neglected. In this paper a multiphysics approach based on the Cell Method is proposed and it is applied to a time dependent thermo-mechanical case study represented by an exhaust manifold simulacrum: the coupled thermal and mechanical problems are solved in an unique run, giving the opportunity to take into account mutual effects. Comparing the results with the traditional FE analysis the advantages in terms of accuracy and computational time achieved through the proposed methodology are highlighted.
Technical Paper

The Influence of Crankcase Clearance Volume on Two-Stroke S.I. Engine Performance

1999-09-28
1999-01-3331
The performance of two-stroke spark-ignition engines is greatly influenced by the scavenging process The variation of the crankcase clearance volume has here been investigated as a method for engine-load reduction. This method allows the reduction of the load without throttling or only by partial throttling with a theoretical increase of the engine efficiency. A comparison of two methods (air throttling and crankcase clearance volume variation) has therefore been carried out. The reduction of pumping work, due to the use of the variable crankcase clearance volume, has not always caused a consequent reduction of the specific fuel consumption. This is mainly due to deterioration of the scavenging process and to the occurrence of pre-ignition which occur above all at light loads.
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

Particle Number, Size and Mass Emissions of Different Biodiesel Blends Versus ULSD from a Small Displacement Automotive Diesel Engine

2011-04-12
2011-01-0633
Experimental work was carried out on a small displacement Euro 5 automotive diesel engine alternatively fuelled with ultra low sulphur diesel (ULSD) and with two blends (30% vol.) of ULSD and of two different fatty acid methyl esters (FAME) obtained from both rapeseed methyl ester (RME) and jatropha methyl ester (JME) in order to evaluate the effects of different fuel compositions on particle number (PN) emissions. Particulate matter (PM) emissions for each fuel were characterized in terms of number and mass size distributions by means of two stage dilutions system coupled with a scanning mobility particle sizer (SMPS). Measurements were performed at three different sampling points along the exhaust system: at engine-out, downstream of the diesel oxidation catalyst (DOC) and downstream of the diesel particulate filter (DPF). Thus, it was possible to evaluate both the effects of combustion and after-treatment efficiencies on each of the tested fuels.
Technical Paper

Optimization of a Variable Geometry Exhaust System Through Design of Experiment

2008-04-14
2008-01-0675
Experimental Design methodologies have been applied in conjunction with objective functions for the optimization of the internal geometry of a rear muffler of a subcompact car equipped with a 1.4 liters displacement s.i. turbocharged engine. The muffler also features an innovative variable geometry design. The definition of an objective function summarising the silencing capability of the muffler has been driving the optimization process with the aim to reduce the tailpipe noise while maintaining acceptable pressure losses and complying with severe space constraints. Design of Experiments techniques for the reduction of experimental plans have been shown to be extremely effective to find out the optimum values of the design parameters, allowing a remarkable reduction of the time required by the design process in comparison with full factorial designs.
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

Numerical and Experimental Analysis of Exhaust Manifold Gasket

2006-04-03
2006-01-1210
The paper presents experimental investigation and numerical simulation of a commercial exhaust manifold gasket. Non-linearities in geometric and material behavior make exhaust manifold gasket modeling quite complicated. In the paper, two different FE modeling techniques are compared in order to suggest the best modeling way. Experimental data are collected in order to validate the numerical models. Differences between the two modeling techniques are emphasized and a choice criterion is suggested.
Technical Paper

Numerical Assessment of the CO2 Reduction Potential of Variable Valve Actuation on a Light Duty Diesel Engine

2018-05-30
2018-37-0006
The increasingly demanding targets in terms of CO2 reduction lead to the adoption of engine technologies left so far for innovation. In diesel engines, some of the primary interests in adopting an advanced air management system, as Variable Valve Actuation (VVA), are related to Miller cycle enabling, and valve timing optimization. In this context, a numerical study was carried out in order to evaluate the impact of VVA on passenger car 4-cylinder diesel engine, 1.6 liters. The engine model, developed in GT-SUITE, features a predictive combustion model (DIPulse) and it is coupled with a fully predictive fuel injector model for the simulation of complex injection patterns. 3 different VVA techniques were evaluated, all targeting CO2 reduction: Late Exhaust Valve Opening (LEVO), Exhaust Phasing, and Late Inlet Valve Closure (LIVC) for enabling Miller cycle.
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

Nano-Sized Additive Synthesis for Lubricant Oils and Compatibility Tests with After-Treatment Catalysts

2011-09-11
2011-24-0101
Molybdenum sulfide nanoparticles have been successfully obtained, for lubricant applications, by means of a wet chemical synthesis in an aqueous solution employing ammonium molybdate, citric acid and ammonium sulfide as the reactants. Some molybdenum-citrate complexes were formed and they reacted with the ammonium sulfide to form MoS₂ nanoparticles. Mo:citrate molar ratio was identified as being the most relevant of the synthesis parameters that affected the phase and morphology of the final products. The optimized nanopowders were softly agglomerated and amorphous, with a mean size of the primary particles of about 30 nm. The compatibility between the thus obtained MoS₂ nanopowders and some commercial after-treatment catalysts for diesel vehicle engines was tested. Diesel oxidation, soot combustion and ammonia-SCR de-NOx catalysts were considered as were the possible effects on the catalytic activity and their possible reaction to the MoS₂ additive.
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.
Technical Paper

Impact of Engine Operating Conditions on Particle Number and Size from a Small Displacement Automotive Diesel Engine

2012-04-16
2012-01-0429
Particulate Matter (PM) particles number and size distribution emitted from a small displacement automotive Common-Rail Diesel engine were analyzed in order to evaluate the impact of different engine operating parameters, such as engine load, EGR rate and injection pattern during DPF regeneration. The engine was equipped with a close coupled aftertreatment system, featuring a Diesel Oxidation Catalyst (DOC) and a Diesel Particulate Filter (DPF) integrated in a single canning. The pollutant emissions were sampled at two locations along the exhaust system: at the engine outlet and downstream of the diesel oxidation catalyst, in order to characterize particles entering the DOC and the DPF respectively. Particle size distributions were measured by means of a two stage dilution system coupled with a downstream Scanning Mobility Particle Sizer (SMPS).
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). 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

Experimental and Computational Analysis of a Tuned Exhaust System for a Small Two-Stroke Engine

1999-09-28
1999-01-3329
The application of computational methods for the development of a tuned exhaust system for a small two stroke scooter engine has here been evaluated. A single dimension fluid dynamic code has been employed, in order to simulate engine performances at full load with a prototype exhaust system, and data predicted from computer simulation have been compared with experimental results, obtained using a test rig and a data acquisition system specifically designed for small two-stroke engines. In this way the accuracy of the computer model has been assessed not only as far as gross engine performance parameters are concerned, but also concerning the prediction of pressure values in several locations inside the engine and the exhaust system. Finally, computer simulation techniques have been applied to the development of the prototype exhaust system, and have been proved to be powerful and effective techniques to identify the modifications required to obtain the engine performance targets.
Technical Paper

Experimental Investigation on Three Different Ceramic Substrate Materials for a Diesel Particulate Filter

2013-09-08
2013-24-0160
Three different ceramic substrate materials (Silicon Carbide, Cordierite and Aluminum Titanate) for a Diesel Particulate Filter (DPF) for a European passenger car diesel engine have been experimentally investigated in this work. The filters were soot loaded under real world operating conditions on the road and then regenerated in two different ways that simulate the urban driving conditions, which are the most severe for DPF regeneration, since the low exhaust flow has a limited capability to absorb the heat generated by the soot combustion. The tests showed higher temperature peaks, at the same soot loading, for Cordierite and Aluminum Titanate compared to the Silicon Carbide, thus leading to a lower soot mass limit, which in turn required for these components a higher regeneration frequency with draw backs in terms of fuel consumption and lube oil dilution.
Technical Paper

Electromechanical Energy Scavenger for Automotive Tires

2011-04-12
2011-01-0097
This paper presents a multi-physic modeling of an electromechanical energy scavenging device able to supply energy inside car tires for wireless sensors. A permanent magnet, connected to the inner liner of a tire, is accelerated along a guide by the tire deformation during car motion; by interacting with coils it generates a power which is conditioned by a proper electronic interfaced to an external load. The original approach implemented in this kind of device is the nonlinear dynamic properties designed and controlled: adaptive resonance in function of car velocity is optimized for increasing its global efficiency. The energy conversion process takes into account the simulation of different phenomena such as: non linear dynamic and adaptive resonant behavior of the seismic mass, electromagnetic and magneto-static coupling between moving mass and coils, transfer of the generated power to an external load by means of a nonlinear circuit interface.
Journal Article

Development and Validation of a Real-Time Model for the Simulation of the Heat Release Rate, In-Cylinder Pressure and Pollutant Emissions in Diesel Engines

2016-01-15
2015-01-9044
A real-time mean-value engine model for the simulation of the HRR (heat release rate), in-cylinder pressure, brake torque and pollutant emissions, including NOx and soot, has been developed, calibrated and assessed at both steady-state and transient conditions for a Euro 6 1.6L GM diesel engine. The chemical energy release has been simulated using an improved version of a previously developed model that is based on the accumulated fuel mass approach. The in-cylinder pressure has been evaluated on the basis of the inversion of a single-zone model, using the net energy release as input. The latter quantity was derived starting from the simulated chemical energy release, and evaluating the heat transfer of the charge with the walls. NOx and soot emissions were simulated on the basis of semi-empirical correlations that take into account the in-cylinder thermodynamic properties, the chemical energy release and the main engine parameters.
Technical Paper

Comparison Between Direct and Indirect Fuel Injection in an S.I. Two-Stroke Engine

1999-09-28
1999-01-3311
Gasoline direct injection in two-stroke engines has led to even more advantageous results, in comparison with four-stroke engines, as far as unburned hydrocarbon emissions and fuel consumption are concerned. A new electronically controlled injection system has therefore been fitted in a crankcase-scavenged two-stroke engine, previously set up with indirect injection equipment. The comparison between the performance of the two gasoline feeding systems has highlighted the potential of the direct injection strategy. The direct injection system here tested has allowed the optimization of the engine torque characteristic at wide open throttle operating conditions. Moreover, the engine original exhaust system, has been replaced with an expansion-chamber exhaust-pipe system, in order to evaluate the impact of direct gasoline injection also with these optimized exhaust configuration.
Technical Paper

Characterization of a New Advanced Diesel Oxidation Catalyst with Low Temperature NOx Storage Capability for LD Diesel

2012-04-16
2012-01-0373
Currently, two consolidated aftertreatment technologies are available for the reduction of NOx emissions from diesel engines: Urea SCR (Selective Catalytic Reduction) systems and LNT (Lean NOx Trap) systems. Urea SCR technology, which has been widely used for many years at stationary sources, is becoming nowadays an attractive alternative also for light-duty diesel applications. However, SCR systems are much more effective in NOx reduction efficiency at high load operating conditions than light load condition, characterized by lower exhaust gas temperatures.
Video

Characterization of a New Advanced Diesel Oxidation Catalyst with Low Temperature NOx Storage Capability for LD Diesel

2012-06-18
Currently, two consolidated aftertreatment technologies are available for the reduction of NOx emissions from diesel engines: Urea SCR (Selective Catalytic Reduction) systems and LNT (Lean NOx Trap) systems. Urea SCR technology, which has been widely used for many years at stationary sources, is becoming nowadays an attractive alternative also for light-duty diesel applications. However, SCR systems are much more effective in NOx reduction efficiency at high load operating conditions than light load condition, characterized by lower exhaust gas temperatures.
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