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Technical Paper

Quantifying Benefits of Dual Cam Phasers, Lean Mixture and EGR on the Operating Range and Fuel Economy of a PFI NVO CAI Engine

2010-04-12
2010-01-0844
Among the existing concepts that help to improve the efficiency of spark-ignition engines at part load, Controlled Auto-Ignition™ (CAI™) is an effective way to lower both fuel consumption and pollutant emissions. This combustion concept is based on the auto-ignition of an air-fuel-mixture highly diluted with hot burnt gases to achieve high indicated efficiency and low pollutant emissions through low temperature combustion. To minimize the costs of conversion of a standard spark-ignition engine into a CAI engine, the present study is restricted to a Port Fuel Injection engine with a cam-profile switching system and a cam phaser on both intake and exhaust sides. In a 4-stroke engine, a large amount of burnt gases can be trapped in the cylinder via early closure of the exhaust valves. This so-called Negative Valve Overlap (NVO) strategy has a key parameter to control the amount of trapped burnt gases and consequently the combustion: the exhaust valve-lift profile.
Technical Paper

A Physical 0D Combustion Model Using Tabulated Chemistry with Presumed Probability Density Function Approach for Multi-Injection Diesel Engines

2010-05-05
2010-01-1493
This paper presents a new 0D phenomenological approach to predict the combustion process in diesel engines operated under various running conditions. The aim of this work is to develop a physical approach in order to improve the prediction of in-cylinder pressure and heat release. The main contribution of this study is the modeling of the premixed part of the diesel combustion with a further extension of the model for multi-injection strategies. In phenomenological diesel combustion models, the premixed combustion phase is usually modeled by the propagation of a turbulent flame front. However, experimental studies have shown that this phase of diesel combustion is actually a rapid combustion of part of the fuel injected and mixed with the surrounding gas. This mixture burns quasi instantaneously when favorable thermodynamic conditions are locally reached. A chemical process then controls this combustion.
Journal Article

Towards an Innovative Combination of Natural Gas and Liquid Fuel Injection in Spark Ignition Engines

2010-05-05
2010-01-1513
In order to address the CO₂ emissions issue and to diversify the energy for transportation, CNG (Compressed Natural Gas) is considered as one of the most promising alternative fuels given its high octane number. However, gaseous injection decreases volumetric efficiency, impacting directly the maximal torque through a reduction of the cylinder fill-up. To overcome this drawback, both independent natural gas and gasoline indirect injection systems with dedicated engine control were fitted on a RENAULT 2.0L turbocharged SI (Spark Ignition) engine and were adapted for simultaneous operation. The main objective of this innovative combination of gas and liquid fuel injections is to increase the volumetric efficiency without losing the high knocking resistance of methane.
Journal Article

Establishing New Correlations Between In-Cylinder Charge Motion and Combustion Process in Gasoline Engines Through a Numerical DOE

2010-04-12
2010-01-0349
This paper presents an innovative methodology and the corresponding results of a study whose goal is to identify the main links between in-cylinder charge motion and the development of combustion without taking into consideration how to create this charge motion (shape of the intake ducts, valve timing, etc …). During this study a specific methodology was developed and used. It is based on the calculation of a “3D numerical test bench” matrix planned following the Design Of Experiments method. Many aerodynamic configurations obtained by combining the three main aerodynamic motions with several different intensities (tumble, cross-tumble or swirl) at the intake valve closing were calculated.
Technical Paper

Compressor Efficiency Extrapolation for 0D-1D Engine Simulations

2016-04-05
2016-01-0554
Abstract 0D-1D codes allow researchers to obtain a prediction of the behavior of internal combustion engines with little computational effort. One of the submodels of such codes is devoted to the centrifugal compressor. This model is often based on the compressor performance maps, therefore requiring the extrapolation of the maps so that all possible operating conditions are covered. Particularly, a suitable extrapolation of isentropic efficiency map is sought. This work first examines different available methods for compressor efficiency extrapolation into off-design conditions. No method is found to provide satisfactory results at all extrapolated regions: low and high compressor speeds and low compression ratio at measured speeds. Hence, a new method is proposed and its accuracy is assessed with the aid of compressor off-design measurements.
Technical Paper

Semi-Empirical 0D Modeling for Engine-Out Soot Emission Prediction in D.I. Diesel Engines

2016-04-05
2016-01-0562
Abstract Due to its harmful effect on both human health and environment, soot emission is considered as one of the most important diesel engine pollutants. In the last decades, the industrial engine manufacturers have been able to strongly reduce its engine-out value by many different techniques, in order to respect the stricter emission norms. Simulation modeling has played and continues to play a key role for this purpose in the engine control system development. In this context, this paper proposes a new soot emission model for a direct injection diesel engine. This soot model is based on a zero-dimensional semi-physical approach coupled with a crank-angle resolved combustion model and a thermodynamic calculation of the burned gas products temperature. Furthermore, a multi linear regression model has been used to estimate the soot emissions as function of significant physical combustion parameters.
Technical Paper

Experimental Study of Automotive Turbocharger Turbine Performance Maps Extrapolation

2016-04-05
2016-01-1034
Abstract Engine downsizing is potentially one of the most effective strategies being explored to improve fuel economy. A main problem of downsizing using a turbocharger is the small range of stable functioning of the turbocharger centrifugal compressor at high boost pressures, and hence the measurement of the performance maps of both compressor and turbine. Automotive manufacturers use mainly numerical simulations for internal combustion engines simulations, hence the need of an accurate extrapolation model to get a complete turbine performance map. These complete maps are then used for internal combustion engines calibration. Automotive manufacturers use commercial softwares to extrapolate the turbine narrow performance maps, both mass flow characteristics and the efficiency curve.
Technical Paper

Experimental and Numerical Investigations of Tumble Motion on an Optical Single Cylinder Engine

2015-04-14
2015-01-1698
This paper is focused on the experimental and numerical investigation of tumble motion on a single cylinder optical engine on three important parameters like engine load conditions, engine speed and level of tumble. Experiments are conducted in an optical engine and the velocity fields are measured with the aid of advanced particle image velocimetry (PIV) measurement technique. For simulation, multiple cases were considered to develop the numerical process for transient in-cylinder aerodynamics to capture the tumble motion and turbulence level in a Spark Ignited (SI) engine. The simulation results, velocity fields of each case were directly compared with the corresponding test results for different crank positions of the engine. On comparison, a good agreement between the measurement and the simulation is obtained for different configurations.
Technical Paper

A Study of the Effects of 30% Biodiesel Fuel on Soot Loading and Regeneration of a Catalytic DPF

2007-07-23
2007-01-2023
Biofuels are a renewable energy source. When used as extenders for transportation fuels, biofuels contribute to the global reduction of Green House Gas and CO2 emissions from the transport sector and to security and independence of energy supply. On a “Well to Wheel” basis they are much more CO2 efficient than conventional fossil fuels. All vehicles currently in circulation in Europe are capable of using 5 % biodiesel. The introduction of higher percentages biodiesel needs new specific standards and vehicle tests validation. The development of vehicles compatible with 30% biodiesel blends in diesel fuel includes the validation of each part of both engine and fuel vehicle systems to guarantee normal operation for the entire life of the vehicle.
Technical Paper

System Optimization for a 2-Stroke Diesel Engine with a Turbo Super Configuration Supporting Fuel Economy Improvement of Next Generation Engines

2014-11-11
2014-32-0011
Abstract The objective of this paper is to present the results of the GT Power calibration with engine test results of the air loop system technology down selection described in the SAE Paper No. 2012-01-0831. Two specific boosting systems were identified as the preferred path forward: (1) Super-turbo with two speed Roots type supercharger, (2) Super-turbo with centrifugal mechanical compressor and CVT transmission both downstream a Fixed Geometry Turbine. The initial performance validation of the boosting hardware in the gas stand and the calibration of the GT Power model developed is described. The calibration leverages data coming from the tests on a 2 cylinder 2-stroke 0.73L diesel engine. The initial flow bench results suggested the need for a revision of the turbo matching due to the big gap in performance between predicted maps and real data. This activity was performed using Honeywell turbocharger solutions spacing from fixed geometry waste gate to variable nozzle turbo (VNT).
Technical Paper

Coupled Fluid-Solid Simulation for the Prediction of Gas-Exposed Surface Temperature Distribution in a SI Engine

2017-03-28
2017-01-0669
Abstract The current trend of downsizing used in gasoline engines, while reducing fuel consumption and CO2 emissions, imposes severe thermal loads inside the combustion chamber. These critical thermodynamic conditions lead to the possible auto-ignition (AI) of fresh gases hot-spots around Top-Dead-Center (TDC). At this very moment where the surface to volume ratio is high, wall heat transfer influences the temperature field inside the combustion chamber. The use of a realistic wall temperature distribution becomes important in the case of a downsized engine where fresh gases hot spots found near high temperature walls can initiate auto-ignition. This paper presents a comprehensive numerical methodology for an accurately prediction of thermodynamic conditions inside the combustion chamber based on Conjugate Heat Transfer (CHT).
Technical Paper

Engine Knock Prediction and Evaluation Based on Detonation Theory Using a Quasi-Dimensional Stochastic Reactor Model

2017-03-28
2017-01-0538
Abstract Engine knock is an important phenomenon that needs consideration in the development of gasoline fueled engines. In our days, this development is supported by the use of numerical simulation tools to further understand and subsequently predict in-cylinder processes. In this work, a model tool chain based on detailed chemical and physical models is proposed to predict the auto-ignition behavior of fuels with different octane ratings and to evaluate the transition from harmless auto-ignitive deflagration to knocking combustion. In our method, the auto-ignition and emissions are calculated based on a new reaction scheme for mixtures of iso-octane, n-heptane, toluene and ethanol (Ethanol consisting Toluene Reference Fuel, ETRF). The reaction scheme is validated for a wide range of mixtures and every desired mixture of the four fuel components can be applied in the engine simulation.
Technical Paper

Spray Modelling for GDI Application: Two Different Approach

2016-02-01
2016-28-0007
Abstract This state of art investigation report explains the limitations of Rosin-Rammler approach in comparison with breakup approach. The injection phenomenon of a commercial injector is simulated at various injection pressures, with Heptane (C7H16) in a spray bomb. It is observed that Breakup approach is better suitable in terms of correlation for spray modelling than the Rosin-Rammler approach when the injection pressures are 10 and 20 MPa, the SMD correlation shows also a good correlation at these pressures. At 4 MPa, correlation is a bit poorer, which is coherent as break-up models are best suited to high injection pressures configurations. Also, in each approach the primary dependent parameters are fine-tuned and their effects are discussed.
Technical Paper

Wind Noise Source Identification by Inverse Method in Wind Tunnel Test

2017-06-05
2017-01-1784
Abstract Wind noise in automobile is becoming more and more important as customer requirements increase. On the other hand great progress has been made on engine and road noises. Thus, for many vehicles, wind noise is the major acoustic source during road and motorway driving. As for other noises, automobile manufacturers must be able for a new car project to specify, calculate and measure each step of the acoustic cascading: Source Transfers, both solid and air borne In the case of automotive wind noise, the excitation source is the dynamic pressure on the vehicle’s panels. This part of the cascading is the one influenced by the exterior design. Even if many others components (panels, seals, cabin trims) have a big influence, the exterior design is a major issue for the wind noise. The wind noise level in the cabin can sometimes change significantly with only a small modification of the exterior design.
Technical Paper

Steering Wheel Torque Rendering: Measure of Driver Discrimination Capabilities

2014-04-01
2014-01-0447
Abstract By the action on the steering wheel, the driver has the capability to control the trajectory of its vehicle. Nevertheless, the steering wheel has also the role of information provider to the driver. In particular, the torque level at the steering wheel informs the driver about the interaction between the vehicle and the road. This information flow is natural due to the mechanical chain between the road and the steering wheel. Many studies have shown that steering wheel torque feedback is crucial to ensure the control of the vehicle. In the context of uncoupled steering (steer-by-wire vehicle or driving simulators), the torque rendering on the steering wheel is a major challenge. In addition, of the trajectory control, the quality of this torque is a key for the immersion of drivers in virtual environment such as in driving simulators. The torque-rendering loop is composed of different steps.
Technical Paper

Direct Injection of CNG on High Compression Ratio Spark Ignition Engine: Numerical and Experimental Investigation

2011-04-12
2011-01-0923
CNG is one of the most promising alternate fuels for passenger car applications. CNG is affordable, is available worldwide and has good intrinsic properties including high knock resistance and low carbon content. Usually, CNG engines are developed by integrating CNG injectors in the intake manifold of a baseline gasoline engine, thereby remaining gasoline compliant. However, this does not lead to a bi-fuel engine but instead to a compromised solution for both Gasoline and CNG operation. The aim of the study was to evaluate the potential of a direct injection spark ignition engine derived from a diesel engine core and dedicated to CNG combustion. The main modification was the new design of the cylinder head and the piston crown to optimize the combustion velocity thanks to a high tumble level and good mixing. This work was done through computations. First, a 3D model was developed for the CFD simulation of CNG direct injection.
Journal Article

Control-Oriented Modeling of a LNT-SCR Diesel After-Treatment Architecture

2011-04-12
2011-01-1307
Lean NOx trap (LNT) and Selective Catalytic Reduction catalysts (SCR) are two leading candidates for diesel NOx after-treatment. Each technology exhibits good properties to reduce efficiently diesel NOx emissions in order to match the forthcoming EURO 6 standards. NOx reduction in LNT is made through a two-step process. In normal (lean) mode, diesel engine exhausts NOx is stored into the NOx trap; then when necessary the engine runs rich during limited time to treat the stored NOx. This operating mode has the benefit of using onboard fuel as NOx reducer. But NOx trap solution is restrained by limited active temperature windows. On the other hand, NH₃-SCR catalysts operate in a wider range of temperature and do not contain precious metals. However, NH₃-SCR systems traditionally use urea-water solution as reducing agent, requiring thus additional infrastructure to supply the vehicles with enough reducer.
Technical Paper

System Approach for NOx Reduction: Double LNT Diesel After-Treatment Architecture

2011-04-12
2011-01-1300
This paper presents an after-treatment architecture combining a close coupled NOx trap and an under floor NOx trap. Instead of simply increasing the volume of the catalyst, we propose to broaden the active temperature window by splitting the LNT along the exhaust line. In order to design this architecture, a complete 1D model of NOx trap has been developed. Validated with respect to experimental data, this model has been useful to define the two volumes of LNT, making significant savings on the test bench exploitation. However, one of the main difficulties to operate the proposed architecture is the NOx purge and sulfur poisoning management. In order to optimize the NOx and sulfur purge launches, we have developed a control strategy based on an embedded reduced LNT model. These strategies have been validated on different driving cycles, by the means of simulation and of vehicle tests using rapid prototyping tools.
Journal Article

Effects of Methane/Hydrogen Blends On Engine Operation: Experimental And Numerical Investigation of Different Combustion Modes

2010-10-25
2010-01-2165
The introduction of alternative fuels is crucial to limit greenhouse gases. CNG is regarded as one of the most promising clean fuels given its worldwide availability, its low price and its intrinsic properties (high knocking resistance, low carbon content...). One way to optimize dedicated natural gas engines is to improve the CNG slow burning velocity compared to gasoline fuel and allow lean burn combustion mode. Besides optimization of the combustion chamber design, hydrogen addition to CNG is a promising solution to boost the combustion thanks to its fast burning rate, its wide flammability limits and its low quenching gap. This paper presents an investigation of different methane/hydrogen blends between 0% and 40 vol. % hydrogen ratio for three different combustion modes: stoichiometric, lean-burn and stoichiometric with EGR.
Journal Article

Computational Fluid Dynamics Calculations of Turbocharger's Bearing Losses

2010-05-05
2010-01-1537
Fuel consumption in internal combustion engines and their associated CO2 emissions have become one of the major issues facing car manufacturers everyday for various reasons: the Kyoto protocol, the upcoming European regulation concerning CO2 emissions requiring emissions of less than 130g CO2/km before 2012, and customer demand. One of the most efficient solutions to reduce fuel consumption is to downsize the engine and increase its specific power and torque by using turbochargers. The engine and the turbocharger have to be chosen carefully and be finely tuned. It is essential to understand and characterise the turbocharger's behaviour precisely and on its whole operating range, especially at low engine speeds. The characteristics at low speed are not provided by manufacturers of turbochargers because compressor maps cannot be achieve on usual test bench.
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