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Technical Paper

New ways of fluid flow control in automobiles: Experience with exhaust gas aftertreatmetn control

2000-06-12
2000-05-0299
Flow control by fluidic devices - without moving parts - offers advantages of reliability and low cost. As an example of their automobile application based on authors'' long-time experience the paper describes a fluidic valve for switching exhaust gas flow in a NOx absorber into a by-pass during regeneration phase. The unique feature here is the fluidic valve being of monostable and of axisymmetric design, integrated into the absorber body. After development in aerodynamic laboratory, the final design was tested on engine test stand and finally in a car. This proved that the performance under high temperature and pulsation existing in exhaust systems is reliable and promising. Fluidic valves require, however, close matching with aerodynamic load. To optimize the exhaust system layout for the whole load-speed range and reaching minimum counter- pressure, both the components of exhaust system and control strategy have to be properly adopted.
Technical Paper

Benefits of GTL Fuel in Vehicles Equipped with Diesel Particulate Filters

2009-06-15
2009-01-1934
Synthetic fuels are expected to play an important role for future mobility, because they can be introduced seamlessly alongside conventional fuels without the need for new infrastructure. Thus, understanding the interaction of GTL fuels with modern engines, and aftertreatment systems, is important. The current study investigates potential benefits of GTL fuel in respect of diesel particulate filters (DPF). Experiments were conducted on a Euro 4 TDI engine, comparing the DPF response to two different fuels, normal diesel and GTL fuel. The investigation focused on the accumulation and regeneration behavior of the DPF. Results indicated that GTL fuel reduced particulate formation to such an extent that the regeneration cycle was significantly elongated, by ∼70% compared with conventional diesel. Thus, the engine could operate for this increased time before the DPF reached maximum load and regeneration was needed.
Technical Paper

Springback Elimination in Structural Components by Means of Electromagnetic Forming

2009-04-20
2009-01-0803
Looking for car weight reduction related to the use of High Strength Steels (HSS) for manufacturing body-in-white components, an innovative application of the high velocity forming techniques has been developed: the Electro Magnetic (EM) calibration and elimination of the spring-back effect (sidewall curl) of High Strength Steel U-channels. Within this paper the initial tests on L and U-shaped parts will be presented. Being the mechanical stiffness the main parameter for improving the coil endurance, the prediction of the coil strains under EM forces is a basic issue, which has been addressed within this study.
Technical Paper

NOx Formation in Diesel Engines for Various Fuels and Intake Gases

1995-02-01
950213
The NO formation is essentially determined by the flame temperature. In an engine the latter depends on the composition of the fuel and the intake gas. In this study the efficiency of various NO reducing measures is analysed by means of a comparison of measurements and computations for the Most frequent operation point of a 1.9 1 DI Diesel engine. The O2 concentration, which is shown to be the dominant source of influence on the flame temperature and NO formation, is varied using synthetic gas mixtures or by EGR. The molar heat capacity of CO2 and H2O in the recirculated exhaust gas, the intake temperature and the H/C ratio in the fuel are less important for the formation of NO. Measures which reduce the NO formation increase the ignition delay and thereby the fraction of the premixed combustion. The impact of EGR on the combustion process is illustrated by high speed filming.
Technical Paper

A PDF-Based Model for Full Cycle Simulation of Direct Injected Engines

2008-06-23
2008-01-1606
In one-dimensional engine simulation programs the simulation of engine performance is mostly done by parameter fitting in order to match simulations with experimental data. The extensive fitting procedure is especially needed for emissions formation - CO, HC, NO, soot - simulations. An alternative to this approach is, to calculate the emissions based on detailed kinetic models. This however demands that the in-cylinder combustion-flow interaction can be modeled accurately, and that the CPU time needed for the model is still acceptable. PDF based stochastic reactor models offer one possible solution. They usually introduce only one (time dependent) parameter - the mixing time - to model the influence of flow on the chemistry. They offer the prediction of the heat release, together with all emission formation, if the optimum mixing time is given.
Technical Paper

Influence of Fuel Composition on NMOG-Emissions and Ozone Forming Potential

1993-10-01
932676
VOLKSWAGEN has conducted a number of investigations on a Multi Fuel Vehicle (MFV), designed for variable fuel operation, to determine the influence of fuel composition and clean fuels on exhaust emissions, mainly on ozone forming potential. Results of the tests indicate a small advantage of Phase II Reformulated Gasoline and a greater one for for methanol fuel M85, compared to today's gasoline. For M85 there is an about 25 % lower ozone forming potential. The most critical components in the exhaust of methanol fueled vehicles (M85) are unburned methanol and formaldehyde, forming more than 60 % of the total ozone forming potential. Therefore improvement of cold start and warmup driving during the first two to three minutes is of great importance, because in this time about 90 % of the mentioned components are formed.
Technical Paper

Catalytic NOx Reduction in Net Oxidizing Exhaust Gas

1990-02-01
900496
Several different possibilities will be described and discussed on the processes of reducing NOx in lean-burn gasoline and diesel engines. In-company studies were conducted on zeolitic catalysts. With lean-burn spark-ignition engines, hydrocarbons in the exhaust gas act as a reducing agent. In stationary conditions at λ = 1.2, NOx conversion rates of approx. 45 % were achieved. With diesel engines, the only promising variant is SCR technology using urea as a reducing agent. The remaining problems are still the low space velocity and the narrow temperature window of the catalyst. The production of reaction products and secondary reactions of urea with other components in the diesel exhaust gas are still unclarified.
Technical Paper

Code Coupling, a New Approach to Enhance CFD Analysis of Engines

2000-03-06
2000-01-0660
A new method for the analysis of the gas flow in an internal combustion engine has been developed. It is based on the interactive coupling between commercially available three (STAR-CD) and one dimensional (PROMO) fluid dynamics codes. With this method the detailed transient flow distribution for any engine component of interest can be calculated taking into account the overall gas dynamic interaction with other engine components. The underlying physics and numerics are outlined. A description of the coupling procedure ensuring proper communication between the two computer codes is given. Also addressed is the averaging procedure adopted at the 3D boundaries, including the influence of the 1D/3D interface placement. A first application of this new method is presented, in which the gas flow in a turbo-charged DI-diesel-engine is simulated.
Technical Paper

Fuel/Air-Ratio Measurements in Direct Injection Gasoline Sprays Using 1D Raman Scattering

2000-03-06
2000-01-0244
One dimensional Spontaneous Raman Scattering measurements (RS) have been performed in a spray (standard gasoline, one-component and multi-component model fuels) which was operated in a high-temperature, high-pressure chamber, so that realistic engine conditions have been simulated. The present work investigates under what conditions 1D-RS can be employed for fuel/air-ratio measurements in realistic DI gasoline sprays. The distance from the spray axis has been determined, til that, coming from the outside, quantitative Raman measurement are possible. The equivalence ratio has been quantified for the one component fuel close to the spray. It turns out that the measurement error depends strongly on the type of fuel. These problems are caused by the PAH (polycyclic aromatic hydrocarbon) content of the fuel, which leads to interfering laser-induced fluorescence signals.
Technical Paper

Research Results and Progress in LeaNOx II -A Co-operation for Lean NOx Abatement

2000-10-16
2000-01-2909
In a consortium of European industrial partners and research institutes, a combination of industrial development and scientific research was organised. The objective was to improve the catalytic NOx conversion for lean burn cars and heavy-duty trucks, taking into account boundary conditions for the fuel consumption. The project lasted for three years. During this period parallel research was conducted in research areas ranging from basic research based on a theoretical approach to full scale emission system development. NOx storage catalysts became a central part of the project. Catalysts were evaluated with respect to resistance towards sulphur poisoning. It was concluded that very low sulphur fuel is a necessity for efficient use of NOx trap technology. Additionally, attempts were made to develop methods for reactivating poisoned catalysts. Methods for short distance mixing were developed for the addition of reducing agent.
Technical Paper

Exhaust Gas Aftertreatment of Volkswagen FSI Fuel Stratified Injection Engines

2002-03-04
2002-01-0346
For substantial reduction of fuel consumption of their vehicle fleet, Volkswagen AG has decided to develop spark-ignition engines with direct fuel injection. To launch this new engine concept with stratified lean operation mode while at the same time meeting the stringent EU IV emission standards, it was necessary to develop a suitable exhaust gas aftertreatment system. This was achieved as part of an intensive co-operation between Volkswagen AG and OMG, formerly dmc2 Degussa Metals Catalysts Cerdec AG. The paper describes the demands for exhaust gas aftertreatment due to lean burn operation. In addition the main development steps of the exhaust gas aftertreatment system for Volkswagen FSI engines and catalyst durability over vehicle lifetime are discussed. Focus is laid on the catalyst system design and coating variations. Volkswagen developed a new closed-loop emission control management system which uses NOx-sensor signals for the first time worldwide.
Technical Paper

Effect of Cell Geometry on Emissions Performance of Ceramic Catalytic Converters

2002-03-04
2002-01-0354
More stringent emissions regulations, space limitations for catalytic converters in modern automotive applications, and new engine technologies constitute design challenges for today's engineers. In that context high cell density thinwall and ultrathinwall ceramic substrates have been designed into advanced catalytic converters. Whereas the majority of these substrates have a square cell geometry, a potential for further emissions improvement has been predicted for hexagonal cell structures. In order to verify these predictions, a ceramic substrate has been developed combining the features of high cell density, ultrathin cell walls, and hexagonal cell structure. Based on modeling data, the actual cell density and wall thickness of the hexagonal cell substrate will be defined. The performance of that substrate will be assessed by comparing experimental emissions results using two modern Volkswagen engines.
Journal Article

Analysis of Cycle-to-Cycle Variations of the Mixing Process in a Direct Injection Spark Ignition Engine Using Scale-Resolving Simulations

2016-11-16
2016-01-9048
Since the mechanisms leading to cyclic combustion variabilities in direct injection gasoline engines are still poorly understood, advanced computational studies are necessary to be able to predict, analyze and optimize the complete engine process from aerodynamics to mixing, ignition, combustion and heat transfer. In this work the Scale-Adaptive Simulation (SAS) turbulence model is used in combination with a parameterized lagrangian spray model for the purpose of predicting transient in-cylinder cold flow, injection and mixture formation in a gasoline engine. An existing CFD model based on FLUENT v15.0 [1] has been extended with a spray description using the FLUENT Discrete Phase Model (DPM). This article will first discuss the validation of the in-cylinder cold flow model using experimental data measured within an optically accessible engine by High Speed Particle Image Velocimetry (HS-PIV).
Technical Paper

European Diesel Research IDEA-Experimental Results from DI Diesel Engine Investigations

1994-10-01
941954
Within the European research programme IDEA (Integrated Diesel European Action), detailed experimental and theoretical studies of the fundamental phenomena of the Diesel engine like flow, injection, mixture formation, auto-ignition, combustion and pollutant formation were carried out to improve knowledge and to set up models for a simulation code. Because this basic research of the Diesel combustion process is very complex and cost intensive, it was carried out jointly by the JRC (Joint Research Committee), an association of European car manufacturers (Fiat, Peugeot SA, Renault, Volvo and Volkswagen). The activities were also subsidized by the Commission of the European Communities and the Swedish National Board of Technical Development. The results of the research work will support the design of even more efficient engines and the further reduction of soot and NOx emissions and will also enable the companies to reduce time and cost in developing new engines.
Technical Paper

Unregulated Exhaust Gas Components of Modern Diesel Passenger Cars

1999-03-01
1999-01-0514
In this paper the emissions of regulated and unregulated exhaust gas components of a fleet of diesel passenger cars measured at Volkswagen in the eighties are compared with the results of a new investigation on modern direct-injection diesel vehicles. The potential of improved diesel fuels to reduce emissions is also examined. The emissions of regulated exhaust gas components as well as fuel consumption have been reduced significantly in the last years as a result of the systematic further development of conventional swirl chamber engines and exhaust gas after-treatment as well as the introduction of SDI/TDI engines. As was to be expected, this has also had a positive effect on the emissions of unregulated exhaust gas components. It has been possible, for example, to reduce the polycyclic aromatic hydrocarbons adsorbed on diesel particulates by more than 95%.
Technical Paper

Research Results on Processes and Catalyst Materials for Lean NOx Conversion

1996-10-01
962041
In a joint research project between industrial companies and a number of research institutes, nitrogen oxide conversion in oxygen containing exhaust gas has been investigated according to the following procedure Basic investigations of elementary steps of the chemical reaction Production and prescreening of different catalytic material on laboratory scale Application oriented screening of industrial catalyst material Catalyst testing on a lean bum gasoline engine, passenger car diesel engines (swirl chamber and DI) and on a DI truck engine Although a number of solid body structures show nitrogen oxide reduction by hydrocarbons, only noble metal containing catalysts and transition metal exchanged zeolites gave catalytic efficiencies of industrial relevance. A maximum of 25 % NOx reduction was found in the European driving cycle for passenger cars, about 40 % for truck engines in the respective European test.
Technical Paper

Operating a Gasoline Engine at Constant low Temperature Conditions. The Influence of Different Fuel Droplet Sizes

1996-10-01
961999
This paper describes an investigation of one operating point of the transient warmup curve of a gasoline engine. Coolant liquid and oil of this engine have been cooled down to a constant low level in order to perform detailed measurements and an analysis of this particular warmup point. The influence of low coolant temperature, different pressure drop in an air assisted fuel injection system and a variation of ignition angles on specific fuel consumption, exhaust emissions, energy conversion etc. will be shown. The results show that the suggested test procedure (keeping the coolant temperature at a constant low level) provides the possibility to simulate the behaviour of an engine with air assisted fuel injection during warmup. During this warmup period it is desired to run the engine with retarded ignition timing to realize a fast catalyst warmup.
Technical Paper

In-Cylinder Measurements and Analysis on Fundamental Cold Start and Warm-up Phenomena of SI Engines

1995-10-01
952394
A recently developed Laser Raman Scattering system was applied to measure the in-cylinder air-fuel ratio and the residual gas content (via the water content) of the charge simultaneously in a firing spark-ignition engine during cold start and warm-up. It is the main objective of this work to elucidate the origin of misfires and the necessity to over-fuel at cool ambient temperatures. It turns out that the overall air-fuel ratio and residual gas content (in particular the residual water content) of the charge appear to be the most important parameters for the occurrence of misfires (without appropriate fuel enrichment), i.e., the engine behaviour from cycle to cycle becomes rather predictable on the basis of these data. An alternative explanation for the necessity to over-fuel is given.
Technical Paper

Non-intrusive Temperature Measurements during the Compression Phase of a DI Diesel Engine

1995-10-01
952461
Non-intrusive temperature measurements based on single-line laser-induced fluorescence of molecular oxygen in the transparent IDEA Diesel engine were investigated. Oxygen molecules were excited to fluorescence with a narrowband, tunable ArF excimer laser at 193 nm. The resulting fluorescence signals were recorded with an image-intensified CCD camera. The temperature increase during the compression phase of the four-cylinder direct injection Diesel engine could be evaluated from the LIF signals. In the crank angle range of the measurements, good agreement between measured and calculated temperatures (polytropic compression) was observed.
Technical Paper

Time-Resolved Analysis of Soot Formation and Oxidation in a Direct-Injection Diesel Engine for Different EGR-Rates by an Extinction Method

1995-10-01
952517
The formation of soot during the first phase and the oxidation of soot during the later phase of the combustion in a direct-injection diesel engine have been investigated in detail by an extinction method. The experiments were performed in a 1.9 l near-production high-speed four-cylinder in-line direct-injection diesel engine for passenger cars for different rates of exhaust gas recirculation (EGR) and for different fuels. The measurements result in crank angle resolved and cycle-averaged soot mass concentrations in the piston bowl and the combustion chamber. The results show that with increasing EGR-rates the amount of soot formed is increased only slightly but the amount of soot oxidized during combustion decreases significantly. This is assumed to be the main reason for the increase of soot in the exhaust gas with increasing EGR-rates.
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