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Technical Paper

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

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

Vw Lupo, the WorldS First 3-Liter Car

After the success of the 4-cylinder 1.9-liter TDI and SDI direct-injection diesel engines in the Passat, Jetta and Polo classes, a new 3-cylinder TDI has been developed for use in the "Lupo 3L,' a compact car with a fuel consumption of 3 liters per 100 km. A new injection system with unit injectors, together with a fully electronically controlled engine management system featuring drive-by-wire- technology, a turbocharger with variable turbine geometry and a fully automated mechanical gearbox and clutch, for the first time ensures the potential to meet the stringent D4 exhaust emissions level and to achieve excellent fuel economy. The wheel-torque based engine and gearbox management systems optimize engine operation in terms of efficiency and emissions.
Technical Paper

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

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

Quantitative In-Cylinder NO LIF Measurements with a KrF Excimer Laser Applied to a Mass-Production SI Engine Fueled with Isooctane and Regular Gasoline

Quantitative 1-D spatially-resolved NO LIF measurements in the combustion chamber of a mass-production SI engine with port-fuel injection using a tunable KrF excimer laser are presented. One of the main advantages of this approach is that KrF laser radiation at 248 nm is only slightly absorbed by the in-cylinder gases during engine combustion and therefore it allows measurements at all crank angles. Multispecies detection turned out to be crucial for this approach since it is possible to calculate the in-cylinder temperature from the detected Rayleigh scattering and the simultaneously acquired pressure traces. Additionally, it allows the monitoring of interfering emissions and spectroscopic effects like fluorescence trapping which turned out to take place. Excitation with 248 nm yields LIF emissions at shorter wavelengths than the laser wavelength (at 237 and 226 nm).
Technical Paper

The New Diesel Engine in the New Beetle

With the introduction of the New Beetle, Volkswagen is offering the next generation of the 1.9l TDI engine. Several evolutionary changes have been made to the TDI concept to further improve its emissions, efficiency and performance. Emissions performance is improved with increased fuel injection pressure, optimized fuel injectors, calibration modifications, EGR cooling and reduced crevice volume in the combustion chamber. Efficiency is improved with new oil pump, vacuum pump and water pump drive systems and the elimination of an auxiliary driveshaft. Performance and efficiency is improved with the addition of a variable geometry turbocharger, which increases torque at lower engine speeds while preserving performance at higher engine speeds. This paper describes the many enhancements found in this latest generation TDI and gives a brief lookout to the future trends in diesel engine development such as a high pressure injection system with unit injectors.
Technical Paper

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

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

Effect of EGR on Spray Development, Combustion and Emissions in a 1.9L Direct-Injection Diesel Engine

The spray development, combustion and emissions in a 1.9L optical, four-cylinder, direct-injection diesel engine were investigated by means of pressure analysis, high-speed cinematography, the two-colour method and exhaust gas analysis for various levels of exhaust gas recirculation (EGR), three EGR temperatures (uncontrolled, hot and cold) and three fuels (diesel, n-heptane and a two-component fuel 7D3N). Engine operating conditions included 1000 rpm/idle and 2000 rpm/2bar with EGR-rates ranging from 0 to 70%. Independent of rate, EGR was found to have a very small effect on spray angle and spray tip penetration but the auto-ignition sites seemed to increase in size and number at higher EGR-rates with associated reduction in the flame luminosity and flame temperature, by, say, 100K at 50% EGR.
Technical Paper

NOx Formation in Diesel Engines for Various Fuels and Intake Gases

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

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

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.
Technical Paper

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

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

Interaction Between Gasoline Properties and Engine Management System and Effects on 3-Way Catalyst Efficiency

The EPEFE study (European Programme on Emissions, Fuels and Engine Technologies), /1/ and other programmes have identified an increase in tailpipe NOx emissions with reduced gasoline aromatics content for modern 3-way controlled catalyst vehicles. This effect occurs with fully warmed-up catalyst under closed-loop operation. In order to understand the reasons for this effect VW and Shell have mechanistically investigated the effects of fuel properties on EMS (engine management system) and catalyst performance. Fuels with independent variation of oxygen, aromatics and mid-range volatility were tested in different VW engines. λ was monitored using sensors located both pre and post catalyst. The results confirmed that reducing gasoline aromatics content reduced engine-out emissions but increased tailpipe NOx emissions. It could be shown that differences in H/C ratio led to differences in the hydrogen content of engine-out emissions which affected the reading of the λ sensor.
Technical Paper

Realizing Future Trends in Diesel Engine Development

Volkswagen is the first automobile manufacturer to supply a passenger car with a direct fuel injection diesel engine to the US market, starting 1996. To meet the stringent US exhaust gas legislation the very successful European 1.9 liter TDI engine has been further developed for the 1996 and 1997 Passat. This TD1 incorporates a number of innovations in advanced diesel technology. Emissions-reducing innovations include: reduced crevice volume higher injection pressures upgraded injection management integrated EGR manifold system EGR cooling diesel catalytic converter This TDI engine configuration is also to be offered in the 1997 Golf and Jetta class and the new Passat in model year 1998. Over the coming years the TDI engine concept will be further optimized by utilizing variations of the above innovations.
Technical Paper

Research Results on Processes and Catalyst Materials for Lean NOx Conversion

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

SMART Catalyst Development Approach Applied to Automotive Diesel Application

Strategic Materials at Reaction Temperatures (SMART) is an approach used to design washcoat systems for passive 4-way emission control catalysts. Light duty diesel vehicles need to meet the European Motor Vehicle Emissions Group (MVEG) cycle or U. S. Federal test procedure (FTP 75). Emissions that are monitored include hydrocarbon (HC), nitrogen oxides (NOx), carbon monoxide (CO) and total particulate matter (TPM). Low engine-exhaust temperatures (< 200°C during city driving) and high temperatures (> 500-800°C under full load and wide-open throttle) make emission control a formidable task for the catalyst designer Gas phase HC, CO and NOx reactions must be balanced with the removal of the soluble organic fraction for the vehicle to be in compliance with regulations. The SMART approach uses model gases under typical operating conditions in the laboratory to better understand the function of individual washcoat components.
Technical Paper

Catalytic NOx Reduction in Net Oxidizing Exhaust Gas

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

A New Generation of Diesel Oxidation Catalysts

An overview is given on the state of the art of a new catalytic exhaust gas aftertreatment device for diesel engines. The function of a precious metal based, flow-through type diesel oxidation catalyst is explained. Much attention is paid to the durability of the diesel oxidation catalyst and especially to the influence of poisoning elements on the catalytic activity. Detailed data on the interaction of poisoning elements such as sulfur, zinc and phosphorus with the catalytic active sites are given. Finally it is demonstrated that it is possible to meet the stringent emission standards for diesel passenger cars in Europe with a new catalyst generation over 80.000 km AMA aging.
Technical Paper

A New Method to Assess the Summer Suitability of Car Seats

A new method has been designed to examine car seats by technical means only, whether they fit summer conditions or not. Test procedures start with the application of a carefully wetted cloth onto the seat to be examined. The test area is then covered by a temperature controlled, electrically heated solid body bloc. This simulates the body temperature and the seat pressure of a real seat user. During test periods of standard three hours, temperature and humidity is measured beneath the test device and in the surrounding air. As an effect of the water impulse the humidity increases under the body bloc. It has been proved that good summer suitability of a car seat is characterised by moderate amount and moderate duration of increased humidity readings. Poor suitability results in higher amount and longer duration of raised humidity. The method is shown to be useful to examine full scale car seats, child safety seats and single design characteristics of car seats as well.
Technical Paper

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

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

Benefits of GTL Fuel in Vehicles Equipped with Diesel Particulate Filters

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.