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Technical Paper

A New Generation of Diesel Oxidation Catalysts

1992-10-01
922330
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

1993-03-01
930106
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

A Study of the Thermochemical Conditions in the Exhaust Manifold Using Secondary Air in a 2.0 L Engine

2002-05-06
2002-01-1676
The California LEV1 II program will be introduced in the year 2003 and requires a further reduction of the exhaust emissions of passenger cars. The cold start emissions represent the main part of the total emissions of the FTP2-Cycle. Cold start emissions can be efficiently reduced by injecting secondary air (SA) in the exhaust port making compliance with the most stringent standards possible. The thermochemical conditions (mixing rate and temperature of secondary air and exhaust gas, exhaust gas composition, etc) prevailing in the exhaust system are described in this paper. This provides knowledge of the conditions for auto ignition of the mixture within the exhaust manifold. The thus established exothermal reaction (exhaust gas post-combustion) results in a shorter time to light-off temperature of the catalyst. The mechanisms of this combustion are studied at different engine idle conditions.
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

Comparison of Different EGR Solutions

2008-04-14
2008-01-0206
This paper compares 4 different EGR systems by means of simulation in GT-Power. The demands of optimum massive EGR and fresh air rates were based on experimental results. The experimental data were used to calibrate the model and ROHR, in particular. The main aim was to investigate the influence of pumping work on engine and vehicle fuel consumption (thus CO2 production) in different EGR layouts using optimum VG turbine control. These EGR systems differ in the source of pressure drop between the exhaust and intake pipes. Firstly, the engine settings were optimized under steady operation - BSFC was minimized while taking into account both the required EGR rate and fresh air mass flow. Secondly, transient simulations (NEDC cycle) were carried out - a full engine model was used to obtain detailed information on important parameters. The study shows the necessity to use natural pressure differences or renewable pressure losses if reasonable fuel consumption is to be achieved.
Journal Article

Development and Demonstration of LNT+SCR System for Passenger Car Diesel Applications

2014-04-01
2014-01-1537
The regulations for mobile applications will become stricter in Euro 6 and further emission levels and require the use of active aftertreatment methods for NOX and particulate matter. SCR and LNT have been both used commercially for mobile NOX removal. An alternative system is based on the combination of these two technologies. Developments of catalysts and whole systems as well as final vehicle demonstrations are discussed in this study. The small and full-size catalyst development experiments resulted in PtRh/LNT with optimized noble metal loadings and Cu-SCR catalyst having a high durability and ammonia adsorption capacity. For this study, an aftertreatment system consisting of LNT plus exhaust bypass, passive SCR and engine independent reductant supply by on-board exhaust fuel reforming was developed and investigated. The concept definition considers NOX conversion, CO2 drawback and system complexity.
Technical Paper

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

1995-10-01
952356
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

Engine-Independent Exhaust Gas Aftertreatment Using a Burner Heated Catalyst

2006-10-16
2006-01-3401
Meeting current exhaust emission standards requires rapid catalyst light-off. Closed-coupled catalysts are commonly used to reduce light-off time by minimizing exhaust heat loss between the engine and catalyst. However, this exhaust gas system design leads to a coupling of catalyst heating and engine operation. An engine-independent exhaust gas aftertreatment can be realized by combining a burner heated catalyst system (BHC) with an underfloor catalyst located far away from the engine. This paper describes some basic characteristics of such a BHC system and the results of fitting this system into a Volkswagen Touareg where a single catalyst was located about 1.8 m downstream of the engine. Nevertheless, it was possible to reach about 50% of the current European emission standard EU 4 without additional fuel consumption caused by the BHC system.
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

Experimental Approach to Optimize Catalyst Flow Uniformity

2000-03-06
2000-01-0865
A uniform flow distribution at converter inlet is one of the fundamental requirements to meet high catalytic efficiency. Commonly used tools for optimization of the inlet flow distribution are flow measurements as well as CFD analysis. This paper puts emphasis on the experimental procedures and results. The interaction of flow measurements and CFD is outlined. The exhaust gas flow is transient, compressible and hot, making in-situ flow measurements very complex. On the other hand, to utilize the advantages of flow testing at steady-state and cold conditions the significance of these results has to be verified first. CFD analysis under different boundary conditions prove that - in a first approach - the flow situation can be regarded as a sequence of successive, steady-state situations. Using the Reynolds analogy a formula for the steady-state, cold test mass flow is derived, taking into account the cylinder displacement and the rated speed.
Technical Paper

Feasible Steps towards Improved Crash Compatibility

2004-03-08
2004-01-1167
Compatibility has been a research issue for many years now. It has gained more importance recently due to significant improvements in primary and secondary safety. Using a rigorous approach, combining accident research and theoretical scientific considerations, measures to improve vehicle-vehicle compatibility, with an emphasis on feasibility, were discussed. German accident research statistics showed that frontal impacts are of higher statistical significance than side impacts. Based on this and the high potential for improvement due high available deformation energy, the frontal impact configuration was identified as the most appropriate collision mode for addressing the compatibility issue. In side impacts, accident avoidance was identified as the most feasible and sensible measure. For frontal vehicle-vehicle impacts, both trucks and passenger cars were identified as opponents of high statistical significance.
Technical Paper

Gasoline HCCI/CAI on a Four-Cylinder Test Bench and Vehicle Engine - Results and Conclusions for the Next Investigation Steps

2010-05-05
2010-01-1488
Internal combustion engines with lean homogeneous charge and auto-ignition combustion of gasoline fuels have the capability to significantly reduce fuel consumption and realize ultra-low engine-out NOx emissions. Group research of Volkswagen AG has therefore defined the Gasoline Compression Ignition combustion (GCI®) concept. A detailed investigation of this novel combustion process has been carried out on test bench engines and test vehicles by group research of Volkswagen AG and IAV GmbH Gifhorn. Experimental results confirm the theoretically expected potential for improved efficiency and emissions behavior. Volkswagen AG and IAV GmbH will utilize a highly flexible externally supercharged variable valve train (VVT) engine for future investigations to extend the understanding of gas exchange and EGR strategy as well as the boost demands of gasoline auto-ignition combustion processes.
Technical Paper

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

1997-10-01
972839
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

Locally Resolved Measurement of Gas-Phase Temperature and EGR-Ratio in an HCCI-Engine and Their Influence on Combustion Timing

2007-04-16
2007-01-0182
Laser-based measurements of charge temperature and exhaust gas recirculation (EGR) ratio in an homogeneous charge compression ignition (HCCI) engine are demonstrated. For this purpose, the rotational coherent anti-Stokes Raman spectroscopy technique (CARS) was used. This technique allows temporally and locally resolved measurements in combustion environments through only two small line-of-sight optical accesses and the use of standard gasoline as a fuel. The investigated engine is a production-line four-cylinder direct-injection gasoline engine with the valve strategy modified to realize HCCI-operation. CARS-measurements were performed in motored and fired operation and the results are compared to polytropic calculations. Studies of engine speed, load, valve timing, and injection pressure were conducted showing the strong influence of charge temperature on the combustion timing.
Technical Paper

NO Laser-Induced Fluorescence Imaging in the Combustion Chamber of a Spray-Guided Direct-Injection Gasoline Engine

2004-06-08
2004-01-1918
In direct-injection gasoline (GDI) engines with charge stratification, minimizing engine-out nitrogen oxide (NOx) emission is crucial since exhaust-gas aftertreatment tolerates only limited amounts of NOx. Reduced NOx production directly lowers the frequency of energy-inefficient catalyst regeneration cycles. In this paper we investigate NO formation in a realistic GDI engine. Quantitative in-cylinder measurements of NO concentrations are carried out via laser-induced fluorescence imaging with excitation of NO (A-X(0,2) band at 248 nm), and subsequent fluorescence detection at 220-240 nm. Engine modifications were kept to a minimum in order to provide results that are representative of practical operating conditions. Optical access via a sapphire ring enabled identical engine geometry as a production line engine. The engine is operated with commercial gasoline (“Super-Plus”, RON 98).
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

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

Realizing Future Trends in Diesel Engine Development

1997-08-06
972686
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

Required Measures to Improve the Structural Interaction Potential of Passenger-Cars

2005-04-11
2005-01-1351
Compatibility has been a passive safety research issue for many years. Great advancements in secondary (passive) safety have been achieved in the last decades through focussing on the self-protection level provided by passenger cars. The next step is to consider the other vehicle involved in the collision as well. Compatibility relates to the simultaneous improvement of both self- and partner- protection. Several tests procedures have been proposed around the world to assess the compatibility of passenger cars. None are considered ready to be implemented. This paper shows that controlling vehicle front-end geometry is the most feasible step to improve both self- and partner-protection. Through this, an increase in the structural interaction potential offered by passenger cars would result. To improve structural interaction, a convergence of front-end structures, to within certain vertical limits, is necessary.
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