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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

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

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

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

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.
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

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

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

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

Evaluation of an UV-Analyzer for the Simultaneous NO and NO2 Vehicle Emission Measurement

2004-06-08
2004-01-1830
For the measurement of NO and NO2 the CLD-analyzer (chemiluminescense detector) has been used for more than twenty-five years. The disadvantage of the CLD is that NO can be measured only. To obtain total NOX (NO+NO2) the exhaust gas sample has to flow through a catalytic converter, which reduces NO2 to NO. The converter has a efficiency between 90 and 100%. For precise NO and NO2 values it is an advantage to analyze NO and NO2 directly. This paper describes a new UV NOX-analyzer for the simultaneous measurement of NO and NO2. Two different configurations, for high and low concentrations, eg. CVS-bag analysis are presented. The performance of the analyzers is documented in comparison to the UV-RAS analyzer with converter for NOX [1] and the conventional CLD-analyzer. The benefits of the new analyzer compared to analyzers equipped with a converter are given in detailed test results.
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

SMART Catalyst Development Approach Applied to Automotive Diesel Application

1996-10-01
962048
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

Virtual Investigation of Real Fuels by Means of 3D-CFD Engine Simulations

2019-09-09
2019-24-0090
The reduction of both harmful emissions (CO, HC, NOx, etc.) and gases responsible for greenhouse effects (especially CO2) are mandatory aspects to be considered in the development process of any kind of propulsion concept. Focusing on ICEs, the main development topics are today not only the reduction of harmful emissions, increase of thermodynamic efficiency, etc. but also the decarbonization of fuels which offers the highest potential for the reduction of CO2 emissions. Accordingly, the development of future ICEs will be closely linked to the development of CO2 neutral fuels (e.g. biofuels and e-fuels) as they will be part of a common development process. This implies an increase in development complexity, which needs the support of engine simulations. In this work, the virtual modeling of real fuel behavior is addressed to improve current simulation capabilities in studying how a specific composition can affect the engine performance.
Technical Paper

Vw Lupo, the WorldS First 3-Liter Car

2000-11-01
2000-01-C044
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.
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.
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