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Technical Paper

Real-Time Estimation of the Exhaust Gas Recirculation Ratio Based on Cylinder Pressure Signals

2007-04-16
2007-01-0493
External Exhaust Gas Recirculation, EGR, is a central issue in controlling emissions in up-to-date diesel engines. An empirical model has been developed that calculates the EGR ratio as a function of the engine speed, the engine load and special characteristics of the heat release rate. It was found that three combustion characteristics correlate well with the EGR ratio. These characteristics are the ignition delay, the premixed combustion ratio and the mixing-controlled combustion ratio. The calculation of these characteristics is based on parameter subsets, which were determined using an optimization routine. The model presented was developed based on these optimized characteristics.
Technical Paper

Numerical Simulation of Zeolite- and V-Based SCR Catalytic Converters

2007-04-16
2007-01-1136
A numerical model describing the ammonia based SCR process of NOX on zeolite catalysts is presented. The model is able to simulate coated and extruded monoliths. The development of the reaction kinetics is based on a study which compares the activity of zeolite and vanadium based catalysts. This study was conducted in a microreactor loaded with washcoat powder and with crushed coated monoliths. A model for the SCR reaction kinetics on zeolite catalysts is presented. After the parameterization of the reaction mechanism the reaction kinetics were coupled with models for heat and mass transport. The model is validated with laboratory data and engine test bench measurement data over washcoated monolith catalysts. A numerical simulation study is presented, aiming to reveal the differences between zeolite and vanadium based SCR catalysts.
Technical Paper

Simulation Of NOx Storage and Reduction Catalyst: Model Development And Application

2007-04-16
2007-01-1117
To fulfill future emission standards for diesel engines, combined after-treatment systems consisting of different catalyst technologies and diesel particulate filters (DPF) are necessary. For designing and optimizing the resulting systems of considerable complexity, effective simulation models of different catalyst and DPF technologies have been developed and integrated into a common simulation environment called ExACT (Exhaust After-treatment Components Toolbox). This publication focuses on a model for the NOx storage and reduction catalyst as a part of that simulation environment. A heterogeneous, spatially one-dimensional (1D), physically and chemically based mathematical model of the catalytic monolith has been developed. A global reaction kinetic approach has been chosen to describe reaction conversions on the washcoat. Reaction kinetic parameters have been evaluated from a series of laboratory experiments.
Technical Paper

Catalyst Temperature Rise during Deceleration with Fuel Cut

2006-04-03
2006-01-0411
Automotive catalysts close coupled to gasoline engines operated under high load are frequently subjected to bed temperatures well above 950 °C. Upon deceleration engine fuel cut is usually applied for the sake of fuel economy, robustness and driveability. Even though catalyst inlet gas temperatures drop down immediately after fuel cut - catalyst bed temperatures may rise significantly. Sources for catalyst temperature rise upon deceleration with fuel cut are discussed in this contribution.
Technical Paper

Numerical Simulation of NO/NO2/NH3 Reactions on SCR-Catalytic Converters:Model Development and Applications

2006-04-03
2006-01-0468
A 1D+1D numerical model describing the ammonia based SCR process of NO and NO2 on vanadia-titania catalysts is presented. The model is able to simulate coated and extruded monoliths. Basing on a fundamental investigation of the catalytic processes a reaction mechanism for the NO/NO2 - NH3 reacting system is proposed and modeled. After the parameterization of the reaction mechanism the reaction kinetics have been coupled with models for heat and mass transport. Model validation has been performed with engine test bench experiments. Finally the model has been applied to study the influence of NO2 on SCR efficiency within ETC and ESC testcycles, Additional simulations have been conducted to identify the potential for catalyst volume reduction if NO2 is present in the inlet feed.
Technical Paper

Numerical Simulation of Ammonia SCR-Catalytic Converters: Model Development and Application

2005-04-11
2005-01-0965
A two-dimensional numerical model describing the ammonia based SCR-process on vanadia-titania catalysts is presented. The model is able to simulate coated and extruded monoliths. For the determination of the intrinsic kinetics of the various NH3-NOx reactions, unsteady microreactor experiments were used. In order to account for the influence of transport effects the kinetics were coupled with a fully transient two-phase 1D+1D monolith channel model. The model has been validated extensively with laboratory data and engine test bench measurements. After validation the model has been applied to calculate catalyst NOx conversion maps, which were used to define catalyst sizes. Additional simulations were conducted studying the influence of cell density and NH3-dosage ratio.
Technical Paper

Deactivation of TWC as a Function of Oil Ash Accumulation - A Parameter Study

2005-04-11
2005-01-1097
The oil ash accumulation on modern three way catalyst (TWC) as well as its influence on catalyst deactivation is evaluated as a parameter of oil consumption, kind of oil additive compound and additive concentration. The oil ash accumulation is characterized by XRF and SEM/EDX in axial direction and into the washcoat depth of the catalyst. The deposition patterns of Ca, Mg, P and Zn are discussed. The catalytic activity of the vehicle and engine bench aged catalysts is measured by performing model gas tests and vehicle tests, respectively. The influence of oil ash accumulation on the lifetime emission behavior of the vehicle is discussed.
Technical Paper

Catalyst Design for High Performance Engines Capable to Fulfill Future Legislation

2004-03-08
2004-01-1276
To meet future emission levels the industry is trying to reduce tailpipe emissions by both, engine measures and the development of novel aftertreatment concepts. The present study focuses on a joint development of aftertreatment concepts for gasoline engines that are optimized in terms of the exhaust system design, the catalyst technology and the system costs. The best performing system contains a close-coupled catalyst double brick arrangement using a new high thermal stable catalyst technology with low precious metal loading. This system also shows an increased tolerance against catalyst poisoning by engine oil.
Technical Paper

Lube Formulation Effects on Transfer of Elements to Exhaust After-Treatment System Components

2003-10-27
2003-01-3109
After-treatment systems (ATS) consisting of new catalyst technologies and particulate filters will be necessary to meet increasingly stringent global regulations limiting particulate matter (PM) and NOx emissions from heavy duty and light duty diesel vehicles. Fuels and lubes contain elements such as sulfur, phosphorus and ash-forming metals that can adversely impact the efficiency and durability of these systems. Investigations of the impact of lubricant formulation on the transfer of ash-forming elements to diesel particulate filters (DPF) and transfer of sulfur to NOx storage catalysts were conducted using passenger car diesel engine technology. It was observed that for ATS configurations with catalyst(s) upstream of the DPF, transfer of ash-forming elements to the DPF was significantly lower than expected on the basis of oil consumption and lube composition. Sulfur transfer strongly correlated with oil consumption and lubricant sulfur content.
Technical Paper

Aftertreatment Catalyst Design for the New DaimlerChrysler Supercharged 4-Cylinder Engine with Direct Gasoline Injection

2003-03-03
2003-01-1161
The launching of direct injection gasoline engines is currently one of the major challenges for the automotive industry in the European Union. Besides its potential for a notable reduction of fuel consumption, the engine with direct gasoline injection also offers increased power during stoichiometric and stratified operation. These advantages will most probably lead to a significant market potential of the direct injection concept in the near future. In order to meet the increasingly more stringent European emission levels (EURO IV), new strategies for the exhaust gas aftertreatment are required. The most promising technique developed in recent years, especially for NOx conversion in lean exhaust gases, is the so-called NOx storage catalyst.
Technical Paper

Model-Based Control of the VGT and EGR in a Turbocharged Common-Rail Diesel Engine: Theory and Passenger Car Implementation

2003-03-03
2003-01-0357
In this article model-based controller design techniques are investigated for the transient operation of a common-rail diesel engine in order to optimize driveability and to reduce soot emissions. The computer-aided design has benefits in reducing controller calibration time. This paper presents a nonlinear control concept for the coordinated control of the exhaust gas recirculation (EGR) valve and the variable geometry turbocharger (VGT) in a common-rail diesel engine. The overall controller structure is set up to regulate the total cylinder air-charge with a desired fresh air-charge amount by means of controlling the intake manifold pressure and estimating the fresh air-charge inducted into the cylinders. During varying engine operating conditions the two control loops are coordinated by a compensation of the EGR valve action through the VGT controller.
Technical Paper

Investigation of Post Oxidation and Its Dependency on Engine Combustion and Exhaust Manifold Design

2002-03-04
2002-01-0744
In response to ever more stringent emission limits (EURO IV, SULEV), engine developers are increasingly turning their attention to engine start-up and warm-up phases. Since in this phase the catalytic converter has not yet reached its operating temperature, problems occur especially with regard to hydrocarbon emissions (HC) which are emitted untreated. Secondary air injection represents one option for heating up the catalytic converter more quickly. The engine is operated during the heating up cycle with retarded ignition angles and a rich mixture. Ambient air (secondary air) is injected close to the exhaust valve seat. During the spontaneously occurring post oxidation phase, the reactive exhaust components ignite and heat up the catalytic converter while simultaneously reducing HC. The various processes which affect the post oxidation, are not well known up to now. In order to achieve concrete improvements, detailed knowledge of its influences are necessary.
Technical Paper

Utilization of Advanced Three-Way Catalyst Formulations on Ceramic Ultra Thin Wall Substrates for Future Legislation

2002-03-04
2002-01-0349
The LEV II and SULEV/PZEV emission standards legislated by the US EPA and the Californian ARB will require continuous reduction in the vehicles' emission over the next several years. Similar requirements are under discussion in the European Union (EU) in the EU Stage V program. These future emission standards will require a more efficient after treatment device that exhibits high activity and excellent durabilty over an extended lifetime. The present study summarizes the findings of a joint development program targeting such demanding future emission challenges, which can only be met by a close and intensive co-operation of the individual expert teams. The use of active systems, e.g. HC-adsorber or electrically heated light-off catalysts, was not considered in this study. The following parameters were investigated in detail: The development of a high-tech three-way catalyst technology is described being tailored for applications on ultra thin wall ceramic substrates (UTWS).
Technical Paper

Plasma-Enhanced Adsorption and Reduction on Lean NOx-Catalysts

2001-09-24
2001-01-3567
The influence of adsorption and desorption processes on the non-thermal plasma enhanced catalytic reduction of NOx on NaZSM5- and Al2O3-based lean-NOx catalysts (Pt-NH4ZSM5, Cu-NaZSM5, Fe-NaZSM5, Pt-Al2O3, Pd-Al2O3, CuO-Al2O3, Ag-Al2O3) was investigated by temperature programmed reaction experiments in the temperature range from 100 °C to 600 °C. Dodecane was used as a reducing agent. Strong HC adsorption- and desorption effects were observed on the zeolite catalysts, which were not influenced by plasma-pretreatment. Adsorption of NO2 and desorption of NO occurred on Al2O3-based catalysts. By plasma-pretreatment adsorption of NO2 was induced at low temperatures. NOx-reduction rates of the catalysts Cu-NaZSM5, Fe-NaZSM5, and the Ag-Al2O3 were increased substantially by plasma-pretreatment. Both plasma-induced and catalytic oxidation of HCs were limiting factors of the NOx-reduction obtained on these catalysts.
Technical Paper

Utilization of Advanced Pt/Rh TWC Technologies for Advanced Gasoline Applications with Different Cold Start Strategies

2001-03-05
2001-01-0927
This paper describes the results of a joint development program focussing on the introduction of the new generation of Pt/Rh-technology for current and future emission standards as a cost effective alternative to the in serial Pd/Rh based exhaust gas concepts. In the initial phase of the program combinations of Pd- and Pt-based three-way catalyst technologies were evaluated on vehicles equipped with a 8 cylinder engine. One goal in this portion of the study was to achieve technical equivalence between a viable Pd-based technology and the new Pt/Rh technology in the underfloor position at lower precious metal loading. A combination of a close-coupled Pd/Rh technology and the new Pt/Rh in the underfloor position was able to meet the emission targets at significant lower costs of the system after a catalyst aging that resembles more than 100.000 km of vehicle German highway driving.
Technical Paper

Potential of Common Rail Injection System for Passenger Car DI Diesel Engines

2000-03-06
2000-01-0944
The improvement of DI diesel engines for passenger cars to fulfil pollutant emission limits and lower fuel consumption and noise is closely linked to continued development of the injection system. Today's injection systems demonstrate varying potential in terms of the flexibility of injection parameters for improving mixture formation and combustion. DaimlerChrysler evaluated the potential of different injection systems, looking particularly at the distributor pump, unit injection system and Common Rail system. Based on the results of these investigations, the Common Rail system was selected. The tests presented in this paper were performed on a single-cylinder engine with Common Rail system. They focused on increased rail pressure in combination with different nozzle geometries. The results show significant benefits in NOx/smoke trade off at part load conditions with high EGR rate.
Technical Paper

Current Status and Prospects for Gasoline Engine Emission Control Technology - Paving the Way for Minimal Emissions

2000-03-06
2000-01-0856
The background for the development activities of the motor vehicle industry is strongly influenced by lawmakers, with engine development, in particular, coming under increasing pressure from the requirements of emissions legislation. Demands for CO2 reduction and thus corresponding savings in consumption contrast with regulations which call for compliance with extremely low emission levels, featuring the extreme of zero tailpipe emissions, and alternative low emission levels which make accurate measurement a problem even with current analysis technology. An example of such requirements are the SULEV limits of California law. These standards have given rise to a wide variety of emission control concepts, each of which, however, has certain limitations in its application. In the context of this general setting, the paper shows that the phase directly subsequent to cold start should be focused upon if these ambitious targets are to be reached.
Technical Paper

The Impact of High Cell Density Ceramic Substrates and Washcoat Properties on the Catalytic Activity of Three Way Catalysts

1999-03-01
1999-01-0272
The present paper describes the results of a joint development program focussing on a system approach to meet the EURO IV emission standards for an upper class passenger car equipped with a newly developed high displacement gasoline engine. Based on the well known catalyst systems of recent V6- and V8-engines for the EURO III emission standards with a combination of close coupled catalysts and underfloor catalysts, the specific boundary conditions of an engine with an even larger engine displacement had to be considered. These boundary conditions consist of the space requirements in the engine compartment, the power/torque requirements and the cost requirements for the complete aftertreatment system. Theoretical studies and computer modeling showed essential improvements in catalyst performance by introducing thin wall substrates with low thermal inertia as well as high cell densities with increased geometric surface area.
Technical Paper

Possible Exhaust Gas Aftertreatment Concepts for Passenger Car Diesel Engines with Sulphur-free Fuel

1999-03-01
1999-01-1328
In order to fulfill future emissions standards, there is a need for new exhaust-gas aftertreatment concepts, with NOx-emissions reduction in passenger car diesel engines being of particular importance. The NOx storage catalyst is one of the technologies currently under discussion with high NOx conversion potential, and which is under development at DaimlerChrysler for EURO IV standards. With this system, the nitrogen oxides contained in the diesel exhaust gas are stored under lean exhaust-gas conditions and are reduced in the catalyst through an enriched air-fuel ratio of the exhaust-gas and favorable thermal conditions. Hydrocarbons, carbon monoxide and hydrogen are used as reducing agents. DaimlerChrysler has analyzed the effect of sulphur contained in the fuel on the operation of various catalysts during laboratory and engine testing. The sulphur dioxide in the exhaust gas generates sulfates, which remain on the catalyst when nitrate compounds are regenerated briefly.
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