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Technical Paper

Fuel Vaporizer: Alternative Solution for DPF Regeneration

Current emission standards for diesel passenger cars in Europe and the US require the use of diesel particulate filters (DPF). For optimal engine performance the accumulated soot on the filter has to be removed periodically at elevated exhaust gas temperature of 600-650\,DC. Since many driving conditions do not allow such exhaust gas temperature additional measures have to be applied to increase the temperature in the exhaust. Post-injection of diesel fuel in the combustion chamber is the more common solution used to increase the exhaust temperature for particulate filter regeneration. Oil dilution is one of the drawbacks of regeneration by post-injection. The use of a fuel vaporizer is another option to increase the exhaust temperature by introducing fuel in vapor form into the exhaust system. The vaporizer can be located in front of the DOC/DPF either in a close coupled position to the engine or in an underfloor position.
Technical Paper

Methods for Determining Muffler Transmission Loss in Octave Bands

Insertion loss in one-third or octave bands is widely used in industry to assess the performance of large silencers and mufflers. However, there is no standard procedure for determining the transmission loss in one-third or octave bands using measured data or simulation. In this paper, assuming that the source is broadband, three different approaches to convert the narrowband transmission loss data into one-third and octave bands are investigated. Each method is described in detail. To validate the three different approaches, narrowband transmission loss data of a simple expansion chamber and a large bar silencer is converted into one-third and octave bands, and results obtained from the three approaches are demonstrated to agree well with one another.
Technical Paper

Possibilities and Constraints for Lightweight in Exhaust Systems

In recent years the automotive industry has been using an increasing number of high powered engines with fewer cylinders, with the goal to reduce weight and fuel consumption and hence to achieve lower CO2 emissions. In the following paper, an overview about the currently existing methods and products within the exhaust development is given which follow automotive lightweight trend. Continuous innovations in new materials, structural design and manufacturing process as well as mastering the integration of the components and modules within the system with a thorough understanding and optimization of the system behavior is enabling the reduction of weight in exhaust system. Another possibility to reduce the weight is the use of additional components such as valves. In the following, a discussion about the different types of valves is presented.
Technical Paper

Nonlinear Acoustic Analysis of Loudspeakers in the Exhaust Dynamic Sound Technology

An ongoing trend among automotive exhaust suppliers is the application of loudspeakers in their systems to tailor the exhaust sound to the customers’ needs. In addition to it, undesirable engine order noise can be cancelled by a closed loop control system. Due to the high sound pressure from the engine, the loudspeaker is often required to run at its power maximum. A higher input power eventually causes a nonlinear behavior, resulting in undesirable sound pressure level or harmonic distortion. Thus, the understanding of nonlinear behavior of loudspeakers and the recognition of dominant effects are required. This paper presents the main nonlinearities of loudspeakers and the comparison of theories on linear and non-linear loudspeaker models. For validation of the model, one loudspeaker enclosure and one typical exhaust system with a loudspeaker have been calculated.
Technical Paper

Development of an Exhaust Thermal Enhancer™ Using an Airless Nozzle Fuel System

This paper describes the development of an exhaust Thermal Enhancer™ using an airless nozzle fuel system. The purpose of the Thermal Enhancer™ is to increase diesel engine exhaust gas temperatures to a level where catalytic heating can be used for Diesel Particulate Filter regeneration. The system can also be used to achieve adequate temperatures for NOx reduction, employing techniques such as Selective Catalytic Reduction. The Thermal Enhancer™ is used to increase exhaust gas temperatures at conditions that would otherwise be too cold for effective catalyst operation. These conditions include idle and low-load operation. The airless-nozzle fuel system is necessary for engines that do not have a compressed-air system. Performance data, including hydrocarbon slip as a function of Thermal Enhancer™ outlet temperature are presented at steady state conditions. Pressure loss as a function of engine speed indicates it is less than 1 kPa at the maximum exhaust flow rate.
Journal Article

Mobility at the Development of Exhaust System

This document describes the advantages of using Mobility transfer function simulations during the development of exhaust systems. The automotive industry demands increasingly stringent levels of acceptable interior noise. The exhaust system is an important contributor to the total vehicle noise and vibration and thus is a target for noise reduction. The use of good vibration isolation systems makes it possible to decrease noise in the vehicle interior compartment. In other words, the vibratory motion in automotive structures results in tactile and acoustic responses. This occurs when the energy coming from the engine (source) is transferred by the Exhaust System (path) and then is transformed into Structural Borne Noise received by the Driver (receiver) through the hanging arrangement of the Exhaust System.
Journal Article

Waste Heat Energy Harvesting for Improving Vehicle Efficiency

Currently, in the typical internal combustion engine, approximately one third of fossil fuel combustion by-product is wasted heat. In the continued effort to improve fuel economy, one area that is being researched today is the harvesting of wasted energy to increase vehicle efficiency. This paper will address how heat emitted by exhaust systems can be captured and used to increase vehicle efficiency. Overall we will compare energy content in the exhaust manifold and exhaust underfloor mid-vehicle position, where potential exhaust heat exchanger concepts can reside. These heat exchanger concepts are designed primarily to capture heat from these locations and transfer the energy for increased passenger heating and comfort during cold conditions and/or supplement other improvements in power train efficiencies. An analysis of the energy exchange to the heated fluid is compared in the exhaust manifold and underfloor position respectively.
Journal Article

The Effect of Phase Difference between Inputs on Insertion Loss for a Two-Inlet Muffler

A recently developed superposition approach for determining the insertion loss of a two-inlet muffler is reviewed. To validate the approach, calculated and measured insertion losses are compared for a small engine muffler with two inlets and one outlet. After which, the phasing between the two inputs is varied and the insertion loss is evaluated. Results show that the insertion loss is strongly affected by the phasing between sources at low frequencies while phasing between sources has a lesser impact at high frequencies. At the conclusion of the paper, the theory for applying the superposition approach to transmission loss is reviewed.
Technical Paper

Development of the Burner Systems for EPA2010 Medium Duty Diesel Vehicles

EPA 2010 emissions regulations - currently the strictest standards in the world - place particular emphasis on exhaust gas thermal control technology. The Burner System, a device developed to control exhaust gas temperatures, is the most effective means of raising exhaust gas temperature, as this system can function under any engine conditions, including low engine speed and torque. The Burner System begins operating immediately when the engine is started, activating the Diesel Exhaust Fluid (DEF) - Selective Catalytic Reduction (SCR) System immediately, because the Burner System is active, it enables the diesel particulate filter active regeneration under any engine operating conditions as well. This technical paper reports Burner System (ActiveClean™ Thermal Regenerator) development results.
Technical Paper

Automatic Geometry Optimization of Exhaust Systems Based on Sensitivities Computed by a Continuous Adjoint CFD Method in OpenFOAM

Meeting backpressure and flow uniformity requirements within severe packaging constraints presents a particular challenge in the layout of catalyst inlet cones. In these cases, a parameterized optimization of the potentially complex cone geometries is inefficient (and inappropriate). Even assuming that a parameterization of the complex surface forms is possible, the choice of parametric shapes invariably affects the achievable results. Additionally, the long computation time for solving the flow fields limits the number of shape parameters that can be considered. To overcome these restrictions, an optimization tool has been developed at EMCON Technologies that is based on the continuous adjoint method (augmented Lagrange method) of Othmer et al. The open source CFD toolbox OpenFOAM® is used as the platform for the implementation.
Journal Article

Advanced Computational Aero-Acoustic Simulation of Complex Automotive Exhaust Systems

In the automotive sector, the time to market has become increasingly important. Consequently, powertrain systems require specific exhaust systems solutions to meet engine performance, pollutant emissions and acoustic targets delivered in a shorten time period. In this context, exhaust system suppliers need to constantly update their development process and according to project demands, tail-pipe noise has to be managed with advanced tools and methodologies. Flow generated noise has a broad band character and depending on the product design, some tonal frequencies could appear and produce a whistling noise. In order to anticipate and solve all these sound quality problems, an innovative computational aeroacoustic methodology has been developed and validated for a large range of exhaust system products.
Journal Article

Determination of Transmission and Insertion Loss for the General Multi-Inlet Multi-Outlet Case

Prior research on assessing multiple inlet and outlet mufflers is limited, and only recently have researchers begun to consider suitable metrics for multiple inlet and outlet mufflers. In this paper, transmission loss and insertion loss are defined for multiple inlet and outlet mufflers using a superposition method that can be extended to any m-inlet n-outlet muffler. Transmission loss is determined assuming that the sources and terminations are anechoic. On the other hand, insertion loss considers reflections. For both metrics, the amplitude and phase relationship between the sources should be known a priori. This paper explains both metrics, and measurement of transmission and insertion loss are demonstrated for a 2-inlet 2-outlet muffler with good agreement.
Journal Article

Evaluation and Prevention of Corrosion Risks for Light Weight Automotive Exhaust Components

The purpose of this paper is to highlight the importance of material and design selection for future light weight exhaust systems. Material validation for new components usually requires various types of tests on different types of test coupons. There are varieties of corrosion test methods which are in practice since years now. Majority of these testing approaches are used to make relative ranking among different materials. In most of these tests a correlation between testing and field behavior is missing. There is also no test available in which both external as well as internal corrosion can be realized simultaneously. Additionally, none of these corrosion tests cover the design aspects of the components. To combat this challenge Faurecia has built and validated a corrosion test setup where complete exhaust silencer can be tested near to real conditions. A comparative study was performed between field parts and test parts to validate the test cycle.
Technical Paper

Compact SCR for Passenger Cars

Stringent emissions standards (Euro 6 and Tier2Bin5) lead to the use of nitrogen oxides (NOx) aftertreatment. One of the most widespread technical solutions able to meet these legislations is Urea Selective Catalytic Reduction (Urea SCR). A urea aqueous solution is introduced into the exhaust system in order to reduce NOx over SCR catalyst. Before reaching the catalyst, the aqueous solution has to be transformed into ammonia. Current serial applications need long distances (≻ 400 mm) from injection point to SCR catalyst and a mixer apparatus to ensure sufficient mixing between exhaust gas and ammonia. Because of this distance, SCR catalyst is located far from the engine. The light-off of the catalyst is penalized and therefore the efficiency of the SCR system is low. The purpose of this paper is to show a compact mixing device able to ensure mixing in a short distance (~ 75 mm).
Technical Paper

On Using a CFD Based Global Kinetic Reaction Model to Simulate Catalyst Exotherm with Exhaust Fuel Dosing Device (Fuel Vaporizer)

Under the current emissions legislation, most of the diesel-powered vehicles have to use Diesel Particulate Filters (DPF) to remove soot particles from the exhaust gas and the accumulated soot particles have to be removed in regular intervals. To initialize the exhaust gas temperature for soot regeneration, diesel fuel is either injected into the combustion chamber in late engine cycle (e.g. post injection) or vaporized and then discharged into the exhaust gas via a dosing device (e.g. fuel vaporizer). Both approaches though require the exothermic catalyst to convert the fuel into thermal energy. For practical reasons, this paper is concentrated on describing how CFD could be used to model the fuel distribution in an aftertreatment system equipped with fuel vaporizer and the exothermic reactions in the catalysts.
Journal Article

Prediction of Life Distribution and Design Robustness of Converter Joint Durability Using CAE Techniques

A variety of parameters influence the durability of a converter to pipe joint of an automotive exhaust system. Some of the parameters are design variables and some factors are related to manufacturing. The design parameters include the thickness of the components, diameter of the pipe, sleeve length of the cone etc. While the variables like the weld penetration and the fit-up of the joint are related to manufacturing. Traditional durability simulations utilizing computer aided engineering (CAE) methods are conducted using nominal values of the design and manufacturing variables. In reality scatter and randomness in parameters are present due to the tolerance in components and limitations of the manufacturing process. In this paper a CAE based stochastic approach to determine the life distribution for a converter joint of an automotive exhaust system is presented.
Technical Paper

The Application of Solid Selective Catalytic Reduction on Heavy-Duty Diesel Engine

Urea SCR technology is the most promising technique to reduce NOx emissions from heavy duty diesel engines. 32.5wt% aqueous urea solution is widely used as ammonia storage species for the urea SCR process. The thermolysis and hydrolysis of urea produces reducing agent ammonia and reduces NOx emissions to nitrogen and water. However, the application of urea SCR technology has many challenges at low temperature conditions, such as deposits formation in the exhaust pipe, lack deNOx performance at low temperature and freezing below -12°C. For preventing deposits formation, aqueous urea solution is hardly injected into exhaust gas stream at temperature below 200°C. The aqueous urea solution used as reducing agent precursor is the main obstacle for achieving high deNOx performances at low temperature conditions. This paper presents a solid SCR technology for control NOx emissions from heavy duty diesel engines.