Vehicle Exhaust System Research Articles

Investigation of the Acoustic Performance of After Treatment Devices

There is a strong competition among automotive manufacturers to reduce the radiated noise levels. One important source is the engine exhaust where the main noise control strategy is by using efficient mufflers. Stricter vehicle noise regulations combined with various exhaust gas cleaning devices, removing space for traditional mufflers, are also creating new challenges. Thus, it is crucial to have efficient models and tools to design vehicle exhaust systems. In addition the need to reduce CO2 emissions puts requirements on the losses and pressure drop in exhaust systems. In this thesis a number of problems relevant for the design of modern exhaust systems for vehicles are addressed. First the modelling of perforated mufflers is investigated. Fifteen different configurations were modeled and compared to measurements using 1D models. The limitations of using 1D models due to 3D or non-plane wave effects are investigated. It is found that for all the cases investigated the 1D model is valid at least up to half the plane wave region. But with flow present, i.e., as in the real application the 3D effects are much less important and then normally a 1D model works well. Another interesting area that is investigated is the acoustic performance of after treatment devices. Diesel engines produce harmful exhaust emissions and high exhaust noise levels. One way of mitigating both exhaust emissions and noise is via the use of after treatment devices such as Catalytic Converters (CC), Selective Catalytic Reducers (SCR), Diesel Oxidation Catalysts (DOC), and Diesel Particulate Filters (DPF). The objective of this investigation is to characterize and simulate the acoustic performance of different types of filters so that maximum benefit can be achieved. A number of after treatment device configurations for trucks were selected and investigated.Finally, addressing the muffler design constraints, i.e., concerning space and pressure drop, a muffler optimization problem is formulated achieving the optimum muffler design through calculating the acoustic properties using an optimization technique. A shape optimization approach is presented for different muffler configurations, and the acoustic results are compared against optimum designs from the literature obtained using different optimization methods as well as design targets.

Pressure Drop Analysis of Square and Hexagonal Cellsand its Effects on the Performance of Catalytic Converters

Stringent emission regulations around the world necessitate the use of high-efficiency catalytic converters in vehicle exhaust systems. Therefore, determining the optimum geometry of the honeycomb monolith structure is necessary. This structure requires a high surface area for treating gases while maintaining a low pressure drop in the engine. In the present paper, an adapted sub-grid scale modeling is used to predict the pressure loss of square- and hexagonal-cell-shaped honeycomb monoliths. This sub-grid scale modeling represents the actual variations in the pressure drop between the inlet and outlet for various combinations of wall thickness and cell density. A comparison is made between the experimental and numerical results established in literature. The present approach is found to provide better and more comprehensive results than the single channel technique.

Prediction of Parts Temperature around Vehicle Exhaust System

Prediction of Parts Temperature around Vehicle Exhaust System

2605 自動車用排気管系の新規構造提案(DSC D&Sコンテスト)

2605 自動車用排気管系の新規構造提案(DSC D&Sコンテスト)

Lean Gasoline Engine Reductant Chemistry During Lean NOx Trap Regeneration

Lean Gasoline Engine Reductant Chemistry During Lean NOx Trap Regeneration

Ignition of Combustible Materials by Motor Vehicle Exhaust Systems - A Critical Review

Ignition of Combustible Materials by Motor Vehicle Exhaust Systems - A Critical Review

The use of multi-variate models for the prediction of heat transfer in vehicle exhaust systems

This paper describes the development of an exhaust system model based on the characterization of heat transfer in a series of 11 test sections designed to represent a range of configurations seen in production exhaust systems. These sections include variations in the wall thickness, diameter, bend angle, and radius. This work is part of a larger activity aimed at the accurate modelling of heat transfer and subsequent catalyst light-off in production exhaust systems consisting of similar geometries. For each section a range of steady state tests was performed on a dynamic test cell using a port injected gasoline engine. In each case a correlation between the observed Reynolds number Re and the Nusselt number Nu was developed. A model of the system was implemented in MATLAB—Simulink in which each pipe element was split into 25 subelements by dividing the pipe into five, both axially and radially. After each individual section had been characterized, a generic model was built that was capable of determining the relationship between the Nusselt number and the Reynolds number for previously unseen pipe geometries. Complex exhaust systems can be constructed from smaller elements of defined geometry. The modelling approach was validated using experimental data gathered from vehicle testing on a chassis dynamometer. The steady state relationship between Re and Nu allows heat transfer in the test section to be predicted over transient test cycles and demonstrates good agreement with relationships in the literature.

System modelling and analysis for design and development of a lean exhaust after-treatment system

A comprehensive system-level modelling methodology for vehicle exhaust and after-treatment system development is presented. Within the constraints required for a development vehicle equipped with a lean-burn direct-injection gasoline engine, system-level analysis was extensively applied to guide the design of the after-treatment system. The size and location of the lean nitrogen oxide (NO x) after-treatment device was determined to achieve the best trade-off between engine back pressure, catalyst light-off, and acceptable thermal ageing under high-speed and high-load conditions. In addition, various after-treatment architecture and layout concepts were efficiently evaluated and screened, requirements for after-treatment components and exhaust thermal management devices were defined, and promising technologies were recommended for further development and testing. Beyond immediate implementation in the development vehicle, several exhaust thermal management strategies (electrically heated converter, lambda split control, engine stop—start, and multiple warm-up) were explored. These technologies have been assessed individually and in combination to formulate effective thermal management strategies under fuel penalty constraints. While the specific applications described in this paper are for a lean-burn gasoline direct-injection development vehicle, the methodology is equally applicable to advanced powertrains with one or more after-treatment devices (diesel engines, alternative fuels, hybrid vehicles, etc.)

A Compact Optical Fibre Based Mid- Infrared Sensor System for Detection of High Level Carbon Dioxide Emissions in Exhaust Automotive Applications

A highly compact optical fibre based sensor system for real-time measurement of CO2 gas emissions in modern automotive exhaust is reported. The sensing principle is based on extrinsic open-path absorption spectroscopy operating in the mid-infrared wavelength range. The sensing system which comprises of low cost and compact mid-infrared components is suitable for applications in the harsh environment of the vehicle exhaust system. It has been shown that the output of developed sensor system correlates closely with the commercial analyser in respond to high concentrations of CO2 gas. The sensor system also demonstrates minimal susceptibility to cross interferences of other gases present in the exhaust system.

Surface nanocrystallization of Al-plated steel for application in the exhaust system of vehicles

Aluminum-plated or aluminized steel has been used in the exhaust system of vehicles, which exhibits a reasonably high corrosion resistance in the exhaust gas condensate environment. However, due to the inhomogeneous element distribution the outmost surface layer, which is directly exposed to the exhaust gas, is more like an aluminum layer (with little intermetallic compounds) that, though corrosion-resistant, may not be strong enough to effectively resist erosion. In this work, efforts were made to increase the service life of Al-plated or aluminized steel surface, particularly to enhance the outmost surface layer by nanocrystallization for improved resistances to corrosion, wear and corrosive wear. The entire process includes dipping steel specimens into a molten Al pool to make an Al coat, sandblasting the surface coat to generate dislocation network or cells, and recovery treatment to turn the dislocation cells into nano-sized grains. Electrochemical properties, electron work function (EWF), wear and corrosive wear of the nanocrystalline surfaces were investigated. It was demonstrated that the nanocrystalline aluminized surface exhibited improved resistances to corrosion, wear and corrosive wear.

Investigation into pedestrian exposure to near-vehicle exhaust emissions.

BackgroundInhalation of diesel particulate matter (DPM) is known to have a negative impact on human health. Consequently, there are regulations and standards that limit the maximum concentrations to which persons may be exposed and the maximum concentrations allowed in the ambient air. However, these standards consider steady exposure over large spatial and time scales. Due to the nature of many vehicle exhaust systems, pedestrians in close proximity to a vehicle's tailpipe may experience events where diesel particulate matter concentrations are high enough to cause acute health effects for brief periods of time.MethodsIn order to quantify these exposure events, instruments which measure specific exhaust constituent concentrations were placed near a roadway and connected to the mouth of a mannequin used as a pedestrian surrogate. By measuring concentrations at the mannequin's mouth during drive-by events with a late model diesel truck, a representative estimate of the exhaust constituent concentrations to which a pedestrian may be exposed was obtained. Typical breathing rates were then multiplied by the measured concentrations to determine the mass of pollutant inhaled.ResultsThe average concentration of diesel particulate matter measured over the duration of a single drive-by test often exceeded the low concentrations used in human clinical studies which are known to cause acute health effects. It was also observed that higher concentrations of diesel particulate matter were measured at the height of a stroller than were measured at the mouth of a mannequin.ConclusionDiesel particulate matter concentrations during drive-by incidents easily reach or exceed the low concentrations that can cause acute health effects for brief periods of time. For the case of a particularly well-tuned late-model year vehicle, the mass of particulate matter inhaled during a drive-by incident is small compared to the mass inhaled daily at ambient conditions. On a per breath basis, however, the mass of particulate matter inhaled is large compared to the mass inhaled at ambient conditions. Finally, it was determined that children, infants, or people breathing at heights similar to that of a passing vehicle's tailpipe may be exposed to higher concentrations of particulate matter than those breathing at higher locations, such as adults standing up.

Simulation and measurement of carbon dioxide exhaust emissions using an optical-fibre-based mid-infrared point sensor

A novel optical-fibre-based sensor for measurement of CO2 gas emission concentrations in exhaust systems of a motor vehicle is reported. The sensing principle is based on open-path direct absorption spectroscopy in the mid-infrared range. The sensor system comprises of low cost and compact mid-infrared components, which make it suitable for insertion into the exhaust system of automotive vehicles. The sensor utilizes a calcium fluoride CaF2 narrow band pass (NBP) filter for detection of CO2 gas without cross-sensitivity to other gases present in the exhaust system. Furthermore, it can be integrated into the mechanical and electronic interface systems of existing vehicles without any problems.

Mechanical Behaviour of Ceramic Beads Used as Medium for Hydroforming at Elevated Temperatures

The need of light weight construction for high efficient vehicles leads to the use of new materials like aluminium and magnesium alloys or high strength and ultra high strength steels. At elevated temperatures the formability of steel increases as the flow stresses decrease. Forming high complex geometries like chassis components or components of the exhaust system of vehicles can be done by hydroforming. The hydroforming process by oils is limited to temperatures of approximately 300 °C and brings disadvantages of possible leakage and fouling. Using granular material like small ceramic beads as medium could be an approach for hydroforming of ultra high strength steels like MS W1200 and CP W800 at temperatures up to 600 °C. The material properties of granular material are in some points similar to solid bodies, in other points similar to liquids. For understanding and simulation of the behaviour of the medium a basic characterisation of ceramic beads with different ball diameters is necessary. Powder mechanics and soil engineering give ideas for experimental setups. For the conversion of these approaches on the one hand the behaviour of the ceramic beads itself has to be characterized, on the other hand the contact between a blank and the beads have to be investigated. For the tests three different kinds of spheres with a diameter between 63 microns and 850 microns are used. In unidirectional compression test compressibility, pressure distribution in compression direction and transversal compression direction and the effect of bead fracture are investigated. The tests are carried out at different compression velocities and for multiple compressions. For determination of friction coefficients between blank and beads and determination of shear stress in bulk under compression a modified Jenike-Shear-Cell for use in universal testing machines with the possibility of hydraulic compression of the beads is built up. The gained data can be used for material modelling in ABAQUS using Mohr-Coulomb or Drucker-Prager model.

From the idea to validation in one step

In recent years, there has been a continuing and increasing trend towards shifting engineering activities from the manufacturers to the suppliers in the automotive industry. In order to handle the closely linked, constantly rising complexity in an efficient way, a new engineering concept for road vehicle exhaust systems was created by Tenneco. The relevant knowledge for the product development is captured, formalised and provided through a knowledge-based design methodology at an early stage of the development process.

The effect of platinum-rhodium active coating application in self-ignition engine on policyclic aromatic hydrocarbons concentration in exhausts

Polycyclic aromatic hydrocarbons (PAHs) are known to be mutagenic and carcinogenic group of substances. One of the most important anthropogenic source of these hydrocarbons is motorization (especially diesel engines). The most effective method of PAHs removal from exhaust gasses is using catalytic converters in vehicle exhaust systems. This paper presents results of measurements of polycyclic aromatic hydrocarbons emissions from self-ignition engine with platinum-rhodium active coating application inside.

Sound producing vehicle exhaust system

A sound producing vehicle exhaust system comprises a housing positionable over an exterior end of a vehicle tailpipe. A turbine has at least one support plate. The support plate is rotatable about a central axis of rotation with the housing and has a plurality of angular blades with interior ends coupled to the support plate for rotation there with. At least one facing disk is positioned within the housing adjacent to the turbine. A central axis is provided through the facing disk and support plate. At least one bearing pin is provided. The bearing pin rotatably couples the support plate to the facing disk. A plurality of apertures extend through the facing disk. In this manner exhaust gasses from a tailpipe will pass through the blades and create a turbine-like sound.

Comparison of Carbonaceous Aerosols in Tokyo before and after Implementation of Diesel Exhaust Restrictions

We compared the status of carbonaceous aerosols in Tokyo before and after the implementation of a diesel vehicle regulation intended to reduce the quantity of particulate carbon from diesel engines in one of the largest scale ever attempts at vehicle exhaust control. Radiocarbon (14C) in elemental carbon (EC) and total carbon (TC) were analyzed to identify fossil fuel carbonaceous particles emitted from diesel-powered vehicles. One-sided paired-month t-tests showed no distinct difference in the absolute concentrations of particles in terms of total mass (19.5 to 18.0 microg m(-3); p = 0.321), EC (3.6 to 3.3 microg m(-3); p = 0.272), and TC (6.3 to 6.2 microg m(-3); p = 0.418) for the finest particles (d(a) < 1.1 microm) after the implementation of the regulation. The ratios of the concentrations of the chemical constituents were, however, altered after the regulation. EC/TC was significantly decreased from 56.7% to 50.2% (p = 0.039). Although it was not statistically significant, the percentage of fossil carbon in EC also decreased (67.8% to 63.8%; p = 0.104). Since EC is predominantly of combustion origin, the observed decrease was likely due to the decrease in fossil EC emissions from diesel-powered vehicles. The decrease in EC/TC after the implementation of the regulation was also likely to have resulted from attachment to diesel vehicle exhaust systems of particulate filters as required as part of the regulation by the Tokyo Metropolitan Government. The EC/TC of fossil carbon of the finest particles decreased from 66.2% to 55.2% (p = 0.066), but EC/TC of biomass carbon did not decrease but rose slightly from 43.6% to 44.5% (p > 0.5). Thus, the relative ratios of components of carbonaceous aerosol particles, such as 14C, could provide a better understanding of the atmospheric pollution status, despite short-term fluctuations, than do measurements of absolute concentrations.

Measuring of exhaust gas emissions using absorption spectroscopy

This paper describes an optical fibre sensor for the detection of NOx (NO2 and NO) and CO2 in the exhaust system of a road vehicle. The measurement is based on a free path interaction zone which is interrogated using UV and NIR light guiding optical fibres and collimated lenses. Results are presented in the absorption spectra of the gases in the UV region for the NOx gases and NIR region for CO2. These demonstrate that using this method it is feasible to identify the individual CO2, NO and NO2 species as well as other gases in the exhaust system. Measurement of concentrations to the level of ten's parts per million (ppm) have been demonstrated for the NOxx gases.

Detection of carbon dioxide emissions from a diesel engine using a mid-infrared optical fibre based sensor

This paper describes an optical fibre based system suitable for monitoring the presence of carbon dioxide, “the Greenhouse gas”, in the exhaust system of a motor vehicle. Conventional automotive pollution sensors fail to meet monitoring requirements as specified by the European Commission for various reasons. The design of this sensor using low cost and compact mid-infrared components, which make it suitable for insertion into a vehicle, is discussed. The response of the sensor to carbon dioxide supplied from a cylinder in the laboratory is presented. An initial measurement of the carbon dioxide concentration in the exhaust system of a commercial diesel engine using the optical fibre sensor is also presented.

System Identification of Nonlinear Mechanical Systems Using Embedded Sensitivity Functions

A novel method of experimental sensitivity analysis for nonlinear system identification of mechanical systems is examined here. It has been shown previously that embedded sensitivity functions, which are quadratic algebraic products of frequency response function data, can be used to identify structural design modifications for reducing vibration levels. It is shown here that embedded sensitivity functions can also be used to characterize and identify mechanical nonlinearities. Embedded sensitivity functions represent the rate of change of the response with variation in input amplitude, and yield estimates of system parameters without being explicitly dependent on them. Frequency response functions are measured at multiple input amplitudes and combined using embedded sensitivity analysis to extract spectral patterns for characterizing systems with stiffness and damping nonlinearities. By comparing embedded sensitivity functions with finite difference frequency response sensitivities, which incorporate the amplitude-dependent behavior of mechanical nonlinearities, models can be determined using an inverse problem that uses system sensitivity to estimate parameters. Expressions for estimating nonlinear parameters are derived using Taylor series expansions of frequency response functions in conjunction with the method of harmonic balance for periodic signals. Using both simulated and experimental data, this procedure is applied to estimate the nonlinear parameters of a two degree-of-freedom model and a vehicle exhaust system to verify the approach.