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A 1990 Ford Taurus operated on reformulated gasoline was tested under three modes of malfunction: disabled heated exhaust gas oxygen (HEGO) sensor, inactive catalytic converter, and controlled misfire. The vehicle was run for four U.S. EPA UDDS driving schedule (FTP-75) tests at each of the malfunction conditions, as well as under normal operating conditions. An extensive set of emissions data were collected. In addition to the regulated emissions (HC, CO, and NOx), a detailed chemical analysis was carried out to determine the gas- and particle-phase non-regulated emissions. The effect of vehicle malfunction on gas phase emissions was significantly greater than it was on particle phase emissions. For example, CO emissions ranged from 2.57 g/mi (normal operation) to 34.77 g/mi (disable HEGO). Total HCs varied from 0.22 g/mi (normal operation) to 2.21 g/mi (blank catalyst). Emissions of air toxics (1,3-butadiene, benzene, acetaldehyde, and formaldehyde) were also significantly effected.

A flexible, easily configuration data acquisition system was designed and built for detailed studies of the steady state and dynamic properties of lean NOx traps for an engine dynamometer environment. The system is based on the industry standard VXI backplane. The overriding design philosophy was to design and develop a data acquisition system that was user friendly and could be operated easily by engine laboratory technicians, as well as by test engineers. The primary requirements guiding the design were the following: (1) the ability easily to configure, save, recall, modify, and print test configurations. (2) The ability to configure the gain, channel name, and engineering units for each analog channel. (3) The ability to trigger from one analog input channel. (4) A provision for numeric auto-incrementing of data file names. (5) The ability to save data in Excel™ compatible ASCII format. (6) The utilization of off-the shelf VXI hardware.

A proportional sampler for vehicle feedgas and tailpipe emissions has been developed that extracts a small, constant fraction of the total exhaust flow during rapid transient changes in engine speed. Heated sampling lines are used to extract samples either before or after the catalytic converter. Instantaneous exhaust mass flow is measured by subtracting the CVS dilution air volume from the total CVS volume. This parameter is used to maintain a constant dilution ratio and proportional sample. The exhaust sample is diluted with high-purity air or nitrogen and is delivered into Tedlar sample bags. These transient test cycle weighted feedgas samples can be collected for subsequent analysis of hydrocarbons and oxygenated hydrocarbon species. This “mini-diluter” offers significant advantages over the conventional CVS system. The concentration of the samples are higher than those collected from the current CVS system because the dilution ratio can be optimized depending on the fuel.

The optimized design of an exhaust emission system in terms of performance, cost, packaging, and engine control strategy will be a key part of competitively meeting future more stringent emission standards. Extensive use of vehicle experiments to evaluate design system tradeoffs is far too time consuming and expensive. Imperative to successfully meeting the challenges of future emission regulations and cost constraints is the development of an exhaust system simulation model which offers the ability to sort through major design alternatives quickly while assisting in the interpretation of experimental data. Previously, detailed catalyst models have been developed which require the specification of intricate kinetic mechanisms to determine overall catalyst performance. While yielding extremely valuable results, these models use complex numerical algorithms to solve multiple partial differential equations which are time consuming and occasionally numerically unstable.

In this study an attempt to understand and demonstrate the effects of various washcoat technologies under active and passive regeneration conditions was performed. Six different formulations, on 1.0" D. x 3.0" L. SiC wall flow filters at the laboratory level were used at various test conditions, including variable NO₂/NO ratios and O₂ concentrations. Samples were regenerated using active and passive conditions to evaluate regeneration rates and the potential impact of regeneration at the vehicle level. Results were applied to vehicle operating conditions to determine passive functionality and potential benefits. Active regenerations at 2% O₂ and 5% O₂ showed no significant difference in time to complete regeneration and soot burn rates. Active regenerations performed at 1% O₂ and 5% O₂ concentration showed that the regeneration temperature was shifted by approximately 50°C.

The purpose of this paper is to make a preliminary assessment of the potential toxicity of compounds that might be emitted from diesel vehicles using urea/SCR technology. The use of urea as a reductant in the removal of NOx from the exhaust of diesel-powered vehicles has the potential to emit at least seven thermal decomposition products and unreacted urea from the tail-pipe. These compounds include: urea, ammonia, cyanate ion, biuret, cyanuric acid, ammelide, ammeline, and melamine. The toxicity data base for these compounds, in general, is poor. In addition, there have been few, if any, studies examining the inhalation route of exposure - the most likely route of exposure for people from vehicle exhaust. The measurement and identification of these compounds from the exhaust of urea/SCR- equipped vehicles is needed to prioritize the kinds of health effects studies required to understand the toxicity of these compounds.

Future Diesel emission standards for passenger cars, light and medium duty vehicles, require the combination of a more efficient NOx reduction performance along with the opportunity to reduce the complexity and the package requirements to facilitate it. With the increasing availability of aqueous urea, DEF or AdBlue® at service stations, and improved package opportunities, the urea SCR technical solution has been demonstrated to be very efficient for NOx reduction; however the complexity in injecting and distributing the reductant remains a challenge to the industry. The traditional exhaust system contains Diesel Oxidation Catalysts (DOC), Diesel Particulate Filters (DPF) and Selective Catalytic Reduction (SCR), all require additional heat to facilitate each of their specific functions.

For urea Selective Catalytic Reduction (SCR) systems, adaptive control is of interest to provide a capability of maintaining high NOx conversion efficiency and low ammonia slip in the presence of uncertainties in the system. In this paper, the dynamics of the urea SCR system are represented by a control-oriented model which is based on a linear transfer function, with parameters dependent on engine operating conditions. The parameters are identified from input-output data generated by a high fidelity full chemistry model of the urea SCR system. The use of the full chemistry model facilitated the representation of the dynamics of stored ammonia (not a directly measurable parameter) as well as post SCR NOx and ammonia slip. A closed-loop Proportional-plus-Integral (PI) controller was first designed using the estimate of stored ammonia as a feedback signal.

For an automotive exhaust system, analytical evaluation of coatings, dual wall, multiwall, and blanket insulation methods indicated that the blanket insulation provided the best method for heat containment. An experimental vehicle was tested with and without a blanket insulation on the exhaust system over a demanding heat protection cycle. The exhaust gas, pipe wall, surrounding air, and adjacent component temperatures at 25 locations along the pipe are reported indicating reduced outer wall temperatures and good containment of the heat. A comparison of the heat lost through the exhaust system walls is presented.

Catalyzed hydrocarbon traps have shown promise in reducing cold-start tailpipe hydrocarbon emissions from gasoline powered vehicles. In this paper, we report the use of catalyzed hydrocarbon trap technology to reduce the non-methane hydrocarbon emissions from a flex-fuel vehicle that can operate on fuel mixtures ranging from pure gasoline to 85% ethanol/15% gasoline. We have found that hydrocarbon traps show a substantially greater reduction in hydrocarbon emissions when used with ethanol fuel than with gasoline. We present laboratory and vehicle test results that show that tailpipe non-methane hydrocarbon emissions from a flex-fuel vehicle can be reduced by 43% when using 85% ethanol/15% gasoline fuel and 16% when using gasoline fuel from a baseline exhaust system using a three-way catalyst. These results were obtained using a catalyzed hydrocarbon trap specifically formulated for use with ethanol fuel.

This paper quantifies typical United States in-vehicle cowl area particulate filter parameters such as temperature, humidity and environmental conditions. Secondly, United States and Germany particulate filter fleet results will be included to help quantify the effect of loading on electret nonwoven particulate filter fractional efficiency and demonstrate the amount and types of particulate matter captured. Finally the paper will address the low submicron fractional filter efficiency of a simulated production “wet and dry” plate-fin automotive evaporator core.

The exhaust blowdown pulse from each cylinder of a multi-cylinder engine propagates through the exhaust manifold and can affect the in-cylinder pressure of other cylinders which have open exhaust valves. Depending on the firing interval between cylinders connected to the same exhaust manifold, this blowdown interference can affect the exhaust stroke pumping work and the exhaust pressure during overlap, which in turn affects the residual fraction in those cylinders. These blowdown interference effects are much greater for a turbocharged engine than for one which is naturally aspirated because the volume of the exhaust manifolds is minimized to improve turbocharger transient response and because the turbines restrict the flow out of the manifolds. The uneven firing order (intervals of 90°-180°-270°-180°) on each bank of a 90° V8 engine causes the blowdown interference effects to vary dramatically between cylinders.

This paper reports on the development of a new methodology for OBD-II catalyst efficiency monitoring. Temperature measurements taken from the center of the catalyst substrate or near the exterior surface of the catalyst brick were used in conjunction with macroscopic energy balances to calculate the instantaneous rate of exothermic energy generation within the catalyst. The total calculated rate of exothermic energy release over the FTP test cycle was within 10% of the actual or theoretical value and provided a good indicator of catalyst light-off for a variety of aged catalytic converters. Normalization of the rate of exothermic energy release in the front section of the converter by the mass flow rate of air inducted through the engine was found to provide a simple yet practical means of monitoring the converter under both FTP and varying types of road driving.

A stochastic simulation based on the Monte-Carlo method was developed to re-target gap bulk density (GBD) in ceramic catalytic converters. The combined effect of manufacturing tolerances, shell spring back and thermal expansion was analyzed by this model. Shell spring back during the canning process was calculated using Finite Element Analysis (FEA). Thermal shell expansion was obtained using can deformation data from the Key-Life Test (KLT). An example of optimized GBD that provides a robust and manufacturable design is also presented.

Two types of catalysts were tested in a fleet of twenty-four 1969 vehicles, operated in customer-type urban driving regimes, on both leaded and nonleaded fuels over a period of 18 months. The two catalyst types and the converter systems chosen for this evaluation were selected on the basis of information obtained from an earlier test program involving four cars that were durability tested on a more rapid “test track mileage accumulation cycle.” Comparisons are made between the vehicles running rapid mileage accumulation and the vehicles running slower customer-type mileage accumulation. Catalyst life and system performance depreciation were relatively similar in both fleets and did not seem to be significantly affected by the method of mileage accumulation. The 24-vehicle fleet was equipped with a programmed protection system (PPS) designed to protect the catalysts from damage due to over-temperature operation. Problems with this prototype protection system are discussed.

In order to further reduce vehicle cold-start emissions, the use of catalytic converters that are “close-coupled” to the exhaust manifold is increasing. To understand the vibrational environment of close-coupled and underbody converters, a laboratory study was conducted on several passenger vehicles. Catalytic converter vibration spectra were measured on a chassis dynamometer with the vehicle operating over a variety of test conditions. Vehicle operating conditions included hard accelerations and extended steady-state speeds at distinct throttle positions over zero-percent and four-percent simulated road grades.

The requirements to produce high specific power, a high torque across a broad engine speed range and very low emissions levels have been seen as mutually exclusive in a conventional normally aspirated SI engine. Ford Motor Co in association with Cosworth Technology Ltd. have developed a port injection SI engine which achieves in excess of 63kW/ltr, a peak torque in excess of 97Nm/ltr, 92Nm/ltr between 2500rpm and 6500rpm and meets European IV and North American LEV emissions levels for the Focus ST170 in Europe and the SVT Focus in the US. To achieve the required torque across the speed range the volumetric efficiency needed to be maximized at all engine speeds. This was done by fitting continuously variable inlet valve timing, variable length intake manifold and a tuned exhaust manifold. To meet the emissions requirements, the catalyst light off time must be kept to a minimum.

Urea-selective catalytic reduction (SCR) after-treatment systems are used for reducing oxides of nitrogen (NOx) emissions in medium and heavy duty diesel vehicles. This paper addresses control-oriented modeling, starting from first-principles, of SCR after-treatment systems. Appropriate simplifications are made to yield governing equations of the Urea-SCR. The resulting nonlinear partial differential equations (PDEs) are discretized and linearized to yield a family of linear finite-dimensional state-space models of the SCR at different operating points. It is further shown that this family of models can be reduced to three operating regions. Within each region, parametric dependencies of the system on physical mechanisms are derived. Further model reduction is shown to be possible in each of the three regions resulting in a second-order linear model with sufficient accuracy.

Exhaust valve temperatures are important in the selection of valve materials, and have strong effects on borderline spark angle and pre-ignition borderline limit. In order to support analytical modeling of exhaust valve temperatures and to correlate exhaust valve temperatures as a function of engine Reynolds number, exhaust valve temperatures were mapped as a function of spark angle and engine coolant temperatures at 2000 rpm. In addition temperatures were measured at wide open throttle at 2000, 3000, and 4000 rpm. The exhaust valve temperature was expressed as a dimensionless temperature using the exhaust gas temperature and the engine coolant temperature, then the dimensionless temperature was correlated as a function of spark angle and engine Reynolds number. The results indicate that once the temperature is known at a given speed and load condition for any one cylinder, the temperature at other speed and load conditions can be reasonably estimated.

The purpose of this work is to analytically investigate automotive exhaust system noise generation and propagation phenomena. The turbulent exhaust gas flow interacts with the exhaust system structure, and as a result of this interaction, the structure vibrates and radiates noise. In the meantime, pressure wave becomes acoustic wave at its outlet. This study focuses on an exhaust system and carrying out transient fluid-structure analysis by using an explicit finite element solver that is capable of solving the Navier Stokes equations for turbulent, compressible viscous fluids as well as the field equations for solid structures in a fully coupled fashion. The time domain signals obtained from the transient analysis are post-processed to yield frequency domain data, sound pressure levels, noise source pattern as well as the selected acoustic field contour snapshots.