Search Results

Recent field data have shown that the occupant protection in vehicle rear seats failed to keep pace with advances in the front seats likely due to the lack of advanced safety technologies. The objective of this study was to optimize advanced restraint systems for protecting rear seat occupants with a range of body sizes under different frontal crash pulses. Three series of sled tests (baseline tests, advanced restraint trial tests, and final tests), MADYMO model validations against a subset of the sled tests, and design optimizations using the validated models were conducted to investigate rear seat occupant protection with 4 Anthropomorphic Test Devices (ATDs) and 2 crash pulses.

This paper presents a review on pedestrian impact reconstruction methodology and offers a comprehensive review of the literature. Several types of analyses are discussed which can be used to reconstruct the accident scenario using the facts collected from the scene. Inclusive in this review is the utilization of skid mark analysis, debris analysis, injury/damage match-up, trajectory analysis, nighttime visibility, and alcohol effects. The pedestrian impact reconstruction methodology is illustrated with a real world case example to point out different observations which can provide insight into the pedestrian/vehicle collision reconstruction approach. The literature review provides a broad foundation of information on pedestrian impact reconstruction and can be used to supplement the techniques presented in this paper in areas related to pedestrian impact. Research advances in the area of pedestrian impact reconstruction are also discussed in this paper.

For over 30 years, field research and laboratory testing has consistently demonstrated that proper utilization of a seat belt dramatically reduces the risk of occupant death or serious injury in motor vehicle crashes. The injury prevention benefits of seat belts require that they remain fastened during collisions. Federal Motor Vehicle Safety Standards and SAE Recommended Practices set forth seat belt requirements to ensure proper buckle performance in accident conditions. Numerous analytical and laboratory studies have investigated buckle inertial release properties. Studies have repeatedly demonstrated that current buckle designs have inertial release thresholds well above those believed to occur in real-world crashes. Nevertheless, inertial release theories persist. Various conceptual amplification theories, coupled with high magnitude accelerations measured on vehicle frame components are used as support for these release theories.

An automated process was developed for the calibration of numerical aftertreatment models. The chemical kinetic mechanism examined in this case was part of a simplified SCR model. The process adopted for calibrating the SCR model was based on a micro-population multi-objective genetic algorithm. The algorithm developed was used to calibrate the SCR model using data derived from another, more detailed model to ensure that the evaluation focused only on the effectiveness of the calibration process and was not affected by issues of experimental inaccuracies or details of the model chemistry involved.

Four of these Particulate Reduction Systems (PMS) were tested on a passenger car and one of them on a HDV. Expectation of the research team was that they would reach at least a PM-reduction of 30% under all realistic operating conditions. The standard German filter test procedure for PMS was performed but moreover, the response to various operating conditions was tested including worst case situations. Besides the legislated CO, NOx and PM exhaust-gas emissions, also the particle count and NO2 were measured. The best filtration efficiency with one PMS was indeed 63%. However, under critical but realistic conditions filtration of 3 of 4 PMS was measured substantially lower than the expected 30 %, depending on operating conditions and prior history, and could even completely fail. Scatter between repeated cycles was very large and results were not reproducible. Even worse, with all 4 PMS deposited soot, stored in these systems during light load operation was intermittently blown-off.

Exhaust gas recirculation, fuel injection strategy and boost pressure are among the key enablers to attain low NOx and soot emissions simultaneously on modern diesel engines. In this work, the individual influence of these parameters on the emissions are investigated independently for engine loads up to 8 bar IMEP. A single-shot fuel injection strategy has been deployed to push the diesel cycle into low temperature combustion with EGR. The results indicated that NOx was a stronger respondent to injection pressure levels than to boost when the EGR ratio is relatively low. However, when the EGR level was sufficiently high, the NOx was virtually grounded and the effect of boost or injection pressure becomes irrelevant. Further tests indicated that a higher injection pressure lowered soot emissions across the EGR sweeps while the effect of boost on the soot reduction appeared significant only at higher soot levels.

How can car designers evaluate device’s position inside a car today? Today only subjective tests or “reachability” tests are made to assess if a generic user is able to reach devices, but it’s no longer enough. The aim of this study is to identify an instrument (index) that is able to provide a numerical information about the discomfort level connected with a posture that is kept inside a car to reach a device, by this instrument it should be possible not only judge a posture, but also compare different solutions and get rapid and accurate evaluations. In the state of the art there are many indexes developed to evaluate postural comfort (like RULA, REBA and LUBA [3, 4, 5]) but none of them has been realized to evaluate postures’ conditions that can be detected inside a car, so their evaluations cannot be acceptable.

Engine operating strategies typically geared towards higher fuel economy and lower NOx widely affect exhaust composition and temperature. These exhaust variables critically drive the performance of After Treatment (AT) components, and hence should guide their screening and selection. Towards this end, the effect of H2 level in diesel exhaust on the performance of a Diesel Oxidation Catalyst (DOC) was studied using flow reactor experiments, vehicle emission measurements and mathematical models. Vehicle chassis dynamometer data showed that exhaust from light-duty and heavy-duty diesel trucks contained very little to almost no H2 (FTP average CO/H2 ∼ 40 to 70) as compared to that of a gasoline car exhaust (FTP average CO/H2 ∼ 3). Two identical flow reactor experiments, one with H2 (at CO/H2 ∼ 3) and another with no H2 in the feed were designed to screen DOCs under simulated feed gas conditions that mimicked these two extremes in the exhaust H2 levels.

Selective catalytic reduction (SCR) is allowing diesel engines to reach NOx emission levels which are unachievable in-cylinder. This technology is still evolving, and new catalyst formulations which provide higher performance and greater durability continue to be developed. Usually, their performance is measured on a flow reactor using ammonia as the reductant. However, in mobile applications a urea-water solution is used instead, and urea decomposition by thermolysis and hydrolysis provides the required ammonia to the catalyst. It is well known that urea decomposition is incomplete by the inlet face of the converter, and this is at least one reason why on-engine performance is generally lower than would be expected from reactor tests. Previous modeling of urea-water droplets has focused on developing detailed sub-models that can be implemented into computational fluid dynamics (CFD) codes.

Empirical models for engine-out oxides of Nitrogen (NOx) and smoke emissions have been developed for the purpose of minimizing transient emissions while maintaining transient response. Three major issues have been addressed: data acquisition, data processing and modeling method. Real and virtual transient parameters have been identified for acquisition. Accounting for the phase shift between transient engine events and transient emission measurements has been shown to be very important to the quality of model predictions. Several methods have been employed to account for the transient transport delays and sensor lags which constitute the phase shift. Finally several different empirical modeling methods have been used to determine the most suitable modeling method for transient emissions. These modeling methods include several kinds of neural networks, global regression and localized regression.

A production version of a V-8 engine was redesigned to run on partially premixed charge compression ignition (PCCI) combustion mode with conventional diesel fuel. The objective of the PCCI combustion experiments was to obtain low engine-out nitrogen oxide (NOx) and after-treatment tolerant soot emission level. Two fuel injection strategies were used during the PCCI combustion experiments: a) pilot-with-main injection strategy (Pil-M), b) pilot-with-main-and-post (PMP) injection strategy. In the Pil-M injection strategy, a significant fraction of the fuel was delivered early during the compression stroke. The early pilot helped to prepare a lean-mixture of enhanced homogeneity before the combustion was initiated. The combustion of this pilot injection followed by the main combustion helped to reduce soot for a constant NOx value. The pilot-injection timing and quantity had to be selected appropriately to retain the fuel-efficiency.

A promising SCR-only solution is presented to meet post-2010 NOx emission targets for heavy duty applications. The proposed concept is based on an engine from a EURO IV SCR application, which is considered optimal with respect to fuel economy and costs. The addition of advanced SCR after treatment comprising a standard and a close-coupled SCR catalyst offers a feasible emission solution, especially suited for EURO VI. In this paper, results of a simulation study are presented. This study concentrates on optimizing SCR deNOx performance. Simulation results of cold start FTP and WHTC test cycles are presented to demonstrate the potential of the close-coupled SCR concept. Comparison with measured engine out emissions of an EGR engine shows that a close-coupled SCR catalyst potentially has NOx reduction performance as good as EGR. Practical issues regarding the use of an SCR catalyst in close-coupled position will be addressed, as well as engine and exhaust layout.

Selective Catalytic Reduction (SCR) catalysts have been demonstrated as effective for controlling NOx emissions from diesel engines, maintaining high NOx conversion even after the extended high temperature exposure encountered in systems with active filter regenerations. As future diesel emission regulations are expected to be further reduced, packaging a large volume of SCR catalysts in diesel exhaust systems, along with DOC and particulate filter catalysts, will be challenging. One method to reduce the total volume of catalysts in diesel exhaust systems is to combine the SCR and DPF catalysts by coating SCR catalyst technology on particulate filters. In this work, engine evaluation of SCR coated filters has been conducted to determine the viability of the technology. Steady-state engine evaluations demonstrated that high NOx conversions can be achieved for SCR coated filters after high temperature oven aging.

A laboratory study was performed to optimize a zoned configuration of an iron (Fe) SCR catalyst and a copper (Cu) SCR catalyst in order to provide high NOx conversion at lean A/F ratios over a broad range of temperature for diesel and lean-burn gasoline applications. With an optimized space velocity of 8,300 hr-1, a 67% (by volume) Fe section followed by a 33% Cu section provided at least 80% NOx conversion from approximately 230°C to 640°C when evaluated with 500 ppm NO and NH3. To improve the lean lightoff performance of the SCR catalyst system during a cold start, a Cu SCR catalyst that was 1/4 as long as the rear Cu SCR catalyst was placed in front of the Fe SCR catalyst. When evaluated with an excess of NH3 (NH3/NO ratio of 2.2), the Cu+Fe+Cu SCR system had significantly improved lightoff performance relative to the Fe+Cu SCR system, although the front Cu SCR catalyst did decrease the NOx conversion at temperatures above 475°C by oxidizing some of the NH3 to N2 or NO.

Selective Catalytic Reduction (SCR) catalysts have been designed to reduce NOx with the assistance of an ammonia-based reductant. Diesel Particulate Filters (DPF) have been designed to trap and eventually oxidize particulate matter (PM). Combining the SCR function within the wall of a high porosity particulate filter substrate has the potential to reduce the overall complexity of the aftertreatment system while maintaining the required NOx and PM performance. The concept, termed Selective Catalytic Reduction Filter (SCRF) was studied using a synthetic gas bench to determine the NOx conversion robustness from soot, coke, and hydrocarbon deposition. Soot deposition, coke derived from propylene exposure, and coke derived from diesel fuel exposure negatively affected the NOx conversion. The type of soot and/or coke responsible for the inhibited NOx conversion did not contribute to the SCRF backpressure.

A laboratory study was performed to assess the effects of SO2 poisoning on the NOx conversion of iron (Fe) and copper (Cu) SCR catalysts. Thermally aged samples of the catalysts were poisoned with SO2 under lean conditions. At various times during the poisonings, the samples were evaluated for NOx conversion with NO and NH3 using lean temperature ramps. The low temperature NOx conversions of both catalysts decreased by 10 to 20% after 1 to 4 hours of poisoning but were stable with continued exposure to the SO2. The poisoned Cu SCR catalyst could be desulfated repeatedly with 5 minutes of lean operation at 600°C. Initially, the poisoned Fe SCR catalyst required 5 minutes of lean operation at 750°C to recover its maximum NOx conversion.

The Euro 6 emission standard requires a strong reduction of NOx and soot emissions for future Diesel engines. One of the ways to reach the Euro 6 standard for new Diesel engines is to adopt the low NOx combustion concept with new injection strategy, but this kind of combustion can give higher combustion noise and worse stability in transient conditions. This paper describes some of the new methodologies developed by Renault for controlling and optimizing Diesel combustion noise, particularly for engines with low NOx combustion modes. In steady working conditions, it was found that a homogeneous combustion mode gave high level of combustion excitation particularly in the 1000 Hz octave band. Thus improvement should be made in the engine structural attenuation (SA) in this frequency range in order to limit engine noise deterioration. This requires not only the technical solutions for improving the structural attenuation, but also reliable methods for measuring engine SA.

Beginning in 2007, heavy-duty engine manufacturers in the U.S. have been responsible for verifying the compliance of in-use vehicles with Not-to-Exceed (NTE) standards under the Heavy-Duty In-Use Testing Program (HDIUT). This in-use testing is conducted using Portable Emission Measurement Systems (PEMS) which are installed on the vehicles to measure emissions during field operation. A key component of the HDIUT program is the generation of measurement allowances which account for the relative accuracy of PEMS as compared to conventional laboratory-based measurement techniques. A program to determine these measurement allowances for gaseous emissions was jointly funded by the U.S. Environmental Protection Agency (EPA), the California Air Resources Board (CARB), and various member companies of the Engine Manufacturer's Association (EMA). The gaseous pollutants examined in the program were carbon monoxide (CO), non-methane hydrocarbons (NMHC), and oxides of nitrogen (NOx).

Under the U.S. Environmental Protection Agency's (EPA's) Heavy-Duty In-Use Testing (HDIUT) program, emission of non-methane hydrocarbons (NMHC), carbon monoxide (CO), and oxides of nitrogen (NOx) have been regulated using Portable Emissions Measurement Systems (PEMS) during in-use field operation for heavy-duty on-highway diesel engines with 2007 or later model year designations. As directed by the EPA, the Engine Manufacturers Association (EMA), and the California Air Resources Board (CARB), additive emission measurement accuracy margins (measurement allowances) were experimentally determined for HDIUT to account for the measurement differences between laboratory testing with laboratory grade equipment and in-use testing with PEMS. As part of a three-paper series, this paper summarizes the HDIUT measurement allowance program while focusing on the laboratory evaluations of the Sensors Inc. SEMTECH-DS PEMS.