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COMPARISON of work capacity per unit mass and volume of different energy carriers shows that liquid hydrocarbons are superior to other energy sources. Solar and nuclear powerplants as well as their use in conjunction with a steam engine are examined in this paper. Suitability of an electric drive is discussed. Using a production 2-stroke diesel engine and its development forecast, a comparison is made of spark ignition, diesel, and gas turbine engines. The status of the free-piston engine turbine combination is reviewed.

Meeting the California Medium-Duty truck emissions standards presents a significant challenge to automotive engineers due to the combination of sustained high temperature exhaust conditions, high flow rates and relatively high engine out emissions. A successful catalyst for an exhaust treatment system must be resistant to high temperature deactivation, maintain cold start performance and display high three-way conversion efficiencies under most operating conditions. This paper describes a catalyst technology and precious metal loading study targeting a California Medium-Duty truck LEV (MDV2) application. At the same time a direction is presented for optimizing toward the Federal Tier 1 standard through reduction of precious metal use. The paper identifies catalytic formulations for a twin substrate, 1.23 L medium-coupled converter. Two are used per vehicle, mounted 45 cm downstream of each manifold on a 5.7 L V8 engine.

As the automobiles move closer to the ULEV, ULEV-2 and SULEV requirements, OBD (on board diagnostic) will become a design challenge. The present OBD II designs involve the use of dual oxygen sensors to monitor the hydrocarbon performance of the catalytic converter. The aim of this study was twofold: to determine the interaction of fuel sulfur and ceria in the catalyst formulation on the performance of a Pd/Rh TWC (three-way catalyst) to elucidate the sulfur and ceria interaction on the ability of the Pd/Rh catalyst to monitor the state of the catalyst relative to hydrocarbon activity and therefore it's utility in the OBD system. Catalyst samples were aged on a spark ignited engine using a “fuel cut” engine aging cycle operated for 50 hours. Maximum catalyst temperatures during this aging cycle were 850-870°C. The effect of sulfur was determined by measuring aged catalyst performance using both indolene (∼100 ppm sulfur) and premium unleaded gasoline (∼350 ppm sulfur).

European car manufacturers have traditionally used Pt/Rh or Pd/Rh TWCs with PM loadings of 40-60 g/ft3. New regulations, however have stimulated interest in high Pd loadings (100 g/ft3 or more) in order to drastically reduce HC emissions. Pd is known to have good HC oxidation activity, high thermal stability and is relatively inexpensive. However, it suffers from excessive sensitivity to poisons and is usually associated with poor NOx conversion. A research program was initiated with the goal of capturing the benefits of high Pd concentrations while minimizing its disadvantages. It was found that trimetal formulations (Pt/Pd/Rh) could achieve high NOx conversions provided the loadings of the PMs were optimized based on a Box-Behnken design. Data showing the high thermal stability and low H2S emissions of these new “TriMax” catalysts will be presented. Their high performance has led to commercial acceptance by several European car manufacturers.

This study evaluated multi-layer steel and composite head gaskets of various thicknesses (0.43 to 1.5 mm) and fire-ring diameters to determine the influence of head gasket crevices on engine-out hydrocarbon (HC) emissions. The upper limit in the percent reduction in HC emissions from gasket-design modifications is estimated to be about 15%. At part-load conditions, the lowest HC emissions were measured for head-gasket thickness of about 1 mm. Significantly smaller thicknesses of the order of 0.4 mm result in an increase in HC emissions. Substantial hydrocarbon-emissions advantage may be realized by minimizing the gasket-to-cylinder bore offset.

Diesel exhaust gas dilution and odor intensity were measured in the immediate vicinity of a transit bus equipped with a rear-mounted horizontal exhaust pipe, a rear-mounted vertical exhaust pipe, and a roof-top diffusion system. Exhaust dilution ratios were measured indoors during vehicle idle operation, using propane added to the exhaust gas as a tracer. Exhaust odor intensities were measured also indoors during vehicle idle operation by a human panel, using a threshold odor measurement technique. On the average, the dilution of the exhaust gas around the bus with the vertical exhaust pipe was about eight times greater than it was with the horizontal pipe. Odor intensity, as measured by the threshold response distance, was about 35% less with the vertical pipe than with the horizontal pipe. The roof-top diffuser was not as effective as the vertical exhaust pipe in increasing exhaust gas dilution or in reducing exhaust odor intensity.

Several factors have influenced the size and design of domestic passenger cars over the past 30 years. Of most significance has been the influx of imported cars, initially from Europe, later from Japan. Interspersed within the fabric of this influx have been two energy crises and several recessions, and the onset of safety, emission, and energy regulations. These factors have led to various responses by domestic manufacturers as indicated by the types of products and vehicle systems that they have introduced during this period. This paper chronicles both the events as well as the responses.

A NOx trap catalyst was evaluated in a light-duty diesel engine bench under steady-state speed/load conditions with alternating lean and rich exhaust streams. The NOx conversion was correlated with several engine operating and control parameters, such as speed, lean / rich timing and catalyst temperature. The NOx conversion is a result of balance between stored NOx in a lean stream and the quantity of reductant applied in a rich transient pulse. The conversion is inversely proportional to the lean / rich ratio, R, (at R< 17) and engine speed. At a given speed and lean/rich ratio, the conversion is proportional to the catalyst inlet temperature. If the temperature is too high, thermal NOx release may decrease the overall NOx conversion. With a fully regenerated NOx trap catalyst, its cumulative NOx storage, at a given trapping period (or an instantaneous NOx trapping efficiency), is proportional to engine speed.

In order to meet progressively stringent regulations on particulate emission from diesel engines, GM has developed and tested a variety of trap oxidizer systems over the years. A particulate trap system for a light duty diesel engine has been selected and developed based on this experience, with particular emphasis on production feasibility. The system components have been designed and developed in collaboration with potential suppliers, to the extent possible. The technical performance of this system has been demonstrated by successful system durability testing in the test cell and vehicle experience in computer controlled automatic operation mode. Although the system shows promise, its production readiness will require more development and extensive vehicle validation under all operating conditions.

Strategic Materials at Reaction Temperatures (SMART) is an approach used to design washcoat systems for passive 4-way emission control catalysts. Light duty diesel vehicles need to meet the European Motor Vehicle Emissions Group (MVEG) cycle or U. S. Federal test procedure (FTP 75). Emissions that are monitored include hydrocarbon (HC), nitrogen oxides (NOx), carbon monoxide (CO) and total particulate matter (TPM). Low engine-exhaust temperatures (< 200°C during city driving) and high temperatures (> 500-800°C under full load and wide-open throttle) make emission control a formidable task for the catalyst designer Gas phase HC, CO and NOx reactions must be balanced with the removal of the soluble organic fraction for the vehicle to be in compliance with regulations. The SMART approach uses model gases under typical operating conditions in the laboratory to better understand the function of individual washcoat components.

A running loss test procedure has been developed which integrates a point-source collection method to measure fuel evaporative running loss from vehicles during their operation on the chassis dynamometer. The point-source method is part of a complete running loss test procedure which employs the combination of site-specific collection devices on the vehicle, and a sampling pump with sampling lines. Fugitive fuel vapor is drawn into these collectors which have been matched to characteristics of the vehicle and the test cell. The composite vapor sample is routed to a collection bag through an adaptation of the ordinary constant volume dilution system typically used for vehicle exhaust gas sampling. Analysis of the contents of such bags provides an accurate measure of the mass and species of running loss collected during each of three LA-4* driving cycles. Other running loss sampling methods were considered by the Auto-Oil Air Quality Improvement Research Program (AQIRP or Program).

The ozone forming potential (OFP) and specific reactivity (SR) of tailpipe exhaust are among the regulated factors that determine the environmental impact of a motor vehicle. OFP and SR measurements require a lengthy determination of about 160 non-methane hydrocarbon species. A rapid gas chromatography (GC) instrument has been constructed to separate both the light (C2 - C4) and the midrange (C5 - C12) hydrocarbons in less than 10 minutes. The limit of detection was about 0.002 parts per million carbon (ppmC). Twelve exhaust samples from two vehicles were analyzed to compare the rapid GC method with the standard GC method, which required 40-minute analyses on two different instruments. Speciation and reactivity data from the two methods were comparable. The increased sample throughput of rapid GC promises to improve OFP and SR measurements, particularly when good statistical data are necessary to insure accurate, precise results for low emission vehicles

Recently Volvo Car Corporation introduced the new PremAir® catalyst system from Engelhard Corporation on their S80 luxury sedan and the new V70 estate wagon. In this paper, performance results of this catalyst system after long-term mileage accumulation will be presented. Urban taxi vehicles were used to test the catalyst over 110,000 miles. The rate of deactivation in long-term catalyst performance was found to be dependent on the radiator design, and was least for the radiator design with the highest total geometric surface area. Subsequently, a new catalyst version was developed in order to minimize the deactivation rate. This new catalyst has been evaluated under similar taxi driving conditions over 80,000 miles, and has shown improved durability performance.

Traditional approaches to pollution control have been to develop benign, non-polluting processes or to abate emissions at the tailpipe or stack before release to the atmosphere. A new technology called PremAir® Catalyst Systems1 takes a different approach and directly reduces ambient, ground level ozone. For mobile applications, the new system involves coating a heat exchange device in a vehicle, such as the radiator or air conditioning condenser. The catalyst converts ozone to oxygen as ozone-containing ambient air passes over the coated surface of the radiator. The technology is relatively simple and provides a positive benefit to the environment while being totally passive to the end user application. Volvo Car Corporation was the first automobile manufacturer to voluntarily introduce the technology on their S80 luxury sedan. Nissan Motor Corporation is also using the technology on their new Sentra CA (Clean Air) certified PZEV vehicle for California.

The development of a plasma jet ignition system is described on a 4-cyl, 140 in3 engine. Performance was evaluated on the basis of combustion flame photographs in a single-cylinder engine at 20/1 A/F dynamometer tests on a modified 4-cyl engine, and cold start emissions, fuel economy, and drivability in a vehicle at 19/1 air fuel ratio. In addition to adjustable engine variables such as air-fuel ratio and spark advance, system electrical and mechanical parameters were varied to improve combustion of lean mixtures. As examples, the air-fuel ratio range was 16-22/1, secondary ignition current was varied from 40 to 6000 mA, and plasma jet cavity and electrode geometry were optimized. It is shown that the plasma jet produces on ignition source which penetrates the mixture ahead of the initial flame front and reduces oxides of nitrogen emission, in comparison to a conventional production combustion chamber.

Base metal oxide diesel oxidation catalyst technology having low sulfate making tendencies was evaluated using the ECE R-49 Test procedure on medium and heavy duty diesel engines and found to achieve substantial reduction of particulate, gas phase HC and CO emissions. Although the engines met the current European standards, further reduction in these emissions for vehicles operated in congested urban areas, such as buses, would have a positive impact on general air quality. A study of varying fuel sulfur levels (110-770 ppm S) showed that the catalyst was effective for control of sulfate-make such that overall particulate removal in the test was not compromised. However, it was found that lower fuel sulfur levels (< 550 ppm S) gave the best results for the ECE R-49 test which places emphasis on test modes yielding the highest exhaust temperatures.

Classical approaches to pollution control have been to develop benign non-polluting processes or to abate emissions at the tailpipe or stack before emitting to the atmosphere. A new technology called PremAir™ Catalyst Systems takes a different approach and reduces the existing ground level ozone. For the automotive application, the new systems involve placing a catalytic coating on a car's radiator and air conditioner condenser. As air which contains ozone passes over the radiator and condenser, the catalyst converts the ozone into oxygen. Tests conducted on a 1991 full size passenger vehicle showed that the PremAir™ Catalyst System could convert up to 90% of the ozone passing over the radiator during a driving cycle lasting 5840 kilometers (3650 miles). The effect of ozone concentration and flow rate were determined as well as the ozone destruction rate over the coated radiator. During the 5840 kilometers of driving, the catalyst exhibited steady ozone conversion.

Catalytic reduction of NOx from heavy duty diesel engines via addition of reductant to the exhaust is accompanied by a substantial exotherm in the catalyst bed which does not occur, for example, in a diesel oxidation catalyst. Engine tests show that thermal management in the aftertreatment system is required for optimum reductant use and maximum NOx conversion by the low-temperature (200-300°C) catalyst NSP-5, but of less importance with the high temperature (> 350°C) Catalyst A. Understanding thermal effects is also important for reconciling test results in the near-adiabatic environment of a full-sized catalyst on an engine with the near-isothermal one of a test piece in a laboratory reactor. The effects of reductant type and concentration on NOx conversion on NSP-5 were shown to result in part from non-steady state behavior of the catalyst during steady state engine operation.

Because of their relatively low particulate make, lean burn natural gas vehicles (NGV's) are a viable approach to meeting the ULEV particulate standards in urban environments where NGV's are substituted for diesel powered buses and other fleet vehicles. Our experience with oxidation catalyst technology for natural gas vehicle emissions abatement has been consistent: that palladium based catalysts maintain excellent NMHC activity and particulate reduction, but methane activity, while initially very high, decreases within the first 50 hours of operation. This paper will show that sulfur oxides at sub-ppm concentrations diminish catalyst methane activity, and that inorganic ash components from the lubricating oil (P, Zn, Ca) do not significantly contribute to the initial catalyst deactivation. Using laboratory simulations, we explore systems approaches to increasing catalyst life.

A novel process for coating and assembling metal converters utilizing precoated foil as building blocks has been developed which yields a converter capable of withstanding typical industry specified hot vibration protocols. The precoating process used here results in uniform catalyst coating distributions with coating adhesion to the foil on a par with the coatings' adhesion to ceramic substrates. FTP and MVEG vehicle emission performance of this unique precoated metal converter design versus a more conventional dip-coated metal monolith (parts with the same volume, cell density, and tri-metal catalyst coating), exhibited improved catalyst emission breakthrough efficiencies with respect to HC, CO, and NOx after two different engine-aging protocols. These advantages were observed on three different test vehicles across most phases of these driving cycles.