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The State of California considers greenhouse gases (GHGs) to be air pollutants and has directed the Air Resources Board to adopt cost effective regulations for GHG emissions from motor vehicles. The northeastern states and Canada through NESCCAF have worked closely with CARB and CO2 equivalent emission regulations have been proposed. The eventual status of these regulations may not be clear, but what is clear is that there is a need to develop cost effective technology to reduce GHG emissions. This paper presents such technology. Advances in turbocharging technology relevant to both gasoline and diesel engines are described. Turbocharging, as a technology has been around for 70 years, but just like the internal combustion engine itself, it is far from being mature. Conventional evolutionary development of turbocharging such as inertia reduction, aerodynamics and bearing improvements have been ongoing.

Heavy-duty diesel engines face increasingly stringent emissions regulations. The trade-off between fuel economy and NOx emissions and between NOx and particulate emissions is becoming even more critical. In the light of these regulations and the trade-off among many variables, air handling and exhaust gas recirculation (EGR) systems become increasingly important. Three advanced turbocharging technologies - variable nozzle turbochargers, integral EGR pump and an ultra-high pressure ratio, long life compressor are described. In this paper an overview of the designs and their impact on fuel economy, low speed torque, emissions and durability is described. It is shown that significant improvements in all four variables are readily possible with the use of these advanced turbocharging technologies. It is shown that variable nozzle (VNT) turbocharging reduces smoke particularly at low speeds by a factor of 5, improves torque at low engine speeds and improves fuel economy by about 3%.

Heavy duty trucks account for about 50 percent of the NOx burden in urban areas and consume about 20 percent of the national transportation fuel in the United States. There is a continuing need to reduce emissions and fuel consumption. Much of the focus of current work is on engine development as a stand-alone subsystem. While this has yielded impressive gains so far, further improvement in emissions or engine efficiency is unlikely in a cost effective manner. Consequently, an integrated approach looking at the whole powertrain is required. A computer model of the heavy duty truck system was built and evaluated. The model includes both conventional and hybrid powertrains. It uses a series of interacting sub-models for the vehicle, transmission, engine, exhaust aftertreatment and braking energy recovery/storage devices. A specified driving cycle is used to calculate the power requirements at the wheels and energy flow and inefficiencies throughout the drivetrain.

Diesel engine optimization for low emissions and high efficiency involves the use of very high injection pressures. It was generally thought that increased injection pressures lead to improved fuel air mixing due to increased atomization in the fuel jet. Injection experiments in a high-pressure, high-temperature flow reactor indicated, however, that high injection pressures, in excess of 150 MPa, leads to greatly increased penetration rates and significant wall impingement. An endoscope system was used to obtain movies of combustion in a modern, 4-valve, heavy-duty diesel engine. Movies were obtained at different speeds, loads, injection pressures, and intake air pressures. The movies indicated that high injection pressure, coupled with high intake air density leads to very short ignition delay times, ignition close to the nozzle, and burning of the plumes as they traverse the combustion chamber.

The optical spark plug probe and ionization head gasket probe developed at Sandia Laboratories were applied to one cylinder of a production multicylinder automotive gasoline engine. The purpose of this application is to eventually study combustion phenomena leading to high emissions under cold start and cold idle conditions. As a first step in studying cold start combustion and emissions issues, diagnostic instrumentation was simultaneously applied to a production engine under steady state idle, road load and an intermediate load-speed condition. The preliminary application of such instrumentation is the subject of the present paper. The spark plug probe was redesigned for ease of use in production engines and to provide a more robust design. The two probes were geometrically oriented to obtain radial line-up between the optical windows and ionization probes. Data were taken simultaneously with both probes at the three load-speed conditions mentioned above.

Low intake manifold temperature, well below ambient, has many applications in internal combustion engines. In diesel engines, it can reduce NOx to a level of 2.0 g/hp-hr or below, going beyond the 1994 heavy duty diesel engine emissions standards. In gasoline engines, it can allow high compression ratio, turbocharged operation without end gas knock. This will permit ready conversion of some heavy duty diesel engines to gasoline operation at increased power density and lower emissions. In natural gas engines, it will allow base diesel engine to be converted to stoichiometric natural gas operation without increasing thermal loads. A three way catalyst can then be used to reduce emissions.

Fundamental regeneration rate data of cellular ceramic particulate traps are presented. The data were obtained from systematic bench experiments using scaled traps and simulated engine conditions. The study was conducted over a wide range of parameters, covering scaled regeneration flow rates from subidle engine flow to full flow at rated engine conditions, trap inlet temperatures from 500 to 650°C, oxygen concentrations from 5 to 21%, and particulate accumulation levels in the trap from a pressure drop ratio (relative to the clean unit) of 2 to 60. The effect of each parameter on the maximum trap temperature and regeneration time is independently studied and described. Favorable regeneration conditions in terms of minimizing the energy requirements for regeneration and avoiding trap destruction are identified. Finally, it is illustrated that regeneration maps of this type can be applied to develop a control logic for an automatic regeneration system.

Particulate and sulfate emission characteristics of two catalyzed radial- flow wire-mesh particulate traps are presented. The traps were found to be ineffective for particulate reduction. The first trap was dynamometer tested for 25 consecutive EPA Heavy Duty Diesel Transient Cycles and 40 hours of steady state operation. During steady state testing, particulates were sampled from both the raw and diluted engine exhaust. The total particulate matter was chemically analyzed for sulfate, organic, moisture, and nonextractable fractions. The data indicate significant conversion of fuel sulfur to hygroscopic sulfuric acid. Although solid carbon fraction was reduced, total particulate mass increased. Sulfuric acid condensation presented operational and particulate sampling difficulties. Sampling from the raw exhaust with heated lines showed good sulfur balance between fuel and exhaust contents, but sulfate emission also exceeded the baseline for total particulate matter.

Some results of a systematic analysis of important sources of hydrocarbon emissions from a direct injection diesel engine are presented. The following sources are considered and investigated: (1) local over-mixing, (2) poor end of injection, (3) fuel emptying from sac volume. The analysis uses systematic engine experiments and an existing two-dimensional thick evaporating spray model to determine the contribution of various hydrocarbon sources to the total hydrocarbon emissions in the exhaust. The results show that at idle and light load conditions, local overmixing is the major source of hydrocarbon emissions. The amount of fuel over-mixed is directly controlled by mixing rate, ignition delay, and the lean limit of combustion. Mixing rate calculations show that the injection rate shape and nozzle geometry are more important than the physical properties of the fuel in determining the amount of fuel overmixed.

Fundamental aspects of performance and regeneration of a porous ceramic particulate trap are described. Dimensionless correlations are given for pressure drop vs. flow conditions for clean and loaded traps. An empirical relationship between estimated particulate deposits and a loading parameter that distinguishes pressure drop changes due to flow variations from particulate accumulation is presented. Results indicate that trapping efficiencies exceed 90% under most conditions and pressure drop doubles when particulate accumulation occupies only 5% of the available void volume. Regeneration was achieved primarily by throttling the engine intake air. For various combinations of initial loading level, trap inlet temperature and oxygen concentration, it was found that regeneration rate peaked after 45 seconds from initiation.

Diesel engine exhaust and blowby gases were sampled and analyzed for nitrosamines. Tenax-GC traps were used as collection media. Three different engines were sampled. Tenax-GC material used contained significant quanities of dimethyl nitrosamine as impurities. A cleaning procedure was developed to precondition the traps. No nitrosamines were detected in either exhaust or blowby down to levels of 90 pptr and 10 pptr respectively.

Some results of a systematic study on sources of unburned hydrocarbons from direct injection diesel engines are presented. The following possible sources are considered and investigated experimentally and/or analytically: local over-mixing, local under-mixing, bulk quenching, cyclic misfire, cyclic variation, and wall effects. The significance of each source under a variety of operating conditions including simulated deceleration, light loads, high loads, and simulated acceleration are discussed. The results show that the formation of unburned hydrocarbons is mainly controlled by transient fuel-air mixing and bulk quenching processes. The fraction of fuel appearing as unburned hydrocarbons in the exhaust is greatest at light loads and retarded conditions.