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The internal combustion engine and associated powertrain are likely to remain the mainstay of mobility over the next twenty years and to remain a significant portion of the portfolio of technologies employed over a much longer period of time. Efficient combustion of all fuels (petroleum based or alternative) requires copious amounts of air particularly with downsized engines. Turbocharging technology thus becomes an even more critical part of reducing both global warming gas and urban pollutant emissions from IC engines. Gasoline engine downsizing and turbocharging have been shown to improve fuel economy by ∼20% in production vehicles. In addition to data over a wide range of engines/vehicles, the results of a simple analysis done on vehicles/engines/drive cycles are presented to show the benefits of turbocharging and downsizing in a parametric variation of downsizing in combination with other technologies.

The objective of the work reported in this paper was to develop and demonstrate an injection nozzle which can be used to inject both diesel fuel and methanol in to a direct injection diesel engine. The constraints on the nozzle were that it must provide acceptable fuel metering and atomization for the diesel fuel so that the engine can be operated at rated load on diesel fuel alone, or operate at full load with the diesel fuel as a pilot for the methanol. An additional constraint was that the nozzle design was to be easily adaptable to the existing injection nozzle so that engine head modifications are not required. The initial design was evaluated in a constant volume test chamber in which the pressure was varied from atmospheric to engine compression pressures.

Methods to reduce direct injected diesel engine emissions in the combustion chamber will be discussed in this paper. The following NOx emission reduction technologies will be reviewed: charge air chilling, water injection, and exhaust gas recirculation (EGR). Emphasis will be placed on the development of an EGR system and the effect of EGR on NOx and particulates. The lower limit of NOx that can be obtained using conventional diesel engine combustion will be discussed. Further reductions in NOx may require changing the combustion process from a diffusion flame to a homogeneous charge combustion system.

During the 1980's, vegetable oils, microemulsions containing fatty alcohols as surfactants, and fatty esters have been extensively investigaed as alternative fuels to #2 diesel fuel (DF-2) used in farm tractors. Despite the importance of vegetable oils (mainly triglycerides) and fatty derivatives to the alternative fuel program, cetane numbers for pure triglycerides and many fatty derivatives were not reported. In the current study, estimated cetane numbers of these materials have been determined by use of a constant volume combustion bomb. Prior research has shown that this equipment can produce cetane numbers that correlate satisfactorily with engine cetane numbers as determied by ASTM D 613. The influence of chemical structure on ignition delay and cetane number was investigated. Evidence is presented that shows the current cetane number scale is not always suitable for these fatty materials. Suggestions are made as to what might be done to remedy this problem.

Data on several hundred family sedan production vehicles over a ten-year period are analyzed to compare turbocharged with non-turbocharged engines. It is shown that for the same power turbocharging enables gasoline engine downsizing by about 30%, improves fuel economy by 8-10% while improving torque and acceleration performance. Data with experimental turbocharged, downsized gasoline engines also shows that in the same vehicle, for the same power and performance, downsized turbocharged engines can give about 18% improvement in fuel economy. The paper discusses these data and analyzes the benefits of engine downsizing and turbocharging and the possible mechanisms of these effects. It is shown that the same basic small engine can be turbocharged using a wide range of turbocharger matching to cover a power range normally covered by 4-5 engine families of progressively increasing displacement. Thus additional benefits can be obtained by rationalizing the engine product lines.

A technology path has been identified for development of a high efficiency, durable, gasoline engine, targeted at achieving performance and emissions levels necessary to meet heavy-duty, on-road standards of the foreseeable future. Initial experimental and numerical results for the proposed technology concept are presented. This work summarizes internal research efforts conducted at Southwest Research Institute. An alternative combustion system has been numerically and experimentally examined. The engine utilizes gasoline as the fuel, with a combination of enabling technologies to provide high efficiency operation at ultra-low emissions levels. The concept is based upon very highly-dilute combustion of gasoline at high compression ratio and boost levels. Results from the experimental program have demonstrated engine-out NOx emissions of 0.06 g/hp/hr, at single-cylinder brake thermal efficiencies (BTE) above thirty-four percent.

A new combustion concept has been developed and tested for improving the low to moderate load efficiency and NOx emissions of natural gas engines. This concept involves operation of a dual-fuel natural gas engine on Homogeneous Charge Compression Ignition (HCCI) in the load regime of idle up to 35 % of the peak torque. A dual-fuel approach is used to control the combustion phasing of the engine during HCCI operation, and conventional spark-ignited natural gas combustion is used for the high-load regime. This concept has resulted in an engine with power output and high-load fuel efficiency that are unchanged from the base engine, but with a 10 - 15 % improvement to the low to moderate load fuel efficiency. In addition, the engine-out NOx emissions during HCCI operation are over 90% lower than on spark-ignited natural gas operation over the equivalent load range.

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%.

This paper reports on the fourth part of a continued study on further research and development with the automated Ignition Quality Tester (IQT™). Research over the past six years (reported in SAE papers #961182, 971636 and 1999-01-3591) has demonstrated the capabilities of this automated apparatus to measure the ignition quality and accurately determine a derived cetane number (DCN) for a wide range of middle distillate and non-conventional diesel fuels. The present paper reports on a number of separate investigations supporting these continued studies.

The engine-out emissions and fuel consumption rates for a modern, heavy-duty diesel engine were compared when fueling with a conventional diesel fuel and three water-blend-fuel emulsions. Four different fuels were studied: (1) a conventional diesel fuel, (2) PuriNOx,™ a water-fuel emulsion using the same conventional diesel fuel, but having 20% water by mass, and (3,4) two other formulations of the PuriNOx™ fuel that contained proprietary chemical additives intended to improve combustion efficiency and emissions characteristics. The emissions data were acquired with three different injection-timing strategies using the AVL 8-Mode steady-state test method in a Caterpillar 3176 engine, which had a calibration that met the 1998 nitrogen oxides (NOX) emissions standard.

Significant reductions of particulate matter (PM) and nitrogen oxides (NOx) emissions from diesel engines have been realized through fueling with water-fuel emulsions. However, the physical and chemical in-cylinder mechanisms that affect these pollutant reductions are not well understood. To address this issue, laser-based and chemiluminescence imaging experiments were performed in an optically-accessible, heavy-duty diesel engine using both a standard diesel fuel (D2) and an emulsion of 20% water, by mass (W20). A laser-based Mie-scatter diagnostic was used to measure the liquid-phase fuel penetration and showed 40-70% greater maximum liquid lengths with W20 at the operating conditions tested. At some conditions with low charge temperature or density, the liquid phase fuel may impinge directly on in-cylinder surfaces, leading to increased PM, HC, and CO emissions because of poor mixing.

An experimental investigation of the effects of partial premixed charge compression ignition (PCCI) combustion and EGR temperature was conducted on a Caterpillar C-12 heavy-duty diesel engine (HDDE). The addition of EGR and PCCI combustion resulted in significant NOx reductions over the AVL 8-mode test. The lowest weighted BSNOx achieved was 2.55 g/kW-hr (1.90 g/hp-hr) using cooled EGR and 20% port fuel injection (PFI). This represents a 54% reduction compared to the stock engine. BSHC and BSCO emissions increased by a factor of 8 and 10, respectively, compared to the stock engine. BSFC also increased by 7.7%. In general, BSHC, BSCO, BSPM, and BSFC increased linearly with the amount of port-injected fuel.

Researchers at Southwest Research Institute (SwRI) have been working for the past several years on the fundamental and practical aspects of homogeneous charge compression ignition (HCCI) operation of reciprocating engines. Much of the work has focused on the use of diesel fuel. The work at SwRI has, however, demonstrated that there are fundamental limitations on the use of current diesel fuels in HCCI engines. The results of engine and constant volume combustion bomb experiments are presented and discussed. The engine experiments were used to identify important fuel properties that must be included in a fuel specification for HCCI fuels. The primary properties relate to the distillation characteristics and the ignition characteristics. The engine test provided preliminary guidance on the distillation requirements and an indication of the important ignition requirements.

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.

Twelve different hole shapes for diesel injector tips were characterized with DF-2 diesel fuel for spray cone angle over a range of injection pressures from 21 MPa (3 kpsi) to 69 MPa (10 kpsi). A baseline and two of the most radical designs were also tested for drop-size distribution and liquid volume fraction (liquid fuel-air ratio) over a range of pressures from 41 MPa (6 kpsi) to 103 MPa (15 kpsi). All hole shapes were circular in cross-section with minimum diameters of 0.4 mm (0.016 in.), and included converging and diverging hole shapes. Overall hole lengths were constant at 2.5 mm (0.098 in.), for an L/d of 6.2. However, the effective L/d may have been less for some of the convergent and divergent shapes.

In-cylinder control of particulate emissions in a diesel engine depends on careful control and understanding of the fuel injection and air/fuel mixing process. It is extremely difficult to measure physical parameters of the injection and mixing process in an operating engine, but it is possible to simulate some diesel combustion chamber conditions in a steady flow configuration whose characteristics can be more easily probed. This program created a steady flow environment in which air-flow and injection sprays were characterized under non-combusting conditions, and emissions measurements were made under combusting conditions. A limited test matrix was completed in which the following observations were made. Grid-generated air turbulence decreased particulates, CO, and unburned hydrocarbons, while CO2 and NOx levels were increased. The turbulence accelerated combustion, resulting in more complete combustion and higher temperatures at the measurement location.

Vegetable oils are candidates for alternative fuels in diesel engines. These oils, such as soybean, sunflower, rapeseed, cottonseed, and peanut, consist of various triglycerides. The chemistry of the degradation of vegetable oils when used as alternate diesel fuels thus corresponds to that of triglycerides. To study the chemistry occurring during the precombustion phase of a vegetable oil injected into a diesel engine, a reactor simulating a diesel engine was constructed. Pure triglycerides were injected into the reactor in order to determine differences in the precombustion behavior of the various triglycerides. The reactor allowed motion pictures to be prepared of the injection event as the important reaction parameters, such as pressure, temperature, and atmosphere were varied. Furthermore, samples of the degradation products of precombusted triglycerides were collected and analyzed (gas chromatography / mass spectrometry).

A “new” concept combining existing technologies of engine downsizing, electrically assisted turbocharging and light hybrid powertrain is proposed. Published analysis of hybrid technology and data of production hybrid vehicles are used to show that much of the benefit is derived from engine downsizing. Engine downsizing results in operation more often at wider open throttle with reduced pumping work and higher efficiency conditions. Results from vehicles using turbocharged, downsized engines are used to further corroborate this conclusion. Fuel shut off during coasting and vehicle stopping/idling also contributes positively to fuel economy improvement. In a “full hybrid” configuration, electric motor and battery energy is used to compensate for engine downsizing to get high torque at low speeds. Brake energy recovery is used to charge batteries.

This paper explores the possibility of on-board fuel classification for fuel property adaptive compression-ignition engine control system. The fuel classifier is designed to on-board classify the fuel that a diesel engine is running, including alternative and renewable fuels such as bio-diesel. Based on this classification, the key fuel properties are provided to the engine control system for optimal control of in-cylinder combustion and exhaust treatment system management with respect to the fuel. The fuel classifier employs engine input-output response characteristics measured from standard engine sensors to classify the fuel. For proof-of-concept purposes, engine input-output responses were measured for three different fuels at three different engine operating conditions. Two neural-network-based fuel classifiers were developed for different classification scenarios. Of the three engine operating conditions tested, two conditions were selected for the fuel classifier to be active.

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.