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The action of exhaust gas recirculation (EGR) is examined numerically to find out whether EGR can be used to enhance the preignition reactions of a cylinder charge in a motoring, compression ignition engine fuelled with a homogeneous gaseous fuel - air mixture. The changes to the concentrations and properties of the contents of the cylinder and the associated changes in the preignition reaction rates are followed over a number of consecutive, calculated working cycles at a constant engine speed to establish whether autoignition will take place and the number of cycles required for its occurrence. It is shown that controlled EGR can enhance the autoignition processes in gas-fuelled compression ignition engines by suitably ‘seeding’ the intake charge of the current cycle with the chemical species found in the exhaust gases of the previous cycle.

For the final goal of developing the natural gas fueled spark ignition engine with high thermal efficiency and low pollutant emission, the effects of the fluid flow inside a combustion chamber on the combustion process of a homogeneous lean mixture of natural gas and air were examined using a rapid compression combustor. The rapid compression combustor was designed to simulate the combustion process in a spark ignition engine involving the rapid compression of a mixture and the heal release during flame propagation. The main advantage of using this combustor is that experiments can be made under the idealized and well-controlled conditions. The time history of pressure in the combustion cylinder was measured with a pressure transducer. The fluid flow in the combustion cylinder was varied using two kinds of experimental technique. First, compression ratio, piston speed and the configuration of the piston head were changed.

A newly-developed time resolved exhaust gas analysis system was utilized in this study. The hydrocarbon compositions upstream and downstream of the catalytic converter were investigated during cold start and warm up of the Federal Test Procedure(FTP), with three fuels of different aromatic contents. Although engine-out hydrocarbon emissions had high concentrations right after cold start, the specific reactivity was low. This can be explained by the selective adsorption of the high boiling point components which had a high Maximum Incremental Reactivity (MIR) in the intake manifold and engine-oil films. Thereafter, the high boiling point components were desorbed rapidly and consequently specific reactivity increased. Hydrocarbon adsorption of high boiling point components and hydrocarbon conversion of low boiling point components occurred simultaneously on the catalyst during warm up.

The geometry and area of the notch in the swirl control valve installed in the intake port were varied to analyze the effects on HC emissions. A swirl control valve functions to promote the formation of a homogeneous mixture, enabling the amount of liquid fuel supplied to the cylinder to be reduced. For this reason, it is difficult to obtain an added effect through the combined use of a swirl control valve and an auxiliary-air type of injector for assisting fuel atomization. Tumble (vertical swirl) flow fields are effective in shortening the combustion period. This results in a higher exhaust gas temperature at an equivalent level of combustion stability. It was thought that swirl flow fields produce residual gas flow in the cylinder after the completion of the main combustion period. It is surmised that the residual gas flow functions to diffuse and promote after-burning of the unburned HC layer.

This paper describes an investigation of emissions from an engine featuring variable valve timing, a swirlcontrol valve and exhaust gas recirculation. Design of experiments has been used to model the response of hydrocarbons and other emissions to the engine operating variables. The experiments identified the potential of VVT for simultaneous NOx, and HC reduction. The type of experiment employed was the Central Composite Rotatable Design; this is a fractional factorial design that maximises the amount of information obtained from a minimal number of test runs. A Fast Response Flame Ionisation Detector has been used to clarify the reasons for the effect of inlet and exhaust VVT on hydrocarbons.

Gasoline properties have changed over the years. The first changes were made to comply with federal and later ASTM gasoline specifications. Beginning in 1960, limitations were placed on gasoline properties to help reduce air pollution. The state of California has led the nation in limiting gasoline properties to improve ambient air quality. The Clean Air Act Amendments of 1990 increased the federal government's role in controlling the properties of gasoline. Wintertime oxygenated gasoline was introduced in 1992 in specified areas with carbon monoxide concerns. Reformulated gasoline was introduced in 1995 in areas of the United States with severe ozone concerns. The strictest control of gasoline properties to date occurred in 1996 when California Phase 2 reformulated gasoline was required.

Lubricity testing of reformulated diesel fuels (sulfur <0 005 w-%, aromatics <20 vol-%) was started in 1990. A 1000 hour in-house test rig with distributor pumps was used for testing fuels and additives. When lubricity is not adequate, excessive wear is seen in the pump. A field test on 140 buses each accumulating 150 000 - 250 000 km with reformulated diesel was carried out. Reformulated diesel has been on the market since 1993 without problems. Lubricity was evaluated with HFRR test and compared to the pump rig results. HFRR overestimated the need for lubricity additives. Fuel sulfur was found to be not the only indicator of lubricity and lubricity of low sulfur diesel was as good as high sulfur when other fuel parameters were kept constant.

Today's lubricant quality is defined by classifications, or specifications, that are established by taking into account metallurgy, equipment design, and or operating conditions For engine oils, the American Petroleum Institute (API), the Society of Automotive Engineers (SAE), and the American Society for Testing and Materials (ASTM) are the key bodies that define industry needs, establish classifications, and develop test methods to assure that lubricants meet the required performance For gear oils, API and the Coordinating Research Council (CRC) play a similar role The U S Military and original equipment manufacturers (OEMs) have their own performance requirements that are usually over and above those of the API/SAE/ASTM and API/CRC The performance requirements of automatic transmission fluids (ATFs) are established by OEMs, such as General Motors Corporation (GM) and the Ford Motor Company Greases are defined by the National Lubricating Grease Institute's (NLGI) classification system The paper follows the history of automotive lubrication from the early 1900s to date It describes the introduction and progression of classifications and specifications with changes in the lubricating environment

The effect of diesel cetane number, total aromatic content T90, and fuel nitrogen content on regulated emissions (HC, CO, NOx, and PM) from a 1991 DDC Series 60 engine were measured Emissions tests were conducted using the EPA heavy-duty transient test (CFR 40 Part 86 Subpart N) at a laboratory located 5,280 feet (1609 m) above sea level. The objective of this work was to determine if the effect of fuel chemistry at high altitude is similar to what is observed at sea level and to examine the effect of specific fuel chemistry variables on emissions. An initial tea series was conducted to examine the effect of cetane number and aromatics. Transient emissions for this test series indicated much higher (50 to 75%) particulate emissions at high altitude than observed on the same model engine and similar fuels at sea level.

Tumble flow has been recognized as an important and positive enhancement of combustion for SI engines. Tumble flow modeling with quasi-dimensional models is difficult because of the transient nature of tumble vortex, compared with swirl flows. Although multi-dimensional models have obtained plenty of attention recently in engine research, quasi-dimensional SI engine models will continue to dominate industrial applications in the near future. In the present research, a bulk flow model has been developed for tumble flows based on angular momentum conservation. Its effect on turbulence was then modeled using a Two-Equation Model (k-ε Model). A methodology has also been developed to use particle tracking velocimetry (PTV) measurement to calibrate the quasi-dimensional bulk flow model at engine BDC to model tumble vortex and tumble-generated turbulence. The Entrainment Combustion Model was used for combustion modeling.

To help predict hydrocarbon emissions during cold-start conditions we are developing a numerical model for the dynamics and vaporization of the liquid wall films formed in port-injected spark-ignition engines and incorporating this model in the KIVA-3 code for complex geometries. This paper summarizes the current status of our project and presents illustrative example calculations. The dynamics of the wall film is influenced by interactions with the impinging spray, the wall, and the gas flow near the wall. The spray influences the film through mass, tangential momentum, and energy addition. The wall affects the film through the no-slip boundary condition and heat transfer. The gas alters film dynamics through tangential stresses and heat and mass transfer in the gas boundary layers above the films. New wall functions are given to predict transport in the boundary layers above the vaporizing films.

A computational fluid dynamics study of the internal flow and the combustion process within two different spark ignition engines has been carried out. Numerical simulations have been performed with the Kiva-II code using an ignition model taking into account the velocity field in the spark plug area and the coherent flame model. This modeling approach was successfully validated in single cylinder research engine under various operating conditions and then was applied in a four valve pent roof production engine. The location and magnitude of heat releases, flame areas and temperature distributions were visualized and analyzed for all cases. The characteristics of these models were also addressed by examining the influence of different engine parameters: speed, load, air-fuel ratio, spark ignition timing. The results were compared with experimental studies including laser Doppler velocimetry, in-cylinder pressure measurements and combustion velocity.

The purpose of this study is to determine if inhomogeneous mixing of EGR and fresh air in the intake ports can lead to a specific spatial distribution of burnt gases in the combustion chamber before ignition. To achieve this goal, several three dimensional computations of a multi-valve, spark ignited engine with a dual intake ports are performed. We study the effect of engine speed (1500 and 3000 rpm), the effect of flow structure and turbulence (one and two operating intake valves) and the effect of the EGR intake technology (in the plenum or in each intake runner). Three dimensional computations are performed with a new version of the KMB code. Numerical improvements (iterative solver. convection scheme …), new sub-models (turbulence, beat transfer and law of the wall), as well as a multi-block strategy with mesh refinement algorithm were developed and implemented in the code. These improvements allow complicated geometries to be modeled.

The effects on engine-out HC emissions of a premixed propane system, and three PFI systems employing different types of injectors and using Phase II gasoline were investigated on a four-cylinder DOHC spark-ignition engine. Cold conditions resulted in significant increases in engine-out HC emissions. Phase II gasoline caused much higher emissions of HC than propane fuel. The difference in the HC emissions from the two fuels increased dramatically with lowering the coolant temperature of the engine. At cold conditions, liquid fuel entering the combustion chamber appears to be the primary source of engine out HC emissions. At the coldest temperature tested the estimated percent contribution of in-cylinder liquid fuel to the observed increase of HC emissions was as much as 96%.

Total and speciated, engine-out, hydrocarbon (HC) emissions have been measured as a function of time after a 23°C cold start of a gasoline-fueled, V-8 engine. Hydrocarbon emissions from two fuel injection systems were compared: a production port-fuel-injection (PFI) system; and a pre-vaporized (heated) central-fuel-injection (PV-CFI) system. The results indicate that, for this particular engine at the chosen operating conditions, the effect of fuel preparation on HC emissions during cold start is minimal at low load (2.57 bar IMEP (gross), MAP = 0.34 bar) but becomes significant at higher load (5.15 bar IMEP, MAP = 0.58 bar) early in the cold start. Comparison of the relative contribution to the exhaust HC of a series of fuel-derived alkanes suggests that fuel absorption in oil films is a minor contributor to HC emissions from this engine during a 23°C cold start.

The reduction of emission levels for low (LEV) and ultra low (ULEV) emissions vehicles requires catalyst with rapid thermal response for quick light-off while providing stable high temperature performance under highway driving conditions. The design of substrates which carry the three-way catalyst formulations are key to meeting the complex dual performance requirements. Enhanced mass transfer and reduced thermal mass can be accomplished while maintaining acceptable back pressure. The design principles and selection of substrate properties are described as is their effect on the emissions from the Federal Test Procedure. Transient driving performance simulations allow for selection of optimum advanced substrate designs.

In this paper the effect of in-cylinder crevices formed by the piston cylinder clearance, above the first ring, and the spark plug cavity, on the entrapment of unburned fuel air mixture during the late compression, expansion and exhaust phases of a spark ignition engine cycle, have been simulated using the Computational Fluid Dynamic (CFD) code KIVA II. Two methods of fuelling the engine have been considered, the first involving the carburetion of a homogeneous fuel air mixture, and the second an attempt to simulate the effects of manifold injection of fuel droplets into the cylinder. The simulation is operative over the whole four stroke engine cycle, and shows the efflux of trapped hydrocarbon from crevices during the late expansion and exhaust phases of the engine cycle.

A sampling system was developed to measure the evolution of the speciated hydrocarbon emissions from a single-cylinder SI engine in a simulated starting and warm-up procedure. A sequence of exhaust samples was drawn and stored for gas chromatograph analysis. The individual sampling aperture was set at 0.13 s which corresponds to ∼ 1 cycle at 900 rpm. The positions of the apertures (in time) were controlled by a computer and were spaced appropriately to capture the warm-up process. The time resolution was of the order of 1 to 2 cycles (at 900 rpm). Results for four different fuels are reported: n-pentane/iso-octane mixture at volume ratio of 20/80 to study the effect of a light fuel component in the mixture; n-decane/iso-octane mixture at 10/90 to study the effect of a heavy fuel component in the mixture; m-xylene and iso-octane at 25/75 to study the effect of an aromatics in the mixture; and a calibration gasoline.

An engine-based test has been developed to measure the oxygen storage capacity of a catalyst. The test utilizes the difference in the engine-out and tailpipe A/F ratios following rich-to-lean and lean-to-rich A/F transitions in order to quantify the storage or release of oxygen. The technique also results in the determination of the water-gas shift constant for the tailpipe exhaust. The technique was used to measure the oxygen storage capacity of a fresh catalytic converter at inlet temperatures of 400, 500, and 600°C for catalyst volumes of 1.5L and 2.8L. The procedure was repeated after the converter had been aged at an inlet temperature of 800°C for 20, 40, and 60 hours. The oxygen storage capacities are related to the emissions performance of the converter on A/F ratio sweep tests. For the fresh converter, the calculated oxygen storage capacity increased with temperature.

The effects of catalyst and fuel formulation changes were investigated on vehicles meeting European Stage II (94/12/EC) emission limits when tested over the modified European test cycle. The OEM standard Pt/Rh catalyst formulation was compared with advanced Pd/Rh catalysts, at nominally the same PGM cost, and with Pd/Rh catalysts at increased PGM loadings. No other changes were made to the vehicles. The largest relative emissions benefits for the advanced Pd/Rh catalysts at equivalent PGM cost were 28% for THC, 30% for CO and 22% for NOx. Pd/Rh catalysts with higher PGM loadings gave further improvements in emissions, with total reductions of 38% for THC, 40% for CO and 31% for NOx compared to the standard OEM catalyst. In addition, one of the vehicles was tested with a Pt/Pd/Rh catalyst formulation. The performance of this catalyst was comparable with the Pd/Rh catalyst at similar PGM loading.