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While emission standards are becoming more stringent with every new legislation level, the engineering of compact aftertreatment system is becoming extremely challenging. This paper outlines a road map for cost-effective, compact aftertreatment systems through use of catalysts with standard and structured foil substrates. The longitudinal-structure (LS) foil disrupts laminar flow regimes within channels enhancing mass transfer and gas reconditioning. The presented results were applied to DOC catalyst functionality including parameters such as cross-section, substrate type and substrate volume. The catalysts were degreend and tested on a production 15ltr ISX Cummins engine calibrated for US 1998 emissions. Various load points were selected to determine catalyst performance as a function of exhaust gas temperature, exhaust flow rate (space velocity) and exhaust gas composition. A HC injector system was used to characterize oxidation performance at various concentration levels.

The application of biodiesel fuel (BDF) to diesel engines is very effective at reducing CO2 emissions, because biodiesel is considered to be carbon neutral in principle. Gas-to-liquid (GTL) fuel, a synthetic fuel, is expected to reduce emissions from diesel engines. This study focused on the effects of driving conditions and fatty acid methyl ester (FAME) and GTL blended fuel on emissions from diesel engines/vehicles meeting Japan's new short-term regulations, or '03 regulations. FAME including rape methyl ester (RME), palm oil methyl ester (PME) and soybean methyl ester (SME) were studied. Major technologies for emissions reduction may include common-rail high-pressure fuel injection system, cooled exhaust gas recirculation (EGR) system, diesel oxidation catalyst (DOC) and diesel particulate filter (DPF).

Palladium-based catalyst can be employed for natural gas exhaust clean up due to its high activity for light hydrocarbon oxidation. Unfortunately, trace amounts of sulfur in the natural gas feed severely deactivate the catalyst. In this paper, SO2 adsorption over a monolithic Pd/Al2O3 oxidation catalyst is monitored in a time-resolved manner in the presence of 100 ppm SO2 under simulated aging conditions of a natural gas engine, which is correlated with the oxidation activity for CO and hydrocarbons such as CH4, C2H6 and C3H8. The SO2 adsorption is saturated in 0.5 h at 400°C and 100,000 h-1. The molar ratio of adsorbed SO2 and Pd is about 2/1, indicating SO2 molecules adsorbed, or transferred to the Al2O3 support. The oxidation activity gets stabilized upon saturation of sulfur adsorption, and the hydrocarbon oxidation activity cannot recover even when 100 ppm SO2 is completely removed from the stream.

A series of paired fuel tests were conducted comparing certification-grade highway diesel fuel with 5 to 50 vol% soy-methyl-ester biodiesel blends. Each fuel pair was tested for up to seven transient cycles representing various load conditions, using a 2006 model year Cummins ISB compression ignition engine equipped with exhaust gas recirculation. Except for the most lightly-loaded cycle, the results show statistically significant differences in NOx emission for all fuel pairs. The average NOx emissions due to biodiesel increased over each cycle, ranging from 0.9 to 6.6% and from 2.2 to 17.2% for the B20/B0 and B50/B0 fuel pairs, respectively. Significant reductions in CO and PM were observed over a majority of the cycles tested. The data also reveal that the change in NOx emissions increases linearly with the average cycle load. To complement the transient results, a single modal point was monitored daily to investigate biodiesel effects on engine operating parameters.

This paper includes a numerical and experimental study of fluid flow in automotive catalytic converters. The numerical work involves using computational fluid dynamics (CFD) to perform three-dimensional calculations of turbulent flow in an inlet pipe, inlet cone, catalyst substrate (porous medium), outlet cone, and outlet pipe. The experimental work includes using hot-wire anemometry to measure the velocity profile at the outlet of the catalyst substrate, and pressure drop measurements across the system. Very often, the designer may have to resort to offset inlet and outlet cones, or angled inlet pipes due to space limitations. Hence, it is very difficult to achieve a good flow distribution at the inlet cross section of the catalyst substrate. Therefore, it is important to study the effect of the geometry of the catalytic converter on flow uniformity in the substrate.

The increasing number of controllable parameters in modern engine systems has led to increasingly complicated and enlarged engine control software. This in turn has created dramatic increases in software development time and cost. Model-based control design seems to be an effective way to reduce development time and costs and also to enable engineers to understand the complex relationship between the many controllable parameters and engine performance. In the present study, we have developed model-based methodologies for the engine calibration process, employing engine cycle simulation and regression analysis. The reliability of the proposed method was investigated by validating the regression model predictions with measured data.

A Controllable Active Thermo-Atmosphere (CATA) Combustor enables the investigation of stabilization mechanisms in an environment that decouples the turbulent chemical kinetics from the complex recirculating flow. Previous studies on combustion of the low-pressure fuel jets in the Controllable Active Thermo-Atmosphere (CATA) showed non-linear effect of coflow temperature on autoignition delay and the randomness of autoignition sites. In this work, a diesel spray is injected into the CATA with the injection pressure at 20MPa from a single-hole injector and the autoignition and combustion process of the spray is recorded by a high-speed camera video. The multipoint autoignition of diesel spray is observed in the CATA and the subsequent combustion process is analyzed. The results show that autoignition phenomenon plays an important role in the stabilization of the lifted flames of diesel spray under low coflow temperature.

Diesel particulate matter collection results of a new design for a non-blocking diesel particulate filter are presented. Engine/dynometer testing with partial flow dilution tunnel DPM sampling show the device is capable of greater than 50% DPM trapping efficiency. Parameters in the design of the device such as, the quantity and type of filtration media is shown to directly impact on the trapping efficiency of the device. Preliminary durability results show minimal effects on device performance. In addition, history effects due to engine mode on DPM trapping performance are discussed

In this study we identify components of a typical biodiesel fuel and estimate both their individual and mixed thermo-physical and transport properties. We then use the estimated mixture properties in computational simulations to gauge the extent to which combustion is modified when biodiesel is substituted for conventional diesel fuel. Our simulation studies included both conventional diesel combustion (DI) and premixed charge compression ignition (PCCI). Preliminary results indicate that biodiesel ignition is significantly delayed due to slower liquid evaporation, with the effects being more pronounced for DI than PCCI. The lower vapor pressure and higher liquid heat capacity of biodiesel are two key contributors to this slower rate of evaporation. Other physical properties are more similar between the two fuels, and their impacts are not clearly evident in the present study.

An experimental method was set up in a single cylinder optical engine in GDI configuration to study UHC origins in both homogeneous and stratified operation. On the one hand, UHC were observed in the combustion chamber by formaldehyde LIF (excitation at 355 nm and collection from 400 to 470 nm). Formaldehyde is a natural UHC tracer since it results from partly decomposed fuel that has not been fully oxidized during combustion. A quartz cylinder liner was used in order to benefit from a large optical access. On the other hand, UHC emissions measurement were simultaneously performed with a fast FID analyzer whose sampling probe was located 2 cm downstream the exhaust valve, in one of the two exhaust ports. An instantaneous exhaust mass flow model was also developed using 0-D simulation. The computed mass flow rate was coupled to fast FID measurements to estimate instantaneous and cycle to cycle UHC emissions.

Extensive literature exists on spray development, mixing and combustion regarding engine modeling and diagnostics using single-component and model fuels. However, often the variation in data between different fuels, particularly relating to spray development and its effect on combustion, is neglected or overlooked. By injecting into a quiescent chamber, this work quantifies the differences in spray development from a multi-hole direct-injection spark-ignition engine injector for two single-component fuels (iso-octane and n-pentane), a non-fluorescing multi-component model fuel which may be used for in-cylinder Laser Induced Fluorescence experiments, and several grades of pump gasoline (with and without additives). High-speed recordings of the sprays were made for a range of fuel temperatures and gas pressures. It is shown that a fuel temperature above that of the lowest boiling point fraction of the tested fuel at the given gas pressure causes a convergence of the spray plumes.

Hydrotreated vegetable oil (HVO) named NExBTL is a 2nd generation renewable diesel fuel made by a refinery-based process converting vegetable oils to paraffins. Also animal fats are suitable for feedstocks. Properties of this non-ester type biobased fuel are very similar to GTL. It contains no sulfur, oxygen, nitrogen or aromatics. Cetane number is very high (∼90). Cloud point can be adjusted by severity of the process from -5 to -30°C, heating value is similar to diesel fuel, storage stability is good, and water solubility is low. Emissions of two heavy duty engines and two city buses are presented with HVO and sulfur free EN 590 diesel fuel. The effect of HVO on regulated emissions compared to EN 590 fuel was: NOx -7 % … -14 % PM -28 % … -46 % CO -5 % … -78 % HC 0 % … -48 % Aldehydes, PAHs, mutagenicity and particulate size were also measured.

The contribution to the engine-out hydrocarbon (HC) emissions from fuel that escapes the main combustion event in piston ring crevices was estimated for an air-cooled, V-twin utility engine. The engine was run with a homogeneous pre-vaporized mixture system that avoids the presence of liquid films in the cylinder, and their resulting contribution to the HC emissions. A simplified ring pack gas flow model was used to estimate the ring pack contribution to HC emissions; the model was tested against the experimentally measured blowby. At high load conditions the model shows that the ring pack returns to the cylinder a mass of HC that exceeds that observed in the exhaust, and thus, is the dominant contributor to HC emissions. At light loads, however, the model predicts less HC mass returned from the ring pack than is observed in the exhaust. Time-resolved HC measurements were performed and used to assess the effect of combustion quality on HC emissions.

By changing the top-land radial clearance, this paper presents the effect of the piston crevice on the transient HC emissions of the first firing cycle at cold start on an LPG SI Engine. A fast-response flame ionization detector (FFID) was employed to measure transient HC emissions of the first firing cycle. At the same time, the transient cylinder pressure and instantaneous crankshaft speed of the engine were measured and recorded. The results show that increasing 50% crevice volume leads to 25% increase of HC emissions in the lean region and 18% increase of HC emissions in the rich region, however, the 50% increase of crevice volume contributes to 32% decease of HC emissions in the stable combustion region. For LPG SI engine, the HC emissions of the first firing cycle during cold start are relatively low in a wide range of the excess air ratio.

In this study different methods to reduce the soot emissions of Diesel engines were investigated and compared to obtain their soot reduction potential. Apart from investigations on the practically usable engine map area with so called homogeneous charge compression ignition (HCCI) combustion processes a new heterogeneous combustion processes was developed and investigated which offers significantly reduced soot emissions while still applicable in the entire engine map. For the HCCI experiments the emphasis was put on the achievable engine load range when using conventional injector nozzles which still allow a conventional heterogeneous engine operation.

In-cylinder and exhaust soot mass were measured in an optically accessible heavy duty diesel engine under various intake oxygen concentrations from 8 vol% to 21 vol% to gain insight into soot formation and destruction processes. Exhaust-gas recirculation (EGR) in the optical engine was simulated by dilution of intake gases with nitrogen. In-cylinder soot, measured by 2-color optical pyrometry, was compared to engine-out soot, measured by a commercial optical smoke meter. Each EGR rate was studied under two separate fueling conditions: (i) constant injection duration, and (ii) constant global equivalence ratio. The in-cylinder and exhaust soot measurements of the current study agree well with findings of previous studies in the literature. Under both fueling conditions, in-cylinder soot temperatures decreased with the reduction of in-cylinder oxygen concentration.

The whirl noise on turbochargers is generated by the self-induced vibration of the oil film in the bearing system. The noise is characterized by its frequency behavior that doesn't increase proportionately to the turbo shaft speed. It tends to be felt annoying. In this paper, to improve the whirl vibration, a statistical analysis approach was applied to the bearing specifications. The results from experiments showed that the bearing clearances played an important role in the reduction of the whirl vibration. To further investigate into this phenomenon, the shaft oscillation behavior was measured. And a vibration simulation program for the turbocharger bearing system was also developed.

Flexibility in running with different fuel is becoming an important issue in the Internal Combustion Engine design due to the increasingly wider use of alternative fuels. The injection systems must deal with fuels having different properties and effects on engine behavior and take proper adjustments in the control strategy. Particularly the transient during which one fuel is being replaced by the second one is a critical point of the injection system operation, and its capability of recognizing the fuel mixture currently available is a fundamental matter in the engine control development. This paper focuses on the multidimensional CFD analysis of a Common Rail type multi-fuel injection system accumulator during the gasoline - ethanol shift. An open source computational fluid dynamics code was used in the modeling.

Thermal efficiency comparisons are made between the low temperature combustion and the conventional diesel cycles on a common-rail diesel engine with a conventional diesel fuel. Empirical studies have been conducted under independently controlled exhaust gas recirculation, intake boost, and exhaust backpressure. Up to 8 fuel injection pulses per cylinder per cycle have been applied to modulate the homogeneity history of the early injection diesel low temperature combustion operations in order to improve the phasing of the combustion process. The impact of heat release phasing, duration, shaping, and splitting on the thermal efficiency has been analyzed with zero-dimensional engine cycle simulations. This paper intends to identify the major parameters that affect diesel low temperature combustion engine thermal efficiency.

Fully flexible valve actuation (FFVA) system, often referred to as camless valvetrain, employs electronically controlled actuators to drive the intake and/or exhaust valves. This technology enables the engine controller to tailor the valve event according to the engine operating condition in real-time to improve fuel economy, emissions and performance. At GM Research and Development Center, we have developed laboratory electro-hydraulic FFVA systems for single cylinder gasoline engines. The objective of this work is to develop a FFVA system for advanced diesel combustion research. There are three major differences between gasoline and diesel engines in terms of applying the FFVA systems. First, the orientation of the diesel engine valves and the location of the fuel injection system complicate the packaging issue. Second, the clearance between the valves and the piston for diesel engines are extremely small.