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One scenario for reducing engine out NOx in a spark ignition engine is to introduce small amounts of supplemental hydrogen to the combustion process. The supplemental hydrogen enables a gasoline engine to run lean where NOx emissions are significantly reduced and engine efficiency is increased relative to stoichiometric operation. This paper reports on a mass and energy balance model that has been developed to evaluate the overall system efficiencies of a thermal reformer-heat exchanger system capable of delivering hydrogen to the air intake of a gasoline engine. The mass and energy balance model is utilized to evaluate the conditions where energy losses associated with fuel reformation may be offset by increases in engine efficiencies.

Thermal conductivity detection has long been used in gas chromatography to detect hydrogen and other diatomic gases in a gas sample. Thermal conductivity instruments that are not coupled to gas chromatographs are useful for detecting hydrogen in binary gas mixtures, but suffer from significant cross-interference from other gas species that are separated when the detector is used with a gas chromatograph. This study reports a method for using a commercially-available thermal conductivity instrument to detect and quantify hydrogen in a diesel exhaust stream. The instrument time response of approximately 40 seconds is sufficient for steady-state applications. Cross-interference from relevant gas species are quantified and discussed. Measurement uncertainty associated with the corrections for the various species is estimated and practical implications for use of the instrument and method are discussed.

G-Equation models represent propagating flame fronts with an implicit two-dimensional surface representation (level-set). Level-set methods are fast, as transport source terms for the implicit surface can be solved with finite-volume operators on the finite-volume domain, without having to build the actual surface. However, they include approximations whose practical effects are not properly understood. In this study, we improved the numerics of the FRESCO CFD code’s G-Equation solver and developed a new method to simulate kernel growth using signed distance functions and the analytical sphere-mesh overlap. We analyzed their role for simulating propane/air flames, using three well-established constant-volume configurations: a one-dimensional, freely propagating laminar flame; a disc-shaped, constant-volume swirl combustor; and torch-jet flame development through an orifice from a two-chamber device.

The widespread adoption of boosted, downsized SI engines has brought pre-ignition phenomena into greater focus, as the knock events resulting from pre-ignitions can cause significant hardware damage. Much attention has been given to understanding the causes of pre-ignition and identify lubricant or fuel properties and engine design and calibration considerations that impact its frequency. This helps to shift the pre-ignition limit to higher specific loads and allow further downsizing but does not fundamentally eliminate the problem. Real-time detection and mitigation of pre-ignition would thus be desirable to allow safe engine operation in pre-ignition-prone conditions. This study focuses on advancing the time of detection of pre-ignition in an engine cycle where it occurs.

An optical-based sensor for detecting particulate matter (PM) in diesel engine exhaust has been demonstrated. The position of the sensor during the experiments was the exhaust manifold prior to the turbocharger. The sensor is constructed of fiber optics which transmit 532-nm laser light into the exhaust pipe and collect backscattered light in a 180° geometry. Due to the optical nature of the probe, PM sensing can occur at high temporal rates. Experiments conducted by changing the fuel injection properties of one cylinder of a four cylinder engine demonstrated that the sensor can resolve cycle dependent events. The feasibility of the probe for examining PM emissions in the exhaust manifold will be discussed.

Continuous efforts to develop a lightweight alloy suitable for the most demanding applications in automotive industry resulted in a number of advanced aluminum (Al) and magnesium alloys and manufacturing routes. One example of this is the application of 319 Al alloy for production of 3.6L V6 gasoline engine blocks. Aluminum is sand cast around Fe-liner cylinder inserts, prior to undergoing the T7 heat treatment process. One of the critical factors determining the quality of the final product is the type, level, and profile of residual stresses along the Fe liners (or extent of liner distortion) that are always present in a cast component. In this study, neutron diffraction was used to characterize residual stresses along the Al and the Fe liners in the web region of the cast engine block. The strains were measured both in Al and Fe in hoop, radial, and axial orientations. The stresses were subsequently determined using generalized Hooke's law.

A central challenge for efficient auto-ignition controlled low-temperature gasoline combustion (LTGC) engines has been achieving the combustion phasing needed to reach stable performance over a wide operating regime. The negative valve overlap (NVO) strategy has been explored as a way to improve combustion stability through a combination of charge heating and altered reactivity via a recompression stroke with a pilot fuel injection. The study objective was to analyze the thermal and chemical effects on NVO-period energy recovery. The analysis leveraged experimental gas sampling results obtained from a single-cylinder LTGC engine along with cylinder pressure measurements and custom data reduction methods used to estimate period thermodynamic properties. The engine was fueled by either iso-octane or ethanol, and operated under sweeps of NVO-period oxygen concentration, injection timing, and fueling rate.

Interest in operational cost reduction is driving engine manufacturers to consider low-cost fuel substitution in heavy-duty diesel engines. These dual-fuel (DF) engines could be operated either in diesel-only mode or operated with premixed natural gas (NG) ignited by a pilot flame of compression-ignited direct-injected diesel fuel. Under certain conditions, dual-fuel operation can result in increased cycle-to-cycle variability (CCV) during combustion. CFD can greatly help in understanding and identifying critical parameters influencing CCV. Innovative modelling techniques and large computing resources are needed to investigate the factors affecting CCV in dual-fuel engines. This paper discusses the use of the High Performance Computing resource Titan, at Oak Ridge National Laboratory, to investigate CCV of a dual-fuel engine.

Lean NOx Trap (LNT) catalysts are capable of reducing NOx in lean exhaust from diesel engines. NOx is stored on the catalyst during lean operation; then, under rich exhaust conditions, the NOx is released from and reduced by the catalyst. The process of NOx release and reduction is called regeneration. One method of obtaining the rich conditions for regeneration is to inject additional fuel into the engine cylinders while throttling the engine intake air flow to effectively run the engine at rich air:fuel ratios; this method is called “in-cylinder” regeneration. In-cylinder regeneration of LNT catalysts has been demonstrated and is a candidate emission control technique for commercialization of light-duty diesel vehicles to meet future emission regulations. In the study presented here, a 1.7-liter diesel engine with a LNT catalyst system was used to evaluate in-cylinder regeneration techniques.

We report a chemical sensing technology composed of engineered bioluminescent bacteria placed on an integrated microluminometer. The bacteria have been engineered to luminesce when the targeted compound is metabolized, while the microluminometer detects, processes, and then reports the magnitude of this optical signal. In this work we report our progress in the development of these biosensors and present data from our prototypes.

We report a chemical sensing technology composed of engineered bioluminescent bacteria placed on an integrated microluminometer. The bacteria have been engineered to luminesce when the targeted compound is metabolized, while the microluminometer detects, processes, and then reports the magnitude of this optical signal. In this work we report our progress in the development of these biosensors and present data from our early prototypes.

The effects of cetane number (CN) on homogeneous charge compression ignition (HCCI) performance and emissions were investigated in a single cylinder engine using intake air temperature for control. Blends of the diesel secondary reference fuels for cetane rating were used to obtain a CN range from 19 to 76. Sweeps of intake air temperature at a constant fueling were performed. Low CN fuels needed to be operated at higher intake temperatures than high CN fuels to achieve ignition. As the intake air temperature was reduced for a given fuel, the combustion phasing was retarded, and each fuel passed through a phasing point of maximum indicated mean effective pressure (IMEP). Early combustion phasing was required for the high CN fuels to prevent misfire, whereas the maximum IMEP for the lowest CN fuel occurred at a phasing 10 crank angle degrees (CAD) later.

Low temperature combustion engine technologies are being investigated for high efficiency and low emissions. However, such engine technologies often produce higher engine-out hydrocarbon (HC) and carbon monoxide (CO) emissions, and their operating range is limited by the fuel properties. In this study, two different fuels, a US market gasoline containing 10% ethanol (RON 92 E10) and a higher reactivity gasoline (RON 80 E0), were compared on Delphi’s second generation Gasoline Direct-Injection Compression Ignition (Gen 2.0 GDCI) multi-cylinder engine. The engine was evaluated at three operating points ranging from a light load condition (800 rpm/2 bar IMEPg) to medium load conditions (1500 rpm/6 bar and 2000 rpm/10 bar IMEPg). The engine was equipped with two oxidation catalysts, between which was located the exhaust gas recirculation (EGR) inlet. Samples were taken at engine-out, between the catalysts, and at tailpipe locations.

One challenge in meeting emission regulations with catalytic aftertreatment systems is maintaining the proper catalyst temperatures that enable the catalytic devices to perform the emissions reduction. In this study, in-cylinder techniques are used to actively control the temperature of a catalyzed diesel particulate filter (DPF) in order to raise the DPF temperature to induce particulate oxidation. The performance of four strategies is compared for two different starting DPF temperatures (150°C and 300°C) on a 4-cylinder 1.7-liter diesel engine. The four strategies include: (1) addition of extra fuel injection early in the combustion cycle for all four cylinders, (2) addition of extra fuel injection late in the combustion cycle for all four cylinders, (3) operating one-cylinder with extra fuel injection early in the combustion cycle, and (4) operating one-cylinder with extra fuel injection late in the combustion cycle.

The focus of the present study was to characterize Reactivity Controlled Compression Ignition (RCCI) using a single-fuel approach of gasoline and gasoline mixed with a commercially available cetane improver on a multi-cylinder engine. RCCI was achieved by port-injecting a certification grade 96 research octane gasoline and direct-injecting the same gasoline mixed with various levels of a cetane improver, 2-ethylhexyl nitrate (EHN). The EHN volume percentages investigated in the direct-injected fuel were 10, 5, and 2.5%. The combustion phasing controllability and emissions of the different fueling combinations were characterized at 2300 rpm and 4.2 bar brake mean effective pressure over a variety of parametric investigations including direct injection timing, premixed gasoline percentage, and intake temperature. Comparisons were made to gasoline/diesel RCCI operation on the same engine platform at nominally the same operating condition.

The effect of biodiesel content on homogeneous charge compression ignition (HCCI) engine performance has been investigated both experimentally and by computer simulation. Combustion experiments were performed in a single cylinder HCCI engine using blends of soy biodiesel in ultra low sulfur diesel, with concentrations ranging from 0 to 50 vol% and equivalence ratios (Φ) from 0.38 to 0.48. Data from the engine tests included combustion analysis and exhaust composition analysis with standard gaseous emissions equipment. The engine utilized a custom port fuel injection strategy to provide highly premixed charges of fuel and air, making it possible to compare the results with single zone chemical kinetics simulations that were performed using CHEMKIN III, with a reaction set including 670 species and over 3000 reactions.

The compatibility of elastomeric materials used in fuel storage and dispensing applications was determined for test fuels representing neat gasoline and gasoline blends containing 10 and 17 vol.% ethanol, and 16 and 24 vol.% isobutanol. The actual test fuel chemistries were based on the aggressive formulations described in SAE J1681 for oxygenated gasoline. Elastomer specimens of fluorocarbon, fluorosilicone, acrylonitrile rubber (NBR), polyurethane, neoprene, styrene butadiene rubber (SBR) and silicone were exposed to the test fuels for 4 weeks at 60°C. After measuring the wetted volume and hardness, the specimens were dried for 20 hours at 60°C and then remeasured for volume and hardness. Dynamic mechanical analysis (DMA) was also performed to determine the glass transition temperature (Tg). Comparison to the original values showed that all elastomer materials experienced volume expansion and softening when wetted by the test fuels.

The compatibility of elastomer materials used in fuel storage and dispensing applications was determined for an off-highway diesel fuel and a blend containing 20% bio-oil (Bio20) derived from a fast pyrolysis process. (This fuel blend is not to be confused with B20, which is a blend of diesel fuel with 20% biodiesel.) The elastomer types evaluated in this study included fluorocarbon, fluorosilicone, acrylonitrile rubber (NBR), styrene butadiene rubber (SBR), polyurethane, neoprene, and silicone. All of these elastomer types are used in sealing applications, but some, like the nitrile rubbers are also common hose materials. The elastomer specimens were exposed to the two fuel types for 4 weeks at 60°C. After measuring the wetted volume and hardness, the specimens were dried for 65 hours at 60°C and then remeasured. A solubility analysis was performed to better understand the performance of plastic materials in fuel blends composed of bio-oil and diesel.

The compatibility of plastic materials used in gasoline storage and dispensing applications was determined for test fuels representing neat gasoline (Fuel C), and blends containing 25% ethanol (CE25a), 16% isobutanol (CiBu16a), and 24% isobutanol (CiBu24a). A solubility analysis was also performed and compared to the volume swell results obtained from the test fuel exposures. The plastic specimens were exposed to each test fuel for16 weeks at 60°C. After measuring the wetted volume and hardness, the specimens were dried for 65 hours at 60°C and then remeasured for volume and hardness. Dynamic mechanical analysis (DMA), which measures the storage modulus as a function of temperature, was also performed on the dried specimens to determine the temperature associated with the onset of the glass-to-rubber transition (Tg). For many of the plastic materials, the solubility analysis was able to predict the relative volume swell for each test fuel.

The compatibility of plastic materials used in fuel storage and dispensing applications was determined for an off-highway diesel fuel and a blend containing 20% bio-oil (Bio20) derived from a fast pyrolysis process. Bio20 is not to be confused with B20, which is a diesel blend containing 20% biodiesel. The feedstock, processing, and chemistry of biodiesel are markedly different from bio-oil. Plastic materials included those identified for use as seals, coatings, piping and fiberglass resins, but many are also used in vehicle fueling systems. The plastic specimens were exposed to the two fuel types for 16 weeks at 60°C. After measuring the wetted volume and hardness, the specimens were dried for 65 hours at 60°C and then remeasured to determine extent of property change. A solubility analysis was performed to better understand the performance of plastic materials in fuel blends composed of bio-oil and diesel.