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Particulate emissions from heavy-duty buses were measured in real time under conditions encountered during the standard Central Business District (CBD) driving cycle. The buses tested were equipped with 1994 Detroit Diesel Engine Corporation 6V92-TA engines, and some included after treatment devices on the exhaust. Instantaneous, time-resolved measurements of CO2 and amorphous carbon concentrations were obtained using an optical extinction technique and compared to simultaneous results obtained using conventional dilution tunnel sampling methods. Good agreement was obtained between the real-time extinction measurements and the diluted CO2 and cycle-integrated filter measurements. The instantaneous measurements revealed that acceleration transients accounted for roughly 80% of the particulate mass emitted during the cycle but only about 45% of the fuel consumption.

Results of comparisons of computed and measured soot and NO in a direct-injection Diesel engine are presented. The computations are carried out using a three-dimensional model for flows, sprays and combustion in Diesel engines. Autoignition of the Diesel spray is modeled using an equation for a progress variable which measures the local and instantaneous tendency of the fuel to autoignite. High temperature chemistry is modeled using a local chemical equilibrium model coupled to a combination of laminar kinetic and turbulent characteristic times. Soot formation is kinetically controlled and soot oxidation is represented by a model which has a combination of laminar kinetic and turbulent mixing times. Soot oxidation appears to be controlled near top-dead-center by mixing and by kinetics as the exhaust is approached. NO is modeled using the Zeldovich mechanism.

Results of three-dimensional computations of non-vaporizing and vaporizing Diesel sprays in a very high pressure (up to 18.4 MPa without combustion) environment are presented. These pressures and corresponding density ratios of ambient gas to injected liquid are about a factor of two greater than those in current Diesel engines. The spray model incorporates a line source for drops, heat, mass and momentum exchange between the gas and liquid phases, turbulent dispersion of drops, collisions and coalescences, and drop breakup. The accuracy of the model is assessed by making comparisons of computed and measured spray penetrations. Reasonable agreement is obtained for a broad range of conditions. A scaling for time and axial distance clarifies these results.

Earlier work [1] shows that kinetics of Diesel soot oxidation is different from that of ethylene diffusion flame soot oxidation [2], possibly due to metals from lube oil. This study investigates the influence of metals on soot oxidation and the exhaust particle emissions using lube oil dosed fuel (2 % by volume). This method does not simulate normal lube oil consumption, but is used as a means of adding metals to particles for oxidation studies. This study also provides insight into the effect of systems that mix lube oil with fuel to minimize oil change service. The HTO-TDMA (High Temperature Oxidation-Tandem Differential Mobility Analyzer) technique [1] was used to measure the surface specific oxidation rate of Diesel particles over the temperature range 500-750 °C. Diesel particles sampled from the exhaust stream of a Diesel engine were size segregated by differential mobility and oxidized in situ in air in a heated flow tube of known residence time and temperature profile.

A two-dimensional optimization process which simultaneously adjusts the spark timing and air-fuel ratio of a lean-burn natural gas fueled engine has been demonstrated. This has been done by first mapping the thermal efficiency against spark timing and equivalence ratio at a single speed and load combination to obtain the 3-D surface of efficiency versus the other two variables. Then the ability of the control system to find and hold the combination of timing and air-fuel ratio which gives the highest thermal efficiency was explored. The control system described in SAE Paper No. 940546 was used to map the thermal efficiency versus equivalence ratio and ignition timing. NOx, CO, and HC maps were also obtained to determine the tradeoffs between efficiency and emissions. A load corresponding to a brake mean effective pressure of 0.467 MPa was maintained by a water brake dynamometer. A speed of 2000 rpm was maintained by a fuel-controlled governor.

Two types of in-cylinder optical probes were applied to a single cylinder CFR engine to detect knocking combustion. The first probe was integrated directly into the engine spark plug to monitor the radiation from burned gas in the combustion process. The second was built into a steel body and installed near the end gas region of the combustion chamber. It measured the radiant emission from the end gas in which knock originates. The measurements were centered in the near infrared region because thermal radiation from the combustion products was believed to be the main source of radiation from a spark ignition engine. As a result, ordinary photo detectors can be applied to the system to reduce its cost and complexity. It was found that the measured luminous intensity was strongly dependent upon the location of the optical sensor.

In this work, engine-out particle mass (PM) and particle number (PN) emissions were experimentally examined from a gasoline direct injection (GDI) engine operating in two lean combustion modes and one stoichiometric mode with a fuel of known properties. Ten steady state operating points, two constant speed load steps, and an engine cold start were examined. Results showed that solid particles emitted from the engine under steady state stoichiometric conditions had a uniquely broad size distribution that was relatively flat between the diameters of 10 and 100 nm. In most operating conditions, lean homogenous modes can achieve lower particle emissions than stoichiometric modes while improving engine thermal efficiency. Alternatively, lean stratified operating modes resulted in significantly higher PN and PM emissions than both lean homogeneous and stoichiometric modes with increased efficiency only at low engine load.

The third long-term ATES cycle (LT3) was conducted between October 1989 and March 1990. Objectives of LT3 were to demonstrate that high-temperature ATES could supply a real heating load and to simplify the water chemistry modeling. For LT3 the Field Test Facility (FTF) was connected to a nearby campus building to demonstrate the FTF's ability to meet a real heating load. For LT3 the wells were modified so that only the most permeable portions of the Ironton-Galesville aquifer were used to simplify water chemistry comparisons and modeling. The campus steam plant was the source for heat stored during LT3. A total volume of 63.2 x 103 m3 of water was injected at a rate of 54.95 m3/hr into the storage well at a mean temperature of 104.7°C from October through December 1989. Tie-in to the Animal Sciences Veterinary Medicine (ASVM) building was not completed until late December.

The focus of this work was the physical characterization of exhaust aerosol from the University of Minnesota Formula SAE team's engine. This was done using two competition fuels, 100 octane race fuel and E85. Three engine conditions were evaluated: 6000 RPM 75% throttle, 8000 RPM 50% throttle, and 8000 RPM 100% throttle. Dilute emissions were characterized using a Scanning Mobility Particle Sizer (SMPS) and a Condensation Particle Counter (CPC). E85 fuel produced more power and had lower particulate matter emissions at all test conditions, but more fuel was consumed.

The history of off-road equipment manufacturing has been based on proven designs and long times between model updates. In sharp contrast with this strategy is the electronic manufacturing services (EMS) industry. The EMS industry is driven by the larger consumer product industry's continuing pressure for lower costs. Because of this, EMS tools, processes, and practices have evolved to support rapid technology and component changes. However the increasing consumer demand for features like better user-interfaces, more efficient fuel consumption, and the desire for increased operational controls in equipment have forced the off-road industry to increase the frequency of product updates to meet customers' needs. Equipment manufacturers make running changes leading to a “Learning-by-doing” development and manufacturing process. But rapid changes sometimes have an unpredictable impact on the reliability of the final product.

Previous studies have shown Late Intake Valve Closure (LIVC) through Variable Valve Timing (VVT) to offer reduced fuel consumption through reduced pumping work. Load modulation through the controlled phasing of one of two intake valves/cylinder is one means of accomplishing the LIVC strategy on a multi-valve engine. Experimental studies of LIVC show that cycle-to-cycle variations and reduced flame velocity in single or synchronized multiple intake valve engines are associated with performance which, though superior to throttled engine performance, falls short of its promised fuel economy. To examine if the higher mixture velocity promised by valve phasing relative to single or synchronized LIVC mitigates cycle-to-cycle variations and flame velocity defects, a modification of the Quad 4 engine has been designed and built and is, at the present writing, being tested. The design employs a third camshaft placed above the original intake valve camshaft.

Results of two- and three-dimensional computations of combustion of Diesel sprays in a very high-pressure chamber are presented. A wide range of experimental conditions are considered. Peak chamber pressure with combustion range from about 6.0 MPa to about 20 MPa. Computed and measured spray penetrations and chamber pressures are compared and shown to be in adequate agreement. Autoignition is modeled using an equation for a progress variable which measures the local and instantaneous tendency of the fuel to autoignite. High temperature chemistry is modeled using a local equilibrium model coupled to a combination of laminar and turbulent characteristic times. It is shown that scaling rules which were found to apply in vaporizing and non-vaporizing sprays also apply in the combusting sprays. The fuel-air mixing rates and burning rates increase as the ratio of the ambient density to injected density increases.

Diesel engine ash emissions are composed of the non-combustible portions of diesel particulate matter derived mainly from lube oil, and over time can degrade diesel particulate filter performance. This paper presents results from a high temperature oxidation method (HTOM) used to estimate ash emissions, and engine oil consumption in real-time. Atomized lubrication oil and diesel engine exhaust were used to evaluate the HTOM performance. Atomized fresh and used lube oil experiments showed that the HTOM reached stable particle size distributions and concentrations at temperatures above 700°C. The HTOM produced very similar number and volume weighted particle size distributions for both types of lube oils. The particle number size distribution was unimodal, with a geometric mean diameter of about 23 nm. The volume size distribution had a geometric volume mean diameter of about 65 nm.

A fully flexible valve actuation (FFVA) system was developed for a single cylinder research engine to investigate high efficiency clean combustion (HECC) in a diesel engine. The main objectives of the study were to examine the emissions, performance, and combustion characteristics of the engine using late intake valve closing (LIVC) to determine the benefits and limitations of this strategy to meet Tier 2 Bin 5 NOx requirements without after-treatment. The most significant benefit of LIVC is a reduction in particulates due to the longer ignition delay time and a subsequent reduction in local fuel rich combustion zones. More than a 95% reduction in particulates was observed at some operating conditions. Combustion noise was also reduced at low and medium loads due to slower heat release. Although it is difficult to assess the fuel economy benefits of LIVC using a single cylinder engine, LIVC shows the potential to improve the fuel economy through several approaches.

Fuel reforming during a Negative Valve Overlap (NVO) period is an effective approach to control Low Temperature Gasoline Combustion (LTGC) ignition. Previous work has shown through experiments that primary reference fuels reform easily and produce several species that drastically affect ignition characteristics. However, our previous research has been unable to accurately predict measured reformate composition at the end of the NVO period using simple single-zone models. In this work, we use a stochastic reactor model (SRM) closed cycle engine simulation to predict reformate composition accounting for in-cylinder temperature and mixture stratification. The SRM model is less computationally intensive than CFD simulations while still allowing the use of large chemical mechanisms to predict intermediate species formation rates.

Negative Valve Overlap (NVO) is a potential control strategy for enabling Low-Temperature Gasoline Combustion (LTGC) at low loads. While the thermal effects of NVO fueling on main combustion are well-understood, the chemical effects of NVO in-cylinder fuel reforming have not been extensively studied. The objective of this work is to examine the effects of fuel molecular structure on NVO fuel reforming using gas sampling and detailed speciation by gas chromatography. Engine gas samples were collected from a single-cylinder research engine at the end of the NVO period using a custom dump-valve apparatus. Six fuel components were studied at two injection timings: (1) iso-octane, (2) n-heptane, (3) ethanol, (4) 1-hexene, (5) cyclohexane, and (6) toluene. All fuel components were studied neat except for toluene - toluene was blended with 18.9% nheptane by liquid volume to increase the fuel reactivity.

The formation of particles in the combustion chamber of a direct injection diesel engine has been studied with the use of the Total Cylinder Sampling Method. With this method, nearly the entire contents of the cylinder of an operating diesel engine can be quickly removed at various times during the combustion process. The particle mass and size distributions present in the sample can then be analyzed. If quenching of the combustion process is quick and complete, the resulting samples are representative of the particle mass and size distributions present in the cylinder near the time sampling begins. This paper discusses the effect of injection timing and piston bowl shape on the particle formation and oxidation. Example size distribution measurements are also shown. The particle concentrations in the cylinder were measured for three different injection timings with the standard piston installed in the engine.

This program used a 0.6 liter DI NA single cylinder diesel engine to study the influence of ferrocene as a fuel additive on particulate and NOx emissions and heat release rates. Previous Studies1,15 have shown efficiency and particulate emission benefits only after engine conditioning. Two engine configurations were tested: standard aluminum piston with normal engine deposits and a second test with the engine cleaned to “new engine condition”, but with the piston replaced with a thermal barrier coated piston. Particle concentration and size in roughly the 7.5 to 750 nm diameter range were measured with a condensation nucleus counter and an electrical aerosol analyzer. Heat release rates and IMEPs were calculated from in-cylinder pressure data. Particle number concentrations increased substantially when the 250 ppm dose was first started with both engine configuration, but decreased 30% to 50% with conditioning.

This report describes tests of a fuel additive in a medium-duty, high-swirl, direct-injection diesel engine. The additive was found to have little influence on general combustion performance or on NOx emissions. On the other hand, it had a profound effect on particulate emissions. This was most clear under high load where particle emissions are highest. Here, when the engine was switched from running on the base fuel to the additive treated fuel, particle emissions at first increased and then fell to levels about 40% lower (by particle volume) than those initially produced by the base fuel. The additive had a long lasting effect. After running with the additive for about 25 hours, emission levels with the base fuel were only slightly higher than those with the additive treated fuel. We believe that the additive action is associated with a combination of cleaning and surface conditioning. More work should be done to understand the relative importance of these two mechanisms.

Experiments were performed to measure the number-weighted particle size distributions emitted from a gasoline direct injection (GDI) engine. Measurements were made on a late model vehicle equipped with a direct injection spark ignition engine. The vehicle was placed on a chassis dynamometer, which was used to load the engine to road load at five different vehicle speeds ranging from 15 - 100 km/hr. Dilution of the exhaust aerosol was carried out using a two-stage dilution system in which the first stage dilution occurs as a free jet. Particle size distributions were measured using a TSI 3934 scanning mobility particle sizer. Generally speaking, the presence of the additives did not have a strong, consistent influence on the particle emissions from this engine. The polyether amine demonstrated a reduction in particle number concentration as compared to unadditized base fuel.