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A single-cylinder, spark-ignited engine was run on a certification test gasoline to saturate the oil in the sump with fuel through exposure to blow-by gas. The sump volume was large relative to production engines making its absorption-desorption time constant long relative to the experimental time. The engine was motored at 1500 RPM, 90° C coolant and oil temperature, and 0.43 bar MAP without fuel flow. Exhaust HC concentrations were measured by on-line FID and GC analysis. The total motoring HC emissions were 150 ppmC1; the HC species distribution was heavily weighted to the low-volatility components in the gasoline. No high volatility components were visible. The engine was then fired on isooctane fuel at the above conditions, producing a total engine-out HC emission of 2300 ppmC1 for Φ = 1.0 and MBT spark timing.

FTP emissions tests on a passenger vehicle equipped with a 1.8 L IDI turbo-charged diesel engine show that the mass emissions of particles decrease by (36±8)% when 16.6% dimethoxymethane (DMM) by volume is added to a diesel fuel. Particle size measurements reveal log-normal accumulation mode distributions with number weighted geometric mean diameters in the 80 - 100 nm range. The number density is comparable for both base fuel and the DMM/diesel blend; however, the distributions shift to smaller particle diameter for the blend. This shift to smaller size is consistent with the observed reduction in particulate mass. No change is observed in NOx emissions. Formaldehyde emissions increase by (50±25)%, while emissions of other hydrocarbons are unchanged to within the estimated experimental error.

The effect of fuel preparation on time-resolved, engine-out hydrocarbon (HC) emissions over a Federal Test Procedure cycle [FTP (75CVS)] for a ULEV vehicle equipped with a 6 cylinder engine has been investigated. Using a single-cone injector, the HC mole fraction in Bag 1 increased by a factor of 3-4 during each of the three accelerations in the first 100 sec after start. No such increases were observed in Bag 3 when the engine was fully warm. The increases during accelerations in Bag 1 were reduced by a factor of 3 when using a Dual-cone fuel injector as a drop-in substitute. The total, tailpipe FTP (75CVS) mass emissions were 25% smaller when using the Dual-cone injector. These results demonstrate that fuel preparation can affect HC emissions from a vehicle very significantly during cold start as has been deduced previously during cold-start tests using a dynamometer-controlled engine.

Collection of diesel exhaust using the Tapered Element Oscillating Microbalance (TEOM) instrument was investigated as an alternative to the traditional method of filter weighing for particulate matter mass determination. Such an approach, if successful, would eliminate considerable manual labor involved in weighing, as well as the delay of hours or days before final results were known. To avoid known artifacts in the second-by-second mode of operation, the TEOM was used in a phase-by-phase mode and was equilibrated with air of constant temperature and humidity before each measurement. Electrically operated valves were used to automate the equilibration and measurement process. The study also included a comparison between two types of TEOM filter - an older type and a new one designed by the TEOM manufacturer for more uniform flow and less flexing. Best results were obtained with the TEOM using the new filter under no-flow conditions.

The effect of engine operating parameters (speed, spark timing, and fuel-air equivalence ratio [Φ]) on hydrocarbon (HC) oxidation within the cylinder and exhaust system is examined using propane or isooctane fuel. Quench gas (CO2) is introduced at two locations in the exhaust system (exhaust valve or port exit) to stop the oxidation process. Increasing the speed from 1500 to 2500 RPM at MBT spark timing decreases the total, cylinder-exit HC emissions by ∼50% while oxidation in the exhaust system remains at 40% for both fuels. For propane fuel at 1500 rpm, increasing Φ from 0.9 (fuel lean) to 1.1 (fuel rich) reduces oxidation in the exhaust system from 42% to 26%; at 2500 RPM, exhaust system oxidation decreases from 40% to approximately 0% for Φ = 0.9 and 1.1, respectively. Retarded spark increases oxidation in the cylinder and exhaust system for both fuels. Decreases in total HC emissions are accompanied by increased olefinic content and atmospheric reactivity.

Modern four-valve engines are running at ever higher compression ratios in order to improve fuel efficiency. Hotter cylinder bores also can produce increased fuel economy by decreasing friction due to less viscous oil layers. In this study changes in compression ratio and coolant temperature were investigated to quantify their effect on exhaust emissions. Tests were run on a single cylinder research engine with a port-deactivated 4-valve combustion chamber. Two compression ratios (9.15:1 and 10.0:1) were studied at three air/fuel ratios (12.5, 14.6 and 16.5) at a part load condition (1500 rpm, 3.8 bar IMEP). The effect of coolant temperature (66 °C and 108°C) was studied at the higher compression ratio. The exhaust was sampled and analyzed for both total and speciated hydrocarbons. The speciation analysis provided concentration data for hydrocarbons present in the exhaust containing twelve or fewer carbon atoms.

Absorption of fuel in engine oil layers has been shown to be a possible source of hydrocarbon (HC) emissions from spark-ignited engines. However, the magnitude of this source in a normally operating engine has not been determined unambiguously. In these experiments, a series of n-alkanes of widely different solubility (n-hexane through undecane) was added (1.5 wt % each) to a Base gasoline (CA Phase 2). Steady-state experiments were carried out at two coolant temperatures (339 and 380 K) using a single-cylinder engine with the combustion chamber of a production V-8. Both total and speciated engine-out HC emissions were measured. The emissions indices of the heavier dopants did not increase relative to hexane at either coolant temperature.

Concentrations of individual species in the engine-out exhaust gas from a gasoline-fueled (101.5 or 91.5 RON), direct-injection, compression-ignition (HCCI) engine have been measured by gas chromatography over the A/F range 50 to 230 for both stratified and nearly homogeneous fuel-air mixtures. The species identified include hydrocarbons, oxygenated organic species, CO, and CO2. A single-cylinder HCCI engine (CR = 15.5) with heated intake charge was used. Measurements of the mass and size distribution of particulate emissions were also performed. The 101.5 RON fuel consisted primarily of five species, simplifying interpretation of the exhaust species data: iso-pentane (24%), iso-octane (22%), toluene (17%), xylenes (10%), and trimethylbenzenes (9%).

PM (Particulate Matter) emitted by vehicles and engines is most often measured quantitatively by collecting diluted exhaust samples on filters that are weighed pre-and post-test. Static charge that builds on filters from handling can dramatically influence the measurement results, especially at low PM levels such as those produced when testing typical gasoline-powered vehicles or diesel-powered vehicles employing DPF (Diesel Particulate Filter) technology. It was found that proper grounding of equipment, furniture, and floor was insufficient to mitigate the effects of static electricity when using the traditional method of weighing from a glass Petri dish in the presence of an ionizing bar. A stainless steel EDP (Electrostatic Discharge Platform), using commercially available ionizing bars, was developed and proven to successfully reduce filter measurement variability when weighing PTFE membrane filters on a 0.1 microgram balance.

Previous research into Particulate Matter (PM) emissions from a spark-ignition engine has shown that the main factor determining the how PM emissions respond to transient engine operating conditions is the effect of those conditions on intake port processes such as fuel evaporation. The current research extends the PM emissions data base by examining the effect of transient load and speed operating conditions, as well as engine start-up and shut-down. In addition, PM emissions are examined during “real-world” driving conditions - specifically, the Federal Test Procedure. Unlike the previous work, which was performed on an engine test stand with no exhaust gas recirculation and with a non-production engine controller, the current tests are performed on a fully-functional, production vehicle operated on a chassis dynamometer to better examine real world emissions.

The numbers, sizes, and derived mass emissions of particles from a production DISI engine are examined over a range of engine operating conditions. Particles are sampled directly from the exhaust pipe using heated ejector pump diluters. The size distributions are measured using a scanning mobility particle sizer. The numbers and sizes of the emitted particles are reported for stratified versus homogeneous operation and as a function of fuel injection timing, spark timing, engine speed, and engine load. The principal finding is that particle number emissions increase by about a factor of 10 - 40 going from homogeneous to stratified charge operation. The particulate emissions exhibit a strong sensitivity to injection timing; generally particle number and volume concentrations increase steeply as the injection timing is retarded, except over a narrow portion of the range where the trend reverses.

This paper explores the extent to which standard dilution tunnel measurements of motor vehicle exhaust particulate matter modify particle number and size. Steady state size distributions made directly at the tailpipe, using an ejector pump, are compared to dilution tunnel measurements for three configurations of transfer hose used to transport exhaust from the vehicle tailpipe to the dilution tunnel. For gasoline vehicles run at a steady 50 - 70 mph, ejector pump and dilution tunnel measurements give consistent results of particle size and number when using an uninsulated stainless steel transfer hose. Both methods show particles in the 10 - 100 nm range at tailpipe concentrations of the order of 104 particles/cm3.

The requirement of reducing HC emissions during cold start and improving transient performance has prompted a study of the fuel injection process. Port-fuel-injection with the Intake-valve open using small droplets is a potentially feasible option to achieve the goals. To gain a better understanding of the injection process, the effects of droplet size, injection timing, and coolant temperature on the total and speciated HC emissions were tested In a Single-cylinder engine. It was found that droplet size plays an important role in the total HC emission increase during open-valve injection, especially with cold operation. Large droplets (300 μm SMD) produced a substantial HC increase while small droplets (14 μm SMD) produced no observable increase. Increase In the total HC emissions was always accompanied by an increase in the heavy fuel components in the exhaust gases.