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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.

It has been reported that particulate emissions from diesel vehicles could be associated with damaging human health, global warming and a reduction in air quality. These particles cover a very large size range, typically 3 to 10 000 nm. Filters in the vehicle exhaust systems can substantially reduce particulate emissions but until very recently it was not possible to directly characterise actual on-road emissions from a vehicle. This paper presents the first study of the effect of filter systems on the particulate emissions of a heavy-duty diesel vehicle during real-world driving. The presence of sulfur in the fuel and in the engine lubricant can lead to significant emissions of sulfate particles < 30 nm in size (nanoparticles).

Particle emissions from four spark ignition engines were measured during steady state and transient chassis dynamometer tests. Transient Unified Drive Cycle tests were conducted at 0 °C and room temperature. Particle number, size distribution, active surface area, and photoelectric activity were determined. The results generally show low emission values for steady state operation of the warm engine. High particle concentrations are emitted in the first phase of the high-speed steady state testing. Once the engine is warmed up high emissions mainly occur during transient operation phases. The formation of nucleation mode particles is favored by the low concentration of carbonaceous soot, which offers volatile material little surface area for condensation.

Experiments were performed to measure the average and time-resolved particle number emissions and number-weighted particle size distributions 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 13 - 90 km/hr. Particle number emissions were measured using a TSI 3020 condensation nucleus counter, and size distributions were measured using a TSI 3934 scanning mobility particle sizer. Average polydisperse number concentration was found to increase from 1.1 × 108 particles/cm3 at 13 km/hr to 2.8 × 108 particles/cm3 at 70 km/hr. Under a closed-loop, stoichiometric homogeneous charge operating mode at 90 km/hr, number emissions fell to 9.3 × 107 particles/cm3 (at all other operating conditions, the engine was in a lean stratified charge operating mode).

Experiments were undertaken to determine some of the characteristics of exhaust particulate emissions in two port fuel injected spark ignition engines. A 2.3L 1993 GM Quad-4 engine and a 4.6L 1994 Ford V8 were tested. Sampling and dilution were accomplished through the use of a single-stage, low residence-time ejector diluter; dilution ratios were maintained at approximately 15:1. Number concentration was measured with a TSI 3020 condensation nucleus counter, and size distributions were measured using two scanning mobility particle sizers. The Quad-4 engine was used to determine the effects of the catalytic converter and deposit control additives on particulate emissions. The catalyst was found to remove particles with an efficiency as high as 78% at low power conditions (∼7 kW), dropping steeply with power, reaching a minimum value of approximately 10% at moderate power conditions (∼18 kW).

Exhaust particulate emissions from a 4-cylinder, 2.25 liter spark ignition engine were measured and characterized. A single-stage ejector-diluter system was used to dilute and cool the exhaust sample for measurement. The particulate measurement equipment included a condensation nucleus counter and a scanning mobility particle sizer. Exhaust measurements were made both upstream and downstream of the catalytic converter using three different fuels. Unlike particulate emissions in diesel engines, spark ignition exhaust particle emissions were found to be highly unstable. Typically, a stable “baseline” concentration on the order of 105 particles/cm3 is emitted. Occasionally, however, a “spike” in the exhaust particle concentration is observed. The exhaust particle concentrations observed during these spikes can increase by as much as two orders of magnitude over the baseline concentration.

Exhaust particle number concentrations and size distributions were measured from the exhaust of a 1995 direct injection, Diesel engine. Number concentrations ranged from 1 to 7.5×107 particles/cm3. The number size distributions were bimodal and log-normal in form with a nuclei mode in the 7-15 nm diameter range and an accumulation mode in the 30-40 nm range. For nearly all operating conditions, more than 50% of the particle number, but less than 1% of the particle mass were found in the nuclei mode. Preliminary indications are that the nuclei mode particles are solid and formed from volatilization and subsequent nucleation of metallic ash from lubricating oil additives. Modern low emission engines produce low concentrations of soot agglomerates. The absence of these agglomerates to act as sites for adsorption or condensation of volatile materials makes nucleation and high number emissions more likely.

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.

As part of an ongoing program to control the emissions of diesel-powered equipment used in underground mines, the U. S. Bureau of Mines evaluated exhaust emissions from a compression ignition engine using oxygenated diesel fuels and a diesel oxidation catalyst (DOC). The fuels include neat (100%) soy methyl ester (SME), and a blend of 30% SME (by volume) with 70% petroleum diesel fuel. A Caterpillar 3304 PCNA engine was tested for approximately 50 hours on each fuel. Compared with commercial low-sulfur diesel fuel (D2), neat SME increased volatile organic diesel particulate matter (DPM) but greatly decreased non-volatile DPM, for a net decrease in total DPM. The DOC further reduced volatile and total DPM NOx emissions were slightly reduced for the case of neat SME, but otherwise were not significantly affected. Peak brake power decreased 9% and brake specific fuel consumption increased 13 to 14% for the neat methyl soyate because of its lower energy content compared with D2.

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.

A system was designed for controlling fuel injection and ignition timing for use on a port fuel injected, gas-fueled engine. Inputs required for the system include manifold absolute pressure, manifold air temperature, a once per revolution crankshaft pulse, a once per cycle camshaft pulse, and a relative encoder pulse train to determine crank angle. A prototype card installed in the computer contains counters and discrete logic which control the timing of ignition and injection events. High current drivers used to control the fuel injector solenoids and coil primary current are optically isolated from the computer by the use of fiber optic cables. The programming is done in QuickBASIC running in real time on a 25 MHz 80486 personal computer. The system was used to control a gas-fueled spark ignition engine at various conditions to map the torque versus air-fuel ratio and ignition timing. Each surface was mapped for a given fuel flow and speed.

This paper examines three strategies of detecting knock that are less dependent of engine noise. The first strategy uses the exhaust temperature, the second uses a dithering method (systematically advancing and retarding the timing), while the third uses the standard deviation of knock intensity as the indicator of knock intensity. The first strategy proves to be difficult to detect knock since the exhaust temperature is strongly dependent on the combustion efficiency instead of knock intensity. The second strategy uses a conventional accelerometer but discriminates against mechanical noise by subtracting the knock intensity during the retarded part from that of the advanced part of a dither cycle. This approach is found to require averaging the signals over large number of engine cycles and using large dither amplitude. The third strategy uses the Difference of Knock Intensity strategy where two cycle standard deviation is used.

Computer modeling of electrical regeneration diesel particulate traps entails a variety of analytical fields including fluid flow, thermodynamics, heat transfer, particle technology, engine simulation, and combustion. Though extensive modeling has been performed on specific areas of electrical regeneration traps, very little has been performed on modeling the entire system. A system level approach to simulating an electrical regeneration trap would greatly improve the design optimization process of these systems. This paper describes a computer model that simulates the operation of an electrical regeneration diesel particulate trap. The model is used to predict a ceramic wall flow trap's performance on an urban bus and a comparison between the predicted values to actual data is made.

A system that allows collection and analysis of all of the exhaust from individual engine cycles has been built. Its development and performance are described. The system was used to study the cyclic variability of a 0.7 liter direct injection diesel cylinder operating at 1500 rpm and an equivalence of 0.6. Particulate emissions exhibited the greatest variability. The cyclic variability (standard deviation) of particulate emissions associated with in-cylinder processes was found to be about 40% of the mean. The variability of NOx emissions that could be associated with in-cylinder processes was much lower, only about 6% of the mean. The variability of pressure development in the combustion process itself, as indicated by IMEP, was very low, less than 2% of the mean.

A modified CFR Cetane engine was used to analyze combustion characteristics and emissions of minimally processed coal liquids (MPCLs). To aid in combustion of the coal liquids, the ability to heat the fuel and inlet air was added. The MPCLs are derived from atmospheric distillation of coal liquids. The coal liquids are byproducts of coal gasification of Elkhorn bituminous and North Dakota lignite using the atmospheric, air blown Wellman-Galusha and pressurized, oxygen blown Lurgi gasifiers, respectively. The MPCLs were compared with three reference fuels: diesel No. 2, U12 (21 cetane number) and #-methyl napthalene (0 cetane number). The inlet air was heated from 340 to 535 K and the compression ratio was varied from 13 to 31 to provide sufficient range in temperature and pressure necessary for the combustion of low cetane number fuels. At each operating condition, fuel consumption, cylinder pressure, ignition delay, and emisions were measured.

Soot formation and oxidation within the cylinder of a divided-chamber diesel engine have been studied experimentally and predicted analytically using a diesel combustion model. Experimental measurements of in-cylinder particle concentration were made using a unique sampling system which samples and quenches nearly the entire contents of the cylinder on a time scale of less than 1 ms. The experimental measurements are compared with predictions made using a stochastic combustion model coupled to an Arrhenius-type soot formation model, and 02 and OH soot oxidation models. Five engine conditions: low-load standard-timing (base case), high-load standard-timing, low-load advanced-timing, low-load standard-timing + EGR, and low-load standard-timing + 02, were examined experimentally, but only the first three were modeled.

A 0.5 liter single-cylinder, indirect-injection diesel engine has been fumigated with producer gas, a mixture of principally H2, CO, and N2 with a heating value of about 160 Btu/ft3. Producer gas is produced by air-blown gasification of coal or biomass. Measurements of power, efficiency, cylinder pressure, and emissions were made. At each operating condition, engine load was held constant, and the gas-to-diesel fuel ratio was increased until abnormal combustion (severe efficiency loss, missfire, knock, or preignition) was encountered. This determined the maximum fraction of the input energy supplied by the gas, Emax, which was found to be dependent upon injection timing and load. At light loads, Emax was limited by severe efficiency loss and missfire, while at heavy loads it was limited by knock or preignition.

An improved system for total cylinder sampling from an indirect injection passenger car type diesel engine has been developed. The system utilizes explosively actuated cutters which cut aluminum diaphragms in both the main combustion chamber and precombustion chamber at a predetermined time. The cylinder charge is rapidly cooled and diluted as it flows from the chambers into the sampling system. When sampling from near top dead center, cylinder pressure decay half times of about 0.5 ms have been achieved. The system has been used to determine NOx concentrations in the cylinder as a function of crankangle position at 1000 rpm with equivalence ratios of 0.32, 0.52, and 0.60. NOx concentrations rise rapidly shortly after the onset of combustion, attain maxima which are 2 to 10% higher than corresponding exhaust concentrations at about 5-10 crankangle degrees after the end of the fuel injection process and then slowly decay to exhaust levels.

A dumping apparatus has been developed and tested for total cylinder sampling from an indirect injection diesel engine. The apparatus design is described in detail along with the experimental system. The system performance is given for one engine operating condition. Graphs of main chamber and pre-chamber pressures versus crankangle are also included. The system demonstrated a sampling accuracy of ±2 degrees of crankangle.

Diesel exhaust aerosol particle size measurements have been made by three techniques and compared. The techniques used were based on electrical mobility, diffusion, and inertial separation. The instruments used were a Thermo Systems Incorporated (TSI) Model 3030 Electrical Aerosol Analyzer, TSI Model 3040 diffusion battery in conjuction with a TSI Model 3020 Condensation Nucleus Counter, and a Univeristy of Minnesota micro-orifice impactor (0.1 μm cut size). Particle samples were also examined by electron microscopy and volatile fractions were determined by vacuum sublimation. Measurements were made on two engines, one direct injection and one indirect injection swirl chamber. Engine operating conditions were chosen to give a wide range of exhaust particle characteristics. The size measurements agreed well in the regions of instrument overlap. Measured number mean diameters varied from 0.01 μm to 0.1 μm.