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Source apportionment analysis for exposure to air toxics from conventional and oxygenated fuel was performed for different microenvironments. Personal toxic exposure data were taken from previous studies conducted in areas where MTBE oxygenated fuels were used. Refueling, commuting, and occupational microenvironments were all examined. The emission source, either tailpipe or evaporative, was estimated using the ratio of MTBE/benzene as an emission finger print. ASPEN simulations were completed to estimate the MTBE to benzene ratio for evaporative emissions from vapor above the fuel using vapor-liquid equilibrium models. Expected MTBE to benzene ratios in the tailpipe exhaust were obtained from previous studies. Refueling exposure was found to be dominated by evaporative emissions, specifically flash from the fuel tank for stations with Stage I controls, and evaporation of whole fuel for stations with Stage II controls.

A durability test was performed with a direct injection turbocharged, intercooled tractor diesel engine, fueled with a vegetable oil pressed from mustard seeds. The unesterized mustard seed oil (MSO) was cleaned by simply letting it stand and clear. A charge air cooler was installed in the engine. Basic performance and exhaust emissions were first determined by operating the engine on diesel fuel oil (DFO). Thereafter, the same measurements were made with MSO as fuel. At the third stage, the engine was operated for 150 hours according to a standard loading cycle using MSO as fuel. After this running period, performance and exhaust emissions were again measured. The results showed that the rated power had decreased somewhat during the period. The maximum torque and brake thermal efficiencies, however, were very similar to that observed before the test. The CO emissions were higher at some low loads, but the exhaust smoke had been reduced.

The methyl ester of soybean oil, known as biodiesel, is receiving increasing attention as an alternative fuel for diesel engines. Biodiesel is a nontoxic, biodegradable, and renewable fuel with the potential to reduce engine exhaust emissions. However, previous results have shown that biodiesel-fueled engines produce a higher fraction of soluble organic material (SOF) in their exhaust particulate matter than when petroleum-based diesel fuel is used even when the total particulate emissions are lowered. Most researchers have also observed that unburned hydrocarbon (HC) emissions decrease with biodiesel. In this project, the formation of SOF in exhaust particulates under different measurement conditions and the possibility of deposition of HC vapor in the sampling lines of the HFID detector were studied experimentally and theoretically when the diesel engine was fueled with biodiesel.

The paper describes an experimental study concerning the feasibility of using bio-oil obtained from flash pyrolysis of wood for fuelling diesel power plants. The research is based on various tests aimed at verifying relevant operative characteristics of the fuel: spray analyses, engine tests, thermogravimetric analyses (TGA), single-drop reactor tests and corrosion tests. The spray analyses show that the achievement of a satisfactory atomisation with flash-pyrolysis oil is problematic. The engine experimentation shows that flash-pyrolysis oil needs to be modified or mixed (e.g. with alcohol) to make self ignition possible. Besides, unacceptable build-up of carbonaceous deposits, injection system clamping and engine seizure occur. Very large char generation is the main finding of the tests in the TGA apparatus and in the single-drop atmospheric reactor (“drop-tube”). The corrosion tests demonstrate that steel undergoes fast erosion by contact of flash-pyrolysis oil.

This paper depicts the main topics of the experimental investigation on alcohol engine development field, aiming at the engineering targets for the emission levels. The first part of this study was focused on engine design optimization for running on ethanol mixed with poly-ethylene glycol (PEG) as ignition improver. It was shown that some design changes in compression ratio, turbine casing, injector nozzle configuration and exhaust pressure governor (EPG) activation, lead to a better engine thermodynamics and its thermochemistry. The second objective of this study was the investigation of engine performance and emission levels, when the ignition improver diethyl ether (DEE) would be generated on board via catalytically dehydration of ethanol, and used directly as soluble mixture or separately fumigated.

This study was carried out in a transparent engine. In this work we have compared results obtained from a natural gas engine fueled with a standard continuous gas injection with results obtained from a gasoline engine fueled with electronic sequential injection. To compare performance between engines of both types, we have carried out quantitative measurements of fuel/air ratio before ignition and flame image recording. Laser induced fluorescence was used with an excimer KrF laser. As the natural gas and gasoline were not fluorescent at the laser wavelength (248nm), a tracer has been mixed to the fuel. Furthermore, as this tracer is also a fuel, the fresh charge in the cylinder was fluorescent, whereas the burnt gas was not, which enable detection of flame fronts. The images recorded at different crank-angles allowed determination of parameters such as inhomogeneity, overall flame width and spatial propagation speed of flame.

This work investigates the mixture formation process in a SI engine with air-assisted port fuel injection. The combination of this injection method with low flow velocities and wall temperatures, typical of engine starting and warm-up conditions, results in the build-up of a fuel film along the walls of the port. This in turn results in increased fuel consumption and high unburned hydrocarbon emissions. This investigation concluded that with the application of air-assisted injectors, the mixture formation process could be improved with a resulting reduction of the fuel-film build-up in the intake ports. Comparative measurements of the drop size distribution from conventional and air-assisted injectors showed that even very small amounts of air resulted in better fuel atomization. An experimental analysis of the effect of unsteady air flow on spray dispersion and fuel film creation characteristics of air supported injectors was undertaken for a straight test section.

The forced level of permissible vehicle exhaust emissions requires accurate control of the air-fuel ratio. In other words, the amount of air flowing into the cylinder and the fuel quantity must be known accurately. The wall mass of deposited fuel in the manifold of an injection system has a significant effect on fuel maldistribution and the air-fuel ratio excursion. This paper outlines an identification process of a mixture preparation model of the fuel injection in a spark ignition engine. A type of a prototype combustion probe integrated into a spark plug has been developed. This in-cylinder sensor which measures the combustion luminosity is characterized by the good correlation with traditional combustion parameters, including the air-fuel ratio. This paper describes the application of in-cylinder probe in the mixture strength examination. The proposed measure method estimates the fuel mass in a cylinder (where air mass has been constant) as well as the fuel film model parameters.

The Fischer-Tropsch (F-T) catalytic conversion process can be used to synthesize diesel fuels from a variety of feedstocks, including coal, natural gas and biomass. Synthetic diesel fuels can have very low sulfur and aromatic content, and excellent autoignition characteristics. Moreover, Fischer-Tropsch diesel fuels may also be economically competitive with California diesel fuel if produced in large volumes. An overview of Fischer-Tropsch diesel fuel production and engine emissions testing is presented. Previous engine laboratory tests indicate that F-T diesel is a promising alternative fuel because it can be used in unmodified diesel engines, and substantial exhaust emissions reductions can be realized. The authors have performed preliminary tests to assess the real-world performance of F-T diesel fuels in heavy-duty trucks. Seven White-GMC Class 8 trucks equipped with Caterpillar 10.3 liter engines were tested using F-T diesel fuel.

This study was performed to quantify the effects of injector targeting and fuel volatility on transient A/F excursions and fuel film mass in a port fuel injected (PFI) engine. Two injector targeting positions as well as injection timing and four different fuels were studied. Warm-up tests were performed with the throttle ramped between two positions over a one second interval to provide smooth changes in airflow and injected fuel. The exhaust A/F was recorded for each transient and fit using the X-τ model to estimate the change in the liquid fuel stored in the port and cylinder due to the throttle ramp. The change in fuel stored in the films was: ∼20% less with valve targeting ∼30% less with IVO injection timing 50-100% higher for hesitation fuel

This work presents an approach for developing a control algorithm for fuel delivery at cold start based on C.F. Aquino's fuel film dynamic model [1]. The control algorithm presented takes into account the fuel delivery both in the fuel film form and in the form of droplets and vapor, that allows setting the limits on the fuel supply calculation in order to achieve good startability (without spark plug wetting) and low CO and HC emission. An algorithm was developed as a computer program and tested in calculation experiments. Although the empirical parameters of mathematical fuel delivery model were determined on a carburetor engine, this control algorithm is also applicable to engines with fuel injection due to similarity of the physical nature of mixture preparation.

The effects of injector targeting and fuel volatility on transient fuel dynamics were studied with a comprehensive quasi-dimensional model and compared with experimental results from Part I of this report (1). The model includes the transient, convective vaporization of four multi-component fuel films coupled with a transient thermal warm-up model for realistic valve, port and cylinder temperatures (2, 3). Two injector targetings were analyzed, first with the fuel impacting the intake valve and in addition, the fuel impacting the port floor directly in front of the intake valve. The model demonstrates the importance of both component temperature and fuel impaction area on fuel vaporization, transient air fuel ratio (AFR) response and the amount of liquid fuel entering the cylinder. Generally, a smaller injector footprint area will lead to more liquid fuel entering the cylinder even if the spray is targeted at the back of the intake valve.

The occurrence of flash boiling in the fuel spray of a Port Fuel Injected (PFI) spark ignition engine has been observed and photographed during normal automotive vehicle operating conditions. The flash boiling of the PFI spray has a dramatic affect on the fuel spray characteristics such as droplet size and spray cone angle which can affect engine transient response, intake valve temperature and possibly hydrocarbon emissions. A new method of correlating the spray behavior using the equilibrium vapor/liquid (V/L) volume ratio of the fuel at the measured fuel temperature and manifold pressure is introduced.

Early research in the application of nonthermal plasma technology to reduce NOx in combustion emissions established that the chemistry resulting from the direct excitation of exhaust gas streams is dominated by oxidation of NO to NO2 and nitric acid, undesirable end products for mobile systems. An alternative to direct plasma generation in diesel exhaust has now been demonstrated to shift this exhaust NOx chemistry from oxidation toward reduction to nitrogen and oxygen. The new approach reacts NO with atomic nitrogen injected into the exhaust stream through multiple electrically excited high-speed nitrogen jets. Chemical reduction of more than half of the NO in diesel exhaust has so far been demonstrated, with only minimal production of N2O. The technology functions well in the sooty and wet conditions characteristic of diesel exhaust. A system is presently being built for testing and evaluation on exhaust slipstreams at a Caterpillar Inc. test facility.

The optimal operating condition of the patented Multi-Stage Corona Discharge System at pulsed mode has been investigated to reduce NOx emission from the exhaust gas of commercial diesel engine vehicles. The design parameters of the system have been tested at numerous operating conditions and upgraded to improve their performance. The compositions of simulated and actual exhaust gas have been measured with a typical exhaust gas analyzer downstream of the system and also analyzed with a FT-IR spectrophotometer. The removal efficiency of NO varied from 20 to 90% depending upon the flow rate and initial NO concentration. The actual residence time of exhaust within the discharge volume played an important role for optimal design. Those results are directly related to the energy consumption of the removal reaction and, ultimately, the design characteristics.

This paper reports efficient treatment of diesel emission with transient, non-equilibrium plasma created by a pulsed corona discharge. The transient plasma (∼50 ns) is found to reduce NOx emission in a flow of 1-10 liters/ second with energy cost ≤10-20 eV/molecule, corresponding to a fraction of source power of ∼5%. The efficiency of NOx reduction is a complex function of parameters that include pulse width, pulse polarity, current density, repetition rate, and reactor design. It was found that best efficiencies are correlated with a low current density (0.2A/cm2) and high repetition rate (1kHz) under high flow rate. Careful optimization of all these parameters is required to reach cost effective NOx reduction.

A set of model fuels has been designed, using the Major-Component Fuel approach, to represent a range of gasoline mid-range and back-end volatilities. The thermo-physical properties of the model fuels have been used, together with a simple model of inlet system, to calculate liquid-vapour mass fractions in the inlet system, and the composition of the inlet port wall film. This has enabled the effects of gasoline volatility, speed, load and inlet port wall temperature to be studied systematically. The results indicate that, in cold start, only some 20-30% of the injected fuel is vapourised in the inlet port, leading to an accumulation of liquid fuel in the inlet port wall film reservoir. As the engine warms up, the mass of fuel in the reservoir decreases, and its composition changes, becoming progressively richer in heavy end species. Mid-range volatility affects the cold start behaviour, whilst back-end volatility affects the approach to fully-warmed up operation.

Recent work has shown that energy efficiencies as well as yields and selectivities of the NOx reduction reaction can be enhanced by combining a plasma discharge with select catalysts. While analysis of gas phase species with a chemiluminescent NOx meter and mass spectrometer show that significant removal of NOx is achieved, high background concentrations of nitrogen preclude the measurement of nitrogen produced from NOx reduction. Results presented in this paper show that N2 from NOx reduction can be measured if background N2 is replaced with helium. Nitrogen production results are presented for a catalyst system where the catalyst is in the plasma region and where the catalyst is downstream from the plasma. The amount of N2 produced is compared with the amount of NOx removed as measured by the chemiluminescent NOx meter. The measured nitrogen from NOx reduction accounts for at least 40% of the total NOx removed for both reactor configurations.

Dielectric barrier discharges offer the advantage to excite molecules to reaction processes on a low temperature level in an O2 containing exhaust gas of gasoline or diesel engines. With the aim of a flexible coaxial reactor and a compact and efficient generator the influence of geometric and electric parameters on the reduction of exhaust gas components was determined. Geometric parameters studied were gap width, length, contour of the reactor. Electric parameters were: voltage curve, voltage height, frequency and electric power. Using the advantage of low temperature reactions it was possible to reduce the HC emission of a gasoline engine by about 35% within an electric power of 1000 W.

Destruction of NOx (200 ppm - 1%) by dielectric barrier corona discharge in zero air and nitrogen was studied at 298 K and pressure 1 atm. Effects of adding of hexane or ammonia were also evaluated. The kinetics and the products of the destruction were determined as functions of the specific discharge energy, contact time and NOx concentration. Two ranges of the specific energy deposition which reflect the competition between the destruction and production of NOx in discharge were found. At low specific energies (< 500 J/L) an efficient removal of NOx both in air and nitrogen is observed.