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Dimethyl Ether (DME) is a promising new alternative fuel for compression ignition DI engines. However, some problems arise from the poor lubricity of DME. Breakdown of the film bearing between needle and sleeve of the injector can lead to mechanical wear and leakage, a problem that is not mitigated easily. For example, the application of returning the leakage to fuel tank could raise a back pressure on the injection needle. This pressure can affect injection rate and consequently engine performance. In this study, fuels based on various DME to gas oil (diesel fuel) ratios were investigated, in part. Physical and chemical properties of DME and gas oil are shown to lead to mutual solubility at any ratio. Blended fuels have a higher lubricity compared with pure’ DME and a better injection spray compared with pure gas oil.

A novel way of using low-cetane-number petroleum gases in a compression ignition (CI) engine is introduced, by directly injecting blends of such fuels with dimethyl ether (DME), a high-cetane-number alternative fuel for low soot emissions. This method both extends advantages of DME and complements its deficiency. Although DME mixes with most hydrocarbon fuels in any ratio, in order to demonstrate the feasibility of the new method and facilitate the analysis, DME-propane blends were investigated in a direct injection CI engine. Some findings of the study are listed. In the engine operated by DME and propane blends, there was no need for significantly increasing the complexity of the fuel system than that employed in the use of neat DME. For the same reason, this method eliminates or minimizes cumbersome hardware necessary when the said gaseous fuels are separately introduced in CI engines.

The CFD model, based on the LANL KIVA-3 computer code, modified to account for the multi-step dimethyl ether, DME/air, oxidation chemistry, was developed and used to study the neat DME combustion dynamics in a constant volume at Diesel-like conditions and in the Volvo AH10A245DI Diesel engine. Constant volume simulations confirm high ignition quality of neat DME in air. The results of engine modeling illustrate that the injection schedule used for Diesel fuel is not optimal for DME. Surprisingly, the positive gain and peak pressure levels comparable with those for Diesel fuel were obtained using an early (∼ -20 ATDC) injection through a nozzle of a larger diameter at reduced injection pressures and velocities (∼150m/s) preventing too rapid spray atomization. At these conditions, combustion heat release has a specific two-stage character with a peak value placed behind the TDC.

The vapor phase of an evaporating spray from a heavy-duty Diesel common-rail injection system has been investigated with an optical diagnostic technique based on linear Raman scattering, which has been extended to the application in fuel sprays. One-dimensional spatially resolved Raman measurements of the air/fuel-ratio have been performed in the spray region with high local and temporal resolution in an injection chamber at an air pressure of 4.5 MPa and at a temperature of 450°C. The influence of different parameters, such as rail pressure, nozzle geometry and injection duration on the temporal evolution of the local air/fuel-ratio in the vapor phase has been studied quantitatively, and results from a selected spatial location are compared. Furthermore, the effect of physical/chemical fuel properties on the evaporation dynamics has been investigated by performing measurements with two different fuels.

The variation of the crankshaft's speed is influenced by the action of the cylinders and shall reflect the contribution of each cylinder to the total engine output. At the same time, the speed variation is influenced by the torsional stiffness of the cranks, the mass moments of inertia of the reciprocating mechanisms and the average speed and load of the engine. As the result, the variation of angular motion of the crankshaft is complex, each particular influence changing its importance as speed and load are modified. The diagnostic method presented in the paper is based on the analysis of the amplitudes and phases of the lowest harmonic orders of the measured speed and is capable to determine the average Indicated Mean Effective Pressure (IMEP), to detect nonuniformities in cylinder operation and to identify the faulty cylinder(s).

A statistical method is described which allows a very accurate determination of the correlation between pressure and volume. The basis of the method is the pressure measurement of an engine under motoring conditions and correcting the pressure diagram with respect to heat and blow-by losses. Computation of the polytropic exponent dependent on error of phase lag determines the correlation in the pressure volume diagram. Since the internal processes in an IC engine under motoring conditions differ significantly from the ones under firing conditions, some modifications in the heat and blow-by losses models are necessary in order to be successfully applied in the proposed method. A simple optimization approach has therefore been used to correct both models. Several pressure diagrams measured under engine motoring conditions and at the different engine speeds have been studied.

The state of Ohio established a project to demonstrate the use of ethanol flexible-fuel vehicles (FFV) in their fleet operations. This study includes ten FFVs and three gasoline vehicles operated by five state agencies. The two-year project included data collection on vehicle maintenance and fueling, cost of operation, and fleet management comments. The project also included emissions testing of two ethanol FFVs and two standard gasoline vehicles.

Dedicated natural gas engines suffer the disadvantages of limited vehicle range and relatively few refueling stations. A vehicle capable of operating on either gasoline or natural gas allows alternative fuel usage without sacrificing vehicle range and mobility. However, the bi-fuel engine must be made to provide equal performance on both fuels. Although bi-fuel conversions have existed for a number of years, historically natural gas performance is degraded relative to gasoline due to reduced volumetric efficiency and lower power density of CNG. Much of the performance losses associated with CNG can be overcome by increasing the compression ratio. However, in a bi-fuel application, high compression ratios can result in severe engine knock during gasoline operation. Variable intake valve timing, increased exhaust gas recirculation and retarded ignition timing were explored as a means of controlling knock during gasoline operation of a bi-fuel engine.

This paper describes an investigation into a method of starting a spark ignition IC engine in cold ambient conditions, that normally operates on methanol or ethanol. Hardware was designed and installed in two Volvo S70 vehicles which allowed the delivery of gasoline to the combustion chamber during starting. The engine management system was modified to control the gasoline delivery and to manage the transition from the gasoline start back to normal operation on methanol or ethanol.

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.