Search Results

Exhaust emissions from cars using reformulated gasoline (RFG) that meets European 2005 regulations for gasoline quality were compared to the emissions from cars using gasoline that meets European 2000 regulations (EU2000). Methyl Tertiary Butyl Ether (MTBE) and Tertiary Amyl Methyl Ether (TAME) were used as oxygenates in the reformulated gasoline. The EU2000 gasoline contained no oxygen. Regulated, particulate and PAH exhaust emissions were measured at 22°C for 7 cars and at -7°C for 5 cars using the European MVEG cycle for year 2000 (ECE+EUDC). One of the cars was equipped with a lean burn engine, one with a direct injection engine and one was a carburetor equipped car without a catalytic converter. All other cars were equipped with multi point port fuel injection and a catalytic converter. Mutagenic activity of particulate mass was evaluated using the Ames test.

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.

Cold flow properties have historically been important for diesel and jet fuels. Reflecting the importance of cold flow properties, several standards have been developed to characterize pour point, cloud point, and filterability. An emphasis on characterizing fuels based on standard testing methods has led to large amounts of data that describe how fuels perform but very little published data that describe what is happening at the molecular level and to the composition of fuels. Motivated by a desire to have an improved understanding of the cold flow behavior of Fischer-Tropsch fuels, an experimental method was developed to provide easy acquisition of data on the changing compositions of liquid and solid phases as Fischer-Tropsch and diesel fuels traverse cloud point, pour point, and additive-enhanced pour point temperatures.

About 10 years ago in the US, an automotive OEM consortium formed the Oxygenated Fuels Task Force which in turn created the SAE Cooperative Research Project Group 2 to develop a simple rational method for qualifying materials. At that time the focus was Methanol/Gasoline blends. This work resulted in SAE J1681, Gasoline/Methanol Mixtures for Materials Testing. Recently this document was rewritten to make it the single, worldwide, generic source for fuel system test fluids. The paper will describe the rationale for selecting the fuel surrogate fluids and why this new SAE standard should replace all existing test fuel or test fluid standards for fuel system materials testing.

Cavitation has been known to occur in injector nozzles. It is known that the mass flow rate from a nozzle and occurrence of cavitation in nozzle holes are dependent on injection pressure and back pressure together with the nozzle geometry and needle effects. Interestingly, injected mass from sharp inlet hole nozzles under these conditions is independent of back pressure for a range of pressures under cavitating flows (similar to choking). In the past, information on the change in the spray parameters and the Sauter mean diameter (SMD) for these varying isolated back pressures has not been available. In this study spray visualizations, SMD measurements and momentum estimates for sharp and rounded inlet nozzles were performed for a range of upstream and back pressures while keeping the ambient density constant. A Live Digital Light Extinction Technique (LDLET) was developed and applied as the optical technique for spray Sauter mean diameter measurements.

This paper presents the results of a study on the effect of fuel physical properties, ambient temperature and fuel droplet initial diameter on droplet evaporation rates. The study was concentrated on comparison of evaporation rates for both diesel and Rapeseed Methyl Ester (RME). Based on results obtained from tests, a mathematical model is developed by using non-dimensional analysis. Tests were carried out at the atmosphere pressure with a temperature variation from 150°C to 250°C. A high-speed video system was used to observe and record images of suspended fuel droplets that were analysed with a purposely-designed image process method. A satisfactory agreement between test results and simulation data has been achieved. It is concluded that diesel fuel vaporisation is more sensitive to ambient temperature and initial diameter than RME droplets.

When developing diesel injection simulation models, accurate data of physical properties of fluids used are needed if best results are to be obtained. This paper presents measured values of density, I.C. (I.C.), viscosity and Vapor pressure of some fluids commonly used in diesel injection systems, such as diesel fuel, normalized testing fluid, rapeseed and sunflower methyl esters. Also, suitable procedures to estimate the values of those properties at high pressures, up to 140 MPa, based on easy to do atmospheric pressure test values are presented.

The accuracy of laser Doppler and phase Doppler measurements in a very dense spray can be affected by the fact that the signals are very noisy and thus the achievable data rate is very low. Indeed, in some cases only a small fraction of the drops passing through the measurement volume will be detected and validated and furthermore, those drops which are validated may also be non-representative of the total drop population, for instance larger drops may be preferentially validated because of their higher scattering intensity. To systematically investigate some of the influencing parameters in such situations, an experimental set-up comprising a common rail Diesel system, a single hole nozzle injector and a commercial Dual-PD system (Dantec) has been assembled. The injection duration was purposely kept very long, up to 8 milliseconds, to better analyze the main injection period.

It is well known the dual fuel operation at lower loads suffers from lower thermal efficiency and higher unburned percentages of fuel. The present work includes a computational investigation to predict the effects of Exhaust gas recirculation (EGR) on the operation of an indirect-injection dual fuel (Ricardo-E6) engine by using a detailed chemical kinetic scheme and a quasi-two zone analytical model. The comprehensive chemical kinetic scheme for methane oxidation consisting of 178 elementary reaction steps with 41 species. A quasi-two zone analytical model is based on the effective energy releases of the pilot diesel fuel while using the detailed chemical reaction kinetic scheme for the oxidation of methane. Through the results, it was shown that, the active species such as H, O and OH produced in the high temperature combustion process and found in the exhaust gases are play a significant role in the preignition reactions.

As standards for hydrocarbon emissions from vehicles become more stringent due to environmental concerns, considerable effort has been devoted to investigate the mechanisms of formation, transport, and oxidation of unburned hydrocarbons in spark ignition engines. In order to understand controlling factors in the processes, a transient one-dimensional reactive-diffusive model has been formulated for simulating the oxidation process taking place in the reactive layer between hot burned gases and cold unreacted air-fuel mixture, and for estimating exhaust hydrocarbon emission levels from natural gas spark ignition engines. The main innovation shown by the model is the consideration also of the expansion of crevice gas in the axial direction. The model takes into consideration the contribution of the top land piston-ring crevice phenomenon, this being the main unburned hydrocarbon source in natural gas engines.

The objective of this research work was to assess the potential of an electrostatic fluid atomization method for application in direct injection systems for combustion engines. The most important finding of this study was that it is possible to detect the influence of electrostatic atomization at injection pressures up to 300 bar using diesel fuel. The electrostatic force affects the liquid core of the fuel spray from typical diesel nozzles in such a way that additional surface waves are produced which in turn cause the spray to breakup earlier, i.e. the spray breakup length is reduced significantly. This early breakup leads to smaller mean droplet diameters, larger spray angles and as a result air entrainment of the fuel spray is enhanced. Theoretical models were derived to explain the effects of electrostatic charge on fluid atomization.

Injection rate profile is a powerful tool to control engine performance and emission levels. In particular, the Common Rail (C.R.) injection system has allowed flexible fuel injection in DI-diesel engines by permitting a free mapping of the start of injection, injection pressure, rate of injection and, in the near future, multiple injections,. This paper deals with improvements of stable operating condition limits of the Common Rail injector for multiple injection purposes. The focus was to optimize the behavior of the solenoid valve in order to reduce the minimum time interval between two consecutive injections required for system stability. An extensive experimental characterization of the valve has been performed in order to measure the main mechanical and electrical parameters of the assembly components. The experimental and the numerical studies have allowed optimizing the current profile and consequently the design of the anchor pin-ring assembly of the solenoid valve.

Published experimental data obtained in well-defined simple cases are discussed in order to qualitatively test various models of premixed turbulent combustion, utilized in multi-dimensional numerical simulations of SI engines. An analysis of such data indicates that there exist several unresolved issues important for flame propagation in SI engines. Two of them, pressure dependence of turbulent flame speed St and turbulent flame development, are discussed in the paper. First, existing experimental data indicate an increase in St by pressure despite the marked decrease in the laminar burning velocity SL by P. Although this well established trend appears to be of substantial importance for SI engine applications, many combustion models utilize SL as the sole mixture characteristic and, hence, predict similar dependencies both of St and of SL on P, contrary to the aforementioned experimental results.

Multidimensional simulation has been carried out to be clear the role of initial combustion in D.I. diesel engines on reduction of NO and soot emissions by reduction of initial injection rate or pilot injection. The multidimensional engine simulation code, FREC-3D(CI), which was developed by IKEGAMI group in Kyoto Univ. at 1988, was modified and was used in this study. The combustion submodel in this code was updated including ignition submodel that was formulated by a one-step global chemical mechanism to simulate measured ignition delay and initial combustion, sufficiently. In-cylinder NO and soot formation models were introduced by present authors. NO and soot were predicted by Zeldovich mechanism and Morel's soot formation and oxidation formulations, respectively.

In-cylinder pressure traces vary significantly from cycle-to-cycle in spark-ignition (SI) engines. The variations, substantially present even when engine is stable, are magnified under certain engine operating conditions. As a result, engine torque output oscillates and engine operation becomes unstable. EGR tolerance, lean burn limit and spark retard capabilities at CSSRE (Cold Start Spark Retard and Enleanment) are mostly determined by the levels of cycle-to-cycle variations. None of the engine computer models, however, have included cyclic variations for routine industrial applications. As the application domain of engine simulation models expands into unstable engine operating conditions, the modeling of cyclic variations becomes increasingly important. In this research, reviews were conducted regarding different approaches for the simulation of cyclic variation.

Autoignition for most fuel-air mixtures in engines is preceded by relatively slow chemical changes. These changes are the main area of interest in this contribution, since a better control of the autoignition process in homogeneously charged motored engines may become potentially more viable through a better understanding of the reactions that lead to autoignition. An approach to modify the partial oxidation process is by changing the composition of the charge through a deliberate recirculation of some of the exhaust gases back into the cylinder. These recycled gases, when not fully cooled, can influence the autoignition process thermally. They may also contain small concentrations of active chemical species that could influence kinetically the partial oxidation processes of the engine.

A progressive reduction in the permitted level of phosphorus in lubricating oils, coupled with concern to maintain engine and transmission durability, means that it is becoming increasingly important to understand the detailed mechanism of antiwear additive behavior. This paper describes a new experimental technique, which is able to measure both the thickness and distribution of antiwear additive films in rolling/sliding contacts. This enables the kinetics of antiwear film build-up to be investigated and the influence of the reaction film on friction and wear to be monitored. In the current paper, this technique is used to compare the film-forming behavior of ash-containing and ashless antiwear additives.

“Without lubricants, all the machines in the whole world would grind to a halt”. This often used sentence, summarises rather well the increasingly important role of lubrication in our modern world in constant evolution.

This paper describes the design, development and operation of a digital electronic piston telemetry system. A feature is the multiplicity of operating modes, including two-way communication. The system has been demonstrated to work with thermocouples and accelerometers embedded in the piston of a very small engine at speeds of over 2000rev/m. The piston-mounted components can be fitted to a piston as small as 80mm diameter, and the size is reduced with every modification as smaller more powerful electronic components become available. Typical results are quoted in the paper