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The interaction of fuel sprays and in-cylinder flow in direct-injection engines is expected to alter kinetic energy and integral length scales at least during some portions of the engine cycle. High-speed particle image velocimetry was implemented in an optical four-valve, pent-roof spark-ignition direct-injection single-cylinder engine to quantify this effect. Non-firing motored engine tests were performed at 1300 RPM with and without fuel injection. Two fuel injection timings were investigated: injection in early intake stroke represents quasi-homogenous engine condition; and injection in mid compression stroke mimics the stratified combustion strategy. Two-dimensional crank angle resolved velocity fields were measured to examine the kinetic energy and integral length scale through critical portions of the engine cycle. Reynolds decomposition was applied on the obtained engine flow fields to extract the fluctuations as an indicator for the turbulent flow.

An experimental study is performed to investigate the effects of charge motion control on in-cylinder fuel-air mixture preparation and combustion inside a direct-injection spark-ignition engine with optical access to the cylinder. High-pressure production injector is used with fuel pressures of 5 and 10 MPa. Three different geometries of charge motion control (CMC) device are considered; two are expected to enhance the swirl motion inside the engine cylinder whereas the third one is expected to enhance the tumble motion. Experiments are performed at 1500 rpm engine speed with the variation in fuel injection timing, fuel pressure and the number of injections. It is found that swirl-type CMC devices significantly enhance the fuel-air mixing inside the engine cylinder with slower spray tip penetration than that of the baseline case without CMC device. Combustion images show that the flame growth is faster with CMC device compared to the similar case without CMC device.

Near-term energy policy for ground transportation is likely to have a strong focus on both gains in efficiency as well as the use of alternate fuels; as both can reduce crude oil dependence and carbon loading on the environment. Stratified-charge spark-ignition direct-injection (SIDI) engines are capable of achieving significant gains in efficiency. In addition, these engines are likely to be run on alternative fuels. Specifically, lower alcohols such as ethanol and iso-butanol, which can be produced from renewable sources. SIDI engines, particularly the spray-guided variant, tend to be very sensitive to mixture preparation since fuel injection and ignition occur within a short time of each other. This close spacing is necessary to form a flammable mixture near the spark plug while maintaining an overall lean state in the combustion chamber. As a result, the physical properties of the fuel have a large effect on this process.

A summary of the design and development process for a Formula SAE engine is described. The focus is on three fundamental elements on which the entire engine package is based. The first is engine layout and displacement, second is the fuel type, and third is the air induction method. These decisions lead to a design around a 4-cylinder 600cc motorcycle engine, utilizing a turbocharger and ethanol E-85 fuel. Concerns and constraints involved with vehicle integration are also highlighted. The final design was then tested on an engine dynamometer, and finally in the 2007 M-Racing FSAE racecar.

A quasi-dimensional, multi-zone, direct injection (DI) diesel combustion model has been developed and implemented in a full cycle simulation of a turbocharged engine. The combustion model accounts for transient fuel spray evolution, fuel-air mixing, ignition, combustion and NO and soot pollutant formation. In the model, the fuel spray is divided into a number of zones, which are treated as open systems. While mass and energy equations are solved for each zone, a simplified momentum conservation equation is used to calculate the amount of air entrained into each zone. Details of the DI spray, combustion model and its implementation into the cycle simulation of Assanis and Heywood [1] are described in this paper. The model is validated with experimental data obtained in a constant volume chamber and engines. First, predictions of spray penetration and spray angle are validated against measurements in a pressurized constant volume chamber.

This work presents a method for simultaneously capturing visible and infrared images along with pressure data in an optical Diesel engine based on the International 4.5L VT275 engine. This paper seeks to illustrate the merits of each imaging technique for visualizing both in-cylinder fuel spray and combustion. The engine was operated under a part load, high simulated exhaust gas recirculation operating condition. Experiments examining fuel spray were conducted in nitrogen. Overlays of simultaneously acquired infrared and visible images are presented to illustrate the differences in imaging between the two techniques. It is seen that the infrared images spatially describe the fuel spray, especially fuel vapors, and the fuel mixing process better than the high-speed visible images.

A high-speed/high-resolution imaging technique and analysis were applied to study fuel injector spray timed evolution in ambient air and in a motored single-cylinder engine. Alcohol fuel was injected from a mid-pressure injection system into the engine cylinder at shaft speed of 1,000 rpm. The fuel injection system with various nozzles was designed for use in the EPA/NVFEL program to develop clean and efficient engines that use alternative fuels. A 15W copper vapor laser with a fiber optic delivery system synchronized with a high-speed drum streak camera was utilized to expose films at 5,000 frames per second (fps). The spray characteristics were investigated at 15.0 MPa injection pressure and injection duration range of 3-5 ms. A sequence of successive frames was selected from the films to examine the influence of the injector parameters and the valve lift on the atomization process. The spray penetration was quantified by analyzing the high-speed films.

Five small two-stroke engine designs were tested at different air/fuel ratios, under steady state and transient cycles. The effects of combustion chamber design, carburetor design, lean burning, and fuel composition on performance, hydrocarbon and carbon monoxide emissions were studied. All tested engines had been designed to run richer than stoichiometric in order to obtain satisfactory cooling and higher power. While hydrocarbon and carbon monoxide emissions could be greatly reduced with lean burning, engine durability would be worsened. However, it was shown that the use of a catalytic converter with acceptably lean combustion was an effective method of reducing emissions. Replacing carburetion with in-cylinder fuel injection in one of the engines resulted in a significant reduction of hydrocarbon and carbon monoxide emissions.

The transient cone angle of a pressure swirl spray from an injector for gasoline direct injection engines was measured from 2D Mie scattering images. Iso-octane was used as the fluid that was delivered at room temperature for two different static pressures, 5MPa and 8.5MPa. The iso-octane was injected into a chamber at room temperature and ambient pressure. After a rapid initial increase, the cone angle oscillates before stabilizing to a steady-state value very close to the nominal cone angle. The period of the oscillation was found to correlate well with oscillations measured in the fuel line pressure.

The transient cone angle of pressure swirl sprays from injectors intended for use in gasoline direct injection engines was measured from 2D Mie scattering images. A variety of injectors with varying nominal cone angle and flow rate were investigated. The general cone angle behavior was found to correlate well qualitatively with the measured fuel line pressure and was affected by the different injector specifications. Experimentally measured modulations in cone angle and injection pressure were forced on a comprehensive spray simulation to understand the sensitivity of pulsating injector boundary conditions on general spray structure. Ignoring the nozzle fluctuations led to a computed spray shape that inadequately replicated the experimental images; hence, demonstrating the importance of quantifying the injector boundary conditions when characterizing a spray using high-fidelity simulation tools.

Alcohol has been promoted and used as a motor fuel for more than 50 years. However, United States ethyl alcohol production is small compared with gasoline production. High latent heat of vaporization of alcohol makes possible some increase of power over gasoline. The heating value of alcohol is low and energy content of alcohol blends is less than that of gasoline; fuel consumption of blends is therefore increased. The ability of ethanol to improve the octane number of gasoline has diminished as the octane number of gasoline has improved. There is no published evidence that alcohols can appreciably reduce air pollution problems.

This paper considers the influence of the properties of gasolines and testing fluids on metering by carburetors. Since the fuel metering is controlled by orifices, the effects of fuel properties on orifice flow are analyzed. The results of an orifice testing program are presented, using the Reynolds number as the primary correlation parameter. The influences of fuel type, fuel temperature, and orifice geometry on the discharge coefficient are discussed, and the effect of a given fuel property change is shown. Experimental values for the variations in fluid properties with fuel type and temperature are presented for commercial gasolines, carburetor testing fluids, and pure hydrocarbons. The variation of carbon-to-hydrogen ratio among gasolines is shown to cause a change in stoichiometry, which is the equivalent of an error in metering.

This paper presents results from a study of the particle size distributions emitted by a heavy-duty diesel engine equipped with a common-rail fuel injection system. The study focused on two key sampling and engine operating variables: dilution ratio and fuel injection pressure. Results show that the number mean diameter of the particle size distributions decreased with increasing dilution ratios. Also, the total number concentration of particles did not change with different dilution ratios. In addition, it was found that fuel injection pressures affected the size distribution of the particles sampled. Under some engine operating conditions increasing the fuel injection pressure resulted in an increased number of nuclei mode particles.

A single-cylinder gasoline direct-injection engine was used for fuel spray and combustion visualizations with optical access to the combustion chamber. Experiments were conducted to investigate the effect of fuel injection pressure on spray and combustion characteristics inside the engine cylinder. A multi-hole high-pressure production injector was used with fuel pressures of 5 and 10 MPa. A Mie scattering technique was used to image the liquid phase of the fuel dispersion. The obtained spray images were then used to study the macroscopic spray characteristics such as spray structure, spray tip penetration and spray angle. Combustion visualization tests were performed to evaluate the effect of fuel injection pressure on combustion characteristics. In-cylinder pressure signals were recorded for the combustion analyses and synchronized with the high-speed combustion imaging recording.

The paper analyzes energy use and emissions per GJ of various fuels delivered to the vehicle fuel tank, covering extraction, fuel production, transportation, storage, and distribution phases of the life cycle of alternative fuels. Drawing on a number of existing studies, the modeling issues and approaches, main results and insights are summarized. The range of estimates in various studies is large; however, common patterns can be observed. The analysis indicates, that conventional gasoline fuel cycle has robust advantages with respect to energy efficiency, conventional pollutant emissions, and most importantly, existing infrastructure compared to alternative fuels. Fossil fuel based alternatives like CNG, NG–Methanol, NG–FTL do not result in significant improvement in fuel cycle environmental performance. Biofuels offer the benefits of lower and even negative GHG emissions, sustainability, and domestic fuel production.

This paper provides data concerning the enrichment of automotive carburetors with variation of inlet air pressure and temperature. These changes occur with weather and the seasons, with altitude, and because of underhood heating. The early opening of the conventional carburetor enrichment value at altitude can add greatly to the “ normal” carburetor enrichment. Means for compensating the mixture ratio for these changes in inlet air conditions are known, but will almost certainly add to the complexity and cost of the engine induction system. The cost of improved devices must be compromised with the possible reduction in exhaust emissions and improvement in fuel economy.