Search Results

The combustion and emission characteristics of a diesel engine running on butanol-diesel blends were investigated in this study. The blending ratio of n-butanol to diesel was varied from 0 to 40 vol% using an increment of 10 vol%, and each blend was tested on a 2.7 L V6 common rail direction injection diesel engine equipped with an EGR system. The test was carried out under two engine loads at a constant engine speed, using various combinations of EGR ratios and injection timings. Test results indicate that n-butanol addition to engine fuel is able to substantially decrease soot emission from raw exhaust gas, while the change in NOx emissions varies depending on the n-butanol content and engine operating conditions. Increasing EGR ratio and retarding injection timing are effective approaches to reduce NOx emissions from combustion of n-butanol-diesel blends.

A very competitive alcohol for use in diesel engines is butanol. Butanol is of particular interest as a renewable bio-fuel, as it is less hydrophilic and it possesses higher heating value, higher cetane number, lower vapor pressure, and higher miscibility than ethanol or methanol. These properties make butanol preferable to ethanol or methanol for blending with conventional diesel or gasoline fuel. In this paper, the spray and combustion characteristics of pure n-butanol fuel was experimentally investigated in a constant volume combustion chamber. The ambient temperatures were set to 1000 K, and three different oxygen concentrations were set to 21%, 16%, and 10.5%. The results indicate that the penetration length reduces with the increase of ambient oxygen concentration. The combustion pressure and heat release rate demonstrate the auto-ignition delay becomes longer with decreasing of oxygen concentrations.

HCCI/PCCI combustion concepts have been demonstrated for both high brake thermal efficiency and low engine-out emissions. However, these advanced combustion concepts still could not be fully utilized partially due to the limitations of conventional fixed spray angle nozzle designs for issues related to wall wetting for early injections. The micro-variable circular orifice (MVCO) fuel injector provides variable spray angles, variable orifice areas, and variable spray patterns. The MVCO provides optimized spray patterns to minimize combustion chamber surface-wetting, oil dilution and emissions. Designed with a concise structure, MVCO can significantly extend the operation maps of high efficiency early HCCI/PCCI combustion, and enable optimization of a dual-mode HCCI/PCCI and Accelerated Diffusion Combustion (ADC) over full engine operating maps. The MVCO variable spray pattern characteristics are analyzed with high speed photographing.

The spray structure and vaporization processes of flash-boiling sprays in a constant volume chamber under a wide range of superheated conditions were experimentally investigated by a high speed imaging technique. The Engine Combustion Network’s Spray G injector was used. Four fuels including gasoline, ethanol, and gasoline-ethanol blends E30 and E50 were investigated. Spray penetration length and spray width were correlated to the degree of the superheated degree, which is the ratio of the ambient pressure to saturated vapor pressure (pa/ps). It is found that parameter pa/ps is critical in describing the spray transformation under flash-boiling conditions. Three distinct stages namely the slight flash-boiling, the transition flash-boiling, and the flare flash-boiling are identified to describe the transformation of spray structures.

Performance and emissions of a common-rail production diesel engine fueled with soybean-derived biodiesel was investigated. The work was broken down into two categories. First, adjustment of injection timing and EGR ratio was investigated as a means to reduce NOx emissions to levels comparable with those obtained when using pure diesel fuel. Next, simultaneous reduction of NOx and soot emissions was investigated using high rates of EGR combined with late injection timings to approach the low-temperature combustion regime. Results from the first part of the study indicate that optimization of engine control parameters for use with biodiesel can be beneficial to performance and emissions. It was found that adjusting the engine's MAF setpoint table to reflect the difference in stoichiometric air-fuel ratio between diesel and biodiesel brought NOx emissions to comparable or lower levels.

This work presents a comprehensive computational study of diesel - natural gas (NG) dual fuel engine. A complete computational model is developed for the operation of a diesel - NG dual fuel engine modified from an AVL 5402 single cylinder diesel test engine. The model is based on the KIVA-3V program and includes customized sub-models. The model is validated against test cell measurements of both pure diesel and dual fuel operation. The effects of NG on ignition and combustion in dual fuel operation are analyzed in detail. Zero-dimensional computations with a diesel surrogate reaction mechanism are conducted to discover the effects of NG on ignition and combustion and to reveal the fundamental chemical mechanisms behind such effects. Backed by the detailed theoretical analysis, the engine operation parameters are optimized with genetic algorithm (GA) for the dual fuel operation of the modified AVL 5402 test engine.

A new approach of NOx reduction in the compression-ignition engine is introduced in this work. The previous research has shown that during the combustion stage, the high temperature ignition tends to occur early at the near-stoichiometric region where the combustion temperature is high and majority of NOx is formed; Therefore, it is desirable to burn the leaner region first and then the near-stoichiometric region, which inhibits the temperature rise of the near-stoichiometric region and consequently suppresses the formation of NOx. Such inverted ignition sequence requires mixture with inverted phi-sensitivity. Fuel selection is performed based on the criteria of strong ignition T-sensitivity, negligible negative temperature coefficient (NTC) behavior, and large heat of vaporization (HoV).

The formation of fuel film in the combustion cylinder affects the mixing process of the air and the fuel, and the process of the combustion propagation in engines. Some models of film evaporation have been developed to predict the evaporation behavior of the film, but rarely experimental results have been produced, especially when the temperature is high. In this study, the evaporation behavior of the film of different species of oil and their blends at different temperature are observed. The 45 μL films of isooctane, 1-propanol, 1-butanol, 1-pentanol, and their blends were placed on a quartz glass substrate in the closed temperature-controlled chamber. The shape change of the film during evaporation was monitored by a high-speed camera through the window of the chamber. First, the binary blends film of isooctane and one of the other three oils were evaporated at 30 °C, 50 °C, 70 °C and 90 °C.

Flash boiling has drawn much attention recently for its ability to enhance spray atomization and vaporization, while providing better fuel/air mixing for gasoline direct injection engines. However, the behaviors of flash boiling spray with multi-component fuels have not been fully discovered. In this study, isooctane, ethanol and the mixtures of the two with three blend ratios were chosen as the fuels. Measurements were performed with constant fuel temperature while ambient pressures were varied to adjust the superheated degree. Macroscopic and microscopic characteristics of flash boiling spray were investigated using Diffused Back-Illumination (DBI) imaging and Phase Doppler Anemometry (PDA). Comparisons between flash boiling sprays with single component and binary fuel mixtures were performed to study the effect of fuel properties on spray structure as well as atomization and vaporization processes.

Inverted phi (ϕ)-sensitivity is a new approach of NOx reduction in compression-ignition (C.I.) engines. Previously, pure ethanol (E100) was selected as the preliminary test fuel in a single injection compression-ignition engine, and was shown to have good potential for low engine-out NOx emissions under low and medium load conditions due to its inverted ignition sequence. Under high load, however, the near-stoichiometric and non-homogeneous fuel/air distribution removes the effectiveness of the inverted ϕ-sensitivity. Therefore, it is desirable to recover the combustion sequence in the chamber such that the leaner region is burned before the near-stoichiometric region. When the combustion in near-stoichiometric region is inhibited, the temperature rise of that region is hindered and the formation of NOx is suppressed.

To face the challenges of fossil fuel shortage and air pollution problems, there is growing interest in the potential usage of alternative fuels such as bio-ethanol and bio-butanol in internal combustion engines. The literature shows that the acetone in the Acetone-Butanol-Ethanol (ABE) blends plays an important part in improving the combustion performance and emissions, owing to its higher volatility. In order to study the effects of acetone addition into commercial gasoline, this study focuses on the differences in combustion, performance and emission characteristics of a port-injection spark-ignition engine fueled with pure gasoline (G100), ethanol-containing gasoline (E30) and acetone-ethanol-gasoline blends (AE30 at A:E volumetric ratio of 3:1). The tests were conducted at 1200RPM with the default calibration (for gasoline), at 3 bar and 5 bar BMEP under various equivalence ratios.

In this paper, experimental investigation on spray atomization and droplet dynamics inside a thermostatic expansion valve (TXV), a component commonly used in vehicle refrigeration system, was conducted. A needle and an orifice were copied from a commercial TXV and machined to be mounted inside a chamber with optical access so that the flow inside the TXV is simulated and visualized at the same time. The break-up and atomization of the refrigerant were documented near the downstream of the orifice under different feed conditions for two TXV with different geometry. A Phase Doppler Anemometry (PDA) system was used later to measure the size and velocity of atomized refrigerant droplets. The results showed that the droplet size variation along the radial direction is slightly decreased at near downstream and increased at farther downstream due to the coalescence.

The performance and emission of an AVL 5402 single-cylinder engine fueled with acetone-butanol-ethanol (ABE) / diesel blends were experimentally investigated at various load conditions and injection timings. The fuels tested in the experiments were ABE10 (10% ABE, 90% diesel), ABE20 and diesel as baseline. Thermodynamics analyses of pressure traces acquired in experiments were performed to show the impact of ABE concentration to the overall combustion characteristics of the fuel mixtures. Cumulative heat release analysis showed that ABE mixtures generally retarded the overall combustion phasing, ignition delays of ABE-containing fuels were significantly extended, however, combustion rate during CA10∼CA50 were accelerated at different extent. Pressure rise rate of ABE-containing fuels further implicated that the premixed combustion were more dominant than that of diesel. Polytropic indices of both expansion and compression strokes were calculated from p-V diagram.

A single nozzle port fuel injector was modified to apply electrostatic charge to the fuel stream, with the intention of studying electrostatically assisted sprays in a practical, port-injected engine. The modifications were kept external to the injector and involved placing an electrode and insulating liner over the tip of the injector. The performance of the modified injector, which combined pressure driven and electrostatic atomization, was characterized in three phases: the injector sprays themselves were studied, combustion of charged fuel droplets was studied, and the injector was installed and tested on a single cylinder spark ignition engine. In the first phase, Fraunhofer diffraction measurements of droplet size, and particle image velocimetry measurements of droplet velocity were performed. The charge transferred by the sprays was measured using an electrometer, and typical forces exerted on droplets in the sprays were estimated.

An experimental investigation was conducted using a Ford single-cylinder spark-ignition research engine to compare the performance and emissions of neat n-butanol fuel to that of gasoline and ethanol. Measurements of brake torque and exhaust gas temperature along with in-cylinder pressure traces were used to study the performance of the engine and measurements of emissions of unburned hydrocarbons, carbon monoxide, and nitrogen oxide ere used to compare the three fuels in terms of combustion byproducts. It was found that gasoline and butanol are closest in engine performance with butanol producing slightly less brake torque. Exhaust gas temperature and nitrogen oxide measurements show that butanol combusts at a lower peak temperature. Of particular interest were the emissions of unburned hydrocarbons which were between two and three times those of gasoline suggesting that butanol is not atomizing as effectively as gasoline and ethanol.

An optically accessible single-cylinder high-speed direct-injection (HSDI) diesel engine equipped with a Bosch common rail injection system was used to study effects of injection pressures on the in-cylinder spray and combustion processes. An injector with an injection angle of 70 degrees and European low sulfur diesel fuel (cetane number 54) were used in the work. The operating load was 2.0 bar IMEP with no EGR added in the intake. The in-cylinder pressure was measured and the heat release rate was calculated. High-speed Mie-scattering technique was employed to visualize the liquid distribution and evolution. High-speed combustion video was also captured for all the studied cases using the same frame rate. NOx emissions were measured in the exhaust pipe. The experimental results indicated that for all of the conditions the heat release rate was dominated by a premixed combustion pattern. Two-stage low temperature reaction was seen for early injection timings.

HTL is a kind of biodiesel converted from wet biowaste via hydrothermal liquefaction (HTL), which has drawn increasing attention in recent years due to its wide range of raw materials (algae, swine manure, and food processing waste). However, from the previous experiments done in a constant volume chamber, it was observed that the presence of 20% of HTL in the blend produced as much soot as pure diesel at in chamber environment oxygen ratio of 21%, and even more soot at low oxygen ratios. It was also observed that n-butanol addition could reduce the soot emission of diesel significantly under all tested conditions. In this work, the spray and combustion characteristics of HTL and diesel blends with n-butanol added were investigated in a constant volume chamber. The in-chamber temperature and oxygen ranged from 800 to 1200 K and 21% to 13%, respectively, covering both conventional and low-temperature combustion (LTC) regimes.

CNG-diesel dual fuel combustion mode has been regarded as a practical operation strategy because it not only can remain high thermal efficiency but also make full use of an alternative fuel, natural gas. However, it is suffering from misfire and high HC emissions under cold start and low load conditions. As known, hydrogen has high flammability. Thus, a certain proportion of hydrogen can be added in the natural gas (named HCNG) to improve combustion performance. In this work, the effect of hydrogen volume ratio on combustion characteristics was investigated on an optically accessible single-cylinder CNG-diesel engine using a Phantom v7.3 color camera. HCNG was compressed into the tank under different hydrogen volume ratios varied from 0% to 30%, while the energy substitution rate of` HCNG remained at 70%.

Due to the increasing consumption of fossil fuels, alternative fuels in internal combustion engines have attracted a lot of attention in recent years. Ethanol is the most common alternative fuel used in spark ignition (SI) engines due to its advantages of biodegradability, positively impacting emissions reduction as well as octane number improvement. Meanwhile, acetone is well-known as one of the industrial waste solvents for synthetic fibers and most plastic materials. In comparison to ethanol, acetone has a number of more desirable properties for being a viable alternative fuel such as its higher energy density, heating value and volatility.

The purpose of this study is to investigate the possibility of acetone-butanol-ethanol (ABE) blended with diesel without further component recovery which has high costs blocking the industrial-scale production of bio-butanol. The combustion characteristics of ABE and diesel blends were studied in a constant volume chamber. In this study, 50% and 80% vol. ABE (without water) were mixed with diesel and the vol. % of acetone, butanol and ethanol were kept at 30%, 60% and 10% respectively. The in-cylinder pressure was recorded using a pressure transducer and the time-resolved natural luminosity was captured by high speed imaging. Combustion visualization using laser diagnostics would provide crucial fundamental information of the fuel's combustion characteristics. With the different percentage of the ABE blended in the diesel, the soot oxidation, the ignition delay and the soot lift-off length were studied in this work.