Engine Performance of High-Acid Oil-Biodiesel through Supercritical Transesterification.

Relatively cheaper high-acid oil was used to make biodiesel through supercritical methanol transesterification, where high FFA contents in feedstock might conversely enhance the reaction extent. A direct-injection diesel engine and a dynamometer were used to analyze the engine characteristics of the high-acid oil-biodiesel. The experimental results show that the biodiesel made in this study had adequate fuel properties. This present biodiesel from high-acid oil was found to bear a lower heating value and equivalence ratio, with higher exhaust gas temperature, brake-specific fuel consumption (bsfc), and excess air ratio, than super-low sulfur diesel (SLSD). The biodiesel appeared to have larger-sized carbon residue left after the burning process in comparison with that of SLSD. The higher engine speed resulted in higher exhaust gas temperature and equivalence ratio, while lower bsfc, excess air ratio, was observed for the biodiesel. Supercritical methanol transesterification has been successfully proven to convert those low-cost feedstocks to renewable biodiesel products which own competitive engine performance in this study.

Emission characteristics of a diesel engine fueled with nanoemulsions of continuous diesel dispersed with solketal droplets.

Solketal is a promising oxygenate additive that can be chemically derived from bioglycerol. Emulsification by a microwave-irradiating method was used to prepare the micro- and nanoemulsions of solketal dispersed in continuous ultra-low sulfur diesel (ULSD) due to the immiscibility of solketal with ULSD. The emissions from a direct-injection, four-stroke and naturally aspirated diesel engine fueled with each of these emulsions, and with neat ULSD, were analyzed and compared. The experimental results show that the nanoemulsion and microemulsions were successfully produced. In addition, an increasing engine speed resulted in lower NOx, CO and O2 but higher CO2 emissions. The nanoemulsion was found to produce the lowest NOx emission while neat ULSD produced the highest NOx emission among these three test fuels. The lowest CO emission was formed by fueling the micro-emulsion of dispersed solketal-in-ULSD. Moreover, the burning of the nanoemulsion in the diesel engine formed the highest CO2 along with the lowest O2 emissions. Hence, the nanoemulsion had the highest burning efficiency among the three test fuels for the diesel engine.

Comparison of Engine Performance between Nano- and Microemulsions of Solketal Droplets Dispersed in Diesel Assisted by Microwave Irradiation.

As a derivative product of bio-glycerol, this study first uses solketal as a combustion improver for enhancing diesel engine characteristics. The emulsions of nanometer- and micrometer-sized droplets of solketal, which disperse evenly in the ultra-low sulfur diesel (ULSD), are formed by the effects of microwave irradiation. The performance of diesel engine fueled with the nanoemulsion of ULSD with scattered solketal droplets is analyzed and compared to that with the microemulsion. The experimental results show that the nanoemulsions can form when over 15 wt. % surfactant mixtures of Span 80 and Tween 80 and less than 5 wt. % solketal are mixed and emulsified with the remaining ULSD content, which acts as the continuous phase of the emulsions. The nanoemulsions are observed to have significantly lower brake-specific fuel consumption (bsfc) and higher fuel conversion efficiency and exhaust gas temperature than those of the microemulsions and the neat ULSD. However, the bsfc of the nanoemulsions increases with greater engine speed and gradually approaches those of the latter two test fuels. In addition, the dispersed solketal droplet sizes are mostly concentrated around 127 nm with peak intensity of 12.65% in the nanoemulsions. The microwave-assisted formation used in this study is found to successfully produce the nanoemulsions in which all of the dispersed droplet sizes are much smaller than 1000 nm.

Thermal performance of a vapor chamber-based plate of high-power light-emitting diodes filled with Al2O3 nanofluid.

Nanofluid that contains Al2O3 nanoparticles evenly dispersed in deionized water is considered to have superior heat transfer characteristics due to the significant increase in both collision frequency and contact surface area between the nanoparticles and the deionized water. The thermal performance of the vapor chamber-based plate of a high power light-emitting diode (LED) filled with Al2O3 nanofluid was experimentally investigated. The thermal characteristics of the vapor chamber were also compared with those of copper- and aluminum-based plates exposed to the heating source of four single-crystal LEDs. The experimental results show that the effective thermal conductivity of the vapor chamber increased with an increase in heat flux. A higher heating power caused an increase in the temperature variation in the vapor chamber, the illumination of the vapor chamber-, copper-, and aluminum-based plates, and the material resistance of the copper- and aluminum-based plates. In contrast, the spreading, convective, and total thermal resistance all decreased with an increase in heating power for all three base plates. The total thermal resistance of the vapor chamber is mostly due to its spreading thermal resistance, and appeared to be lower than that of the copper- and aluminum-based plates under a heating power of over 5 Watts.

Correlation of black smoke and nitrogen oxides emissions through field testing of in-use diesel vehicles.

Diesel vehicles are one of the major forms of transportation, especially in metropolitan regions. However, air pollution released from diesel vehicles causes serious damage to both human health and the environment, and as a result is of great public concern. Nitrogen oxides and black smoke are two significant emissions from diesel engines. Understanding the correlation between these two emissions is an important step toward developing the technology for an appropriate strategy to control or eliminate them. This study field-tested 185 diesel vehicles at an engine dynamometer station for their black smoke reflectivity and nitrogen oxides concentration to explore the correlation between these two pollutants. The test results revealed that most of the tested diesel vehicles emitted black smoke with low reflectivity and produced low nitrogen oxides concentration. The age of the tested vehicles has a significant influence on the NOx emission. The older the tested vehicles, the higher the NOx concentrations emitted, however, there was no obvious correlation between the age of the tested diesel vehicles and the black smoke reflectivity. In addition, if the make and engine displacement volume of the tested diesel vehicles are not taken into consideration, then the correlation between the black smoke reflectivity and nitrogen oxides emission weakens. However, when the tested vehicles were classified into various groups based on their makes and engine displacement volumes, then the make of a tested vehicle became a dominant factor for both the quantity and the trend of the black smoke reflectivity, as well as the NOx emission. Higher emission indices of black smoke reflectivity and nitrogen oxides were observed if the diesel vehicles were operated at low engine speed and full engine load conditions. Moreover, the larger the displacement volume of the engine of the tested vehicle, the lower the emission indices of both black smoke reflectivity and nitrogen oxides emitted. The emission indices of black smokes reflectivity and nitrogen oxides emission of the tested diesel vehicles were also influenced by the make of the vehicle. It was observed that the emission indices of black smoke reflectivity decreased nearly linearly with the increase of the emission indices of NOx for the tested vehicles belonging to the same group of make and engine displacement volume.

Effects of diesel engine speed and water content on emission characteristics of three-phase emulsions.

The effects of water content of three-phase emulsions and engine speed on the combustion and emission characteristics of diesel engines were investigated in this study. The results show that a larger water content of water-in oil (W/O) and oil-in-water-in-oil (O/W/O) emulsion caused a higher brake specific fuel consumption (bsfc) value and a lower O2, as well as a lower NOx emission, but a larger CO emission. The increase in engine speed resulted in an increase of bsfc, exhaust gas temperature, fuel-to-air ratio, CO2 emission and a decrease of NOx, CO emission, and smoke opacity. Because of the physical structural differences, the three-phase O/W/O emulsions were observed to produce a higher exhaust gas temperature, a higher emulsion viscosity and a lower CO emission, in comparison with that of the two-phase W/O emulsion. In addition, the use of W/O emulsions with water content larger than 20% may cause diesel engines to shut down earlier than those running on O/W/O emulsions with the same water content. Hence, it is suggested that the emulsions with water content larger than 20% are not suitable for use as alternative fuel for diesel engines.

Influences of calcium oxide content in marine fuel oil on emission characteristics of marine furnaces under varying humidity and temperature of the inlet air.

A marine furnace made of stainless steel. combined with an automatic small-size oil-fired burner, was used to experimentally investigate the influences of calcium oxide content in fuel oil on the combustion and emission characteristics under varying temperatures and humidity of the inlet air. Marine fuel oil generally contains various extents of metallic oxides such as CaO, Fe2O3, V2O5, etc which might affect its burning properties. In this study, an air-conditioner was used to adjust the humidity and temperatures of the inlet air to preset values prior to entering the burner. The adjusted inlet air atomized the marine diesel oil A containing a calcium oxide compound, to form a heterogeneous reactant mixture. The reactant mixture was thereafter ignited by a high-voltage electrode in the burner and burned within the marine furnace. The probes of a gas analyzer, H2S analyzer and a K-type thermocouple were inserted into the radial positions of the furnace through the eight rectangular slots which were cut in the upper side of the furnace. The experimental results showed that an increase of either humidity or temperature of the inlet air caused the promotion of the reaction rate of the fuel. The existence of calcium oxide compound in the diesel fuel also facilitated the oxidation reaction in the combustion chamber. The addition of CaO in the diesel fuel under the conditions of higher temperature or higher relative humidity of the inlet air produced the following: higher concentrations of CO2, SO2, and H2S emissions, an increased burning efficiency, a lowered O2 level, production of excess air and NOx emissions as well as a lower thermal loss and a lower burning gas temperature, as compared with the conditions of a lower temperature or a lower humidity of the inlet air. In addition, the burning of diesel fuel with added CaO compound caused a large variation in the burning efficiency, thermal loss, plus CO2, O2, and excess air emissions between the conditions of higher temperature/higher humidity and lower temperature/lower humidity inlet air compared with no CaO addition in the fuel. Moreover, the burning efficiency and the concentrations of excess air and O2 emissions increased, while the thermal loss, burning gas temperature and H2S, SO2, NOx, and CO2 emissions decreased with the increase of the axial distance from the measured location to the burner nozzle.

Emission of burning emulsified diesel oil with sodium sulfate in salty atmospheric air.

The effects of sodium sulfate in fuel oil and salty atmospheric air on the emission characteristics of furnaces or boilers burned with emulsified diesel oils are considered in this study. An industrial cylindrical furnace made of stainless steel associated with an automatic oil-fired burner was used for the emission measurements. Both neat diesel oil and emulsified diesel oil with distilled water were used as the tested oils. A homogenizing and emulsifying machine was employed to stir the diesel oil and sodium sulfate powder into a homogeneous oil mixture, and to prepare emulsions of micro-droplets of water dispersed in diesel oil. The experimental results showed that the existence of sodium chloride in atmospheric air enhanced SO2 formation. The use of emulsified diesel oil with 300-ppm sodium sulfate as fuel reduced the burning gas temperature and NOx emission while increased O2 emission. Moreover, the presence of sodium chloride in atmospheric air hindered the completeness of the combustion process and thus resulted in lower burning efficiency and larger excess oxygen emission.