1,720,967 research outputs found
Near Nozzle Flow and Atomization Characteristics of Biodiesel Fuels in a Constant Volume Chamber
No full textNanostructure characterization of soot particles from biodiesel and diesel spray flame in a constant volume combustion chamber
No full textThis study investigates the effect of biodiesel fuels on morphological characteristics of soot particles from spray flame in a constant volume combustion chamber. The experiments were carried out under simulated diesel engine condition. The auto-ignition of injected fuel was carried out at an ambient pressure of 5 MPa and ambient temperature of 978.15 K. The soot particles were captured with a transmission electron microscope (TEM) grid inside the flame by thermophoretic effect. They were characterized as primary particle diameter, graphene layer ( fringe) length, fringe tortuosity, and fringe spacing based on the image processing from original TEM image. Three different kinds of biodiesel fuels, waste cooking oil biodiesel, Jatropha biodiesel and Karanja biodiesel were used in the test. Conventional diesel fuel was utilized as a baseline fuel for the comparison. The tested fuels were injected with injection pressures of 40, 80, and 120 MPa by means of common-rail injection system. The experimental result showed that all of the biodiesel fuels had smaller primary particle diameter than that of conventional diesel regardless of injection pressures. The soot particles from biodiesel fuels were also distinguished showing characteristically shorter fringe length and lower tortuosity. These experiments unveiled a correlation between the nano-structural parameters for the early stage of oxidation inside the flame.
In-Cylinder Spray and Combustion Investigations in a Heavy-Duty Optical Engine Fueled With Waste Cooking Oil, Jatropha, and Karanja Biodiesels
No full textIn this experimental study, spray and combustion characteristics of a single cylinder optical engine were evaluated by varying the fuel injection pressure (FIP) (40, 80, and 120 MPa). Karanja, Jatropha, and waste cooking oil (WCO) biodiesels were the test fuels and their results were compared with baseline mineral diesel. There was no significant difference observed in the spray tip penetration amongst all test fuels, however the spray cone angles of biodiesels were slightly higher than baseline mineral diesel. Mineral diesel showed relatively shorter injection delay compared to biodiesels at 40 and 80 MPa FIP. Jatropha and Karanja biodiesels showed higher flame luminosity at all FIPs, while WCO biodiesel showed lower flame luminosity, especially at higher FIPs of 80 and 120 MPa, primarily due to lower viscosity of WCO biodiesel. Flame spatial fluctuation (FSF) and flame nonhomogeneity (FNH) were also found to be higher for biodiesels at lower FIP of 40 MPa. Karanja and Jatropha biodiesels showed higher FSF and FNH at higher FIPs compared to WCO biodiesel.
An Experimental Investigation on Spray Characteristics of Waste Cooking Oil, Jatropha, and Karanja Biodiesels in a Constant Volume Combustion Chamber
No full textIn this study, macroscopic spray characteristics of Waste cooking oil (WCO), Jatropha oil, Karanja oil based biodiesels and baseline diesel were compared under simulated engine operating condition in a constant volume spray chamber (CVSC). The high pressure and high temperature ambient conditions of a typical diesel engine were simulated in the CVSC by performing pre-ignition before the fuel injection. The spray imaging was conducted under absence of oxygen in order to prevent the fuels from igniting. The ambient pressure and temperature for non-evaporating condition were 3 MPa and 300 K. Meanwhile, the spray tests were performed under the ambient pressure and temperature of 4.17 MPa and 804 K under evaporating condition. The fuels were injected by a common-rail injection system with injection pressure of 80 MPa. High speed Mie-scattering technique was employed to visualize the evaporating sprays. Liquid tip penetration length, spray cone angle and spray area were determined from captured images. The equivalence ratio along the axial direction of the spray was also calculated based on mathematical correlations. Results showed that biodiesels had longer spray tip penetration length and narrow spray cone angle than those of baseline diesel. Amongst the biodiesels, Jatropha and Karanja biodiesels exhibited longer spray tip penetration length and narrower spray angle than those of Waste cooking oil biodiesel. On the other hand, baseline diesel showed much shorter liquid tip penetration length and faster evaporation process than biodiesels. The reason is that higher density and viscosity of biodiesels attenuated the fuel atomization and evaporation process. However, despite deteriorated atomization characteristics, biodiesels showed lower equivalence ratio than baseline diesel due to inherent oxygen content in the fuel molecules
Microscopic Spray Characteristics of Biodiesels Derived From Karanja, Jatropha, and Waste Cooking Oils
No full textThis study aims to assess the microscopic characteristics of Jatropha, Karanja, and Waste cooking oil-based biodiesels vis-a-vis conventional diesel under different ambient conditions in order to understand the in-cylinder processes, while using biodiesels produced from different feedstocks in the compression ignition engines. All test-fuels were injected in ambient atmosphere using a common-rail direct injection (CRDI) fuel injection system at a fuel injection pressure (FIP) of 40 MPa. Microscopic spray characteristics were measured using phase Doppler interferometer (PDI) in the axial direction of the spray at a distance of 60-90 mm downstream of the nozzle and at 0 to 3-mm distance from the central axis in the radial direction. All biodiesels exhibited relatively larger Sauter mean diameter (SMD) of the spray droplets and higher droplet velocities compared to baseline mineral diesel, possibly due to relatively higher fuel viscosity and surface tension of biodiesels. It was also observed that SMD of the spray droplets decreased with increasing distance in the radial and axial directions and the same trend was observed for all test-fuels.
HRTEM evaluation of primary soot particles originated in a small-bore biofuel compression-ignition engine
No full textNanostructure of soot particles from a small-bore compression-ignition engine was investigated by high-resolution transmission electron microscopy (HRTEM). Four test fuels namely conventional diesel, waste cooking oil (WCO) biodiesel, Jatropha biodiesel, and Karanja biodiesel were studied. Lacey carbon TEM grids were utilized to capture soot particles from engine exhaust gas. An in-house image processing algorithm was developed to measure primary particle diameter, fringe length, fringe tortuosity, and fringe spacing. The HRTEM image revealed the presence of thicker absorbed hydrocarbon layers surrounding biodiesel soot primary particles than those of diesel soot. The primary particle size of WCO biodiesel was smaller than diesel, on the other hand, Jatropha biodiesel and Karanja biodiesel showed slightly larger particles. In terms of nano-structure analysis, WCO biodiesel and Jatropha biodiesel particles exhibited shorter fringe length than diesel, while the Karanja biodiesel particles showed the longest fringe length of 0.91 nm. Fringe tortuosity of biodiesels was smaller than diesel because of relatively lower portion of core area, where highly curved fringes existed. The soot particles from biodiesels exhibited larger fringe spacing than diesel, especially the Karanja biodiesel showed the longest fringe spacing of 0.67 nm compared to 0.55 rim in case of diesel.
Comparative compression ignition engine performance, combustion, and emission characteristics, and trace metals in particulates from Waste cooking oil, Jatropha and Karanja oil derived biodiesels
No full textIn the present study, comparison of performance, combustion and emission characteristics of a single cylinder compression ignition (CI) genset engine fueled by biodiesels derived from Waste cooking oil (WCO), Jatropha and Karanja oils vis-a-vis baseline mineral diesel has been carried out. Performance and combustion investigations were carried out at constant engine speed (1500 rpm) and six engine loads (0-100%). WCO biodiesel showed slightly higher heat release rate (HRR) than baseline mineral diesel, while it was slightly lower for Karanja and Jatropha biodiesels. Hydrocarbons (HC) and oxides of nitrogen (NOX) emissions were lower, while carbon monoxide (CO) emission was relatively higher for biodiesels compared to baseline diesel. Smoke opacity was higher for Karanja and Jatropha biodiesels compared to baseline diesel. WCO biodiesel exhibited comparable smoke opacity with baseline mineral diesel except at full load, where it was relatively lower. Particulates were collected from the engine exhaust on a quartz filter paper using a partial flow dilution tunnel at 50 and 100% engine loads, for trace metal analysis using inductively coupled plasma optical emission spectroscopy (ICP-OES). It was found that trace metals such as Ca, Cu, Fe, K, Mg, Na, Zn and Al showed higher concentrations in particulates from all test fuels, while Ba, Cd, Cr, Mn and Mo showed relatively lower concentrations in the particulates collected.
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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