1,720,963 research outputs found
Experimental and numerical investigation of a high boost and high injection pressure Diesel engine concept for heavy duty applications
Full text linkThe upcoming European Stage V emissions regulation for Non-Road Heavy Duty Diesel Engines will force OEMs to adopt Diesel Particulate Filters, adding a further degree of complexity to the aftertreatment system, which in several cases already includes specific devices for NOx reduction. Since complex aftertreatment systems can rise packaging problems as well as reliability issues, a project in collaboration with Kohler, Politecnico di Torino, Ricardo and Denso, has been carried out to explore the feasibility of a Stage V compliant SCR-free architecture for a 90kW Non Road Diesel engine. To this scope a prototype engine based on the Kohler KDI3404, was equipped with a low-pressure Exhaust Gas Recirculation system, a two-stage turbocharger and a 3000 bar injection pressure-capable Fuel Injection System.
This thesis focuses on the experimental and numerical assessment of emissions and performances of this engine architecture over the Stage V certification procedure. It will be shown how the high-pressure Fuel Injection System is the key technology to meet the stringent requirements, demonstrating how increasing the injection pressure from 2000 to 3000 bar can dramatically improve the NOx-Soot and NOx-Particulate Number trade-off, together with engine efficiency, without adversely affecting the emission of nanoparticles. Moreover, the use of extremely high injection pressures in conjunction with after injection as a soot reduction technique, was found to be capable of achieving up to 50% smoke reduction with a more than acceptable engine efficiency degradation.
Thanks to a dedicated steady state and transient calibration, the engine was able to run a compliant NRSC and NRTC with more than 10% margin on NOx and a level of particulate matter and particulate number which can be easily managed by the DOC+DPF aftertreatment system. However, some components of the tested engine, such as the turbochargers, were found to be far from the optimal, thus resulting into relatively poor efficiency figures.
Therefore, a 1D-CFD model featuring predictive combustion and emissions models was developed in order to assess the full potentials of this architecture on a kind of “virtual test rig”, on which different components could be easily evaluated.
The model results proved that, with a better design of the exhaust and EGR line, and with a slightly higher performance turbocharger, consistent engine efficiency improvements could be obtained, making the SCR-free solution as a valuable alternative to the SCR architecture to meet the Stage V emissions regulations
Numerical and experimental investigation of a piston thermal barrier coating for an automotive diesel engine application
Full text linkThis paper investigates the potential of coated pistons in reducing fuel consumption and pollutant emissions of a 1.6l automotive diesel engine. After a literary review on the state-of-the-art of the materials used as Thermal Barrier Coatings for automotive engine applications, anodized aluminum has been selected as the most promising one. In particular, it presents very low thermal conductivity and heat capacity which ensure a high “wall temperature swing” property. Afterwards, a numerical analysis by utilizing a one-dimensional Computational Fluid Dynamics engine simulation code has been carried out to investigate the potential of the anodized aluminum as piston Thermal Barrier Coating. The simulations have highlighted the potential of achieving up to about 1% in Indicated Specific Fuel Consumption and 6% in heat transfer reduction. To confirm the simulation results, the coated piston technology has been experimentally evaluated on a prototype engine and compared to the baseline aluminum pistons. Despite the promising potential for Indicated Specific Fuel Consumption reduction highlighted by the numerical simulation, the experimental campaign has indicated a slight worsening of the engine efficiency (up to 2% at lower load and speed) due to the slowdown of the combustion process. The primary cause of these inefficiencies is attributed to the roughness of the coating
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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