1,720,964 research outputs found
Experimental fitting of redesign electrified turbocompressor of a novel mild hybrid power train for a city car
Full text linkAs part of a project for the realization of a hybrid vehicle with an innovative power train system, the proposal presented is to disconnect the turbocharger group and study the different behavior of the compressor and turbine, so decoupled. In an actual turbocharger, when the power ofthe turbine exceeds that required by the compressor, the wastegate valve opens. In this way, a part of the flue gases does not evolve into a turbine and limits the power generated. In the solution proposed here (the paper considers only “compressor side”) all the flow rate of the flue gases is processed by the turbine. In this way, for each rpms of the IC engine, the turbine generates more power than that required by the compressor. This makes it possible to use this surplus of power for the auxiliaries and/or to recharge the battery pack of the considered hybrid vehicle. An additional advantage is, thanks to this surplus generated, that the battery pack can be smaller and can be recharged while driving. Therefore, the entire system operates as a “Range Extended”. As mentioned above, this work is focused on the direct compressor—innovative electric motor coupling will be sized and realized, and a subsequent series of experimental tests will confirm the feasibility of this phase of the project
Optimization of an innovative cooling system for motorsport application
Full text linkOne of the most critical issues in electric vehicle engineering concerns the thermal management of the battery pack, especially in high-performance applications, which are increasingly demanded by the market. Very interesting, from this point of view, is the study of motorsport applications, almost always characterized by a high ratio between power output and energy stored in the battery pack, which makes the problem of thermal management particularly important. It should be noted that motorsports applications typically have a particularly demanding trend of current discharging and charging from the battery pack, with numerous positive and negative peaks at high c-rates; this obviously produces, due to the Joule effect, a much higher amount of heat per kWh than in con-ventional road cars and therefore makes efficient and high-performance thermal management very important. In this work was defined, analyzed and optimized an innovative mixed solution with forced air cooling and PCM material (phase change material) for high performance battery modules with cylindrical cells used in a Formula Student car. In the various battery thermal management technologies, Air cooling is one of the most used solutions and can be successfully integrated with PCM cooling technique. In the work proposed here, the optimization and numerical simulation of different solutions and configurations is described. The target parameters considered are: airflow rate, cell spacing and mass of PCM. Fluid dynamic simulations were used to identify the optimal value of the radial gap between the cells, a fundamental construction parameter, and the speed of the air coming out of the fans. The choice of the mass of the PCM sheets was made on the basis of the quantity of heat to be removed to obtain a significant effect on the final temperature of the cells during the test (<50°C) and compatibly with the spaces available between the modules inside the battery pack. The simulations of the optimal solution will be compared to experimental results for validation, by the realization of the most promising configuration and its real experimentation on the car, in order to validate the expected performance of the thermal management system
Preliminary analysis of a new power train concept for a city hybrid vehicle
Full text linkThis research aims to test the feasibility of a prototype of a newly designed thermal engine for a hybrid propulsion vehicle. This study consists of the implementation of an innovative supercharger for city car internal combustion engine ICE (900 cc). The preliminary proposal presented here is to mechanically disconnect the compressor/turbine device, supporting the rotation of the compressor with a dedicated electric motor and connecting a turbine to a generator. Mechanical decoupling will allow both machines to be designed for operating closer to their maximum performance point, for most of the expected real field of operation. Specifically, the turbine is likely to have a lower rotation speed than the original group and will, therefore, be slightly larger. The advantage is that, while in the current supercharger groups the surplus at high regimes is discharged through the waste-gate valve without expanding in a turbine, in the configuration proposed, all the energy of the combustible gases is used by the turbine to generate electrical power that can be used where required. Once the motorization of the vehicle (999 cc) has been fixed, the two turbomachines will have to be studied and designed, looking where possible, for commercial components. Finally, a computational fluid dynamic CFD will be needed to verify the validity of the choice, followed by careful experimentation campaigns
Peristaltic roller pump: parametric optimization for hemolysis control
No full textThis work aims to analyze the various types of peristaltic pumps by studying, in particular, the use of the peristaltic roller pump to highlight its critical issues and propose new effective and innovative solutions. One possible application of this device is in hemodialysis, which is a physical therapy substitution of kidney function that allows, in almost all cases, recovery and maintenance of the main biological functions while remaining the uremic condition. As for the extracorporeal one, the equipment used to purify the blood from toxic substances that are no longer normally eliminated by kidney filtration is divided mainly into two types: rotary peristaltic pump and a linear peristaltic pump. Having to work with a very particular fluid such as blood and in direct contact with the patient, they need to be extremely accurate and must ensure a constant and continuous functioning. The rotary peristaltic pump is the most widely used for hemodialysis and having been extensively studied in literature it has since found extensive solutions in the application field. As is well known, peristaltic pump refers to a device that exploits the principle of peristalsis to function, i.e. the transit of a bottleneck on a tube, in this case, the catheter, to push the fluid contained outwards. In particular, a roundabout peristaltic pump consists of a rotating structure consisting of two or more rollers that in turn revolve around their axis. With their displacement, the rollers clog adjacent catheter sections at a time so that after the first roller has passed the tube returns to its initial size creating the vacuum and then sucking the fluid. In this way, the liquid is pushed from the tube towards the patient. The motion of all these components is powered by an electric motor connected directly to the main rotating structure. The pumping of fluids through hoses using the propagation of a peristaltic wave has been the subject of design and scientific studies for more than 4 decades. This is easily justifiable since the phenomenon of peristalsis is known to be an important responsible mechanism of fluid transport in many biological organs. The goal is (starting on studies on the blood, a variable density fluid) to analyze in detail the peristaltic roller pump and propose its parametric optimization, aimed at determining the critical speed, beyond which the machine damages any kind of fluid that needs special treatment (blood, food, special gel, medical ointments and so on)
Study, development and prototyping of a novel mild hybrid power train for a city car: Design of the turbocharger
Full text linkWithin a large, state-funded, Italian National Project aimed to test the feasibility of an on-the-road prototype of a mild hybrid city vehicle, one of the tasks was to conceive, design and implement an innovative turbocharger that would allow for some energy recovery. The selected vehicle is propelled by a 3-cylinder, 998 cc turbocharged engine (the 66 kW Mitsubishi-Smart W451). The idea is to implement two types of energy recovery: one via the new turbocharger and one through a standard braking energy recovery (also known as KERS). The study of the former is the object of this paper. The proposed turbocharger configuration consists of mechanically separated, electrically coupled compressor and turbine, possibly mounting only slightly modified commercial equipment to reduce construction costs. This paper reports the results of the calculation of the behavior of the new turbocharging group across the entire engine operating range and describes the preliminary design of the unit. An accurate simulation of a mixed (urban and extra-urban) driving mission demonstrates that a net saving of about 5.6% can be attained by the installation of the novel turbocharger unit
Experimental fitting of efficiency Hill chart for Kaplan hydraulic turbine
Full text linkThe development of hydroelectric technology and much of the “knowledge” on hydraulic phenomena derive from scale modeling and “bench” tests to improve machinery efficiency. The result of these experimental tests is mapping the so-called “hill chart”, representing the “DNA” of a turbine model. Identifying the efficiency values as a function of the specific parameters of the flow and energy coefficient (which both identify the operating point) allows us to represent the complete behavior of a turbine in hydraulic similarity with the original model developed in the laboratory. The present work carries out a “reverse engineering” operation that leads to the definition of “an innovative research model” that is relatively simple to use in every field. Thus, from the experimental survey of the degree of efficiency of several prototypes of machines deriving from the same starting model, the hill chart of the hydraulic profile used is reconstructed. The “mapping” of all the characteristic quantities of the machine, together with the physical parameters of the regulating organs of a four-blade Kaplan turbine model, also made it possible to complete the process, allowing to identify not only the iso-efficiency regions but also the curves relating to the trend of the angle of the impeller blades, the specific opening of the distributor, and the identification of critical areas of cavitation. The development of the hill chart was made possible by investigating the behavior of 33 actual prototypes and 46 characteristic curves derived from the same reference model based on practical experiments for finding the optimal blade distributor “setup curve”. To complete this, theoretical characteristic curves of “not physically realized” prototypes were also mapped, allowing us to complete the regions comprising the diagram. The study of the unified hill charts found in previous documentation of the most famous manufacturers was of great help. Finally, the validation of the “proposed procedure” was obtained through the experimental survey of the actual efficiency of the new prototype based on the theoretical values defined in the design phase on the chart obtained with the method described
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
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