Analysis and modeling of PEM fuel cell systems

Analisi e modellazione di sistemi a celle a combustibile di tipo PEMThe purpose of this thesis is to create a transient model of a PEM fuel cell system, based on Matlab Simulink, as general, flexible and adaptable as possible, in order to be easily set on different type of systems. The object of the study is the development of the simulation tool, and its validation against literature and experimental data. An important aim of the developed dynamic semi-empirical model is to try to adopt a theoretical physics-based approach whenever possible, in order to have an accurate scientific correlation between experimental output and theoretical laws, without neglecting the accuracy that could be provided by empirical equations. The major work is focused on the fuel cell stack modeling and involves also a large review of literature analysis concerning the simulation of PEM-FCs. In order to guarantee the adaptability of the model, taking inspiration from the latest studies in this field, a differential evolution algorithm is developed to realize the fitting process of the modeled polarization curve, by means of the stack voltage model, on experimental data. This algorithm has a strategic importance for the choice and the setting of the stack voltage equations on the real static performance of the PEM fuel cell system analyzed, with a proved error of about 2-3%. The transient behaviors captured in the model includes flow characteristics, inertia dynamics, lumped-volume manifold filling dynamics, time evolving-homogeneous reactant pressure or mole fraction, membrane humidity and thermal response of fuel cell and cooling system. From one side, the validation against literature data of Section 4 is realized after the development of a general dynamic PEM-FC system model described in Section 2 and 3, comprising all the components normally present in these systems. The comprehensive dynamic model proposed, usually not presented in literature, perform very well respect to the experimental data, comprising the thermic data and the hydration of the membrane, the most important operative parameters but also the most complex ones to simulate. On the other side, the HI-SEA Joint Laboratory, between Fincantieri S.p.A. and the University of Genoa, allows to study a PEM fuel cell system of 8 stacks sized 33 kW each for a total maximum power of 260 kW. The adaptation and the simplification of the dynamic model to this plant layout helps to study a bigger and more complex PEM-FC system and to validate the model to the experimental data. The simplification of the dynamic model starts form the necessity to set the equations only by the commercially available data, usually limited to the datasheet information. This limitation makes the HI-SEA model less detailed but, at the same time, simpler and able to provide different important results, as the stack and cooling system thermal balances, starting from few easily obtainable data

Numerical resolution of an exact heat conduction model with a delay term

In this paper we analyze, from the numerical point of view, a dynamic thermoelastic problem. Here, the so-called exact heat conduction model with a delay term is used to obtain the heat evolution. Thus, the thermomechanical problem is written as a coupled system of partial differential equations, and its variational formulation leads to a system written in terms of the velocity and the temperature fields. An existence and uniqueness result is recalled. Then, fully discrete approximations are introduced by using the classical finite element method to approximate the spatial variable and the implicit Euler scheme to discretize the time derivatives. A priori error estimates are proved, from which the linear convergence of the algorithm could be derived under suitable additional regularity conditions. Finally, a two-dimensional numerical example is solved to show the accuracy of the approximation and the decay of the discrete energy.Peer ReviewedPostprint (published version

Turbocharged Solid Oxide Fuel Cell System: Design and Emulation

This paper presents a design model of a turbocharged solid oxide fuel cell system fueled by biogas. The aim of this plant layout is the development of a low-cost solution considering the coupling of the solid oxide fuel cell (SOFC) with a low-cost machine such as a turbocharger (instead of a microturbine). The whole system model calculates the operational conditions and realizes the coupling between the turbocharger, the recuperator and the solid oxide fuel cell system (comprising SOFC, air preheater, fuel compressor and pre-heater, reformer, off-gas burner and anodic ejector). This model also supports the design of an emulator test rig in which a burner, located inside a thermal insulated vessel, replaces the solid oxide fuel cell system. The emulator test rig will be useful to study the matching between the turbocharger and the fuel cell to validate simulation models, design innovative solutions and test the control system of the whole plant

How to classify the stylohyoid complex syndrome in the ICHD

We have read the International Classification of Headache Disorders, third edition (beta) (ICHD-3 beta), and for the first time headaches are attributed to inflammation of the stylohyoid ligament (SL). It is included among the secondary headaches in “Headache or facial pain attributed to disorder of the cranium, neck, eyes, ears, nose, sinuses, teeth, mouth or other facial or cervical structure.

Numerical analysis of a thermoelastic problem with dual-phase-lag heat conduction

In this paper we study, from the numerical point of view, a thermoelastic problem with dual-phase-lag heat conduction. The variational formulation is written as a coupled system of hyperbolic linear variational equations. An existence and uniqueness result is recalled. Then, fully discrete approximations are introduced by using the finite element method and the implicit Euler scheme. A discrete stability result is proved and a priori error estimates are obtained, from which the linear convergence of the algorithm is deduced under suitable additional regularity conditions. Finally, some two-dimensional numerical simulations are presented to demonstrate the accuracy of the approximation and the behaviour of the solution.Peer ReviewedPostprint (author's final draft

Laser microsurgery versus radiotherapy versus open partial laryngectomy for T2 laryngeal carcinoma: a systematic review of oncological outcomes

The aim of the current systematic review is to update the pooled survival outcome of patients with T2 glottic carcinoma treated with either laser surgery (CO2 transoral laser microsurgery [CO2 TOLMS]), radiotherapy (RT), or open partial laryngectomy (OPL)

Modelado y control inteligente del cuatrirotor Quanser Qball-X4

En este proyecto se ha desarrollado el modelado, diseño y aplicación de controladores inteligentes en un cuatrirotor, en concreto, el modelo Quanser Qball-X4. Este vehículo autónomo aéreo (UAV) es altamente inestable, por lo que para que su comportamiento sea eficiente debe estar bien controlado, una tarea que es compleja. En este proyecto se propone, en primer lugar, partiendo de modelos disponibles del vehículo aéreo, refinarlos para poder simularlo y estudiar su comportamiento. Tras esta fase, en la que se generan modelos mejorados, se plantea el diseño de controladores, tanto convencionales como inteligentes o una hibridación de ambos, con el objetivo de que despegue y aterrice en una plataforma, y que recorra una trayectoria. Además se dota de una visión tridimensional sencilla para observar los resultados. [ABSTRACT] System modeling, design and implementation of intelligent contalabeoers in a cuatrirotor, specifically, the model Quanser Qball-X4 . This autonomous air vehicle (UAV) is highly unstable, so in order to get an efficient behavior a good contalabeoer is needed, and that is a complex task. This project proposes the study and simulation of air vehicle models. After this phase, in which improved models are generated, the design of contalabeoers is considered, both conventional and intelligent or a hybrid form of both, with the goal to archieve a takeoff and landing from and on a platform, and a travel path. It also gives a simple three-dimensional view to observe results

Zotarolimus-Eluting Versus Bare-Metal Stents in Uncertain Drug-Eluting Stent Candidates

BACKGROUND The use of drug-eluting stents (DES) in patients at high risk of bleeding or thrombosis has not been prospectively studied; limited data are available in patients who have a low restenosis risk. OBJECTIVES This study sought to compare a hydrophilic polymer-based, second-generation zotarolimus-eluting stent (ZES) with a unique drug fast-release profile versus bare-metal stents (BMS) under similar durations of dual-antiplatelet therapy (DAPT). METHODS We randomly assigned 1,606 patients with stable or unstable symptoms, and who on the basis of thrombotic bleeding or restenosis risk criteria, qualified as uncertain candidates for DES, to receive ZES or BMS. DAPT duration was on the basis of patient characteristics, rather than stent characteristics, and allowed for a personalized 1-month dual antiplatelet regimen. The primary endpoint was the risk of 1-year major adverse cardiovascular events (MACE), which included death, myocardial infarction (MI), or target vessel revascularization (TVR). RESULTS Median DAPT duration was 32 days (interquartile range [IQR]: 30 to 180 days) and did not differ between the groups. In the ZES group, 140 patients (17.5%) reached the primary endpoint, compared with 178 patients (22.1%) in the BMS group (hazard ratio: 0.76; 95% confidence interval: 0.61 to 0.95; p = 0.011) as a result of lower MI (2.9% vs. 8.1%; p < 0.001) and TVR rates (5.9% vs. 10.7%; p = 0.001) in the ZES group. Definite or probable stent thrombosis was also significantly reduced in ZES recipients (2.0% vs. 4.1%; p = 0.019). CONCLUSIONS Compared with BMS, DES implantation using a stent with a biocompatible polymer and fast drug-eluting characteristics, combined with an abbreviated, tailored DAPT regimen, resulted in a lower risk of 1-year MACE in uncertain candidates for DES implantation. (Zotarolimus-eluting Endeavor Sprint Stent in Uncertain DES Candidates [ZEUS] Study; NCT01385319) (C) 2015 by the American College of Cardiology Foundation

Tachyon-Chaplygin inflationary universe model

Tachyonic inflationary universe model in the context of a Chaplygin gas equation of state is studied. General conditions for this model to be realizable are discussed. By using an effective exponential potential we describe in great details the characteristic of the inflationary universe model. The parameters of the model are restricted by using recent astronomical observations.Comment: 13 pages, 1 figure, Accepted by Physics Letters