PARTIAL NEEDLE LIFT AND INJECTION RATE SHAPE EFFECT ON THE FORMATION AND COMBUSTION OF THE DIESEL SPRAY

Fuel direct injection represents one of the key turning points in the development of the Diesel engines. The appeal of this solution has been growing thanks to the parallel advancement in the technology of the injection hardware and in the knowledge of the physics involved in the spray formation and combustion. In the present thesis, the effect of partial needle lift and injection rate shaping has been investigated experimentally using a multi-orifice Diesel injector. Injection rate shaping is one of the most attractive alternatives to multiple injection strategies but its implementation has been for long time impeded by technological limitations. A novel direct-acting injector prototype made it possible to carry out the present research: this injector features a mechanical coupling between the nozzle needle and the piezo-stack actuator, allowing a fully flexible control on the nozzle needle movement and enabling partial needle lift as well as the implementation of alternative injection rate shapes typologies. Different optical diagnostics were applied to study the spray development and combustion in a novel continuous flow test chamber that allows an accurate control on a wide range of thermodynamic conditions (up to 1000K and 15MPa). In addition, hydraulic characterization tests were carried out to analyze the fuel flow through the injector nozzle. Partial needle lift has been found to affect the injection event, reducing the mass flow rate (as expected) but also causing a reduction in the effective orifice area and an increase on the spreading angle. Moreover, at this condition, higher hole-to-hole dispersion and flow instabilities were detected. Needle vibrations caused by the needle interactions with fuel flow and by the onset of cavitation in the needle seat are likely the causes of this behavior. Injection rate shaping has a substantial impact on the premixed phase of the combustion and on the location where the ignition takes place. Furthermore, the results proved that the modifications in the internal flow caused by the partial needle lift are reflected on the ignition timing. On the other hand, the analysis of the experimental data through a 1D spray model revealed that an increasing mass flow rate (e.g. ramp or boot injection rate profiles) causes an increase in the fuelair equivalence ratio at the lift-off length and a consequent higher soot formation during the diffusive phase of the combustion. Finally, the wide range of boundary conditions tested in all the experiments served to draw general conclusions about the physics involved in the injection/combustion event and, in some cases, to obtain statistical correlations.Bardi, M. (2014). PARTIAL NEEDLE LIFT AND INJECTION RATE SHAPE EFFECT ON THE FORMATION AND COMBUSTION OF THE DIESEL SPRAY [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/37374TESI

Engine combustion network: Influence of the gas properties on the spray penetration and spreading angle

In this work, three Engine Combustion Network (ECN) single-hole nozzles with the same nominal characteristics have been tested under a wide range of conditions measuring spray penetration and spreading angle. n-Dodecane has been injected in non-evaporative conditions at different injection pressures ranging from 50 to 150 MPa and several levels of ambient densities from 7.6 to 22.8 kg/m(3). Nitrogen and Sulphur Hexafluoride (SF6) atmospheres have been explored and, in the first case, a temperature sweep from 300 to 550 K at constant gas density has been executed. Mie scattering has been used as the optical technique by employing a fast camera, whereas image processing has been performed through a home-built Mat lab code. Differences in spray penetration related to spray orifice diameter, spreading angle and start of injection transient have been found for the three injectors. Significant differences have been obtained when changing the ambient gas, whereas ambient temperature hardly affects the spray characteristics up to 400 K. However, a reduction in penetration has been observed beyond this point, mainly due to the sensitivity limitation of the technique as fuel evaporation becomes important. The different behavior observed when injecting in different gases could be explained due to the incomplete momentum transfer between spray droplets and entrained gas, together with the fact that there is an important change in speed of sound for the different gases, which affects the initial stage of the injection. (C) 2014 Elsevier Inc. All rights reserved.This work was sponsored by "Ministerio de Economia y Competitividad" of the Spanish Government in the frame of the Project "Comprension de la influencia de combustibles no convencionales en el proceso de injeccion y combustion tipo diesel", Reference TRA2012-36932.Payri González, F.; Payri Marín, R.; Bardi, M.; Carreres Talens, M. (2014). Engine combustion network: Influence of the gas properties on the spray penetration and spreading angle. Experimental Thermal and Fluid Science. 53:236-243. https://doi.org/10.1016/j.expthermflusci.2013.12.014S2362435

A study on diesel spray tip penetration and radial expansion under reacting conditions

The shape of Diesel spray was investigated at real engine conditions in a constant pressure combustion chamber. Schlieren imaging technique was used to make quantitative measurements of spray tip penetration and radial width stressing the impact that the fuel combustion and heat release have on the spray shape. The heat-release region and the Lift-off length were identified measuring OH* chem-iluminescence. The fuel (n-dodecane) as well as the operating conditions and the injector used (single axially-oriented hole, 89 mu m-diameter) were chosen following the guidelines of the Engine Combustion Network. The effects of different operating parameters on the axial and radial expansion were also investigated. According to the results the reacting spray can be divided into three parts: an inert part, a transient one, and a quasi-steady one that lays between the two other regions. A new method for evaluating this radial expansion of reacting spray was developed, which was evaluated under the different operating conditions. Results show that the radial expansion increases with increasing injection pressure and decreasing ambient temperature and ambient density. The oxygen concentration has no obvious effect on the radial expansion. (C) 2015 Elsevier Ltd. All rights reserved.Authors acknowledge that some equipment used in this work has been partially supported by FEDER project funds (FEDER-ICTS-2012-06), framed in the operational program of unique scientific and technical infrastructure of the Ministry of Science and Innovation of Spain.Payri, R.; García Oliver, JM.; Xuan, T.; Bardi, M. (2015). A study on diesel spray tip penetration and radial expansion under reacting conditions. Applied Thermal Engineering. 90:619-629. https://doi.org/10.1016/j.applthermaleng.2015.07.042S6196299

Transcatheter aortic valve implantation with the novel-generation Navitor device. Procedural and early outcomes

Transcatheter aortic valve implantation (TAVI) has proved beneficial in patients with severe aortic stenosis, especially when second-generation devices are used. We aimed at reporting our experience with Navitor, a third-generation device characterized by intrannular, large cell, and cuffed design, as well as high deliverability and minimization of paravalvular leak. Between June and December 2021, a total of 39 patients underwent TAVI with Navitor, representing 20% of all TAVI cases. Mean age was 80.0 +/- 6.7 years, and 14 (36.8%) women were included. Severe aortic stenosis was the most common indication to TAVI (37 [97.4%] cases), whereas 2 (5.3%) individuals were at low surgical risk. Device and procedural success was obtained in all patients, with a total hospital stay of 6.6 +/- 4.5 days. One (2.9%) patient required permanent pacemaker implantation, but no other hospital events occurred. At 1-month follow-up, a cardiac death was adjudicated in an 87-year-old man who had been at high surgical risk. Echocardiographic follow-up showed no case of moderate or severe aortic regurgitation, with mild regurgitation in 18 (47%), and none or trace regurgitation in 20 (53%). The Navitor device, thanks to its unique features, is a very promising technology suitable to further expand indications and risk-benefit profile of TAVI

Experimental study of the relationship between injection rate shape and Diesel ignition using a novel piezo-actuated direct-acting injector

Injection rate shaping is one of the most attractive alternatives to multiple injection strategies; however, its implementation has been for long time impeded by limitations in the injector technology and therefore, the experimental information available in the literature about this topic is lacking. In this work, a novel prototype common-rail injector featuring direct control of the nozzle needle by means of a piezo-stack (direct-acting) allowed a fully flexible control on the nozzle needle movement and enabled the implementation of alternative injection rate shapes typologies. This state of the art injector, fitted with a 7-hole nozzle, was tested at real engine conditions studying the spatial-temporal evolution of CH* and OH* chemiluminescence intensity produced by the fuel combustion. A wide test matrix was performed in an optically accessible hot-spray test rig to understand the influence that partial needle lift and alternative injection rate shapes have on the Diesel ignition The results showed that alternative injection rate profiles have a substantial impact on the ignition event affecting the premixed phase of the combustion and the location where the ignition takes place. Moreover, the results proved that the modifications in the internal flow caused by the partial needle lift are reflected on the ignition timing: although partial needle lift and injection pressure have similar effects on the mass flow rate, in the first case, the ignition delay is reduced, while in the second, the combustion is delayed as a consequence of a different spray development.This work was sponsored by General Motors R&D, Warren, MI. The authors would like to thank Jose Enrique del Rey, Moises Ferrandez Hermosilla and Juan Pablo Viera for their precious help in the laboratory during the tests.Macian Martinez, V.; Payri Marín, R.; Ruiz Rosales, S.; Bardi, M.; Plazas, AH. (2014). Experimental study of the relationship between injection rate shape and Diesel ignition using a novel piezo-actuated direct-acting injector. Applied Energy. 118:100-113. doi:10.1016/j.apenergy.2013.12.025S10011311

The OpenAIRE Research Community Dashboard: On blending scientific workflows and scientific publishing

First Online 30 August 2019Despite the hype, the effective implementation of Open Science is hindered by several cultural and technical barriers. Researchers embraced digital science, use “digital laboratories” (e.g. research infrastructures, thematic services) to conduct their research and publish research data, but practices and tools are still far from achieving the expectations of transparency and reproducibility of Open Science. The places where science is performed and the places where science is published are still regarded as different realms. Publishing is still a post-experimental, tedious, manual process, too often limited to articles, in some contexts semantically linked to datasets, rarely to software, generally disregarding digital representations of experiments. In this work we present the OpenAIRE Research Community Dashboard (RCD), designed to overcome some of these barriers for a given research community, minimizing the technical efforts and without renouncing any of the community services or practices. The RCD flanks digital laboratories of research communities with scholarly communication tools for discovering and publishing interlinked scientific products such as literature, datasets, and software. The benefits of the RCD are show-cased by means of two real-case scenarios: the European Marine Science community and the European Plate Observing System (EPOS) research infrastructure.This work is partly funded by the OpenAIRE-Advance H2020 project (grant number: 777541; call: H2020-EINFRA-2017) and the OpenAIREConnect H2020 project (grant number: 731011; call: H2020-EINFRA-2016-1). Moreover, we would like to thank our colleagues Michele Manunta, Francesco Casu, and Claudio De Luca (Institute for the Electromagnetic Sensing of the Environment, CNR, Italy) for their work on the EPOS infrastructure RCD; and Stephane Pesant (University of Bremen, Germany) his work on the European Marine Science RCD

Study liquid length penetration results obtained with a direct acting piezo electric injector

A state of the art prototype common rail injector featuring direct control of the needle by means of a piezo stack (direct acting) has been tested. Liquid phase penetration of the sprays in diesel engine-like conditions has been studied via imaging technique in a novel continuous flow test chamber that allows an accurate control on a wide range of thermodynamic conditions (up to 1000 K and 15 MPa). This state of the art injector fitted with a 7-hole nozzle, allows a fully flexible control on the nozzle needle movement, enabling various fuel injection rates typology. The temporal evolution of the seven sprays has been studied recording movies of the injection event in evaporative conditions via Mie scattering imaging technique and using a high speed camera. The results showed a strong influence of needle position on the stabilized liquid length while the effect of the injection pressure is negligible: the decrease of the needle lift causes a pressure drop in the needle seat and thus a reduction in the effective pressure upstream of the orifices (in the nozzle sac). According to known literature the stabilized liquid-length depends mainly on effective diameter, spray cone-angle and fuel/air properties and does not depend on fuel velocity at the orifice outlet. Therefore, due to small change in the spray cone-angle, higher injection pressures give slightly lower liquid length. However, partial needle lifts has an opposite effect: when needle is partially lifted a dramatic increase of the spray cone-angle and a consequent reduction of the liquid length are observed. A deeper analysis revealed that low charges are linked also to higher hole to hole dispersion and flow instabilities. Needle vibrations caused by the fuel-needle interactions with fuel flow at partial needle lift and the onset of cavitation in the needle seat are likely the causes of this unexpected behavior. Finally, the effect of injection rate shaping on the transient liquid penetration is presented, showing the capability of the injector to control the liquid length along the injection event. This feature, when applied in a real engine, yields to develop new injection strategies to avoid fuel wall impingement.This work was sponsored by General Motors R&D, Warren, MI. The authors would like to thank Jose Enrique del Rey and David Fuertes Munoz for their precious work in the laboratory during the tests.Payri, R.; Gimeno, J.; Bardi, M.; Plazas, AH. (2013). Study liquid length penetration results obtained with a direct acting piezo electric injector. Applied Energy. 106:152-162. doi:10.1016/j.apenergy.2013.01.027S15216210

Revisional Surgery After One Anastomosis/Minigastric Bypass: an Italian Multi-institutional Survey

Background: Efficacy and safety of OAGB/MGB (one anastomosis/mini gastric bypass) have been well documented both as primary and as revisional procedures. However, even after OAGB/MGB, revisional surgery is unavoidable in patients with surgical complications or insufficient weight loss. Methods: A questionnaire asking for the total number and demographics of primary and revisional OAGB/MGBs performed between January 2006 and July 2020 was e-mailed to all S.I.C. OB centres of excellence (annual caseload > 100; 5-year follow-up > 50%). Each bariatric centre was asked to provide gender, age, preoperative body mass index (BMI) and obesity-related comorbidities, previous history of abdominal or bariatric surgery, indication for surgical revision of OAGB/MGB, type of revisional procedure, pre- and post-revisional BMI, peri- and post-operative complications, last follow-up (FU). Results: Twenty-three bariatric centres (54.8%) responded to our survey reporting a total number of 8676 primary OAGB/MGBS and a follow-up of 62.42 ± 52.22 months. A total of 181 (2.08%) patients underwent revisional surgery: 82 (0.94%) were suffering from intractable DGER (duodeno-gastric-esophageal reflux), 42 (0.48%) were reoperated for weight regain, 16 (0.18%) had excessive weight loss and malnutrition, 12 (0.13%) had a marginal ulcer perforation, 10 (0.11%) had a gastro-gastric fistula, 20 (0.23%) had other causes of revision. Roux-en-Y gastric bypass (RYGB) was the most performed revisional procedure (109; 54%), followed by bilio-pancreatic limb elongation (19; 9.4%) and normal anatomy restoration (19; 9.4%). Conclusions: Our findings demonstrate that there is acceptable revisional rate after OAGB/MGB and conversion to RYGB represents the most frequent choice

Geophysical surveys integrated in the "Il Piano" area (Isola d'Elba, Italy) to goal census and cataloging cavities anthropic origin

Numerosi sprofondamenti si sono verificati nell’ultimo decennio in un’area di fondovalle compresa nel territorio di Rio Marina all’Isola d’Elba (località Il Piano), ed hanno interessato abitazioni, aree agricole e la strada di collegamento tra Rio Marina e Rio nell’Elba, la SP26. Nell’intorno affi ora la formazione del Calcare Cavernoso dove si è sviluppato un sistema caveale, la “Grotta di San Giuseppe”; inizialmente ciò faceva ipotizzare anche la presenza di cavità all’interno del substratocarbonatico. L’integrazione di diversi metodi geofisici indiretti ha evidenziato invece un altro motivo causale di origine antropica nella formazioni di questi sinkhole. Gli obiettivi dello studio sono stati ottenere un modello geologico e idrogeologico della zona; individuare possibili cavità e/o carenze di massa/densità che sarebbero potute evolvere in sprofondamenti; valutare la suscettibilità della zona agli sprofondamenti. Tra i risultati delle indagini geofisiche integrate: a) i modelli gravimetrici 2D e 3D hanno fornito informazioni sulla distribuzione spaziale delle densità nel sottosuolo; b) la 3D-ERT ha caratterizzato il comportamento elettrico dei materiali; c) il metodo H/V ha permesso di stimare lo spessore medio delle alluvioni. Le indagini geofisiche integrate, unite ad un’accurata ricostruzione della trasformazione ambientale dell’area, hanno consentito una caratterizzazione geomorfologica e idrogeologica del territorio. L’interpretazione di questi dati ha permesso di comprendere l’innesco dei fenomeni di sprofondamento e di redarre mappe delle aree a rischio.Published81-907A. Geofisica per il monitoraggio ambientale7SR AMBIENTE – Servizi e ricerca per la societàJCR Journa

Experimental characterization of diesel ignition and lift-off length using a single-hole ECN injector

In this work, lift-off length and ignition delay have been measured via chemiluminescence techniques in a wide range of conditions for a single-hole injector from the Engine Combustion Network (ECN) dataset and using a single component fuel (n-dodecane). In addition, Schlieren technique was used to characterize the ignition event using a new developed post-processing methodology capable of characterizing the "disappearance" phenomenon linked to the start of cool flames. Experiments have been carried out in a novel constant-pressure flow facility able of reproducing engine-like thermodynamic conditions. Results show that oxygen concentration seems to have a negligible impact on the start of cool flames. Empirical correlations have been obtained for the three measured parameters and they manifest similar trends of other previously published correlations for lift-off length and second stage ignition. These correlations also underline that the effect of oxygen concentration and ambient density is caught differently by chemiluminescence and Schlieren techniques, even though the absolute value of the measurements remains close. (C) 2013 Elsevier Ltd. All rights reserved.This work was sponsored by "Ministerio de Economia y Competitividad" of the Spanish Government in the frame of the Project "Comprension de la influencia de combustibles no convencionales en el proceso de inyeccion y combustion tipo diesel", Reference TRA2012-36932. Additionally, the Ph.D student Michele Bardi was financed by a grant from "Conselleria de educacio, cultura y esport" of the "Generalitat Valenciana" with Reference GRISOLIA/2010/010. This support is gratefully acknowledged by the authors.Benajes Calvo, JV.; Payri Marín, R.; Bardi, M.; Marti-Aldaravi, P. (2013). Experimental characterization of diesel ignition and lift-off length using a single-hole ECN injector. Applied Thermal Engineering. 58(1-2):554-563. https://doi.org/10.1016/j.applthermaleng.2013.04.044S554563581-