Gas Exchange and Injection Modeling of an Advanced Natural Gas Engine for Heavy Duty Applications

The scope of the work presented in this paper was to apply the latest open source CFD achievements to design a state of the art, direct-injection (DI), heavy-duty, natural gas-fueled engine. Within this context, an initial steady-state analysis of the in-cylinder flow was performed by simulating three different intake ducts geometries, each one with seven different valve lift values, chosen according to an estabilished methodology proposed by AVL. The discharge coefficient (Cd) and the Tumble Ratio (TR) were calculated in each case, and an optimal intake ports geometry configuration was assessed in terms of a compromise between the desired intensity of tumble in the chamber and the satisfaction of an adequate value of Cd. Subsequently, full-cycle, cold-flow simulations were performed for three different engine operating points, in order to evaluate the in-cylinder development of TR and turbulent kinetic energy (TKE) under transient conditions. The latest achievements in open source mesh generation and motions were applied, along with time-varying and case-fitted inizialization values for the fields of intake pressure and temperature. Finally, direct-injection of natural gas in the cylinder was incorporated in full-cycle simulations, to evaluate the effects of injection on charge motions and charge homogeneity at the estimated spark timing. Three specific engine operating points were simulated and different combinations of turbochargers and valve lift laws were tested. Results consistency was verified by means of validations with data from 1D simulations and literature

Impact of Isolated Tricuspid Valve Repair on Right Ventricular Remodelling in an Adult Congenital Heart Disease Population

BackgroundSurgical repair of isolated congenital tricuspid valve (TV) disease is rare with no well-defined indication and outcomes. Moreover, the role of right ventricle (RV) in this context has not yet been investigated.ObjectivesWe sought to assess the impact of congenital TV repair on cardiac remodelling and clinical–functional status and the importance of the RV function in an adult congenital heart disease (ACHD) population.Methods and resultsFrom January 2005 to December 2015, 304 patients underwent TV surgery in our centre. Of these, 27 (ACHD) patients had isolated TV repair. Patients were evaluated with preoperative and postoperative transthoracic echocardiogram. Survival rate has been investigated with a mean clinical follow-up (FU) of 3.7 ± 2.3 years, whereas the mean echocardiographic FU was 2.9 ± 1.8 years. The clinical and functional status of patients showed a statistically significant improvement after the surgical repair in terms of New York Heart Association class (66.7 vs 7.4%; p < 0.01), clinical signs of heart failure (29.6 vs 7.4%; p < 0.01), and left ventricular function (14.8 vs 7.4%; p < 0.01). The RV and right atrium diameter were significantly reduced after surgery (5.15 ± 1.21 vs 4.32 ± 1.16; p < 0.01) and (44.7 ± 16.7 vs 26.7 ± 9.2; p < 0.01), respectively. The degree of postoperative pulmonary hypertension was also significantly reduced (40.7 vs 7.4%; p < 0.01). The survival rate was 96.3% at 1 year and 93.7% at 5 years. One patient (3.7%) had early failure of the tricuspid repair requiring a reoperation.ConclusionIsolated TV repair for adult congenital disease significantly improved patients’ clinical and functional status and allowed right ventricular remodelling and functional improvement

Experimental investigation on the optimal injection and combustion phasing for a direct injection hydrogen-fuelled internal combustion engine for heavy-duty applications

In the current context of increasing demand for clean transportation, hydrogen usage in internal combustion engines (ICEs) represents a viable solution to abate all engine-out criteria pollutants and almost zeroing CO2 tailpipe emissions. Indeed, the wider flammability limits thanks to the higher flame propagation speed and the lower minimum ignition energy compared with conventional fuels, extend the stable combustion regime to leaner mixtures thus allowing high thermal efficiency keeping under control the NOX emissions. To fully exploit the potential of hydrogen as a fuel and to avoid undesired abnormal combustion processes, a deep characterization of the combustion process is needed. With this aim, a 6-cylinder, 12.9-L heavy-duty engine was converted from a port-fuel injected compressed natural gas to a direct injected hydrogen spark ignition one. A wide experimental campaign was carried out, consisting of several sweeps of relative air-fuel ratios, spark advances, and injection timings at different engine speeds and loads, aiming to define a preliminary engine map. The effect of each calibration parameter at different engine load and speed has been analyzed through the combination of relevant combustion parameters, as well as NOX emissions. The results have demonstrated the critical influence of the mixture inhomogeneity when the injection is retarded through the top dead center firing, as indicated by the increase in NOX emissions and combustion variability. The analysis of the combustion timing has indicated the dependence of the optimal MFB50 on the relative air-fuel ratio. Lastly, the analysis of 200 consecutive cycles for each operating condition has allowed the evaluation of the influence of the main calibration parameters on the cyclic variability, thus providing further insights about the lean limit of hydrogen in ICE

Allogeneic Mesenchymal Stromal Cell Injection to Alleviate Ischemic Heart Failure Following Arterial Switch Operation.

Cell therapy is a promising tool to prevent and treat heart failure in congenital heart disease. We report the first case of intramyocardial injection of allogeneic mesenchymal stromal cells as rescue therapy in a neonate with ischemic heart failure following arterial switch procedure for isolated transposition of the great arteries. (Level of Difficulty: Advanced.

Exiliados-migrantes y reconciliación en los Países Bajos después de la Paz de Arras (1579)

This article contributes to the assessment of the management of migrants at the end of the 16th century as part of the challenge, by both central and municipal authorities, for ending the civil war in the Spanish Low Countries. In particular, it questions to what extent experiences of exiles, returnees and migrants presented a challenge for families, economic regulation and public order in the French-speaking reconciled provinces (Hainaut, Artois and the Walloon Flanders), in the new framework of the pacification and religious normalization. It focuses on how did the towns, when confronted with various forms of mobility, attempt to apply the practice of reconciliation. On the one hand, the general policy of reconciliation tried to build a post bellum society under the Roman Catholic faith and the King’s sovereignty, not only by excluding those who refused to recant in order to conform to the rules of the pacification, but also by forgiving and reincorporating the migrants who crossed confessional boundaries. Then, it considers how, at their level, the municipal authorities had to take various patterns of migration into account, in particular those that connected most of the towns of the Union of Arras to the Protestant Refuge in England and the Dutch Republic, reducing the importance of the migrants’ religious status in their selection criteria. Finally, theses practices opened a space for discussion and a shy civic toleration between the Catholic aldermen, the ex-Calvinists who had chosen official reconciliation, and the textile workers migrants while still being accommodated and welcomed into the exile Protestant Churches, relegating the debate about personal confessional practices and religion from public space to the family sphere.Este artículo tiene como objetivo entender la gestión de los emigrantes a finales del siglo XVI como parte del objetivo de terminar la guerra civil en los Países Bajos Españoles al que se enfrentaron tanto autoridades centrales como locales. En concreto, ese texto plantea hasta qué punto las experiencias de exilio, retorno y migración representaron un desafío para las familias que lo sufrieron y para la regulación económica y el orden público en las provincias de habla francesa reconciliadas con el monarca (Hainaut, Artois y la Flandes Valona) en el marco de la pacificación y normalización religiosa. El análisis se concentra en cómo las ciudades intentan poner en práctica la reconciliación a la hora de hacer frente a varias formas de movilidad. Por un lado, la política general de reconciliación intentó construir una sociedad de postguerra en torno al catolicismo romano y la soberanía del rey, no solamente excluyendo a aquellos que se negaron a retractarse para acogerse a la política de pacificación, sino también perdonando y reincorporando a los emigrantes que cruzaban las fronteras confesionales. Por otro lado, las autoridades municipales tuvieron que tener en cuenta varias pautas migratorias a la hora de aplicar la reconciliación, en particular las que conectaban la mayor parte de las ciudades de la Unión de Arrás con el refugio protestante en Inglaterra y las Provincias Unidas. De esta forma redujeron considerablemente la importancia del status religioso de los emigrantes y los criterios de selección que les permitían incorporarse a la sociedad. Por último, estas prácticas abrieron un espacio para la negociación de una modesta tolerancia cívica entre ediles católicos, ex-calvinistas que habían optado por la reconciliación oficial y los trabajadores textiles que seguían practicando su religión en las iglesias protestantes del exilio, relegando el debato sobre las prácticas confesionales personales y religión del espacio público a la esfera familiar