Analysis of the Pre-Injection System of a Marine Diesel Engine Through Multiple-Criteria Decision-Making and Artificial Neural Networks

[Abstract] The present work proposes several pre-injection patterns to reduce nitrogen oxides in the Wärtsilä 6L 46 marine engine. A numerical model was carried out to characterise the emissions and consumption of the engine. Several pre-injection quantities, durations, and starting instants were analysed. It was found that oxides of nitrogen can be noticeably reduced but at the expense of increasing consumption as well as other emissions such as carbon monoxide and hydrocarbons. According to this, a multiple-criteria decision-making (MCDM) model was established to select the most appropriate parameters. Besides, an artificial neural network (ANN) was developed to complement the results and analyse a huge quantity of alternatives. This hybrid MCDM-ANN methodology proposed in the present work constitutes a useful tool to design new marine engines

Multi-criteria analysis to determine the most appropriate fuel composition in an ammonia/diesel oil dual fuel engine

[Abstract] The possibility to employ alternative fuels is gaining special interest in the marine sector. There are several suitable candidates for traditional fossil fuels substitution. Among them, ammonia is a promising solution that allows progress on decarbonization since the ammonia molecule does not contain carbon. Hence, the present work analyzes the use of ammonia as a potential fuel for a marine engine. Particularly, a dual fuel mode ammonia/diesel oil operation is proposed. As expected, the carbon dioxide emissions are reduced as the proportion of ammonia is increased. Nevertheless, other non-desirable substances are generated such as non-reacted ammonia, NOx and N2O. Due to these opposing effects, a multi-criteria analysis is proposed to characterize the most appropriate proportion of ammonia in the fuel. The environmental damage of the different pollutants was considered. Due to the important environmental adverse effects of NOx and N2O, only a maximum 20% ammonia percentage on the fuel was obtained as the most appropriate option. A higher ammonia content leads to excessive concentrations of NOx and N2O being emitted to the environment

Possibilities of Ammonia as Both Fuel and NOᵪ Reductant in Marine Engines: A Numerical Study

[Abstract] Nowadays, the environmental impact of shipping constitutes an important challenge. In order to achieve climate neutrality as soon as possible, an important priority consists of progressing on the decarbonization of marine fuels. Free-carbon fuels, used as single fuel or in a dual-fuel mode, are gaining special interest for marine engines. A dual fuel ammonia-diesel operation is proposed in which ammonia is introduced with the intake air. According to this, the present work analyzes the possibilities of ammonia in marine diesel engines. Several ammonia-diesel proportions were analyzed, and it was found that when the proportion of ammonia is increased, important reductions of carbon dioxide, carbon monoxide, and unburnt hydrocarbons are obtained, but at the expense of increments of oxides of nitrogen (NOᵪ), which are only low when too small or too large proportions of ammonia are employed. In order to reduce NOᵪ too, a second ammonia injection along the expansion stroke is proposed. This measure leads to important NOᵪ reductions

Computational Fluid Dynamic Simulation on NACA 0026 Airfoil with V-Groove Riblets

The aims of this research is to look into the percentage drag reduction on a NACA 0026 airfoil with V-Groove riblets installed around at some locations around its surface. NACA 0026 is a symmetrical airfoil mostly used as turbine blade and aircraft wing. Research on drag reduction by using riblets on the surface was introduced by NASA Langley Research Centre in 1970s. There are many types of riblet designed in this research area such as V groove, segmented blade and continuous sawtooth. This research used NACA 0026 with external geometry 500 mm spans, 615 mm chord and 156 mm thickness. V-groove riblets with 1 mm pitch and 1 mm high and 30 mm width are attached at peak points of the airfoil profile. The CFD simulation used ANSYS Fluent to analyze the velocity, pressure gradient, turbulent kinetic energy and vortex development. The result shows the percentage in drag reduction compared to clean surface for the zero angle of attack is 11.8% and 300 angle of attack is 1.64%. By this condition the airfoil will have better motion performance in their applications

EPIdemiology of Surgery-Associated Acute Kidney Injury (EPIS-AKI) : Study protocol for a multicentre, observational trial

More than 300 million surgical procedures are performed each year. Acute kidney injury (AKI) is a common complication after major surgery and is associated with adverse short-term and long-term outcomes. However, there is a large variation in the incidence of reported AKI rates. The establishment of an accurate epidemiology of surgery-associated AKI is important for healthcare policy, quality initiatives, clinical trials, as well as for improving guidelines. The objective of the Epidemiology of Surgery-associated Acute Kidney Injury (EPIS-AKI) trial is to prospectively evaluate the epidemiology of AKI after major surgery using the latest Kidney Disease: Improving Global Outcomes (KDIGO) consensus definition of AKI. EPIS-AKI is an international prospective, observational, multicentre cohort study including 10 000 patients undergoing major surgery who are subsequently admitted to the ICU or a similar high dependency unit. The primary endpoint is the incidence of AKI within 72 hours after surgery according to the KDIGO criteria. Secondary endpoints include use of renal replacement therapy (RRT), mortality during ICU and hospital stay, length of ICU and hospital stay and major adverse kidney events (combined endpoint consisting of persistent renal dysfunction, RRT and mortality) at day 90. Further, we will evaluate preoperative and intraoperative risk factors affecting the incidence of postoperative AKI. In an add-on analysis, we will assess urinary biomarkers for early detection of AKI. EPIS-AKI has been approved by the leading Ethics Committee of the Medical Council North Rhine-Westphalia, of the Westphalian Wilhelms-University Münster and the corresponding Ethics Committee at each participating site. Results will be disseminated widely and published in peer-reviewed journals, presented at conferences and used to design further AKI-related trials. Trial registration number NCT04165369

Gaia Early Data Release 3: The celestial reference frame (Gaia-CRF3)

Context. Gaia-CRF3 is the celestial reference frame for positions and proper motions in the third release of data from the Gaia mission, Gaia DR3 (and for the early third release, Gaia EDR3, which contains identical astrometric results). The reference frame is defined by the positions and proper motions at epoch 2016.0 for a specific set of extragalactic sources in the (E)DR3 catalogue. Aims. We describe the construction of Gaia-CRF3 and its properties in terms of the distributions in magnitude, colour, and astrometric quality. Methods. Compact extragalactic sources in Gaia DR3 were identified by positional cross-matching with 17 external catalogues of quasi-stellar objects (QSO) and active galactic nuclei (AGN), followed by astrometric filtering designed to remove stellar contaminants. Selecting a clean sample was favoured over including a higher number of extragalactic sources. For the final sample, the random and systematic errors in the proper motions are analysed, as well as the radio-optical offsets in position for sources in the third realisation of the International Celestial Reference Frame (ICRF3). Results. Gaia-CRF3 comprises about 1.6 million QSO-like sources, of which 1.2 million have five-parameter astrometric solutions in Gaia DR3 and 0.4 million have six-parameter solutions. The sources span the magnitude range G = 13-21 with a peak density at 20.6 mag, at which the typical positional uncertainty is about 1 mas. The proper motions show systematic errors on the level of 12 μas yr-1 on angular scales greater than 15 deg. For the 3142 optical counterparts of ICRF3 sources in the S/X frequency bands, the median offset from the radio positions is about 0.5 mas, but it exceeds 4 mas in either coordinate for 127 sources. We outline the future of Gaia-CRF in the next Gaia data releases. Appendices give further details on the external catalogues used, how to extract information about the Gaia-CRF3 sources, potential (Galactic) confusion sources, and the estimation of the spin and orientation of an astrometric solution

Centrality Dependence Of The Pseudorapidity Density Distribution For Charged Particles In Pb-pb Collisions At √snn=2.76tev

7264/Mai61062