Optical study on characteristics of non-reacting and reacting diesel spray with different strategies of split injection

[EN] Even though studies on split-injection strategies have been published in recent years, there are still many remaining questions about how the first injection affects the mixing and combustion processes of the second one by changing the dwell time between both injection events or by the first injection quantity. In this article, split-injection diesel sprays with different injection strategies are investigated. Visualization of n-dodecane sprays was carried out under both non-reacting and reacting operating conditions in an optically accessible two-stroke engine equipped with a single-hole diesel injector. High-speed Schlieren imaging was applied to visualize the spray geometry development, while diffused backgroundillumination extinction imaging was applied to quantify the instantaneous soot production (net result of soot formation and oxidation). For non-reacting conditions, it was found that the vapor phase of second injection penetrates faster with a shorter dwell time and independently of the duration of the first injection. This could be explained in terms of onedimensional spray model results, which provided information on the local mixing and momentum state within the flow. Under reacting conditions, interaction between the second injection and combustion recession of the first injection is observed, resulting in shorter ignition delay and lift-off compared to the first injection. However, soot production behaves differently with different injection strategies. The maximum instantaneous soot mass produced by the second injection increases with a shorter dwell time and with longer first injection duration.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was partially funded by the Spanish Ministry of Economy and Competitiveness in the frame of the advanced spray combustion models for efficient powertrains (COMEFF) (TRA2014-59483-R) project. Funding for Tiemin Xuan's PhD studies was granted by Universitat Politecnica de Valencia through the Programa de Apoyo para la Investigacion y Desarrollo (PAID) (grant reference FPI-2015-S2-1068)Desantes, J.; García-Oliver, JM.; García Martínez, A.; Xuan, T. (2019). Optical study on characteristics of non-reacting and reacting diesel spray with different strategies of split injection. International Journal of Engine Research. 20(6):606-623. https://doi.org/10.1177/1468087418773012S606623206Arrègle, J., Pastor, J. 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Design of energy control method for three-phase buck-type rectifier with very demanding load steps

Conventional three-phase rectifiers are controlled to achieve good power factor and low THD in the input. In the case of pulsating power loads, the fast dynamic response implies that the load pulses are reflected in the generator. These pulsating loads affect the life time operation of the generator, especially when it is not oversized (that is the case in aircraft applications). In order to smooth the power demanded from the generator, it is preferable to reduce the bandwidth of the controller to the rectifier but it affects its stability due to the fact that the right half plane pole given by the negative impedance of a constant power load requires high bandwidth control loop to compensate it. In this paper, an energy control method is proposed to employ the energy stored in the output capacitor of the rectifier to control the amount of power demanded through the rectifier. In such a way the bandwidth restriction for stability is eliminated and the bandwidth of the loop can be set slow enough to ensure smooth power demanded from the generator

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

Fabrication of near-zero thermal expansion of fully dense beta-eucryptite ceramics by microwave sintering

Microwave heating is proposed as non-conventional technique for the sintering of optimal lithium aluminosilicate compositions of β-eucryptite system. The coefficient of thermal expansion and mechanical properties of the sintered samples has been studied under the influence of microwave heating. The ad hoc synthesized β-eucryptite together with the microwave sintering technique developed in this work open the opportunity to produce breakthrough materials with low or negative coefficient of thermal expansion and excellent mechanical properties, as a Young s modulus of 110 GPa. The combination of rapid heating with low energy applied by the microwave technology (eco-friendly process) and the dramatic reduction in cycle time allows densification without glass phase formation. Results of the coefficient of thermal expansion of the β-eucryptite ceramics presented here under cryogenic conditions will be of value, for example, in the future design of new composite materials for space applicationsThe authors would like to thank Dr. Emilio Rayon for performing the nanoindentation analysis in the Materials Technology institute (ITM) of the Polytechnic University of Valencia (UPV) and your financial support received of UPV under Projects SP20120621 and SP20120677 and Spanish Government through the Project MONIDIEL (TEC2008-04109). A. Borrell, acknowledges the Spanish Ministry of Science and Innovation for a Juan de la Cierva contract (JCI-2011-10498) and SCSIE of the University of Valencia.Benavente Martínez, R.; Borrell Tomás, MA.; Salvador Moya, MD.; Garcia-Moreno, O.; Penaranda-Foix, FL.; Catalá Civera, JM. (2014). Fabrication of near-zero thermal expansion of fully dense beta-eucryptite ceramics by microwave sintering. Ceramics International. 40(1):935-941. https://doi.org/10.1016/j.ceramint.2013.06.089S93594140

Axially symmetric spacetimes: numerical and analytical perspectives

Some new aspects of axially symmetric spacetimes are discussed. These results open the door for future interplay between analytical and numerical studies. The new developments are based on the role of the total mass in axial symmetry. Finally, a list of relevant open problems is presented. These problems can be hopefully solved with an interaction between numerical and analytical insights.Comment: To appear in the proceedings of the Spanish Relativity Meeting (ERE2010). Plenary Tal

Neutrophils instruct homeostatic and pathological states in naive tissues

Immune protection relies on the capacity of neutrophils to infiltrate challenged tissues. Naive tissues, in contrast, are believed to remain free of these cells and protected from their toxic cargo. Here, we show that neutrophils are endowed with the capacity to infiltrate multiple tissues in the steady-state, a process that follows tissue-specific dynamics. By focusing in two particular tissues, the intestine and the lungs, we find that neutrophils infiltrating the intestine are engulfed by resident macrophages, resulting in repression of Il23 transcription, reduced G-CSF in plasma, and reinforced activity of distant bone marrow niches. In contrast, diurnal accumulation of neutrophils within the pulmonary vasculature influenced circadian transcription in the lungs. Neutrophil-influenced transcripts in this organ were associated with carcinogenesis and migration. Consistently, we found that neutrophils dictated the diurnal patterns of lung invasion by melanoma cells. Homeostatic infiltration of tissues unveils a facet of neutrophil biology that supports organ function, but can also instigate pathological states.S

Fuel temperature influence on diesel sprays in inert and reacting conditions

The detailed knowledge of the evaporationecombustion process of the Diesel spray is a key factor for the development of robust injection strategies able to reduce the pollutant emissions and keep or increase the combustion efficiency. In this work several typical measurement applied to the diesel spray diagnostic (liquid length, lift-off length and ignition delay) have been employed in a novel continuous flow test chamber that allows an accurate control on a wide range of thermodynamic test conditions (up to 1000 K and 15 MPa). A step forward in the control of the test boundary conditions has been done employing a special system to study the fuel temperature effect on the evaporation and combustion of the spray. The temperature of the injector body has been controlled with a thermostatic system and the relationship between injector body and fuel temperature has been observed experimentally. Imaging diagnostics have been employed to visualize the liquid phase penetration in evaporative/inert conditions and, lift-off length and ignition delay in reactive condition. The results underline a clear influence of the injector body temperature on both conditions, evaporative and, in a lesser degree, reactive; finally the physical models found in the literature have been compared with the results obtained experimentallyThis research has been funded in the frame of the project FLEXIFUEL reference TRA2010-17564 from Ministerio de Ciencia e Innovacion. The injectors are part of the ECN international project.Payri Marín, R.; García Oliver, JM.; Bardi, M.; Manin, J. (2012). Fuel temperature influence on diesel sprays in inert and reacting conditions. Applied Thermal Engineering. 35:185-195. https://doi.org/10.1016/j.applthermaleng.2011.10.027S1851953

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO

Current Bioengineering and Regenerative Strategies for the Generation of Kidney Grafts on Demand

[EN] Currently in the USA, one name is added to the organ transplant waiting list every 15 min. As this list grows rapidly, fewer than one-third of waiting patients can receive matched organs from donors. Unfortunately, many patients who require a transplant have to wait for long periods of time, and many of them die before receiving the desired organ. In the USA alone, over 100,000 patients are waiting for a kidney transplant. However, it is a problem that affects around 6% of the word population. Therefore, seeking alternative solutions to this problem is an urgent work. Here, we review the current promising regenerative technologies for kidney function replacement. Despite many approaches being applied in the different ways outlined in this work, obtaining an organ capable of performing complex functions such as osmoregulation, excretion or hormone synthesis is still a long-term goal. However, in the future, the efforts in these areas may eliminate the long waiting list for kidney transplants, providing a definitive solution for patients with end-stage renal disease.This study was supported by a grant from ALCER-TURIA, ASTELLAS and PRECIPITA CROWDFUNDING.Garcia-Dominguez, X.; Vicente Antón, JS.; Vera Donoso, CD.; Marco-Jiménez, F. (2017). Current Bioengineering and Regenerative Strategies for the Generation of Kidney Grafts on Demand. Current Urology Reports. 18(1):1-8. https://doi.org/10.1007/s11934-017-0650-6S18181Ott HC, Mathisen DJ. Bioartificial tissues and organs: are we ready to translate? Lancet. 2011;378:1977–8.Salvatori M, Peloso A, Katari R, Orlando G. Regeneration and bioengineering of the kidney: current status and future challenges. Curr Urol Rep. 2014;15:379.D’Agati VD. Growing new kidneys from embryonic cell suspensions: fantasy or reality? J Am Soc Nephrol. 2002;11:1763–6.Abouna GM. Organ shortage crisis: problems and possible solutions. 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