Using a one-dimensional spray model to improve liquid length and ignition delay estimations for diesel flames

[EN] In the current paper, a methodology based on the combination of a one-dimensional spray model and experimental correlations has been proposed to predict the physical time associated with ignition delay in diesel diffusion flames. This physical time depends significantly on the nozzle geometry, and its influence is not captured in traditional Arrhenius-like correlation. To assess this influence, three multi-hole nozzles with different degrees of conicity (expressed in terms of k-factor) have been tested onan optically accessible 2-stroke single-cylinder engine. First, the hydraulic behavior of the nozzles is assessed from the point of view of injection rate and spray momentum. Later, the effect of the geometry on vapor spray angle has been analyzed through a Schlieren visualization technique. Mie-scattering has allowed to determine the stabilized liquid length. Then, chemiluminescence imaging was used to obtain the temporal and spatial appearance of OH radicals, which are used as indicators to the ignition delay. Finally, all the results are combined with a one-dimensional spray model to determine the physical induction time and include it into a new ignition delay correlation, which shows up to 4% accuracy improvement compared to a traditional Arrhenius equation. (C) 2017 Elsevier Ltd. All rights reserved.This work was partly sponsored by "Ministerio de Economia y Competitividad", of the Spanish Government, in the frame of the Project "Estudio de la interaccion chorro-pared en condiciones realistas de motor", Reference TRA2015-67679-c2-1-R.Payri, R.; Salvador, F.; De La Morena, J.; Pagano, V. (2017). Using a one-dimensional spray model to improve liquid length and ignition delay estimations for diesel flames. Applied Thermal Engineering. 124:1090-1102. https://doi.org/10.1016/j.applthermaleng.2017.06.1021090110212

Experimental investigation of the effect of orifices inclination angle in multihole diesel injector nozzles. Part 2-Spray characteristics

[EN] Diesel spray development is a key research topic due to its impact on the combustion characteristics. On the current paper, the effect of the orifices inclination angle on the spray penetration characteristics is evaluated. For this purpose, three nozzles with included angles of 90, 140 and 155 degrees are selected. Visualization tests are performed on a room-temperature constant-pressure vessel pressurized with a high-density gas (SF6), in order to reproduce the density conditions inside the combustion chamber at the start of the injection event. Both frontal and lateral Mie-scattering visualization are used, depending on the particular nozzle configuration. Results show how the spray penetration is slower as the inclination angle increases, which is linked to its lower nozzle outlet velocity. A statistical correlation of the spray penetration as a function of the area and velocity coefficients is obtained and discussed.This work was partly sponsored by "Ministerio de Economia y Competitividad", of the Spanish Government, in the frame of the Project "Estudio de la interaccion chorro-pared en condiciones realistas de motor", Reference TRA2015-67679-c2-1-R.Payri, R.; Salvador, FJ.; De La Morena, J.; Pagano, V. (2018). Experimental investigation of the effect of orifices inclination angle in multihole diesel injector nozzles. Part 2-Spray characteristics. Fuel. 213:215-221. https://doi.org/10.1016/j.fuel.2017.07.076S21522121

One-dimensional modeling of the interaction between close-coupled injection events for a ballistic solenoid injector

This is the author s version of a work that was accepted for publication in International Journal of Engine Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published as https://doi.org/10.1177/1468087418760973[EN] In this article, an investigation of a solenoid common-rail injector has been carried out to understand the hydraulic interactions between close-coupled injection events. For this purpose, a one-dimensional model of the injector was developed on GT-SUITE software. The geometrical and hydraulic characteristics of the internal elements of the injector, needed to construct the model, were obtained by means of different custom-made experimental tools. The dynamic behavior of the injector was characterized using an EVI rate of injection meter. The hydraulic results from the model show a good alignment with the experiments for single injections and a varied degree of success for multiple injections. Once the model was validated, it has been used to understand the injector performance under multiple-injection strategies. The mass of a second injection has shown to highly depend on the electrical dwell time, especially at low values, mostly due to the dynamic pressure behavior in the needle seat. The critical dwell time, defined as the minimum electrical dwell time needed to obtain two independent injection events, has been numerically obtained on a wide range of operating conditions and correlated to injection pressure and energizing time of the first injection. Finally, the increase in the needle opening velocity of the second injection compared to the single-injection case has been analyzed for close-coupled injection events.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The authors would like to thank Jaguar Land Rover Limited for sponsoring this work.Payri, R.; De La Morena, J.; Pagano, V.; Hussain, A.; Sammut, G.; Smith, L. (2019). One-dimensional modeling of the interaction between close-coupled injection events for a ballistic solenoid injector. International Journal of Engine Research. 20(4):452-469. https://doi.org/10.1177/1468087418760973S452469204Khalek, I. A., Blanks, M. G., Merritt, P. M., & Zielinska, B. (2015). Regulated and unregulated emissions from modern 2010 emissions-compliant heavy-duty on-highway diesel engines. Journal of the Air & Waste Management Association, 65(8), 987-1001. doi:10.1080/10962247.2015.1051606Kim, H. J., Park, S. H., & Lee, C. S. (2016). Impact of fuel spray angles and injection timing on the combustion and emission characteristics of a high-speed diesel engine. Energy, 107, 572-579. doi:10.1016/j.energy.2016.04.035Mohan, B., Yang, W., & Chou, S. kiang. (2013). Fuel injection strategies for performance improvement and emissions reduction in compression ignition engines—A review. Renewable and Sustainable Energy Reviews, 28, 664-676. doi:10.1016/j.rser.2013.08.051Payri, R., Salvador, F. J., Gimeno, J., & de la Morena, J. (2009). Effects of nozzle geometry on direct injection diesel engine combustion process. Applied Thermal Engineering, 29(10), 2051-2060. doi:10.1016/j.applthermaleng.2008.10.009Payri, R., Viera, J. P., Gopalakrishnan, V., & Szymkowicz, P. G. (2016). The effect of nozzle geometry over internal flow and spray formation for three different fuels. Fuel, 183, 20-33. doi:10.1016/j.fuel.2016.06.041Hulkkonen, T., Sarjovaara, T., Kaario, O., Hamalainen, I., & Larmi, M. (2015). EXPERIMENTAL STUDY OF CONICAL DIESEL NOZZLE ORIFICE GEOMETRY. Atomization and Sprays, 25(6), 519-538. doi:10.1615/atomizspr.2015010383Kuti, O. A., Zhu, J., Nishida, K., Wang, X., & Huang, Z. (2013). Characterization of spray and combustion processes of biodiesel fuel injected by diesel engine common rail system. Fuel, 104, 838-846. doi:10.1016/j.fuel.2012.05.014Pickett, L. M., & Siebers, D. L. (2004). Soot in diesel fuel jets: effects of ambient temperature, ambient density, and injection pressure. Combustion and Flame, 138(1-2), 114-135. doi:10.1016/j.combustflame.2004.04.006Wang, X., Huang, Z., Zhang, W., Kuti, O. A., & Nishida, K. (2011). Effects of ultra-high injection pressure and micro-hole nozzle on flame structure and soot formation of impinging diesel spray. Applied Energy, 88(5), 1620-1628. doi:10.1016/j.apenergy.2010.11.035Agarwal, A. K., Dhar, A., Gupta, J. G., Kim, W. I., Choi, K., Lee, C. S., & Park, S. (2015). Effect of fuel injection pressure and injection timing of Karanja biodiesel blends on fuel spray, engine performance, emissions and combustion characteristics. Energy Conversion and Management, 91, 302-314. doi:10.1016/j.enconman.2014.12.004Zhuang, J., Qiao, X., Bai, J., & Hu, Z. (2014). Effect of injection-strategy on combustion, performance and emission characteristics in a DI-diesel engine fueled with diesel from direct coal liquefaction. Fuel, 121, 141-148. doi:10.1016/j.fuel.2013.12.032Park, S. H., Yoon, S. H., & Lee, C. S. (2011). Effects of multiple-injection strategies on overall spray behavior, combustion, and emissions reduction characteristics of biodiesel fuel. Applied Energy, 88(1), 88-98. doi:10.1016/j.apenergy.2010.07.024Mancaruso, E., Sequino, L., & Vaglieco, B. M. (2016). Analysis of the pilot injection running Common Rail strategies in a research diesel engine by means of infrared diagnostics and 1d model. Fuel, 178, 188-201. doi:10.1016/j.fuel.2016.03.066O’Connor, J., & Musculus, M. (2013). Post Injections for Soot Reduction in Diesel Engines: A Review of Current Understanding. SAE International Journal of Engines, 6(1), 400-421. doi:10.4271/2013-01-0917Bosch, W. (1966). The Fuel Rate Indicator: A New Measuring Instrument For Display of the Characteristics of Individual Injection. SAE Technical Paper Series. doi:10.4271/660749Payri, R., Salvador, F. J., Gimeno, J., & Bracho, G. (2008). A NEW METHODOLOGY FOR CORRECTING THE SIGNAL CUMULATIVE PHENOMENON ON INJECTION RATE MEASUREMENTS. Experimental Techniques, 32(1), 46-49. doi:10.1111/j.1747-1567.2007.00188.

Quantifying the Role of Homophily in Human Cooperation Using Multiplex Evolutionary Game Theory.

Nature shows as human beings live and grow inside social structures. This assumption allows us to explain and explore how it may shape most of our behaviours and choices, and why we are not just blindly driven by instincts: our decisions are based on more complex cognitive reasons, based on our connectedness on different spaces. Thus, human cooperation emerges from this complex nature of social network. Our paper, focusing on the evolutionary dynamics, is intended to explore how and why it happens, and what kind of impact is caused by homophily among people. We investigate the evolution of human cooperation using evolutionary game theory on multiplex. Multiplexity, as an extra dimension of analysis, allows us to unveil the hidden dynamics and observe non-trivial patterns within a population across network layers. More importantly, we find a striking role of homophily, as the higher the homophily between individuals, the quicker is the convergence towards cooperation in the social dilemma. The simulation results, conducted both macroscopically and microscopically across the network layers in the multiplex, show quantitatively the role of homophily in human cooperation

Phoenix Rising: Legal Reforms and Changes in Valuations in Finland During the Economic Crisis

Finland experienced an extremely severe economic depression in the early 1990s. As a part of the government\u27s crisis management policies, significant new legislation was passed that increased supervisory powers of financial market regulators and reformed bankruptcy procedures significantly decreasing the protection of creditors. We show that the introduction of these new laws resulted in positive abnormal stock returns. The new laws also lead to increases in firms’ Tobin\u27s q, especially for more levered firms. In contrast to previous studies, our results also suggest that public supervision of financial markets fosters rather than hampers financial market development

Dipolar degrees of freedom and Isospin equilibration processes in Heavy Ion collisions

Background: In heavy ion collision at the Fermi energies Isospin equilibration processes occur- ring when nuclei with different charge/mass asymmetries interacts have been investigated to get information on the nucleon-nucleon Iso-vectorial effective interaction. Purpose: In this paper, for the system 48Ca +27 Al at 40 MeV/nucleon, we investigate on this process by means of an observable tightly linked to isospin equilibration processes and sensitive in exclusive way to the dynamical stage of the collision. From the comparison with dynamical model calculations we want also to obtain information on the Iso-vectorial effective microscopic interaction. Method: The average time derivative of the total dipole associated to the relative motion of all emitted charged particles and fragments has been determined from the measured charges and velocities by using the 4? multi-detector CHIMERA. The average has been determined for semi- peripheral collisions and for different charges Zb of the biggest produced fragment. Experimental evidences collected for the systems 27Al+48Ca and 27Al+40Ca at 40 MeV/nucleon used to support this novel method of investigation are also discussed.Comment: Submitted for publication on Phys. Rev. C. 0n 24-oct-201

Corporate boards, ownership structure and firm performance in an environment of severe political and economic crisis

This study examines the relationship between board and ownership structures and firm performance in an environment of severe political and economic crisis. Using panel data from the Zimbabwe Stock Exchange (ZSE) for the period 2000-2005, we split the period into prepresidential election period (2000-2002) (a relatively stable political and economic period) and post-presidential election period (2003-2005) (a hostile political and economic period) to capture the differences in the political and economic landscape. We find that board size, ownership concentration and executive directors’ share ownership increased whilst the proportion of nonexecutive directors reduced in the post-presidential election period. Employing a system Generalized Method of Moments (GMM) approach, we find that performance is positively related to board size and ownership concentration in the post- (but not in the pre-) presidential election period. The results also show that performance is negatively related to executive directors’ share ownership in the post-presidential election period, but positively related in the pre-presidential election period. The proportion of non-executive directors is negative and significant in both periods. These findings support the notion that the effects of board and ownership structures depend on the nature of the firm’s environment, and therefore have important implications for policy-makers

Multiple large shareholders, excess leverage and tunneling: evidence from an emerging market

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Manuscript Type: Empirical Research Question/Issue: Past empirical efforts in corporate governance have examined the effects of large shareholders with the excess control rights on tunneling activities. However, no study has systematically investigated the effects of multiple large shareholders on excess leverage policies and tunneling in an emerging country environment where minority rights protection is weak. In this study, we examine the role of multiple large shareholders and the effects of control contestability of multiple large shareholders on firm excess leverage decision and tunneling by controlling shareholders. Research Findings/Insights: Using a sample of 2,341 Chinese firms for the years 2001 to 2013, we document that the contestability of multiple non-controlling large shareholders relative to controlling shareholders reduces the adoption of excess leverage policies, tunneling and enhances capital investment. Another intriguing finding is that the government as a controlling shareholder exerts significant influence and reduces the monitoring effectiveness of multiple larger shareholders. Theoretical/Academic Implications: By addressing the role of multiple large shareholders on excess leverage decisions, this study makes an important contribution to the corporate governance literature. We extend the recent developments in agency theory regarding the role of multiple large shareholders in constraining expropriation of controlling shareholders with excess control rights and their effect on firm leverage decisions. Our results support the theoretical models which indicate that the presence of multiple large shareholders is an important and efficient internal governance mechanism that mitigates a firm’s agency costs, particularly, in an emerging market environment where corporate governance is weak and inadequate to curb tunneling problem. JEL classification: G15; G34; G3

Targeting PDZ domains as potential treatment for viral infections, neurodegeneration and cancer

The interaction between proteins is a fundamental event for cellular life that is generally mediated by specialized protein domains or modules. PDZ domains are the largest class of protein–protein interaction modules, involved in several cellular pathways such as signal transduction, cell–cell junctions, cell polarity and adhesion, and protein trafficking. Because of that, dysregulation of PDZ domain function often causes the onset of pathologies, thus making this family of domains an interesting pharmaceutical target. In this review article we provide an overview of the structural and functional features of PDZ domains and their involvement in the cellular and molecular pathways at the basis of different human pathologies. We also discuss some of the strategies that have been developed with the final goal to hijack or inhibit the interaction of PDZ domains with their ligands. Because of the generally low binding selectivity of PDZ domain and the scarce efficiency of small molecules in inhibiting PDZ binding, this task resulted particularly difficult to pursue and still demands increasing experimental efforts in order to become completely feasible and successful in vivo