4,496 research outputs found
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. V., López, J. J., & García, A. (2008). Insights on postinjection-associated soot emissions in direct injection diesel engines. Combustion and Flame, 154(3), 448-461. doi:10.1016/j.combustflame.2008.04.021Mendez, S., & Thirouard, B. (2008). Using Multiple Injection Strategies in Diesel Combustion: Potential to Improve Emissions, Noise and Fuel Economy Trade-Off in Low CR Engines. SAE International Journal of Fuels and Lubricants, 1(1), 662-674. doi:10.4271/2008-01-1329He, Z., Xuan, T., Jiang, Z., & Yan, Y. (2013). Study on effect of fuel injection strategy on combustion noise and exhaust emission of diesel engine. Thermal Science, 17(1), 81-90. doi:10.2298/tsci120603159hKook, S., Pickett, L. M., & Musculus, M. P. B. (2009). Influence of Diesel Injection Parameters on End-of-Injection Liquid Length Recession. SAE International Journal of Engines, 2(1), 1194-1210. doi:10.4271/2009-01-1356Musculus, M. P. B., & Kattke, K. (2009). Entrainment Waves in Diesel Jets. SAE International Journal of Engines, 2(1), 1170-1193. doi:10.4271/2009-01-1355O’Connor, J., Musculus, M. P. B., & Pickett, L. M. (2016). Effect of post injections on mixture preparation and unburned hydrocarbon emissions in a heavy-duty diesel engine. Combustion and Flame, 170, 111-123. doi:10.1016/j.combustflame.2016.03.031O’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:10.4271/2013-01-0917O’Connor, J., & Musculus, M. (2014). In-Cylinder Mechanisms of Soot Reduction by Close-Coupled Post-Injections as Revealed by Imaging of Soot Luminosity and Planar Laser-Induced Soot Incandescence in a Heavy-Duty Diesel Engine. SAE International Journal of Engines, 7(2), 673-693. doi:10.4271/2014-01-1255Bruneaux, G., & Maligne, D. (2009). Study of the Mixing and Combustion Processes of Consecutive Short Double Diesel Injections. SAE International Journal of Engines, 2(1), 1151-1169. doi:10.4271/2009-01-1352Pickett, L. M., Kook, S., & Williams, T. C. (2009). Transient Liquid Penetration of Early-Injection Diesel Sprays. SAE International Journal of Engines, 2(1), 785-804. doi:10.4271/2009-01-0839Skeen, S., Manin, J., & Pickett, L. M. (2015). Visualization of Ignition Processes in High-Pressure Sprays with Multiple Injections of n-Dodecane. SAE International Journal of Engines, 8(2), 696-715. doi:10.4271/2015-01-0799Bolla, M., Chishty, M. A., Hawkes, E. R., & Kook, S. (2017). Modeling combustion under engine combustion network Spray A conditions with multiple injections using the transported probability density function method. International Journal of Engine Research, 18(1-2), 6-14. doi:10.1177/1468087416689174Blomberg, C. K., Zeugin, L., Pandurangi, S. S., Bolla, M., Boulouchos, K., & Wright, Y. M. (2016). Modeling Split Injections of ECN «Spray A» Using a Conditional Moment Closure Combustion Model with RANS and LES. SAE International Journal of Engines, 9(4), 2107-2119. doi:10.4271/2016-01-2237Cung, K., Moiz, A., Johnson, J., Lee, S.-Y., Kweon, C.-B., & Montanaro, A. (2015). Spray–combustion interaction mechanism of multiple-injection under diesel engine conditions. Proceedings of the Combustion Institute, 35(3), 3061-3068. doi:10.1016/j.proci.2014.07.054Moiz, A. A., Cung, K. D., & Lee, S.-Y. (2017). Simultaneous Schlieren–PLIF Studies for Ignition and Soot Luminosity Visualization With Close-Coupled High-Pressure Double Injections of n-Dodecane. Journal of Energy Resources Technology, 139(1). doi:10.1115/1.4035071Maes, N., Bakker, P. C., Dam, N., & Somers, B. (2017). Transient Flame Development in a Constant-Volume Vessel Using a Split-Scheme Injection Strategy. SAE International Journal of Fuels and Lubricants, 10(2), 318-327. doi:10.4271/2017-01-0815Moiz, A. A., Ameen, M. M., Lee, S.-Y., & Som, S. (2016). Study of soot production for double injections of n-dodecane in CI engine-like conditions. Combustion and Flame, 173, 123-131. doi:10.1016/j.combustflame.2016.08.005PASTOR, J., JAVIERLOPEZ, J., GARCIA, J., & PASTOR, J. (2008). A 1D model for the description of mixing-controlled inert diesel sprays. Fuel, 87(13-14), 2871-2885. doi:10.1016/j.fuel.2008.04.017Desantes, J. M., Pastor, J. V., García-Oliver, J. M., & Pastor, J. M. (2009). A 1D model for the description of mixing-controlled reacting diesel sprays. Combustion and Flame, 156(1), 234-249. doi:10.1016/j.combustflame.2008.10.008Pastor, J., Garcia-Oliver, J. M., Garcia, A., Zhong, W., Micó, C., & Xuan, T. (2017). An Experimental Study on Diesel Spray Injection into a Non-Quiescent Chamber. SAE International Journal of Fuels and Lubricants, 10(2), 394-406. doi:10.4271/2017-01-0850Settles, G. S. (2001). Schlieren and Shadowgraph Techniques. doi:10.1007/978-3-642-56640-0Pastor, J. V., Payri, R., Garcia-Oliver, J. M., & Briceño, F. J. (2013). Schlieren Methodology for the Analysis of Transient Diesel Flame Evolution. SAE International Journal of Engines, 6(3), 1661-1676. doi:10.4271/2013-24-0041Pastor, J. V., Garcia-Oliver, J. M., Novella, R., & Xuan, T. (2015). Soot Quantification of Single-Hole Diesel Sprays by Means of Extinction Imaging. SAE International Journal of Engines, 8(5), 2068-2077. doi:10.4271/2015-24-2417Pickett, 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.2004.04.006Ko¨ylu¨, U. O., & Faeth, G. M. (1994). Optical Properties of Overfire Soot in Buoyant Turbulent Diffusion Flames at Long Residence Times. Journal of Heat Transfer, 116(1), 152-159. doi:10.1115/1.2910849Manin, J., Pickett, L. M., & Skeen, S. A. (2013). Two-Color Diffused Back-Illumination Imaging as a Diagnostic for Time-Resolved Soot Measurements in Reacting Sprays. SAE International Journal of Engines, 6(4), 1908-1921. doi:10.4271/2013-01-2548Choi, M. Y., Mulholland, G. W., Hamins, A., & Kashiwagi, T. (1995). Comparisons of the soot volume fraction using gravimetric and light extinction techniques. Combustion and Flame, 102(1-2), 161-169. doi:10.1016/0010-2180(94)00282-wKnox, B. W., & Genzale, C. L. (2015). Reduced-order numerical model for transient reacting diesel sprays with detailed kinetics. International Journal of Engine Research, 17(3), 261-279. doi:10.1177/1468087415570765Burke, S. P., & Schumann, T. E. W. (1928). Diffusion Flames. Industrial & Engineering Chemistry, 20(10), 998-1004. doi:10.1021/ie50226a005Desantes, J. M., García-Oliver, J. M., Xuan, T., & Vera-Tudela, W. (2017). A study on tip penetration velocity and radial expansion of reacting diesel sprays with different fuels. Fuel, 207, 323-335. doi:10.1016/j.fuel.2017.06.108Nerva, J.-G. (s. f.). An Assessment of fuel physical and chemical properties in the combustion of a Diesel spray. doi:10.4995/thesis/10251/29767Payri, 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.xPayri, R., Gimeno, J., Novella, R., & Bracho, G. (2016). On the rate of injection modeling applied to direct injection compression ignition engines. International Journal of Engine Research, 17(10), 1015-1030. doi:10.1177/1468087416636281Malbec, L.-M., Eagle, W. E., Musculus, M. P. B., & Schihl, P. (2015). Influence of Injection Duration and Ambient Temperature on the Ignition Delay in a 2.34L Optical Diesel Engine. SAE International Journal of Engines, 9(1), 47-70. doi:10.4271/2015-01-1830Payri, R., García-Oliver, J. M., Xuan, T., & Bardi, M. (2015). A study on diesel spray tip penetration and radial expansion under reacting conditions. Applied Thermal Engineering, 90, 619-629. doi:10.1016/j.applthermaleng.2015.07.042Knox, B. W., & Genzale, C. L. (2017). Scaling combustion recession after end of injection in diesel sprays. Combustion and Flame, 177, 24-36. doi:10.1016/j.combustflame.2016.11.021García-Oliver, J. M., Malbec, L.-M., Toda, H. B., & Bruneaux, G. (2017). A study on the interaction between local flow and flame structure for mixing-controlled Diesel sprays. Combustion and Flame, 179, 157-171. doi:10.1016/j.combustflame.2017.01.02
Development of a soot radiation model for diesel flames
[EN] This paper describes a radiation model for diesel sprays that can predict the heat losses based on spray characteristics to the spray plume due to radiation. The model is based on three sub-models: spray model, soot model and radiation model. The spray model is a one-dimensional model that simulates the axial and radial distribution of a fuel spray for each instant. The soot model is a one-dimensional tool, which is based on formation and oxidation processes calculating the axial and radial soot concentration profile for each instant. The output results of the two sub-models are used as input information for the radiation model, which obtains the radiation heat transfer values for a diesel flame. The experimental measurements used to adjust the different constants and to validate the sub-models were performed in a high-pressure high-temperature vessel using three different optical techniques: Schlieren, to obtain spray penetration, Diffused Back-Illumination technique (DBI) for the soot concentration and the 2-color method for calculating the soot temperature and concentration. The radiant fraction shows values from 0.11% to 0.43% with respect to the total energy of the fuel depending on the operating condition. Taking into account the different assumptions taken for modeling the spray radiation, these results are consistent with those obtained in the literature, in which the radiation was characterized under similar conditions.The authors acknowledge FEDER and Spanish Ministerio de Economía y Competitividad for partially supporting this research through TRANCO project (TRA2017-87694-R).López, JJ.; García-Oliver, JM.; García Martínez, A.; Villalta-Lara, D. (2019). Development of a soot radiation model for diesel flames. Applied Thermal Engineering. 157:1-10. https://doi.org/10.1016/j.applthermaleng.2019.04.120S11015
A phenomenological explanation of the autoignition propagation under HCCI conditions
[EN] A phenomenological explanation about the autoignition propagation under HCCI conditions is developed in this paper. To do so, diffusive effects from the burned zones to the fresh mixture, pressure waves based effects and expansion effects caused by combustion are taken into account. Additionally, different Damkohler numbers have been defined and evaluated in order to characterize the phenomenon and quantify the relevance of each effect. The theoretical explanation has been evaluated by means of chemiluminescence measurements performed in a Rapid Compression Expansion Machine (RCEM), which allow to estimate the velocity of propagation of the autoignition front. The results showed that under HCCI conditions the autoignition propagation is controlled, in general, by the pressure waves established in the combustion chamber, since the characteristic time of the autoignition propagation is too short to assume the absence of pressure gradients in the chamber. Thus, the thermodynamic conditions reached behind the pressure wave promote the autoignition and explain the high propagation velocities associated to the reaction front. Besides, the results also showed that the contribution of diffusive phenomena on the propagation is negligible, since the characteristic time of diffusion is too long compared to the characteristic time of the autoignition propagation. Finally, the experimental measurements showed that the autoignition propagation is affected by a really relevant cycle-to-cycle variation. The turbulence generated by the combustion has, by definition, an aleatory behavior, leading to random heterogeneity distribution and, therefore, to somewhat random autoignition propagation.The authors would like to thank different members of the CMT-Motores TTrmicos team of the Universitat Politecnica de Valencia for their contribution to this work. The authors would also like to thank the Spanish Ministry of Education for financing the PhD. Studies of Dario Lopez-Pintor (grant FPU13/02329). This research has been partially funded by FEDER and the Spanish Government through project TRA2015-67136-R.Desantes, J.; López, JJ.; García-Oliver, JM.; López-Pintor, D. (2017). A phenomenological explanation of the autoignition propagation under HCCI conditions. Fuel. 206:43-57. https://doi.org/10.1016/j.fuel.2017.05.075S435720
Experimental validation and analysis of seven different chemical kinetic mechanisms for n-dodecane using a Rapid Compression-Expansion Machine
[EN] Seven different chemical kinetic mechanisms for n-dodecane, two detailed and five reduced, have been evaluated under Engine Combustion Network (ECN) thermodynamic conditions by comparison to experimental measurements in a Rapid Compression-Expansion Machine (RCEM). The target ECN conditions are imposed at Top Dead Center (TDC), which cover a wide range of temperatures (from 850 K to 1000 K), oxygen molar fractions (0.21 and 0.15) and equivalence ratios (0.8, 0.9 and 1), while the pressure is fixed to keep a constant density at TDC equal to 22.8 kg/m(3). The results obtained have been used to validate the chemical kinetic simulations, which have been performed with CHEMKIN, by comparing both cool flames and high temperature ignition delays, as well as the heat released in each stage of the combustion process in case of having a two-stage ignition pattern. The experimental results show good agreement with the chemical kinetic simulations. In fact, the mean relative deviation in ignition delay between experiments and simulations among all the chemical mechanisms is equal to 18.0% (3 CAD) for both cool flames and high temperature ignition. In general, closer correspondence has been obtained for the ignition delay referred to the high-temperature stage of the process, being the cool flames phenomenon more difficult to reproduce. Moreover, the differences between the reduced mechanisms and the most detailed one have been analyzed, concluding that the enhanced specific reaction rates of the most reduced mechanisms cause differences not only on the ignition delays, but also on the Negative Temperature Coefficient (NTC) behavior and on the heat released during cool flames. (C) 2017 The Combustion Institute. Published by Elsevier Inc. All rights reserved.The authors would also like to thank the Spanish Ministry of Education for financing the PhD. Studies of Dario Lopez-Pintor (grant FPU13/02329). This study was partially funded by the Spanish Ministry of Economy and Competitiveness in the frame of the COMEFF (TRA2014-59483-R) project.Desantes, J.; López, JJ.; García-Oliver, JM.; López-Pintor, D. (2017). Experimental validation and analysis of seven different chemical kinetic mechanisms for n-dodecane using a Rapid Compression-Expansion Machine. Combustion and Flame. 182:76-89. https://doi.org/10.1016/j.combustflame.2017.04.004S768918
Ordenación de recursos naturales renovables. Especies migratorias cinegéticas y piscícolas
By the economical, social and scientific importance of the study and management of migratory species, an unexplored field in the natural renewable resources management, but really complicated, we propose a new management systems for it based on: • Standing crop make with true data capture. • Future projection of actual situation • Estimate the true number trough data on biological management • Results in capture unite in relation with the density This way to work permit us to have a sustainable management in each place without considering international agreement.Ante la importancia económica, social y científica del estudio y ordenación de las especies migratorias, un universo inexplorado en la ordenación de los recursos naturales renovables, pero especialmente complejo e ilustrativo, se propone un sistema de ordenación para las mismas basado en: • Censo indicativo establecido por la eficacia real de los actos actuales de captura. • Proyección hacia el futuro de la situación actual. • Estima de “unidades de cosa cierta” (controlables) mediante cálculos sobre intangibles de ordenación con base biológica. • Resultados en unidades de captura (tangibles) a resultas de la densidad o del paso anual. El procedimiento permite la racionalización de la presión de aprovechamiento en cada lugar concreto, al margen de la existencia previa, o no, de acuerdos internacionales u otros en la materia
Synthesis, X-ray characterization and regium bonding interactions of a trichlorido(1-hexylcytosine)gold(III) complex
Power distribution in a 13 kW three-phase rectifier system: impact on weight, volume and efficiency
This paper addresses the power delivery strategy on an aircraft application consisting on seven isolated DC loads to be supplied from the AC grid. Distributed or centralized power processing is evaluated taking into account weight and efficiency. Additionally, the rectifier switching frequency has to be synchronized with an external frequency clock to minimize the interference of the converter harmonics with the loads
Photodetection of propagating quantum microwaves in circuit QED
We develop the theory of a metamaterial composed of an array of discrete
quantum absorbers inside a one-dimensional waveguide that implements a
high-efficiency microwave photon detector. A basic design consists of a few
metastable superconducting nanocircuits spread inside and coupled to a
one-dimensional waveguide in a circuit QED setup. The arrival of a {\it
propagating} quantum microwave field induces an irreversible change in the
population of the internal levels of the absorbers, due to a selective
absorption of photon excitations. This design is studied using a formal but
simple quantum field theory, which allows us to evaluate the single-photon
absorption efficiency for one and many absorber setups. As an example, we
consider a particular design that combines a coplanar coaxial waveguide with
superconducting phase qubits, a natural but not exclusive playground for
experimental implementations. This work and a possible experimental realization
may stimulate the possible arrival of "all-optical" quantum information
processing with propagating quantum microwaves, where a microwave photodetector
could play a key role.Comment: 27 pages, submitted to Physica Scripta for Nobel Symposium on "Qubits
for Quantum Information", 200
Further results on the cross norm criterion for separability
In the present paper the cross norm criterion for separability of density
matrices is studied. In the first part of the paper we determine the value of
the greatest cross norm for Werner states, for isotropic states and for Bell
diagonal states. In the second part we show that the greatest cross norm
criterion induces a novel computable separability criterion for bipartite
systems. This new criterion is a necessary but in general not a sufficient
criterion for separability. It is shown, however, that for all pure states, for
Bell diagonal states, for Werner states in dimension d=2 and for isotropic
states in arbitrary dimensions the new criterion is necessary and sufficient.
Moreover, it is shown that for Werner states in higher dimensions (d greater
than 2), the new criterion is only necessary.Comment: REVTeX, 19 page
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
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