A study on the interaction between local flow and flame structure for mixing-controlled Diesel sprays

[EN] A detailed study on the spray local flow and flame structure has been performed by means of PIV and laser-sheet LIF techniques under Diesel spray conditions. Operating conditions were based on Engine Combustion Network recommendations. A consistent comparison of inert and reacting axial velocity fields has produced quantitative information on the effect of heat release on the local flow. Local axial velocity has been shown to increase 50-60% compared to the inert case, while the combustion-induced radial expansion of the spray has been quantified in terms of a 0.9-2.1 mm radius increase. As a result, the drop in entrainment rate has been quantified around 25% compared to the inert case. Streamline analysis also hints at a reduced entrainment under reacting conditions. A 1D spray model under reacting condition has been used, which confirms the modifications obtained in the main flow metrics when moving from inert to reacting conditions. When comparing the flow evolution with the flame structure, little effect of chemical activity on the spray flow upstream the lift-off length has been evidenced, in spite of the presence of formaldehyde in such regions. Only downstream of the lift-off length, as defined by OH LIF, has a strong change in flow pattern been observed as a result of combustion-induced heat release. (C) 2017 The Combustion Institute. Published by Elsevier Inc. All rights reserved.This work was carried out during a scientific visit period by J.M. Garcia-Oliver at IFPEN in 2015, which was funded by the Spanish Ministry of Education, Culture and Sport (Grant PRX14/00192). This study was partially funded by the Spanish Ministry of Economy and Competitiveness in the frame of the COMEFF (TRA2014-59483-R) project.García-Oliver, JM.; Malbec, L.; Toda, HB.; 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. https://doi.org/10.1016/j.combustflame.2017.01.023S15717117

A conceptual model of the flame stabilization mechanisms for a lifted Diesel-type flame based on direct numerical simulation and experiments

This work presents an analysis of the stabilization of diffusion flames created by the injection of fuel into hot air, as found in Diesel engines. It is based on experimental observations and uses a dedicated Direct Numerical Simulation (DNS) approach to construct a numerical setup, which reproduces the ignition features obtained experimentally. The resulting DNS data are then used to classify and analyze the events that allow the flame to stabilize at a certain Lift-Off Length (LOL) from the fuel injector. Both DNS and experiments reveal that this stabilization is intermittent: flame elements first auto-ignite before being convected downstream until another sudden auto-ignition event occurs closer to the fuel injector. The flame topologies associated to such events are discussed in detail using the DNS results, and a conceptual model summarizing the observation made is proposed. Results show that the main flame stabilization mechanism is auto-ignition. However, multiple reaction zone topologies, such as triple flames, are also observed at the periphery of the fuel jet helping the flame to stabilize by filling high-temperature burnt gases reservoirs localized at the periphery, which trigger auto-ignitions

Inflammatory Cytokine Expression Is Associated with Chikungunya Virus Resolution and Symptom Severity

The Chikungunya virus infection zones have now quickly spread from Africa to parts of Asia, North America and Europe. Originally thought to trigger a disease of only mild symptoms, recently Chikungunya virus caused large-scale fatalities and widespread economic loss that was linked to recent virus genetic mutation and evolution. Due to the paucity of information on Chikungunya immunological progression, we investigated the serum levels of 13 cytokines/chemokines during the acute phase of Chikungunya disease and 6- and 12-month post-infection follow-up from patients of the Italian outbreak. We found that CXCL9/MIG, CCL2/MCP-1, IL-6 and CXCL10/IP-10 were significantly raised in the acute phase compared to follow-up samples. Furthermore, IL-1β, TNF-α, Il-12, IL-10, IFN-γ and IL-5 had low initial acute phase levels that significantly increased at later time points. Analysis of symptom severity showed association with CXCL9/MIG, CXCL10/IP-10 and IgG levels. These data give insight into Chikungunya disease establishment and subsequent convalescence, which is imperative to the treatment and containment of this quickly evolving and frequently re-emerging disease

HIV-1 suppression and durable control by combining single broadly neutralizing antibodies and antiretroviral drugs in humanized mice

Effective control of HIV-1 infection in humans is achieved using combinations of antiretroviral therapy (ART) drugs. In humanized mice (hu-mice), control of viremia can be achieved using either ART or by immunotherapy using combinations of broadly neutralizing antibodies (bNAbs). Here we show that treatment of HIV-1–infected hu-mice with a combination of three highly potent bNAbs not only resulted in complete viremic control but also led to a reduction in cell-associated HIV-1 DNA. Moreover, lowering the initial viral load by coadministration of ART and immunotherapy enabled prolonged viremic control by a single bNAb after ART was withdrawn. Similarly, a single injection of adeno-associated virus directing expression of one bNAb produced durable viremic control after ART was terminated. We conclude that immunotherapy reduces plasma viral load and cell-associated HIV-1 DNA and that decreasing the initial viral load enables single bNAbs to control viremia in hu-mice

Ertüchtigung der Flachschleifmaschine ELB SF 30

Aufbauend auf dem Praktikumsbericht wird in der vorliegenden Bachelorarbeit, das Thema „Ertüchtigung der Flachschleifmaschine ELB“ weiter behandelt. Es wird dabei speziell die Einführung eines neuen Bedienpanels an der Maschine konkretisiert. Zu Beginn erfolgt die Auswahl eines geeigneten Panels, welches zu der vorhandenen Steuerung kompatibel ist. Daraufhin folgt die Vorstellung der Visualisierungssoftware, sowie der Software zum Testen der projektierten Oberfläche des Bediengerätes. Im weiteren Verlauf finden sich Erläuterungen zur Programmierung des Panels, bezogen auf das ELB-Projekt wieder. Das letzte Kapitel bezieht sich auf die konkrete SPS-Lösung zwei ausgewählter Steuerungsfunktionen, zum einen die Magnetsteuerung und zum anderen die Querantriebsteuerung

Study of culinary sayings in traditional Lebanese recipes by means of molecular gastronomy

National audienc

Characterization of a set of ECN Spray A injectors : nozzle to nozzle variations and effect on spray characteristics

The Engine Combustion Network (ECN) is becoming a leading group concerning the experimental and computational analysis of Engine combustion. In order to establish a coherent database for model validation, all the institutions participating to the experimental effort carry out experiments at well-defined standard conditions (in particular at Spray A conditions: 22.8kg/m3, 900K, 0% and 15% O2) and with Diesel injectors having the same specifications. Due to the rising number of ECN participants and also to unavoidable damages, additional injectors are required. This raises the question of injector's characteristics reproducibility and of the appropriate method to introduce such new injectors in the ECN network. In order to investigate this issue, a set of 8 new injectors with identical nominal Spray A specification were purchased and 4 of them were characterized using ECN standard diagnostics. In particular, the measurements include the nozzle hole diameter, the rate of injection, the liquid and vapor penetrations, the auto-ignition delay and the lift-off length. Variations of ambient temperature, oxygen concentration and density have also been performed. In general the results show similar behavior to ECN standard injectors, confirming that this set of new injectors can be integrated into the pool of ECN injectors. However, discrepancies between spray characteristics were observed, although the injector specifications and the boundary conditions were sensibly the same. The sources of variations from injector to injector are analyzed in order to provide new information on the reproducibility of injectors characteristics, and improve the comparison methodology between experimental data and simulation

Regulation of high-affinity IgE receptor-mediated mast cell activation by murine low-affinity IgG receptors.

Allergic symptoms result from the release of granular and lipidic mediators and of cytokines by inflammatory cells. The whole process is initiated by the aggregation of mast cell and basophil high-affinity IgE receptors (Fc epsilon RI) by IgE and antigen. We report here that IgE-induced release of mediator and cytokine can be inhibited by cross-linking Fc epsilon RI to low-affinity IgG receptors (Fc gamma RII) which are constitutively expressed on mast cells and basophils. Using a model of stable transfectants in RBL-2H3 cells expressing endogeneous rat Fc epsilon RI and recombinant murine Fc gamma RII, we showed that inhibition requires that Fc epsilon RI be crosslinked to Fc gamma RII by the same multivalent ligand. Inhibition of cross-linked receptors left non-cross-linked Fc epsilon RI capable of triggering mediator release and was reversible upon disengagement. Both isoforms of wild-type Fc gamma RII were equally capable of inhibiting Fc epsilon RI-mediated mast cell activation provided they had an intact intracytoplasmic domain. Our results demonstrate that mast cell secretory responses triggered by high-affinity receptors for IgE may be controlled by low-affinity receptors for IgG. This regulation of Fc epsilon RI-mediated mast cell activation is of potential interest in mast cell physiology and in allergic pathology

Characterization of a set of ECN Spray A injectors : nozzle to nozzle variations and effect on spray characteristics

The Engine Combustion Network (ECN) is becoming a leading group concerning the experimental and computational analysis of Engine combustion. In order to establish a coherent database for model validation, all the institutions participating to the experimental effort carry out experiments at well-defined standard conditions (in particular at Spray A conditions: 22.8kg/m3, 900K, 0% and 15% O2) and with Diesel injectors having the same specifications. Due to the rising number of ECN participants and also to unavoidable damages, additional injectors are required. This raises the question of injector's characteristics reproducibility and of the appropriate method to introduce such new injectors in the ECN network. In order to investigate this issue, a set of 8 new injectors with identical nominal Spray A specification were purchased and 4 of them were characterized using ECN standard diagnostics. In particular, the measurements include the nozzle hole diameter, the rate of injection, the liquid and vapor penetrations, the auto-ignition delay and the lift-off length. Variations of ambient temperature, oxygen concentration and density have also been performed. In general the results show similar behavior to ECN standard injectors, confirming that this set of new injectors can be integrated into the pool of ECN injectors. However, discrepancies between spray characteristics were observed, although the injector specifications and the boundary conditions were sensibly the same. The sources of variations from injector to injector are analyzed in order to provide new information on the reproducibility of injectors characteristics, and improve the comparison methodology between experimental data and simulation

0D Modelling: a Promising Means for After-treatment Issues in Modern Automotive Applications

For modern automotive applications, after-treatment systems have become essential to respect the new emission standards. All the automotive world's attention is focused on catalysis systems because they seem to be one of the best ways to reach the future standards. As a result, after-treatment issues are more and more significant in the cost of the whole engine and vehicle development process. For example, the Euro 6 Diesel after-treatment line might for some applications be composed of nothing less than five distinct after-treatment bricks. This complex architecture implies developing advanced tools to help the exhaust line conception and also the design of associated control strategies. The present paper demonstrates that zero-dimensional (0D) simulation can be a relevant approach to develop exhaust line simulators compatible with accuracy and CPU time required performances. This paper proposes an original zero-dimensional model of the monolith. This approach is based on resistive and capacitive elements according to the bond graph theory [Karnopp D.C., Margolis D.L., Rosenberg R.C. (1990) Systems dynamics: a unified approach, Second Edition, John Wiley & Sons, New-York]. The described dynamic model takes into account the pneumatic flow and the thermal behaviour of the monolith. Models of several catalysts are built by plugging this monolith model with some well-known simplified chemical reaction schemes [Koltsakis G.C., Konstandinis P.A., Stamatelos A.M. (1997) Development and application range of mathematical models for 3-way catalytic converters, Appl. Catal. B: Environ. 12, 161-191]. Splitting a monolith model into several elementary zero-dimensional blocks in series allows having a good representation of the specific internal dynamic of one catalyst and to access some local information as in conventional well-known one-dimensional models with low CPU time cost [Koltsakis G.C., Konstandinis P.A., Stamatelos A.M. (1997) Development and application range of mathematical models for 3-way catalytic converters, Appl. Catal. B: Environ. 12, 161-191]. Such an approach can be used as a way to get a phenomenological understanding of the catalytic system, which is known to be a very complex multi-physical system. It also represents a relevant simulation tool for the definition of after-treatment line architecture and pollutant emission control. The approach's potential to deal with all modern after-treatment bodies is illustrated by results for a Three-Way Catalyst (3WC), a Diesel Oxidation Catalyst (DOC), a Lean NOx Trap (LNT) system, a Selective Catalyst Reduction of NOx (SCR) system and a Diesel Particulate Filter (DPF). This ability to give, with a good compromise between accuracy/low CPU time cost, some interesting information to help the development of more and more complex exhaust system makes zero-dimensional simulation relevant