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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Transdisciplinary working to shape systematic reviews and interpret the findings: Commentary

This is the final version. Available from BMC via the DOI in this record. Important policy questions tend to span a range of academic disciplines, and the relevant research is often carried out in a variety of social, economic and geographic contexts. In efforts to synthesise research to help inform decisions arising from the policy questions, systematic reviews need conceptual frameworks and ways of thinking that combine knowledge drawn from different academic traditions and contexts; in other words, transdisciplinary research. This paper considers how transdisciplinary working can be achieved with: conceptual frameworks that span traditional academic boundaries; methods for shaping review questions and conceptual frameworks; and methods for interpreting the relevance of findings to different contexts. It also discusses the practical challenges and ultimate benefits of transdisciplinary working for systematic reviews.World Health OrganizationUK Department for International DevelopmentUK aidNational Institute for Health Research (NIHR

Ignition and combustion development for high speed direct injection diesel engines under low temperature cold start conditions

Diesel engine cold start is an important issue for current technology at low (below 0 °C) temperatures and for future applications. The aim of this work is to develop a description of how, when and where does fuel spray ignition occur in a glow-plug assisted engine under simulated low temperature cold start conditions. In-cylinder pressure analysis is combined with high speed visualization in an optical engine. A pilot plus main injection strategy is used. Visualization results show that pilot ignition occurs in the vicinity of the glow plug, and strongly influences main combustion initiation. Main combustion starts from the pilot flame, and propagates to the rest of the combustion chamber showing a strong visible reaction zone. After end of main injection, the rapid leaning of the mixture suppresses the strong radiation, and OH radiation is observed to progress to the rest of the combustion chamber. The combustion process shows a strong scattering, which has been quantified by combustion parameters. At higher rail pressures scattering increases, which eventually inhibits combustion initiation. However, if ignition occurs at higher rail pressures, cycle performance is better.Authors thank the Spanish Ministry of Innovation and Science for the financial support through the project OPTICOMB (reference code: TRA2007-67961-C03-C01). Authors also thank Daniel Lerida Sanchez de las Heras for his outstanding work in the facility set-up and adaptation and for his support during the tests.Pastor Soriano, JV.; García Oliver, JM.; Pastor Enguídanos, JM.; Ramírez Hernández, JG. (2011). Ignition and combustion development for high speed direct injection diesel engines under low temperature cold start conditions. Fuel. 90(4):1556-1566. https://doi.org/10.1016/j.fuel.2011.01.008S1556156690

Quality of private and public ambulatory health care in low and middle income countries: systematic review of comparative studies

Paul Garner and colleagues conducted a systematic review of 80 studies to compare the quality of private versus public ambulatory health care in low- and middle-income countries

Spending by primary care practices-does it show what we expect?

Background Over recent years, a number of policies and financial incentives in primary care have been proposed to tackle issues such as deprivation and health outcomes. This article investigates the association between healthcare spending, deprivation and outcomes. It argues that individual practice data are analysed before blanket application and acceptance that one size fits all in a local area. Methods Financial data were analysed alongside key outcome data, including quality and outcomes framework (QOF) indicators for a large urban primary care trust (PCT) in the UK. The PCT had a large population and number of practices, including single-handed practices and an average list size in excess of 5000. The PCT will remain anonymous. Results There was no relationship between primary care investment and the practices' deprivation score. There was a strong statistically significant negative correlation between QOF payments and deprivation, (correlation = −0.46, p < 0.001). There were only weak links between primary care investment and health outcomes. There was no relationship between high emergency spending and health outcome. Conclusions The data presented suggest that one size does not necessarily fit all—in terms of providing the appropriate incentives in primary care, nor do national incentives and policies always have the desired effect

VLA imaging of the XMM-LSS/VIDEO deep field at 1–2 GHz

Modern radio telescopes are routinely reaching depths where normal star-forming galaxies are the dominant observed population. Realizing the potential of radio as a tracer of star formation and black hole activity over cosmic time involves achieving such depths over representative volumes, with radio forming part of a larger multiwavelength campaign. In pursuit of this, we used the Karl G. Jansky Very Large Array (VLA) to image ∼5 deg2 of the VIDEO/XMM-LSS extragalactic deep field at 1–2 GHz. We achieve a median depth of 16 μJy beam−1 with an angular resolution of 4.5 arcsec. Comparisons with existing radio observations of XMM-LSS showcase the improved survey speed of the upgraded VLA: we cover 2.5 times the area and increase the depth by ∼20 per cent in 40 per cent of the time. Direction-dependent calibration and wide-field imaging were required to suppress the error patterns from off-axis sources of even modest brightness. We derive a catalogue containing 5762 sources from the final mosaic. Sub-band imaging provides in-band spectral indices for 3458 (60 per cent) sources, with the average spectrum becoming flatter than the canonical synchrotron slope below 1 mJy. Positional and flux density accuracy of the observations, and the differential source counts are in excellent agreement with those of existing measurements. A public release of the images and catalogue accompanies this article

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

Rapid Acoustic Survey for Biodiversity Appraisal

Biodiversity assessment remains one of the most difficult challenges encountered by ecologists and conservation biologists. This task is becoming even more urgent with the current increase of habitat loss. Many methods–from rapid biodiversity assessments (RBA) to all-taxa biodiversity inventories (ATBI)–have been developed for decades to estimate local species richness. However, these methods are costly and invasive. Several animals–birds, mammals, amphibians, fishes and arthropods–produce sounds when moving, communicating or sensing their environment. Here we propose a new concept and method to describe biodiversity. We suggest to forego species or morphospecies identification used by ATBI and RBA respectively but rather to tackle the problem at another evolutionary unit, the community level. We also propose that a part of diversity can be estimated and compared through a rapid acoustic analysis of the sound produced by animal communities. We produced α and β diversity indexes that we first tested with 540 simulated acoustic communities. The α index, which measures acoustic entropy, shows a logarithmic correlation with the number of species within the acoustic community. The β index, which estimates both temporal and spectral dissimilarities, is linearly linked to the number of unshared species between acoustic communities. We then applied both indexes to two closely spaced Tanzanian dry lowland coastal forests. Indexes reveal for this small sample a lower acoustic diversity for the most disturbed forest and acoustic dissimilarities between the two forests suggest that degradation could have significantly decreased and modified community composition. Our results demonstrate for the first time that an indicator of biological diversity can be reliably obtained in a non-invasive way and with a limited sampling effort. This new approach may facilitate the appraisal of animal diversity at large spatial and temporal scales