scholarly journals Polydisperse spray flame ignition by a pulsed heat flux

2021 ◽  
pp. 175682772110141
Author(s):  
G Kats ◽  
JB Greenberg
Keyword(s):  
Critical Energy ◽  
Operating Conditions ◽  
Ignition Process ◽  
Fuel Droplets ◽  
Spray Flame ◽  
Theoretical Predictions ◽  
History Of ◽  
Flame Ignition ◽  
Entire History ◽  
Global Reaction

A mathematical analysis of the ignition of a polydisperse spray/air mixture by an infinite surface heated in a pulsed manner is presented. In contrast to previous work in the literature, the entire history of the ignition process is accounted for starting from the flame-embryo progenitor stage, through the thermal runaway stage to the final flame propagation stage. For tractability at the current stage, the chemical kinetics is taken to be that of a single global reaction. The spray is modeled using the sectional approach and the influence of fuel spray characteristics on ignition is determined. Good agreement was found between the theoretical predictions and full numerical simulations. Delay in ignition due to the build-up of vapor from the fuel droplets as well as heat loss to the droplets for evaporation are found to play a significant role under certain operating conditions. Comparison between the critical energy flux and the initial spray polydispersity revealed small differences for larger values of the pulse duration but more significant minor differences for smaller pulse durations. Despite these seemingly minor differences, it was shown that the initial spray polydispersity can have a critical influence on whether flame ignition will occur or fail, even for sprays having the same initial SMD.

scholarly journals Theory of Stagnation-Point Spray Flame Ignition

2017 ◽  
Author(s):  
J. Barry Greenberg ◽  
Gershon Kats
Keyword(s):  
Flow Field ◽  
Small Parameter ◽  
Stagnation Point ◽  
Fuel Spray ◽  
Asymptotic Approach ◽  
Fuel Droplets ◽  
Spray Flame ◽  
Flame Ignition ◽  
Hot Surface ◽  
First Time

A theory of stagnation-point spray flame ignition by an isothermal hot surface is presented for the first time. A mixture of fuel droplets and air flowing against an isothermal hot surface (such as a hot ignition probe) is considered. The spray of droplets is modelled using the sectional approach and a mono-sectional case is adopted for simplicity. A single global chemical reaction is assumed for the case when ignition occurs. The mathematical analysis makes use of a small parameter that is exploited for an asymptotic approach. The analysis produces a criterion for ignition that includes effects of the flow field, the reactants and the fuel spray-related parameters. Numerical computations reveal the way in which the latter impact on whether ignition will occur or not.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4643

Organization of restrictive quarantine measures to prevent especially dangerous infections

2020 ◽  
pp. 6-11
Author(s):  
Petr Ilyin
Keyword(s):  
Infectious Diseases ◽  
Clinical Symptoms ◽  
International Health ◽  
World Health ◽  
The World ◽  
History Of ◽  
Entire History ◽  
Health Organization ◽  
Former Ussr ◽  
Health Regulations

Especially dangerous infections (EDIs) belong to the conditionally labelled group of infectious diseases that pose an exceptional epidemic threat. They are highly contagious, rapidly spreading and capable of affecting wide sections of the population in the shortest possible time, they are characterized by the severity of clinical symptoms and high mortality rates. At the present stage, the term "especially dangerous infections" is used only in the territory of the countries of the former USSR, all over the world this concept is defined as "infectious diseases that pose an extreme threat to public health on an international scale." Over the entire history of human development, more people have died as a result of epidemics and pandemics than in all wars combined. The list of especially dangerous infections and measures to prevent their spread were fixed in the International Health Regulations (IHR), adopted at the 22nd session of the WHO's World Health Assembly on July 26, 1969. In 1970, at the 23rd session of the WHO's Assembly, typhus and relapsing fever were excluded from the list of quarantine infections. As amended in 1981, the list included only three diseases represented by plague, cholera and anthrax. However, now annual additions of new infections endemic to different parts of the earth to this list take place. To date, the World Health Organization (WHO) has already included more than 100 diseases in the list of especially dangerous infections.

The Paving Stone Theory of World Tectonics

2018 ◽  
Author(s):  
Roy Livermore
Keyword(s):  
Indian Ocean ◽  
Plate Tectonics ◽  
Earth Science ◽  
Transform Faults ◽  
Plate Motions ◽  
Euler’S Theorem ◽  
History Of ◽  
New Ideas ◽  
Entire History ◽  
The Indian Ocean

Tuzo Wilson introduces the concept of transform faults, which has the effect of transforming Earth Science forever. Resistance to the new ideas is finally overcome in the late 1960s, as the theory of moving plates is established. Two scientists play a major role in quantifying the embryonic theory that is eventually dubbed ‘plate tectonics’. Dan McKenzie applies Euler’s theorem, used previously by Teddy Bullard to reconstruct the continents around the Atlantic, to the problem of plate rotations on a sphere and uses it to unravel the entire history of the Indian Ocean. Jason Morgan also wraps plate tectonics around a sphere. Tuzo Wilson introduces the idea of a fixed hotspot beneath Hawaii, an idea taken up by Jason Morgan to create an absolute reference frame for plate motions.

scholarly journals Overcoming barriers to the registration of new plant varieties under the DUS system

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Chin Jian Yang ◽  
Joanne Russell ◽  
Luke Ramsay ◽  
William Thomas ◽  
Wayne Powell ◽  
...  
Keyword(s):  
Current System ◽  
Registration System ◽  
Crop Varieties ◽  
Property System ◽  
Dus Testing ◽  
History Of ◽  
New Varieties ◽  
Entire History ◽  
Combinatorial Space ◽  
New Crop

AbstractDistinctness, Uniformity and Stability (DUS) is an intellectual property system introduced in 1961 by the International Union for the Protection of New Varieties of Plants (UPOV) for safeguarding the investment and rewarding innovation in developing new plant varieties. Despite the rapid advancement in our understanding of crop biology over the past 60 years, the DUS system has changed little and is still largely dependent upon a set of morphological traits for testing candidate varieties. As the demand for more plant varieties increases, the barriers to registration of new varieties become more acute and thus require urgent review to the system. To highlight the challenges and remedies in the current system, we evaluated a comprehensive panel of 805 UK barley varieties that span the entire history of DUS testing. Our findings reveal the system deficiencies such as inconsistencies in DUS traits across environments, limitations in DUS trait combinatorial space, and inadequacies in currently available DUS markers. We advocate the concept of genomic DUS and provide evidence for a shift towards a robust genomics-enabled registration system for new crop varieties.

scholarly journals Modification to the Hawking temperature of a dynamical black hole by a flow-induced supertranslation

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Hsu-Wen Chiang ◽  
Yu-Hsien Kung ◽  
Pisin Chen
Keyword(s):  
Black Hole ◽  
Coordinate Transformation ◽  
Information Loss ◽  
Hawking Temperature ◽  
Asymptotic Region ◽  
Unruh Effect ◽  
Anisotropic Flow ◽  
Information Loss Paradox ◽  
History Of ◽  
Entire History

Abstract One interesting proposal to solve the black hole information loss paradox without modifying either general relativity or quantum field theory, is the soft hair, a diffeomorphism charge that records the anisotropic radiation in the asymptotic region. This proposal, however, has been challenged, given that away from the source the soft hair behaves as a coordinate transformation that forms an Abelian group, thus unable to store any information. To maintain the spirit of the soft hair but circumvent these obstacles, we consider Hawking radiation as a probe sensitive to the entire history of the black hole evaporation, where the soft hairs on the horizon are induced by the absorption of a null anisotropic flow, generalizing the shock wave considered in [1, 2]. To do so we introduce two different time-dependent extensions of the diffeomorphism associated with the soft hair, where one is the backreaction of the anisotropic null flow, and the other is a coordinate transformation that produces the Unruh effect and a Doppler shift to the Hawking spectrum. Together, they form an exact BMS charge generator on the entire manifold that allows the nonperturbative analysis of the black hole horizon, whose surface gravity, i.e. the Hawking temperature, is found to be modified. The modification depends on an exponential average of the anisotropy of the null flow with a decay rate of 4M, suggesting the emergence of a new 2-D degree of freedom on the horizon, which could be a way out of the information loss paradox.

scholarly journals Extensive introgression and mosaic genomes of Mediterranean endemic lizards

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Weizhao Yang ◽  
Nathalie Feiner ◽  
Catarina Pinho ◽  
Geoffrey M. While ◽  
Antigoni Kaliontzopoulou ◽  
...  
Keyword(s):  
Evolutionary History ◽  
Mediterranean Islands ◽  
The Past ◽  
Island Endemics ◽  
Extant Species ◽  
Mediterranean Island ◽  
History Of ◽  
Entire History ◽  
The Mediterranean ◽  
The Mediterranean Basin

AbstractThe Mediterranean basin is a hotspot of biodiversity, fuelled by climatic oscillation and geological change over the past 20 million years. Wall lizards of the genus Podarcis are among the most abundant, diverse, and conspicuous Mediterranean fauna. Here, we unravel the remarkably entangled evolutionary history of wall lizards by sequencing genomes of 34 major lineages covering 26 species. We demonstrate an early (>11 MYA) separation into two clades centred on the Iberian and Balkan Peninsulas, and two clades of Mediterranean island endemics. Diversification within these clades was pronounced between 6.5–4.0 MYA, a period spanning the Messinian Salinity Crisis, during which the Mediterranean Sea nearly dried up before rapidly refilling. However, genetic exchange between lineages has been a pervasive feature throughout the entire history of wall lizards. This has resulted in a highly reticulated pattern of evolution across the group, characterised by mosaic genomes with major contributions from two or more parental taxa. These hybrid lineages gave rise to several of the extant species that are endemic to Mediterranean islands. The mosaic genomes of island endemics may have promoted their extraordinary adaptability and striking diversity in body size, shape and colouration, which have puzzled biologists for centuries.

Influence of Main Swirler Vane Angle on the Ignition Performance of TeLESS-II Combustor

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Bo Wang ◽  
Chi Zhang ◽  
Yuzhen Lin ◽  
Xin Hui ◽  
Jibao Li
Keyword(s):  
High Speed ◽  
Inlet Temperature ◽  
Main Stage ◽  
Ignition Process ◽  
High Speed Camera ◽  
Fuel Distribution ◽  
Fuel Droplets ◽  
Planar Laser ◽  
Cfd Method ◽  
Vane Angle

In order to balance the low emission and wide stabilization for lean premixed prevaporized (LPP) combustion, the centrally staged layout is preferred in advanced aero-engine combustors. However, compared with the conventional combustor, it is more difficult for the centrally staged combustor to light up as the main stage air layer will prevent the pilot fuel droplets arriving at igniter tip. The goal of the present paper is to study the effect of the main stage air on the ignition of the centrally staged combustor. Two cases of the main swirler vane angle of the TeLESS-II combustor, 20 deg and 30 deg are researched. The ignition results at room inlet temperature and pressure show that the ignition performance of the 30 deg vane angle case is better than that of the 20 deg vane angle case. High-speed camera, planar laser induced fluorescence (PLIF), and computational fluids dynamics (CFD) are used to better understand the ignition results. The high-speed camera has recorded the ignition process, indicated that an initial kernel forms just adjacent the liner wall after the igniter is turned on, the kernel propagates along the radial direction to the combustor center and begins to grow into a big flame, and then it spreads to the exit of the pilot stage, and eventually stabilizes the flame. CFD of the cold flow field coupled with spray field is conducted. A verification of the CFD method has been applied with PLIF measurement, and the simulation results can qualitatively represent the experimental data in terms of fuel distribution. The CFD results show that the radial dimensions of the primary recirculation zone of the two cases are very similar, and the dominant cause of the different ignition results is the vapor distribution of the fuel. The concentration of kerosene vapor of the 30 deg vane angle case is much larger than that of the 20 deg vane angle case close to the igniter tip and along the propagation route of the kernel, therefore, the 30 deg vane angle case has a better ignition performance. For the consideration of the ignition performance, a larger main swirler vane angle of 30 deg is suggested for the better fuel distribution when designing a centrally staged combustor.

Experimental and Theoretical Rotordynamic Characteristics of a Hybrid Journal Bearing

1997 ◽  
Vol 119 (1) ◽  
pp. 132-141 ◽  
Author(s):  
J. T. Sawicki ◽  
R. J. Capaldi ◽  
M. L. Adams
Keyword(s):  
Journal Bearing ◽  
Operating Conditions ◽  
Dynamic Force ◽  
Test Results ◽  
Force Measurements ◽  
Lubrication Equation ◽  
Load Cells ◽  
Theoretical Predictions ◽  
Stiffness And Damping

This paper describes an experimental and theoretical investigation of a four-pocket, oil-fed, orifice-compensated hydrostatic bearing including the hybrid effects of journal rotation. The test apparatus incorporates a double-spool-shaft spindle which permits independent control over the journal spin speed and the frequency of an adjustable-magnitude circular orbit, for both forward and backward whirling. This configuration yields data that enables determination of the full linear anisotropic rotordynamic model. The dynamic force measurements were made simultaneously with two independent systems, one with piezoelectric load cells and the other with strain gage load cells. Theoretical predictions are made for the same configuration and operating conditions as the test matrix using a finite-difference solver of Reynolds lubrication equation. The computational results agree well with test results, theoretical predictions of stiffness and damping coefficients are typically within thirty percent of the experimental results.

THE RUSSIAN OUTPOST OF PURE SCIENCE IN THE GLOBAL OCEAN (TO THE 75-TH ANNIVERSARY OF SIO RAS, 1946–2021)

2021 ◽  
Vol 49 (3) ◽  
pp. 12-32
Keyword(s):  
Research Team ◽  
General Information ◽  
Global Ocean ◽  
Recent Past ◽  
Historical Events ◽  
Pure Science ◽  
History Of ◽  
Entire History ◽  
Academy Of Sciences ◽  
Large Research

A brief overview of the main historical events that accompanied the formation and establishment of the Laboratory of Oceanology in the Academy of Sciences in 1941 is given. Then, a few years later, the Laboratory was transformed into the Institute of Oceanology, the director of which was appointed the Minister of the Merchant Fleet of the USSR, Academician P. P. Shirshov. By his initiative in 1949, the Institute became the owner of its first large research vessel "Vityaz". It is shown that the entire history of the institute and its research team was primarily based on the development and generalization of the results of regular sea and ocean expeditions. The article provides general information about the results obtained in the recent past, and their development and deepening in the works of the institute at present.

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