Comparative study of non-premixed and partially-premixed combustion simulations in a realistic Tay model combustor

A comparative study of two combustion models based on non-premixed assumption and partially premixed assumptions using the overall models of Zimont Turbulent Flame Speed Closure Method (ZTFSC) and Extended Coherent Flamelet Method (ECFM) are conducted through Reynolds stress turbulence modelling of Tay model gas turbine combustor for the first time. The Tay model combustor retains all essential features of a realistic gas turbine combustor. It is seen that the non-premixed combustion model fails to predict the combustion completely due to an incorrect assumption of diffusion flame scenario invoking infinitely fast chemistry in complicated flow environments while the two partially premixed combustion models accurately predict the flame pattern in the primary region of the combustor. The ZTFSC model outperformed the ECFM model by producing a better temperature agreement with the experimental result. The latter model predicts lower temperature due to the underestimation of reaction progress. Additionally, a cross-comparison of the present RSM prediction invoking ZTFSC model with LES prediction reported in the literature is conducted. The former produces more accurate species concentration and flame pattern than the latter. This is mainly due to the incorrect assumption of non-premixed combustion used in LES prediction reported in the literature. It is interesting to find that when non-premixed combustion model is used for both RSM and LES predictions, the LES predicts higher temperature closer to the injection nozzle of combustor than the RSM model, though the flame shape in both cases is incorrect. This is mainly due to the fact that the traditional RANS model dissipates the energy of swirling flow too fast in the primary region of the combustor. The weaker centre recirculation zone (CRZ) created by vortex breakdown recirculate less air to the area near the injection nozzle resulting in fuel rich combustion. It indicates that the temperature difference between predicted results using RSM in conjunction with ZTFC model and experimental results can be improved by using less energy dissipating turbulence models such as scale resolving simulation (SRS)

Gauged motion in general relativity and in Kaluza-Klein theories

In a recent paper [1] a new generalization of the Killing motion, the {\it gauged motion}, has been introduced for stationary spacetimes where it was shown that the physical symmetries of such spacetimes are well described through this new symmetry. In this article after a more detailed study in the stationary case we present the definition of gauged motion for general spacetimes. The definition is based on the gauged Lie derivative induced by a threading family of observers and the relevant reparametrization invariance. We also extend the gauged motion to the case of Kaluza-Klein theories.Comment: 42 pages, revised version, typos correction along with some minor changes, Revtex forma

Art as a Vehicle for Social Change: The Harlem Renaissance

The black gatherings particularly in Harlem, constituting a community with its peculiarities, thanks to the effective contributions of intellectuals and artists through a new movement called the Harlem Renaissance urging the Blacks to struggle peacefully to gain more rights. For about thirty years, African Americans used arts in their battle to dispel common stereotypes. The origins of the movement were articulated in the philosophies of some prominent figures like W. E. Dubois and Allen Locke. The black community is a reality within the U.S.A, no one can deny its rights and this thanks to the struggles it has led, and to artistic contribution which has made the USA a nation with specificities, different from white man‘s country of origin. It sheds light also on the work of Toni Morrison’s Song of Solomon to stress the continuing heritage of the Harlem. A descriptive analytical analysis based on Cultural pluralism and Americanism concepts of Franz Boas‘ theories of race and culture (1930) is used in this research. The aim of the study is to show the role the elites can play to improve their communities’ status and the importance of art in shaping identities and giving insights for a better future. The Harlem Renaissance established the careers of many important African American writers, artists and thinkers who were influential for decades. It brought forth a body of creative cultural work that have become classics in African American and American culture. It created an ongoing interest in African American culture that continues up to this day.   Keywords: African Americans, Harlem Renaissance, New Negro movement, ar

Scale-Resolving Simulation of a Propane-Fuelled Industrial Gas Turbine Combustor Using Finite-Rate Tabulated Chemistry

The scale-resolving simulation of a practical gas turbine combustor is performed using a partially premixed finite-rate chemistry combustion model. The combustion model assumes finite-rate chemistry by limiting the chemical reaction rate with flame speed. A comparison of the numerical results with the experimental temperature and species mole fraction clearly showed the superiority of the shear stress transport, K-omega, scale adaptive turbulence model (SSTKWSAS). The model outperforms large eddy simulation (LES) in the primary region of the combustor, probably for two reasons. First, the lower amount of mesh employed in the simulation for the industrial-size combustor does not fit the LES’s explicit mesh size dependency requirement, while it is sufficient for the SSTKWSAS simulation. Second, coupling the finite-rate chemistry method with the SSTKWSAS model provides a more reasonable rate of chemical reaction than that predicted by the fast chemistry method used in LES simulation. Other than comparing with the LES data available in the literature, the SSTKWSAS-predicted result is also compared comprehensively with that obtained from the model based on the unsteady Reynolds-averaged Navier–Stokes (URANS) simulation approach. The superiority of the SSTKWSAS model in resolving large eddies is highlighted. Overall, the present study emphasizes the effectiveness and efficiency of coupling a partially premixed combustion model with a scale-resolving simulation method in predicting a swirl-stabilized, multi-jets turbulent flame in a practical, complex gas turbine combustor configuration

Evoking Emotion through Stories in Creative Dementia Care

This paper reports research to refine the design of a mobile creativity support app to improve person-centred care for older people with dementia. One barrier to previous app use during creative thinking appeared to be the negative activation emotions associated with problem avoidance and prevention exhibited by care staff when resolving challenging behaviours. Therefore we investigated the redesign of the app’s content so that care staff were more likely to positive activation associated with creative thinking through storytelling through a first formative evaluation

Attenuation of serum laminin concentrations upon treatment of chronic hepatitis

Objectives: The aim of this work was to determine the serum laminin level cutoff point for predicting liver fibrosis highlighting its diagnostic value and determining the effect of treatment on serum laminin concentrations. Methods: Serum laminin concentrations in chronic hepatitis patients (n=62) and controls (n=20) were compared by ELISA and stages of fibrosis were assessed according to the modified Knodell score system. Results: Mean serum laminin concentration in patients (91.9 ± 20.9 ng/ml) was greater than controls (46.2 ± 10.2 ng/ml; p <0.001). Serum concentrations of laminin in all stages of hepatic fibrosis were significantly higher than those of healthy controls (p <0.05). A cutoff point of 52ng laminin/ml of serum was obtained for the discrimination of various stages of liver fibrosis showing a good sensitivity (96.8%) and specificity (80%). After 6 months of treatment, a gradual decrease in serum laminin concentrations were observed, however the level was still higher than that of the healthy group (p<0.05). Conclusions: Our findings suggest that the serum laminin concentration is a useful noninvasive marker of liver fibrosis and shows a strong positive correlation with different stages of the disease

Optimization of regeneration and transformation parameters in tomato and improvement of its salinity and drought tolerance

As part of our efforts to improve tomato tolerance to abiotic stress, we have undertaken this study to introduce two candidate genes encoding: a sodium antiporter and a vacuolar pyrophosphatase, previously shown to enhance drought and salt tolerance in transgenic Arabidopsis plants. First, we evaluated the potential of primary leaves from three to four week-old in vitro-grown tomato seedlings as alternative explants to cotyledons for tomato transformation. Our results demonstrated that primaryleaves are three times more efficient then cotyledons in terms of regeneration percentage, productivity, and transformation frequencies independently of the medium and genetic construct used. Second,primary leaves were used to introduce the genes of interest using Agrobacterium-mediated transformation. Many transgenic tomato plants were easily recovered. The presence of the transgenes and their expression were confirmed by PCR and RT-PCR analysis. The transformation frequencies for primary leaf explants ranged from 4 to 10% depending on the genetic construct used. The time requiredfrom inoculation of primary leaves with Agrobacterium cells to transfer of transgenic tomato plants to soil was only 2 months compared to 3 to 4 months using standard tomato transformation protocols. The transgenic tomato plants obtained in the current study were more tolerant to salinity and drought stress than their wild-type counterparts

Diet of arbuscular mycorrhizal fungi: bread and butter ?

Most plants entertain mutualistic interactions known as arbuscular mycorrhiza (AM) with soil fungi (Glomeromycota) which provide them with mineral nutrients in exchange for reduced carbon from the plant. Mycorrhizal roots represent strong carbon sinks in which hexoses are transferred from the plant host to the fungus. However, most of the carbon in AM fungi is stored in the form of lipids. The absence of the type I fatty acid synthase (FAS-I) complex from the AM fungal model species Rhizophagus irregularis suggests that lipids may also have a role in nutrition of the fungal partner. This hypothesis is supported by the concerted induction of host genes involved in lipid metabolism. We explore the possible roles of lipids in the light of recent literature on AM symbiosis