Abstract

Swirl stabilized combustion is one of the most successful technologies for flame and nitrogen oxides control in gas turbines. However, complex fluid dynamics and lean conditions pose a problem for stabilization of the flame. The problem is even more acute when alternative fuels are used for flexible operation. Although there is active research on the topic, there are still various gaps in the understanding of how interaction of large coherent structures during the process affect flame stabilization and related phenomena. Thus, this paper approaches the phenomenon of lean premixed swirl combustion of CH4/H2/CO blends to understand the impacts of these fuels on flame blowoff. An atmospheric pressure generic swirl burner was operated at ambient inlet conditions. Different exhaust nozzles were used to alter the Central Recirculation Zone and observe the impacts caused by various fuel blends on the structure and the blowoff phenomenon. Methane content in the fuel was decreased from 50% to 10% (by volume) with the remaining amount split equally between carbon monoxide and hydrogen. Experimental trials were performed using Phase Locked PIV. The Central Recirculation Zone and its velocity profiles were measured and correlated providing details of the structure close to blowoff. The results show how the strength and size of the recirculation zone are highly influenced by the fuel blend, changing stability based on the carbon-hydrogen ratios. Nozzle effects on the shear flow and Re numbers were also observed. Modelling was carried out using the k-ω SST CFD model which provided more information about the impact of the CRZ and the flame nature close to blowoff limit. It was observed that the model under-predicts coherent structure interactions at high methane fuel content, with an over-prediction of pressure decay at low methane content when correlated to the experimental results. Thus, complex interactions between structures need to be included for adequate power prediction when using very fast/slow syngas blends under lean conditions. 

لقد تزايد الاهتمام المحلي والدولي بمكافحة الفساد المالي والإداري وخاصة في ظل التطورات المتلاحقة للحياة الإقتصادية والتي تُحتم على منظمات الأعمال ضرورة مكافحة الفساد المالي والإداري حتى يتسنى لها البقاء الأمن في بيئة الأعمال. وتعد المحاسبة القضائية من الآليات الحديثة في مجال منع واكتشاف الغش والفساد المالي والإداري، لذا فقد هدفت هذه الدراسة إلى التعرف المفاهيم الأساسية للمحاسبة القضائية و توضيح السمات الشخصية التي يجب أن يتميز بها و التعرف على المعايير المهنية الصادرة عن جمعية ممتحني الاحتيال المعتمدين بخصوص ممارسة مهنة المحاسبة القضائية، ولتحقيق هذه الاهداف تم تقسيم الدراسة إلى ثلاثة اجزاء، تناول الجزء الاول الاطار العام للدراسة وتناول الجزء الثاني الإطار النظري للمحاسبة القضائية في حين خصص الجزء الثالث للدراسة الميدانية والذي تم فيه اختبار مدى توفر تلك المعايير الدولية في ممارسي مهنة المحاسب القضائي في ليبيا، وقد خلصت الدراسة إلى عدم توفر تلك المعايير مما يستوجب ضرورة العمل على تطوير القدرات والمهارات لدى المحاسب القضائي حتى يتسنى له أداء مهامه بكل كفاءة واقتدار.

Data required for calculation the static re-crystallization kinetics have been evaluated from laboratory simulations. Series of two hit isothermal tests were conducted on high temperature torsion machine. These tests were conducted on four different temperatures and using inter-pass times between 0.5 and 5s with aim to investigate the influence of thermal activation on static re-crystallization. All tests were conducted on temperatures over TNR temperature, i.e. in temperature range in which all niobium is present only in solid solution. Method of evaluation of re-crystallization fraction was mechanical metallography, i.e. evaluation based on shape of each stress- strain curve. The fraction softening was calculated for all temperatures, together with avrami exponent, nA, and activation energy for re-crystallization, QSRX. Activation energy for static re-crystallization QSRX  281 KJ/mol and avrami exponent nA  1 determined in this work are in excellent agreement with previously reported data.

The aim of this work is focused on nucleation stages with emphasis on the development of intra-granular ferrite morphologies during isothermal austenite transformation in titanium free micro-alloyed steel. Isothermal treatment was carried out in the temperature range 350 to 600οC. These treatments were interrupted at different times between 2 and 1800 s in order to analyze the evolution of the microstructure. Metallographic evaluation was done by using optical and scanning electron microscopy (SEM) enabled determination of the nucleation onset at all treatments and subsequent on the development of intra-granular ferrite of isothermally treated Ti free micro-alloyed steel. The results show that at high temperatures ( 500  C) polygonal intra-granularly nucleated ferrite idiomorphs, combined with grain boundary ferrite and pearlite were produced and followed by an incomplete transformation phenomenon, At intermediate temperatures (450 and 500  C) an interlocked acicular ferrite (AF) microstructure is produced, and at low temperatures (400 and 350  C) the sheave of parallel acicular ferrite plates, similar to bainitic sheaves but intra-granularly nucleated were observed. In addition to sheaf type acicular ferrite, the grain boundary nucleated bainitic sheaves are observed.

Abstract

This paper provides a CFD comparison of tow turbulence modeling approaches (SST) and (K-epsilon), with application to the simulation of a teardrop. As well as, the study investigates and compares among 3 different models in a range these types in order to assess the suitability of CFD for use when calculating drag co-efficient. Moreover, the study focuses on 3 different velocities to be impacted with the drag co-efficient. Whereas, the pressure over the body was used to calculate the drag co-efficient for each of the 3 teardrops shapes.

The purpose of this study is to contribute to the understanding of how BSC is developed and applied in evaluating the performance of The Jumhouria Bank (JB) in Libya. Using the concepts of Kaplan and Norton, and the data made available from the bank, a BSC was derived to measure the performance of the bank between 2007-2010. The analysis assisted the cause-effect relationships between the non-financial, and the financial dimensions of the BSC. Due to lack of research work, in this area, in the banking sector in Libya, this study shall contribute to the knowledge on how banks in Libya may apply the BSC to evaluate their performance, and how they might turn strategic vision into potential performance. The author proposed some future research needs required in this area. The use of the BSC developed here is limited to the bank studied; however, the approach could trigger off reflections among policy makers and other banks to start using the BSC.