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Vibration-Based Analysis for Detecting Turbocharger Blade Defect on High-Power Diesel Generator

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World Journal of Mechanics 2020年第1期10卷 1-10页

作者： Metaga Jeremi Sogoba Badié Diourté moussa magara traoré Ecole Nationale d’Ingénieurs Abderhamane Baba TOURE (ENI-ABT) Bamako Mali

This study is concerned with 12-MW capacity turbochargers on diesel power generators. These are generators equipped with 18 cylinders. Our previous studies [1] showed that the processing of vibration signature collected from a power generator is very complex, insomuch the dominant vibration remains the one originating from explosion frequency in the diesel generator cylinders, with a fairly high number of cylinders. This vibration drowns out all other possible vibrations, which can expose defects. The study at hand is focused on turbochargers with 20,940 rpm, while the rotation speed in the diesel engine is 600 rpm only. With the turbocharger rotating at very high speed, it results in severe mechanical constraints on the rotor shaft in the turbocharger and its related organs (turbine blades). The wear of turbine blades can result in breakdowns in the turbocharger. This article is an attempt to early detect defaults in turbine blades based on vibration signature that can be experimentally determined. We noted in our investigations that a diesel engine and its turbochargers do not bear the same mechanic loads. While the diesel engine is the seat of violent shocks brought about by explosions in cylinders, the turbochargers are driven by the action of exhaust gas from explosions, without being affected by explosion shocks. The study found that explosion frequency in the diesel engine cylinders, which disrupted the vibration signals in the diesel engine and alternator, did not impact on the vibration signals in the turbocharger. We experimentally determined, following several campaigns of measurements, a vibration signature on the turbochargers under study, which corresponds to a defect in turbine blades.

关键词： Vibration Signature Fast Fourier Transform Method (FFT) Turbocharger Tur-bine Blades

Influences of the Textured Surface Micro-Texture Depth on the Friction Coefficient

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World Journal of Mechanics 2020年第12期10卷 221-228页

作者： moussa magara traore State Key Laboratory for Manufacturing Systems Engineering School of Mechanical Engineering Xi’an Jiaotong University Xi’an China Ecole Normale d’Enseignement Technique et Professionnel du Mali Cité Universitaire de Kabala Bamako Mali

The use of textured surfaces in lubrication to improve the tribological characteristics has been widely studied. The understanding of the textured surface geometric parameters influences on these tribological characteristics could help to improve their applications in industry. In this paper, we purpose to analyze the influence of the micro-texture depth on the friction coefficient experimentally. The experiment is conducted using different copper alloy samples have been the first laser textured with different micro-hole depth (40.83 μm and 46.36 μm). A 3D electronic Olympus microscope is used to visualize the shapes of the holes and find the depths. Then, the friction test has been conducted using these samples with the same velocity. The time variation of the friction coefficient is plotted and analyzed. The analysis of time variation of the friction coefficient shows a reduction of friction coefficient with the increase of the micro-hole depth has been observed. In some cases, this reduction is significant.

关键词： Friction Coefficient Tribology Textured Surfaces

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高速微孔钻床主轴系统的动态特性分析

机械设计与研究 2005年第6期21卷 93-97页

作者： traorE moussa magara 裴永臣李晶谭庆昌吉林大学南岭校区机械科学与工程学院吉林长春130025

依据转子动力学理论,利用Timoshenko梁轴理论,建立了包含旋转惯性力、陀螺力矩、离心力、弯曲变形、扭转变形、钻削轴向力和钻头的三种边界条件在内的高速微孔钻床主轴系统动力学模型.在利用实验和现有文献对所建立的模型进行了检验的... 详细信息

依据转子动力学理论,利用Timoshenko梁轴理论,建立了包含旋转惯性力、陀螺力矩、离心力、弯曲变形、扭转变形、钻削轴向力和钻头的三种边界条件在内的高速微孔钻床主轴系统动力学模型.在利用实验和现有文献对所建立的模型进行了检验的基础上,对高速微孔钻床主轴系统的临界转速、临界轴向压力进行了分析.结果表明高速微孔钻床主轴系统的临界转速随钻削轴向压力的增大而减小,并且钻削过程中比刚入钻时能承受更高的转速,更大的轴向力;临界轴向压力随高速微孔钻床主轴系统转速的升高而降低,即随着钻削转速的提高,应适当减小钻削轴向力.

关键词：转子动力学微小孔钻床临界转速临界压力

Prevalence and Etiologies of Obstructive Renal Failure in the Nephrology Department of the University Hospital Center of Point G, Bamako, Mali

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Open Journal of Nephrology 2020年第3期10卷 187-198页

作者： Seydou Sy magara Samaké Moctar Coulibaly moussa Salifou Diallo Atabième Kodio Hamadoun Yattara Abdoul Aziz Mahamane Seribah Coulibaly Aboubacar Sidiki Fofana Djénèba Diallo Sah Dit Baba Coulibaly Modi Sidibé Moustapha Tangara Alkaya Touré Saharé Fongoro Nephrology and Haemodialysis Department of the University Hospital Center (UHC) of Point G Bamako Mali Faculty of Medicine and Odontostomatology of Bamako Bamako Mali Nephrology Unit of the Fousseyni Daou Hospital in Kayes Kayes Mali Nephrology Unit of the Mali Gavardo Hospital of Sébénikoro Bamako Mali Urology Department of University Hospital Center of Kati Kati Mali

Introduction: Obstructive renal failure (ORF) or obstructive uropathy is defined by the simultaneous presence of impaired renal function and urinary excretory tract dilatation on medical imaging. It accounts for 2% to 10% of the causes of acute renal failure (ARF). Objective: To determine the prevalence and etiologies of ORF in the nephrology department of the University Hospital Center of Point G. Methodology: This was a descriptive study with retrospective data collection conducted from January 1, 2017 to June 30, 2018. All patients hospitalized with renal failure due to urinary tract obstruction were included. The parameters studied were age, gender, etiology, type of renal impairment, procedures performed, surgical outcomes of the procedure, pre-and post-management creatinine levels. Information on these clinical and paraclinical variables was collected from individual hospitalization and patient follow-up records. Results: Among 1133 patients, 83 had obstructive renal failure, a prevalence of 7.32%. The sex ratio was 1.86. The mean age was 48.99 ± 6.81 years with extremes of 7 and 102 years. Signs suggestive of lower urinary tract obstruction were, in order of frequency: dysuria (50.6%), urinary burns (44.6%), urinary frequency (44.6%), pollakiuria (44.6%), macroscopic hematuria (25.3%), low back pain (21.6%), total anuria (18.1%). The etiologies were dominated by lithiasis 36 cases (43.4%), tumours 32 cases (38.55%) followed by sequelae of bilharziasis 12 cases (14.50%). Conclusion: Obstructive renal failure is becoming more and more common. The etiology is essentially of lithiasic and tumor origin. It must be treated early to allow total or partial recovery of renal function.

关键词： Prevalence Etiologies Obstructive Renal Failure Mali