Mohy Mansour | Cairo University (original) (raw)

Papers by Mohy Mansour

Flow, turbulence and combustion, Mar 19, 2024

The International Conference on Applied Mechanics and Mechanical Engineering, 2010

Design of laser cavities is a complicated process. It includes several optical, geometrical and m... more Design of laser cavities is a complicated process. It includes several optical, geometrical and material parameters. Computer Aided Design of laser cavities reduces the time and effort required to reach the optimum design. In this paper an accurate and fast three dimensional CAD model for simulating solid-state laser systems is developed. Numerical estimations of the geometrical transfer efficiency of various cavities are presented. Analytical and iterative methods to achieve a feasible converged solution for designing optimum pumping champers which contains different geometrical dimensions of laser rods, flash lamps and walls reflectivity are discussed. A simulation study of the pumping efficiency of the laser heads with respect to the cavity geometry, different geometries of laser rods and flashlamps, and reflecting coatings have been carried out. The goal is to achieve a maximum concentration of the light flux of the pumping source towards the active medium. Results are presented using Matlab and Microsoft office excel. Computer aided design is then used to create three dimensional parametric model of laser cavity assembly. The proposed model has been compared with published results and shown to be very accurate and efficient for modeling three-dimensional solid-state laser chambers.

It is now a fact that focusing an intense ultra short laser pulse onto a gas jet or thin targets,... more It is now a fact that focusing an intense ultra short laser pulse onto a gas jet or thin targets, generates energetic collimated electrons or ions forming ultra short beams of energies &amp;gt; 100 MeV. The different mechanisms to explain such laser accelerated electrons or ions will be discussed. Data obtained by recent experiments will be presented. We report the

Flow, turbulence and combustion, Sep 18, 2012

The stabilization characteristics and local extinction structures of partially premixed methane/a... more The stabilization characteristics and local extinction structures of partially premixed methane/air flames were studied using simultaneous OH-PLIF/PIV techniques, and large eddy simulations employing a two-scalar flamelet model. Partial premixing was made in a mixing chamber comprised of two concentric tubes, where the degree of partial premixing of fuel and air was controlled by varying the mixing length of the chamber. At the exit of the mixing chamber a cone was mounted to stabilize the flames at high turbulence intensities. The stability regime of flames was determined for different degree of partial premixing and Reynolds numbers. It was found that in general partially premixed flames at low Reynolds numbers become more stable when the level of partial premixing of air to the fuel stream decreases. At high Reynolds numbers, for the presently studied burner configuration there is an optimal partial premixing level of air to the fuel stream at which the flame is most stable. OH-PLIF images revealed that for the stable flames not very close to the blowout regime, significant local extinction holes appear already. By increasing premixing air to fuel stream successively, local extinction holes grow in size leading to eventual flame blowout. Local flame extinction was found to frequently attain to locations where locally high velocity flows impinging to the flame. The local flame extinction poses a future challenge for model simulations and the present flames provide a possible test case for such study.

WORLD SCIENTIFIC eBooks, 2010

High-Power Lasers and Interactions (C Chatwin & R Young) Laser Accelerators (L El-Nadi) Laser... more High-Power Lasers and Interactions (C Chatwin & R Young) Laser Accelerators (L El-Nadi) Laser Manipulation of Atoms (L El-Nadi et al.) Analytical Studies of Laser Beam Propagation Through the Atmosphere (M I El-Saftawy et al.) Optical Design Alternatives: A Survey Study (A A K Ismail et al.) Materials for Digital Optical Design: A Survey Study (S H Ahmed et al.) Proposed Design for Optical Digital Circuits (A A Ismail et al.) Photo-Induced Effect on Bacterial Cells (M H El-Batanouny et al.) Molecular Mechanisms and Apoptosis in PDT (B Krammer et al.) and other papers.

$Research paper thumbnail of Evaluation of partially premixed flame stability from mixture fraction statistics in a turbulent slot burner$

HAL (Le Centre pour la Communication Scientifique Directe), 2017

International audienc

Proceedings of the Combustion Institute, 2021

Turbulent flames with compositionally inhomogeneous mixtures are common in many combustion system... more Turbulent flames with compositionally inhomogeneous mixtures are common in many combustion systems. Turbulent jet flames with a circular nozzle burner were used earlier to study the impact of inhomogeneous mixtures, and these studies showed that the nozzle radius affects the flame stability. Accordingly, planar turbulent flames with inhomogeneous turbulent jet are created in a concentric flow slot burner (CFSB) to avoid this effect in the present study. The stability characteristics, the mixing field structure, and the flame front structure were measured, and the correlations between stability and the mixing field structure were investigated. The mixture fraction field was measured in non-reacting jets at the nozzle exit using highly resolved Rayleigh scattering technique, and the flame front was measured in some selected turbulent flames using high-speed Planar Laser-Induced Fluorescence (PLIF) of OH technique. The data show strong correlations between flame stability and the range of mixture fraction fluctuations. The flames are highly stabilized within a mixing field environment with the range of fluctuation in mixture fraction close to the range of the flammability limits. The mixing field structure is also illustrated and discussed using a mixing regime diagram and showed that the scatter of the data of the different cases is consistent with the classified mixing regimes. Lean flames are stabilized in the current slot burner. The flame front structure topology varies consistently

$Research paper thumbnail of Evaluation of partially premixed turbulent flame stability from mixture fraction statistics in a slot burner$

Combustion Science and Technology, Apr 11, 2018

Partially premixed combustion is characterized by mixture fraction inhomogeneity upstream of the ... more Partially premixed combustion is characterized by mixture fraction inhomogeneity upstream of the reaction zone and occurs in many applied combustion systems. The temporal and spatial fluctuations of the mixture fraction have tremendous impact on the combustion characteristics, emission formation, and flame stability. In this study, turbulent partially premixed flames are experimentally studied in a slot burner configuration. The local temperature and gas composition is determined by means of one-dimensional, simultaneous detection of Rayleigh and Raman scattering. The statistics of the mixture fraction are utilized to characterize the impact of the Reynolds number, the global equivalence ratio, the progress of mixing within the flame, as well as the mixing length on the mixing field. Furthermore, these effects are evaluated by means of a regime diagram for partially premixed flames. In this study, it is shown that the increase of the mixing length results in a significantly more stable flame. The impact of the Reynolds number on flame stability is found to be minor.

Energy, 2021

Abstract The scope of this study was twofold: to define the most suitable Egypt's biodiesel s... more Abstract The scope of this study was twofold: to define the most suitable Egypt's biodiesel source, and to assess the impact of this biodiesel source with the addition of carbon nano additives on diesel engine performance and emissions. Environmental Key Performance Indicators were used as metrics to identify the appropriate biodiesel source with respect to several criteria including environmental, economic, ecological, and demographic situation. The most suitable Egypt's biodiesel source was identified from different sources including algae, Jatropha, coffee waste, rice straw, sugarcane, and switchgrass. Then, the production process of biodiesel from this renewable source by transesterification was carried out using chemical catalyst or biocatalyst. Following this, this source's impact with carbon nano additives on the performance and emissions of a 0.825-L single-cylinder diesel engine was further examined at engine loads varying between 0 and 4 kW and 1500 rpm constant engine speed. The carbon nano additives were added at a different mass fractions of 25, 50 and 100 ppm to Jatropha biodiesel and diesel blend (20 % jatropha biodiesel+ 80 % diesel) by volume. The results showed Jatropha as the most efficient biodiesel source among all the tested fuels to be produced in Egypt. Furthermore, the experimental engine test results revealed that Jatropha biodiesel without and with carbon nano additives consistently has a higher brake thermal efficiency and lower brake specific fuel consumption in comparison to that of diesel fuel. Likewise, Jatropha biodiesel without and with carbon nano additives enhanced the engine performance and consequently reduced the exhaust emissions including CO, CO2, HC, NOx, and smoke in comparison to that of diesel fuel.

Combustion Science and Technology, May 3, 2016

before, the objective of the symposium was to give combustion scientists, engineers and students ... more before, the objective of the symposium was to give combustion scientists, engineers and students from Mediterranean as well as from other countries, an opportunity to get together for the dissemination of the international state-of-the-art and recent advances in the field and to enhance future collaborative research activities between scientists from different countries of the region. About 280 scientists from all over the world participated in the meeting. The program included 6 invited lectures, 5 parallel sessions for oral presentation and a poster session. The invited lectures were delivered by well-known experts in the field (J.

Combustion Science and Technology, Apr 23, 2014

The Eighth Mediterranean Combustion Symposium, jointly co-sponsored by the Combustion Institute a... more The Eighth Mediterranean Combustion Symposium, jointly co-sponsored by the Combustion Institute and the International Centre for Heat and Mass Transfer, was held in Cesme, Izmir, Turkey, on Septemb...

Fuel, 2019

Many Nanoparticles (NPs) were reported to significantly enhance the production of biogas from the... more Many Nanoparticles (NPs) were reported to significantly enhance the production of biogas from the anaerobic digestion of organic wastes. Herein, two types of NPs (Ni-Ferrite and Ni-Co-Ferrite) were synthesized using the co-precipitation method and characterized using X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM) with energy dispersive X-ray spectroscopy (EDS) techniques. Three different concentrations (20, 70 and 130 mg/l) of each type were added to separate biogas reactors to study their effect on the biogas production compared to blank reactor. A pressure-based biogas reactor was designed and manufactured specifically to test the effect of the NPs on the anaerobic digestion process. The pressure of the daily produced biogas was monitored using a pressure transducer and the volume of the biogas was calculated at standard conditions of pressure (1.013 bar) and temperature (15°C). The results showed an increase in the biogas production of 6.6%, 5.9% and 32.9% upon the use of Ni-Co-Ferrite NPS at concentrations of 20, 70, and 130 mg/l compared to blank reactor, respectively. In addition, the Ni-Ferrite NPs achieved biogas enhancements of 30.8%, 28.5%, and 17.9% at concentrations of 20, 70 and 130 mg/l, respectively.

The Open Nuclear & Particle Physics Journal

A level of the Nd:YAG oscillator stability has been experimentally determined for different setup... more A level of the Nd:YAG oscillator stability has been experimentally determined for different setups of resonator Q-switches. Performed experiments quantify an influence of an active modulation element on generated laser pulses stability. Different types of saturable absorbers were investigated and improved stability of double switching (active mode locker plus passive saturable absorber mode-locker) was confirmed. The best stability has been achieved with the aid of dual switching of an acousto-opticmodulator and a saturable absorber-dye solution 3955 in ethylalcohol to be used for satellite laser radar station at Helwan city in Egypt. The energy stability of the laser output can improve the accuracy and reliability of the satellite laser ranging station. The oscillator output picosecond pulses resulting from both the saturable absorber dye and three different multiple quantum well (semiconductor) saturable absorbers have been compared.Experimental results revealed that thedye ML51 m...

Energy, Apr 1, 2021

Abstract Enhancement of biogas combustion characteristics will increase the possibility of the di... more Abstract Enhancement of biogas combustion characteristics will increase the possibility of the direct utilization of such an eco-friendly fuel in practical combustors. We report a full study of biogas combustion under partially premixed mode to investigate the stability of biogas free-jet flames using a concentric flow slot burner was used to evaluate the biogas combustion characteristics. Five mixtures of biogas ranging from 0%CO2 up to 40%CO2 were investigated to study the effect of CO2 proportion on the stability of biogas flames. A new well-defined stability procedure was followed by studying the four major observed phenomena in biogas flames: Stable Flame, Partially-lifted Flame, Fully-lifted Flame, and Extinction. Each phenomenon was clearly defined in addition to describing the operating conditions in terms of Reynolds Number (Re) and Equivalence ratio (ϕ). The effect of the premixing ratio (LD) on the combustion stability of biogas flames was also studied for five premixing ratios LD3, LD5, LD7, LD10, and LD16 to optimize the flame stability. The temperature of stable biogas flames was also measured at different CO2 percentages. The results showed that LD10 is the optimum premixing ratio to generate a stable biogas flame at all tested CO2 proportions. Partially premixed combustion in slot burner manages to sustain a stable biogas flame up to 30%CO2. However, increasing the CO2 to 40% eventually led to a weak and unstable flame regardless of the premixing ratio.

Experimental Thermal and Fluid Science, May 1, 2016

Experimental Thermal and Fluid Science, Apr 1, 2007

... Mohy S. Mansour, The American University in Cairo, Cairo, Egypt Pinar Menguc, University of K... more ... Mohy S. Mansour, The American University in Cairo, Cairo, Egypt Pinar Menguc, University of Kentucky, Lexington, KY, USA ... Reaction kinetics of combustion Adel Sarofim, University of Utah, Salt Lake City UT, USA Omer L. Gulder, University of Toronto, ON, Canada ...

Experimental Thermal and Fluid Science, Jul 1, 2018

Partially premixed turbulent flames with non-homogeneous jet of propane were generated in a conce... more Partially premixed turbulent flames with non-homogeneous jet of propane were generated in a concentric flow conical nozzle burner in order to investigate the effect of the coflow on the stability and flame structure. The flame stability is first mapped and then high-speed stereoscopic particle image velocimetry, SPIV, plus OH planar laserinduced fluorescence, OH-PLIF, measurements were conducted on a subset of four flames. The jet equivalence ratio Φ = 2, Jet exit Reynolds number Re = 10,000, and degree of premixing are kept constant for the selected flames, while the coflow velocity, Uc, is progressively changed from 0 to 15 m/s. The results showed that the flame is stable between two extinction limits of mixture inhomogeneity, and the optimum stability is obtained at certain degree of mixture inhomogeneity. Increasing Φ, increases the span between these two extinction limits, while these limits converge to a single point (corresponding to optimum mixture inhomogeneity) with increasing Re. Regardless the value of Φ, increasing the coflow velocity improves the flame stability. The correlation between recessed distance of the burner tubes and the fluctuation of the mixture leads to optimum flame stability. The time averaged SPIV results show that the coflow induces a big annular recirculation zone surrounds the jet flames. The size and the location of this zone is seen to be sensitive to Uc. However, the instantaneous images show the existence of a small vortical structure close to the shear layer, where the flame resides there in the case of no-coflow. These small vertical structures are seen playing a vital role in the flame structure, and increasing the flame corrugation close to the nozzle exit. Increasing the coflow velocity expands the central jet at the expense of the jet velocity, and drags the flame in the early flame regions towards the recirculation zone, where the flame tracks and matches the spatial locations of low axial velocity fluctuations. At downstream, the flame is seen to conform to the passage of large scale structure. At Uc = 10 and 15 m/s, part of the primary reaction zone is rolled up towards upstream burner nozzle, anchoring the flame to the nozzle tip. This indicates that the