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Evaluation of pressure oscillations by a laboratory motor

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Chinese Journal of Aeronautics 2020年第3期33卷 805-825页

作者： roohollah TAHERINEZHAD Gholamreza ZAREPOUR Department of Mechanical Engineering University of GuilanRasht 51665-315Iran

Aeroacoustic pressure oscillation is one of the important challenges in segmented solid rocket motors with high slenderness *** reason for these oscillations can be searched in vortex shedding due to grain burning surfaces, holes and *** this paper, a novel sub-scaled motor was used for evaluation of aeroacoustic pressure ***, the related parameters to scale down using Buckingham's Pi-theorem were determined and then the sub-scaled motor was designed and *** this, Strouhal number in various grain forms and vortex shedding prediction criteria have been ***, one-dimensional linear and non-linear solution approaches have been *** understand the motor internal flow and vortex shedding formation, steady state computational fluid dynamic performed for seven regression steps and finally, two static tests have been *** show that various definitions for Strouhal number are useful only for primarily glance on vortex shedding and pressure oscillations and so CFD solution and the test program are inevitable for a correct understanding of the ballistic operational condition of the *** results demonstrated the existence of such oscillations with frequencies nearly equal to axial *** seems that non-linear parameters have small effects on aeroacoustic pressure oscillation and therefore the linear solution is acceptable to obtain approximate *** course,it should be emphasized that linear solution represents oscillations on overall motor action time,whereas the output of non-linear solution depends on thermochemistry properties of solid propellant and combustion ***, with a non-linear solution, oscillations maybe occur in some intervals of action ***(Fast Fourier Transformation) results demonstrated that although both first and second acoustic modes have been excited, the position of longitudinal oscillation has an important role on which one is dominant.

关键词： Aeroacoustic Pressure oscillation Solid rocket motor Strouhal number Sub-scale Vortex shedding

Investigation of a novel pyrogenic pulser in a laboratory motor

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Chinese Journal of Aeronautics 2020年第1期33卷 134-148页

作者： roohollah TAHERINEZHAD Gholamreza ZAREPOUR Department of Mechanical Engineering University of GuilanRasht 51665-315Iran

In this paper,a novel pyrogenic pulser was designed both analytically and numerically and was evaluated with empirical *** motivation of this study was the need for active control of the aero acoustic pressure oscillations by injecting the secondary flow into the solid rocket ***,in brief,pyrotechnic and pyrogenic pulsers were introduced,and then analytical governing equations were presented in three transient,sinusoidal and Hercules *** order to understand the internal pressure of the pulsar and its plume length,the injection flow field was evaluated using the ANSYS-Fluent software with both k-ωSST and k-εRealizable models both at ambient and motor *** that,the design and manufacturing of the pulser hardware and the test process were ***,analytical,numerical and experimental results were *** results show that there is a good correlation between the transient analysis in theory and the numerical solution by the k-ωSST model and the empirical test *** addition,pyrogenic pulsers design depends on various parameters of motor and pulser charge performance *** quality of pulser charge bonding to its insulator and erosion of its throat path due to injection have an important role to obtain a desirable pulser mass flow rate and plume length.

关键词： Aero acoustic Pressure oscillation Pyrogenic pulsers Secondary injection Solid rocket motors

Microstructure and mechanical properties of AA6063 aluminum alloy wire fabricated by friction stir back extrusion(FSBE) process

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International Journal of Minerals,Metallurgy and Materials 2019年第8期26卷 1005-1012页

作者： Ghasem Jamali Salman Nourouzi roohollah Jamaati Department of Materials Engineering Babol Noshirvani University of Technology

In the present work,the friction stir back extrusion(FSBE)process was used as a novel method for the fabrication of AA6063 aluminum alloy *** electron microscopy(SEM)equipped with energy dispersive spectroscopy(EDS),tensile and hardness tests were *** FSBE via the rotational speed of 475 r/min resulted in fine equiaxed grains,and the mean grain size decreased from 179.0μm to 15.5μm due to the occurrence of dynamic recrystallization(DRX).Heat generated by the FSBE changed the size and volume fraction of the Mg2Si precipitated *** minimum particle size and maximum volume fraction obtained in the sample were processed by rotational speeds of 475 and 600 r/min,*** 475-r/min sample had the maximum hardness value due to having the lowest grain size(i.e.,15.5μm)and the presence of many fine Mg2Si precipitates in the aluminum *** increasing rotational speed up to 600 r/min,the hardness decreased,owing to the growth of both grains and *** FSBE process with a rotational speed of 475 r/min increased the tensile strength(from 150 to 209 MPa)and ductility(from 21.0%to 30.2%)simultaneously.

关键词： aluminum alloys friction stir back extrusion microstructure mechanical properties

Analytical model of sound transmission through laminated composite cylindrical shells considering transverse shear deformation

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Applied Mathematics and Mechanics(English Edition) 2008年第9期29卷 1165-1177页

作者： Kamran Daneshjou Ali Nouri roohollah Talebitooti Department of Mechanical Engineering Iran University of Science and TechnologyNarmak

Composite structures are often used in the aerospace industry due to the advantages offered by a high strength to weight ratio. Sound transmission through an infinite laminated composite cylindrical shell is studied in the context of the transmission of airborne sound into the aircraft interior. The shell is immersed in an external fluid medium and contains internal fluid. Airflow in the external fluid medium moves with a constant velocity. An exact solution is obtained by simultaneously solving the first-order shear deformation theory （FSDT） of a laminated composite shell and the acoustic wave equations. Transmission losses （TL） obtained from numerical solutions are compared with those of other authors. The effects of structural properties and flight conditions on TL are studied for a range of values, especially, the Mach number, stack sequences, and the angle of warp. Additionally, comparisons of the transmission losses are made between the classical thin shell theory （CST） and FSDT for laminated composite and isotropic cylindrical shells.

关键词： plane wave transmission loss laminated composite shell first-order

Effect of salts and their interaction with ingenious surfactants on the interfacial tension of crude oil/ionic solution

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Chinese Journal of Chemical Engineering 2020年第1期28卷 224-235页

作者： Mostafa Lashkarbolooki roohollah Parvizi Shahab Ayatollahi Ebrahim Ghaseminejad Raeeni School of Chemical Engineering Babol Noshirvani University of TechnologyBabolIran Department of Chemical Engineering Islamic Azad UniversityIran School of Chemical and Petroleum Engineering Sharif University of TechnologyTehranIran National Iranian South Oil Company Iran

Understanding the roles of asphaltene and resin as natural surfactants existed in crude oil can enlighten contradicting reported results regarding interfacial tension(IFT) of crude oil/aqueous solution as a function of salinity and ion type. In this way, this study is aimed to investigate the effect of these natural surface active agents on IFT of with special focus on SO4^2-anion and Mg^2+cation. Two different synthetic oil solutions of 8 wt% of the extracted asphaltene and resin dissolved in toluene are prepared, and then IFT values are measured. After that,the obtained results are compared with the IFT of intact crude oil in contact with the same saline solutions examined in the previous stage. The obtained results showed a synergistic effect of Na2SO4+ MgCl2 solution unlike the MgSO4+ MgCl2 and CaSO4+ MgCl2 solutions on IFT reduction of resin at MgCl2 concentration of 15000 mg·kg^-1. In summary, it is found that the affinity of asphaltene molecules towards the interface of oleic phase/ionic solution leads to higher IFT variation.

关键词： IFT Resin Asphaltene Mg^2+ SO4^2-

Power quality assessment in different wind power plant models considering wind turbine wake effects

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Clean Energy 2023年第4期7卷 843-858页

作者： Mohsen Khatamiaghda Saeed Bahraminejad roohollah Fadaeinedjad Department of Electrical and Computer Engineering Graduate University of Advanced TechnologyKermanIran

The intense increase in the installed capacity of wind farms has required a computationally efficient dynamic equivalent model of wind *** types of wind-farm modelling aim to identify the accuracy and simulation time in the presence of the power *** this study,dynamic simulation of equivalent models of a sample wind farm,including single-turbine representation,multiple-turbine representation,quasi-multiple-turbine representation and full-turbine representation models,are performed using a doubly-fed induction generator wind turbine model developed in DIgSILENT *** developed doubly-fed induction generator model in DIgSILENT is intended to simulate inflow wind turbulence for more accurate *** wake effects between wind turbines for the fullturbine representation and multiple-turbine representation models have been considered using the Jensen *** developed model improves the extraction power of the turbine according to the layout of the wind *** accuracy of the mentioned methods is evaluated by calculating the output parameters of the wind farm,including active and reactive powers,voltage and instantaneous flicker *** study was carried out on a sample wind farm,which included 39 wind *** simulation results confirm that the computational loads of the single-turbine representation(STR),the multiple-turbine representation and the quasi-multiple-turbine representation are 1/39,1/8 and 1/8 times the full-turbine representation model,*** the other hand,the error of active power(voltage)with respect to the full-turbine representation model is 74.59%(1.31%),43.29%(0.31%)and 7.19%(0.11%)for the STR,the multiple-turbine representation and the quasi-multiple representation,respectively.

关键词： wind-farm models DIgSILENT software flicker intensity wake effect DFIG turbine

Routine magnetic resonance cholangiography compared to intra-operative cholangiography in patients with suspected common bile duct stones

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Hepatobiliary & Pancreatic Diseases International 2008年第5期7卷 525-528页

作者： Fariborz Eshghi roohollah Abdi Department of General Surgery Faculty of MedicineMazandaran University of Medical SciencesSariIran Department of Radiology Faculty of MedicineMazandaran University of Medical SciencesSariIran

BACKGROUND:Magnetic resonance cholangiography (MRC)is a non-invasive method for imaging biliary *** used to exclude common bile duct(CBD) stones,MRC may obviate the need for intra-operative cholangiography(IOC).In this prospective study,MRC and IOC were compared for the diagnosis of suspected stones of the CBD. METHODS:Thirty patients with gallstones and suspected CBD lithiasis(abnormal serum liver tests and CBD>7 mm on ultrasound)had MRC followed by open cholecystectomy and *** imaging was done using a 1.5-T whole body scanner(Signa,General Electric Medical Systems).A torso phased-array coil with a 4-channel receiver was used for data acquisition. RESULTS:Over a period of 18 months,30 patients(average age 53.9±13.3 years;range 38-76 years)were enrolled in this *** patients were male(36.7%)and 19 female(63.3%).MRC revealed CBD stones in 19 patients, while IOC revealed CBD stones in *** sensitivity of MRC in detecting CBD stones was 81.8%,and the specificity was 87.5%.The positive predictive value was 94.7%,and the negative predictive value was 63.3%. CONCLUSIONS:Pre-operative MRC may obviate the need for *** reduces operative time,is less invasive, and may also alleviate damage to the CBD that can occurduring *** can identify CBD stones pre-operatively and can help surgeons plan safe ***-operative MRC should be done routinely in patients whose clinical or biochemical findings suggest the possibility of CBD stones.

关键词： cholelithiasis magnetic resonance cholangiography cholangiography

Enhanced removal of benzene in nonthermal plasma with ozonation, flow recycling, and flow recirculation

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Plasma Science and Technology 2019年第9期21卷 91-100页

作者： roohollah ROSTAMI Gholamreza MOUSSAVI Sara DARBARI Ahmad JONIDI JAFARI Research Center for Health Sciences and Technologies Semnan University of Medical Sciences Semnan *** Iran Department of Environmental Health Engineering Faculty of Medical Sciences Tarbiat Modares University Tehran *** Iran ECE Department Tarbiat Modares University Tehran *** Iran Department of Environmental Health Engineering Faculty of Health Iran University of Medical Sciences Tehran *** Iran

A double stage AC/DC sequential high voltage reactor has been developed to study the decomposition of benzene in the air stream at atmospheric pressure. The removal efficiency was measured as a function of ozonation, flow recycling, and flow recirculation. Ozonation in the inlet, and recycling of the exhaust stream increased the removal of benzene, also with increasing of specific input energy(J l^-1) the effect of inlet flow ozonation on benzene decomposition was enhanced. The highest removal efficiency was obtained up to >99% in recirculation six times,while CO2 selectivity reached 99.9% and energy efficiency was 0.59 g kWh^-1. O3 production/decomposition > production of OH radicals > electronic and ionic collisions were indicated as the main mechanisms influencing benzene abatement in this research.

关键词： plasma benzene positive corona air pollution

Long term exposure to ambient air particulate matter and mortality effects in Megacity of Tehran,Iran:2012-2017

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Particuology 2021年第5期19卷 139-146页

作者： Mehdi Fazlzadeh roohollah Rostami Fatemeh Yousefian Masud Yunesian Hosna Janjani Social Determinants of Health Research Center Ardabil University of Medical SciencesArdabilIran Research Center for Health Sciences and Technologies Semnan University of Medical SciencesSemnanIran Department of Environmental Health Engineering School of Public HealthTehran University of Medical SciencesTehranIran Department of Research Methodology and Data Analysis Institute for Environmental ResearchTehran University of Medical SciencesTehranIran

Ambient particulate matter(PM)is the major environmental concern in Tehran,*** to such particles is a serious global health concern and substantial evidence indicates that exposure to particulate matter contributes to cardiovascular and respiratory ***,we provide a detailed health impact of ambient air pollution in Tehran by linking PM pollution with mortality caused by cardiovascular and respiratory *** quality data of PM obtained from Tehran Air Quality Monitoring Stations(TAQMSs)during 2012–*** mining methods conducted by Spatio-temporal outlier detection and“Air Pollution and Health:a European Approach(APHEA)project”was applied to impute missing ***-series data were analyzed to estimate the associations between PM pollution and cause-specific mortality at different lags in *** on descriptive analysis,PM_(2.5) is expected to be a major influencing factor in the increased cardiovascular-related death(CVD)and respiratory dysfunction related death(RD)*** cross-correlation analysis showed the same source for PM_(2.5) and PM_(10) in the ambient air of ***,the results indicated delays of about 7-15 days from the increased concentrations of PMs and the observed rising in CVD and RD *** analysis showed a more decreasing trend for PM_(2.5) pollutions than PM_(10) pollution and a slightly increasing trend for cause-specific deaths during *** term exposure to high PM levels increases the CVD and RD deaths and control strategies along with control regulations should be considered to control PM.

关键词： Air pollution Particulate matter Cardiovascular related death Respiratory dysfunction related death Tehran