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مرکز اطلاعات علمی SID1
اسکوپوس
دانشگاه غیر انتفاعی مهر اروند
ریسرچگیت
strs
Author(s): 

DERMIBAS A.

Issue Info: 
  • Year: 

    2004
  • Volume: 

    30
  • Issue: 

    2
  • Pages: 

    219-230
Measures: 
  • Citations: 

    452
  • Views: 

    37595
  • Downloads: 

    27293
Keywords: 
Abstract: 

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Author(s): 

KIM H.J. | LU G.Q.

Issue Info: 
  • Year: 

    2001
  • Volume: 

    123
  • Issue: 

    -
  • Pages: 

    27-31
Measures: 
  • Citations: 

    408
  • Views: 

    20947
  • Downloads: 

    19410
Keywords: 
Abstract: 

Yearly Impact:

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Author(s): 

Shreekala n. | SRIDHARA S.N.

Issue Info: 
  • Year: 

    2019
  • Volume: 

    12
  • Issue: 

    4
  • Pages: 

    1013-1021
Measures: 
  • Citations: 

    0
  • Views: 

    48720
  • Downloads: 

    53404
Abstract: 

Numerical analysis plays vital role in designing gas turbine combustors for improving its performance. It requires deep understanding of turbulent and multiphase reactive flow physics inside the combustor. Hence present work focusses on numerical investigation of turbulent flow and reactive interaction between liquid spray of aviation kerosene droplets and air for the experimentally investigated combustor configuration. The present analysis results agree well with the experimental test results. Mixture fraction based Probability Density Function flamelet COMBUSTION model is used to solve transport equations by generating the flamelet library for Jet-A fuel. The analysis provides good insight into the multiphase COMBUSTION process and the flow phenomena occurring inside the combustor. Further, COMBUSTION performance CHARACTERISTICS at different design point operations are investigated in the present work keeping the air fuel ratio constant. Results show rise in peak velocity by 2. 5 times and pressure loss factor by 6 for design point operating at higher flow rates in comparison with the baseline design operating point.

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گارگاه ها آموزشی
Issue Info: 
  • Year: 

    2007
  • Volume: 

    NEW SERIES (23)
  • Issue: 

    37
  • Pages: 

    89-97
Measures: 
  • Citations: 

    0
  • Views: 

    968
  • Downloads: 

    295
Keywords: 
Abstract: 

Liquid rocket engines occasionally experience severe pressure fluctuations and flame oscillations resulting in injector damage and total engine failure. High frequency COMBUSTION instability is caused by the coupling between the COMBUSTION process and the COMBUSTION chamber acoustic field. Therefore, knowledge of the COMBUSTION chamber acoustic CHARACTERISTICS is essential in dealing with this phenomenon. An experimental approach for determination of the COMBUSTION chamber acoustic CHARACTERISTICS is outlined here. An acoustic laboratory, consisting of a hemi-anechoic room, sound generation, recording devices and complete three dimensional sweeping capabilities, has been designed and built. The experimental set up and the measurement procedures have been validated by determining natural acoustic modes of several sizes of open and closed ended cylindrical combustor. Such measurements and comparisons have provided insight into acoustic interaction in the three dimensional chamber and the effects of different boundary conditions. The phenomenon of the destruction of standing waves has been observed. Experimental results indicate that, at frequencies where the ratio of the wave length of the standing wave to the diameter of the chamber is about 1/7, the destruction of the standing wave is observed.Acoustic mode shapes and frequencies for combustor chambers, including the convergent part of the nozzle, have been measured and the results have been fitted with modified theoretical relations.

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Issue Info: 
  • Year: 

    2008
  • Volume: 

    6
  • Issue: 

    2
  • Pages: 

    31-38
Measures: 
  • Citations: 

    1
  • Views: 

    3530
  • Downloads: 

    692
Abstract: 

Background and Aim: Job enrichment is a method that has been used to increase employee satisfaction and work motivation. The Hackman and Oldham job CHARACTERISTICS model (1976) has served as the foundation for many job enrichment efforts. In particular, a considerable amount of research has been devoted to the study of the job CHARACTERISTICS-job satisfaction relations. Te purpose of this study was to statistically determine the relation between job CHARACTERISTICS and job satisfaction among employees of hospitals affiliated to Tehran University of Medical Sciences (TUMS) in 2007. Materials and Methods: This study was a cross-sectional one, including 6 TUMS-affiliated hospitals-Emam, Shariati, Baharlo, Ziaeian, Madaen and Azadi. The sample size was 400, consisting of 200 administrative employees (50%), 151 nurses (38%) and 49 physicians (12%). The random sampling and stratified proportional sampling methods were used to select the hospitals and interviewees, respectively. Two questionnaires were developed and used to identify job CHARACTERISTICS and job satisfaction: 1) job diagnostics surveys (JDS) and 2) Hertzberg's job satisfaction questionnaire. The reliability of the questionnaires was ascertained by test-retest using the Pearson correlation coefficient (r = 0.88). Linear-by-linear association and ordinal logistics regression analysis were used for analyzing the data gathered.Results:The relations between the Motivational Potential Score (MPS) and job CHARACTERISTICS (except for feedback) with job satisfaction were statistically significant (p<0.05). Task identity was the most effective determinant of job satisfaction. Conclusion: It appears that all the job CHARACTERISTICS (except feedback) are important determinants of job satisfaction of the hospital employees. Although the work environment is in need of restructuring, it is important to note, from a positive perspective, that the job CHARACTERISTICS discussed in this study are readily amenable to change job satisfaction at the organizational level.

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Issue Info: 
  • Year: 

    2019
  • Volume: 

    5
  • Issue: 

    3
  • Pages: 

    36-45
Measures: 
  • Citations: 

    0
  • Views: 

    35621
  • Downloads: 

    20826
Abstract: 

Tungsten oxide (WO3) and tungsten oxide hydrate (WO3. H2O) nanoparticles were synthesized via microwave-assisted solution COMBUSTION in comparison with the acidic precipitation method. Oxalic acid was used as a surfactant and forming agent in the acidic precipitation method. In addition to oxalic acid, glycine and citric acid were also used as fuels in the microwave-assisted COMBUSTION method. The synthesis process was investigated by thermogravimetric (TG) and Differential Thermal Analysis (DTA) analysis. The obtained nanoparticles were analyzed using the scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The sample synthesized via the acidic precipitation method showed an orthorhombic crystal structure. One of the samples synthesized via the microwave-assisted solution COMBUSTION method was monoclinic and the two others were amorphous. The acidic precipitation method resulted in uniform plate-like structures while the combusted samples indicated irregular spherical morphology. Fourier-transform infrared (FTIR) analysis revealed stretching-vibrating bands relating to W-O bonds in the synthesized tungsten oxide nanoparticles. The bandgap energy of the nanoparticles calculated using UV-Vis spectra and Tauc plot extrapolation increased with decreasing the particle size. The data of reflectance and colorimetry had good agreement with the maximum peak position in the absorption spectra. The results indicated that the acidic precipitation method controls the particle's morphology as well as the size distribution. Although the COMBUSTION of fuels releases a lot of heat, the synthesis by solution COMBUSTION can control the size and shape of the nanoparticles, which can be an appropriate method for mass production of nanoparticles.

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strs
Issue Info: 
  • Year: 

    2018
  • Volume: 

    9
  • Issue: 

    4
  • Pages: 

    457-472
Measures: 
  • Citations: 

    0
  • Views: 

    54807
  • Downloads: 

    52014
Abstract: 

Grate firing is one of the main competing technologies in biomass COMBUSTION for steam and electricity generation. Ashgenerated in the furnace during COMBUSTION process would greatly reduce the boiler thermal performance and may lead tounscheduled shutdown. The focus of this study is to optimize the COMBUSTION CHARACTERISTICS of the mixture of palm kernelshell (PKS) and selected additives (Al2O3, MgO and CaO) to develop a fuel mixture of low ash yield and higher heatingvalue (HHV). D-Optimal Design under Cross Methodology of Design Expert (6. 08) was employed to mix the componentsalongside various particle sizes. The mixed samples were ashed in a muffle furnace (848 K) to a constant weight and theirHHV were determined using Ballistic Bomb Calorimeter. COMBUSTION test based on optimized PKS additive mixture wasconducted with a 5 kW grate furnace from which the effects of varying the ratio of primary to secondary air flow rate ontemperatures and flue gas compositions from the furnace were measured. The ash obtained after COMBUSTION process wascharacterized using X-ray diffraction (XRD) for the purpose of identifying the mineral phase compounds that are present inPKS and PKS-additive ash. The optimum composition obtained for the process was 2. 5, 0. 0, 5. 0, 92. 5% and 5. 50 mm foradditives (Al2O3, MgO, CaO), PKS and particle size, respectively. The composition resulted in lowest ash yield (0. 56%) andHHV (20. 64 kJ/g). The coefficient of determination (R2) (0. 7951 and 0. 7344) and least-square errors (0. 19 and 0. 024) of theprediction model indicated a close fitness to the experiment results obtained for ash yield and HHV. Primary to secondaryair ratio of (40: 60) recorded maximum temperature (1058 K), minimum level of CO (285 ppm) and 6% oxygen. XRD resultsshowed excellent interaction between PKS and additives. The appearance of potassium-alumino silicate (KAlSiO4) in thePKS-additive ash prevented the release of potassium chloride which has the ability to increase ash deposition and corrosion.

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Issue Info: 
  • Year: 

    2015
  • Volume: 

    9
  • Issue: 

    3 (24)
  • Pages: 

    3-12
Measures: 
  • Citations: 

    0
  • Views: 

    657
  • Downloads: 

    129
Abstract: 

Pyrolants are an important class of energetic materials which because of the high energy content and the solid fused residues, serve a remarkably wide range of military and civilian applications. Pyrolant incendiaries can be either fuel rich or provide a surplus of oxidizer to facilitate COMBUSTION of a target substrate. The requirements and CHARACTERISTICS of an incendiary pyrolant not clearly identified. However, the heat of reaction, thermal kinetic data and macroscopic COMBUSTION parameters are of the basic requirements for the designing of these compounds. In this work, for the first time, the multicomponent Al/MnO2/PTFE pyrolant is introduced as an incendiary charge. Thermal reaction kinetics (activation energy, frequency factor, critical temperature and self-accelerating decomposition temperature) were studied with differential scanning calorimetry (DSC). Also this work investigations the macroscopic COMBUSTION behaviors (such as flame speed and ignition delay time) along with experimental results focusing on open burn experimental setup. Results indicate that the incorporation of nano-Al higher than 30%, significantly reduces ignition temperatures and produces unique reaction behavior that can be attributed to a different chemical kinetic mechanism than observed with micron-Al particles.

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Issue Info: 
  • Year: 

    2009
  • Volume: 

    5
  • Issue: 

    14
  • Pages: 

    71-78
Measures: 
  • Citations: 

    0
  • Views: 

    65210
  • Downloads: 

    23181
Abstract: 

Homogeneous Charge Compression Ignition (HCCI) COMBUSTION is a pioneer method of COMBUSTION in which pre-mixed fuel and oxidizer (typically air) are compressed to the point of auto-ignition. HCCI engines can operate with most alternative fuels, especially, dimethyl ether (DME) which has been tested as a possible diesel fuel due to its simultaneously low NOx and PM emissions. In this paper a single zone detailed chemistry COMBUSTION model for determining the time evolution of the homogenous reacting gas mixture in the COMBUSTION chamber and performance CHARACTERISTICS of the engine has been developed. The aim of this paper is to analyse the effect of intake temperature and EGR on the CHARACTERISTICS of auto-ignition and operating window of the HCCI COMBUSTION considering knock and misfire boundaries.

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Author(s): 

Madihi R. | Pourfallah M. | Armin M.

Issue Info: 
  • Year: 

    2020
  • Volume: 

    -
  • Issue: 

    60
  • Pages: 

    77-89
Measures: 
  • Citations: 

    0
  • Views: 

    0
  • Downloads: 

    291
Abstract: 

Reactivity controlled compression ignition (RCCI) is a new COMBUSTION model in which a mixture of fuel inside the cylinder is provided by injection of low reactivity fuel in the fuel inlet manifold and multi-stage injection of high reactivity fuel inside the cylinder. By changing the engine input parameters and determining the conditions, this study attempted to approximate a biodiesel dual-fuel (C11H22O2) / natural gas engine to the COMBUSTION phase of reactivity controlled compression ignition (RCCI) to examine and compare the efficiency and output emissions. The understudy influencing factors included the comparison between the biodiesel-natural gas and diesel-natural gas fuels with similar energy generation, relevant strategies, and fuel emission rate. In this research, the 3401E Caterpillar engine geometry was employed for the numerical simulation by the commercial Converge Software and SAGE COMBUSTION model. The results showed that, due to the high Cetane number and high oxygen present in its composition, the biodiesel fuel gave rise to earlier COMBUSTION as compared with diesel. The injection time precession, shortened injection time, and increased injection rate in the first phase increased pressure, average temperature, and the heat release rate, and the power and yield of COMBUSTION enhanced. Likewise, due to complete COMBUSTION, the rates of output emissions, including CO2, HC, and soot, decreased.

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