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SRM performance improvement: Erosive burning phenomenon
, Article AIAA/ASME/SAE/ASEE 42nd Joint Propulsion Conference, Sacramento, CA, 9 July 2006 through 12 July 2006 ; Volume 10 , 2006 , Pages 7649-7653 ; 1563478188 (ISBN); 9781563478185 (ISBN) ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2006
Abstract
In this paper, the internal ballistics of solid propellant rocket motor with an arbitrary grain configuration is numerically investigated using quasi one dimensional simulation of Inviscid conservation equations. The upwind Roe's scheme is used to calculate the convective fluxes. Appropriate burning rate model to predict the erosive burning in solid propellant is used here. By using this phenomenon and accurate simulation, tactical motor performance can be considerably improved
Optimal apogee burn time for low thrust spinning satellite in low altitude
, Article European Journal of Operational Research ; Volume 222, Issue 2 , 2012 , Pages 386-391 ; 03772217 (ISSN) ; Assadian, N ; Sharif University of Technology
2012
Abstract
In this study, the optimal burn time for low-thrust impulsive propulsion systems is investigated to raise the perigee altitude of a low-Earth orbit. The maneuver is done using spin-stabilized attitude control and impulsive thrusting system for a time interval centered about apogee point. On the one hand, the low value of the thrust level causes more burn time needed to accomplish the transfer. This, in turn, will cause more thrust loss due to the deviation between the thrust axis (spin axis) and the velocity vector of the satellite. On the other hand, for small thrust duration, the transfer needs more revolutions around the Earth and more travel in lower altitudes with dense atmosphere and...
Optimal power generation from low concentration coal bed methane in Iran
, Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Volume 38, Issue 4 , 2016 , Pages 590-596 ; 15567036 (ISSN) ; Fahimi, M ; Saboohi, Y ; Sharif University of Technology
Taylor and Francis Inc
2016
Abstract
Development of a model for optimal power generation from the thermal oxidation of a low concentration coal bed mine has been considered as the main objective of this investigation. The model has been applied to identify the optimal thermodynamic characteristics of the power generation system through using a mixture with 1.6% methane concentration in a recuperative lean-burn gas turbine and coupling a gas engine to the system for more power generation from the remaining coal bed methane. The implementation of the model based on the real site condition would lead to the generation of 6.97 MW electricity in Tabas coal mine of Iran. © 2016 Taylor & Francis
Experimental Study of Acceleration Effect on Combustion Chamber Pressure Field
, M.Sc. Thesis Sharif University of Technology ; Farahani, Mohammad (Supervisor) ; Mohammadi, Alireza (Co-Supervisor)
Abstract
This thesis is conducted to study acceleration effect on the burning rate augmentation of a solid propellant. A centrifugal experimental setup is designed to obtain a uniform acceleration field. An internal burning tube is used as grain, so acceleration vector is always perpendicular to burning surface of propellant. Inner radius of tube is small, so the magnitude of acceleration increases as the grain burns back. The pressure of combustion chamber was changed from 30 bar to 80 bar by changing the nozzle throat and the magnitude of acceleration changed from 2g to 60g by changing the rotational speed of SRM. Burning time of all tests was below 2 sec. due to small web of the grain. Pressure of...
Validation of a new MCNP-ORIGEN linkage program for burnup analysis
, Article Progress in Nuclear Energy ; Volume 63 , 2013 , Pages 27-33 ; 01491970 (ISSN) ; Abbaspour, A ; Pazirandeh, A ; Sharif University of Technology
2013
Abstract
The analysis of core composition changes is complicated by the fact that the time and spatial variation in isotopic composition depend on the neutron flux distribution and vice versa. Fortunately, changes in core composition occur relatively slowly and hence the burnup analysis can be performed by dividing the burnup period into some burnup spans and assuming that the averaged flux and cross sections are constant during each step. The burnup span sensitivity analysis attempts to find that how much the burnup spans could be increased without any significant deviation in results. This goal has been achieved by developing a new MCNP-ORIGEN linkage program named as MOBC (MCNP-ORIGEN Burnup...
Fire dynamics simulation of multiple ethanol poll fires
, Article Research Journal of Chemistry and Environment ; Volume 17, Issue 9 , 2013 , Pages 3-9 ; 09720626 (ISSN) ; Bab, V ; Rashtchian, D ; Reniers, G ; Sharif University of Technology
2013
Abstract
In this study, a well-known Computational Fluid Dynamics software, so-called Fire Dynamics Simulator (FDS), has been used to simulate multiple ethanol pool fire scenarios. Influences and reciprocal impacts in terms of dynamics and growth of the pool fires have been investigated. Heat release rates temperature and flame shapes have been monitored as the main outputs of the simulations. Based on the simulation results, it can be concluded that the amounts of mass burning rate, the radiation energy and the pool fire flame height were significantly higher in multiple pool fires, when compared with the theoretical values obtained by the mere summation of single pool fires. Furthermore, the...
Calculation of fuel burn up and radioactive inventory for HEU fuel element of Tehran Research Reactor
, Article International Conference on Nuclear Engineering, Proceedings, ICONE, 17 May 2010 through 21 May 2010 ; Volume 2 , 2010 ; 9780791849309 (ISBN) ; Vosoughi, N ; Hosseini, M ; Nuclear Engineering Division ; Sharif University of Technology
Abstract
This paper presents a new approach for fuel burn up evaluation and radioactive inventory calculation used in Tehran Research Reactor. The approach is essentially based upon the utilization of a program written by C# which integrates the cell and core calculation codes, i.e., WIMSD-4 and CITVAP, respectively. Calculation of fuel burn up and radioactive inventories has been done for 26 core configuration of Tehran Research Reactor with HEU fuel element. The present inventory and fuel enrichment of each fuel element have been calculated
A theoretical analysis of the effects of erbium ion pair on the dynamics of an optical gain stabilized fiber amplifier
, Article Optics Communications ; Volume 265, Issue 1 , 2006 , Pages 283-300 ; 00304018 (ISSN) ; Mahjoei, M ; Rasouli, A ; Sharif University of Technology
2006
Abstract
In this paper, the effects of ion-pair formation on the gain dynamics of multi cavity optical automatic gain control erbium doped fiber amplifier is modelled. The inhomogeneous Cabezas simple model is used to write the rate and propagation equations for the active medium. The solution of the governing equations shows that in high concentration of the erbium ions, depending on the pumping rate, the relaxation oscillations are converted to nT-Periodic or even to chaotic behavior. Although the high concentration erbium ion in the optical amplifiers decreases the conversion efficiency and increases the threshold pump power, amplitude of the transient effects is reduced in the multi feedback-loop...
Effect of Air by Oxygen Enrichmenton Burning Rate of Polyethylen in Vortex Ramjet
, M.Sc. Thesis Sharif University of Technology ; Ghafoorian, Akbar (Supervisor) ; Ghorbanian, Kaveh (Supervisor) ; Saeedi, Mohammad Hassan (Co-Advisor) ; Mozaffari, Ali Asghar (Co-Advisor)
Abstract
Bidirectional axial vortex flow and air enriched with oxygen are used in order to increase solid fuel burning rate in both subsonic and supersonic ramjet engines experimentally. Vortex flow enhances combustion by causing erosive burning on the surface of the solid fuel. Air enriched by oxygen increases the combustion temperature. Therefore, they make the usage of subsonic ramjet engines possible for applications in which a low thrust is need for a long duration. An experimental ramjet engine with the capability of simulating subsonic and supersonic flight conditions was designed and fabricated. Polyethylene and oxygen enriched air are used as solid fuel and oxidizer respectively. ...
Conceptual Design of a Solid Propellant Nanolauncher
, M.Sc. Thesis Sharif University of Technology ; Farahani, Mohammad (Supervisor) ; Mohammadi, Alireza (Co-Supervisor)
Abstract
Nanolaunchers are launch vehicles capable of carring light payloads (under 50 kg) to Low Earth orbit and received much attention in the few past years. Launching the nanosatellites grown about 30 times from 2008 to 2017. Since this category of launch vehicles has fewer developing costs and lower thechnology level, they fit developing space technology in our country. Conversely, the demand of high propellant mass fraction and specific impulse may be a serious difficulty to attain this technology.The only operating nanolauncher in the world is SS-520-5 which belongs to Japan and is a three-stage solid propellant launcher. The goal of this project is also the conceptual design and feasiblity...
Thermodynamic modeling of partially stratified charge engine characteristics for hydrogen-methane blends at ultra-lean conditions
, Article International Journal of Hydrogen Energy ; Volume 38, Issue 25 , August , 2013 , Pages 10640-10647 ; 03603199 (ISSN) ; Chitsaz, I ; Mozafari, A. A ; Sharif University of Technology
2013
Abstract
A thermodynamic model considering flame propagation is presented to predict SI engine characteristics for hydrogen-methane blends. The partially charge stratification approach which involves micro direct injection of pure fuel or a fuel-air mixture, to create a rich zone near the spark plug, is proposed as a method to improve engine performance. Presented approach was validated with experimental data for the natural gas at lean condition. The model was generalized to predict the performance of engine for a variety of hydrogen contents in hydrogen-methane blends. Hydrogen molar concentrations of 0%, 15%, 30%, and 45% were used in the simulations. Results showed that partially charge...
Comparison of synthesis and purification of carbon nanotubes by thermal chemical vapor deposition on the nickel-based catalysts: NiSio2 and 304-type stainless steel
, Article Journal of Applied Sciences ; Volume 10, Issue 9 , 2010 , Pages 716-723 ; 18125654 (ISSN) ; Jafari, A ; Fekri, S ; Shafikhani, A ; Vesaghi, M ; Behzadi, G ; Sharif University of Technology
2010
Abstract
In this study by Thermal Chemical Vapor Deposition (TCVD) method, the synthesis of carbon nanotubes (CNTs) and temperature affects on the grown CNTs on the NiSio2 catalyst and 304-type stainless steel was investigated. The purification of the grown CNTs on the 304-type stainless steel was also investigated in this study. The synthesis and purification of the samples were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), termogravimetric analysis (TGA) and Raman spectroscopy. Our obtained result by SEM and TEM shows that densities of CNTs growth on the 304-type stainless steel are more than the CNTs growth on the NiSio2 catalyst and both of them have...
Experimental study of fuel regression rate in an HTPB/N2O hybrid rocket motor
, Article Scientia Iranica ; Volume 25, Issue 1 , 2018 , Pages 253-265 ; 10263098 (ISSN) ; Soltani, M. R ; Mohammadi, A. R ; Sharif University of Technology
Sharif University of Technology
2018
Abstract
The performance of an HTPB/N2O hybrid motor was experimentally investigated. A hybrid motor was designed and manufactured in a laboratory with the purpose of studying the effects of various parameters on the motor's performance, including fuel regression rate and specific impulse. A series of tests were conducted to find a correlation between the fuel regression rate and the oxidizer's mass flux. The effects of chamber's pressure on the regression rate as well as other performance parameters were investigated. While the burning rate did not change dramatically, both the efficiency and ISP of the motor increased. The local fuel regression rate and the fuel port were also calculated. In...
Improvement and experimental validation of a multi-zone model for combustion and NO emissions in CNG fueled spark ignition engine
, Article Journal of Mechanical Science and Technology ; Volume 26, Issue 4 , 2012 , Pages 1205-1212 ; 1738494X (ISSN) ; Hannani, S. K ; Ebrahimi, R ; Sharif University of Technology
2012
Abstract
This article reports the experimental and theoretical results for a spark ignition engine working with compressed natural gas as a fuel. The theoretical part of this work uses a zero-dimensional, multi-zone combustion model in order to predict nitric oxide (NO) emission in a spark ignition (SI) engine. The basic concept of the model is the division of the burned gas into several distinct zones for taking into account the temperature stratification of the burned mixture during combustion. This is especially important for accurate NO emissions predictions, since NO formation is strongly temperature dependent. During combustion, 12 products are obtained by chemical equilibrium via Gibbs energy...
Nanomedicine and advanced technologies for burns: Preventing infection and facilitating wound healing
, Article Advanced Drug Delivery Reviews ; Volume 123 , 2018 , Pages 33-64 ; 0169409X (ISSN) ; Sahandi Zangabad, P ; Moosavi Basri, S. M ; Sahandi Zangabad, K ; Ghamarypour, A ; Aref, A. R ; Karimi, M ; Hamblin, M. R ; Sharif University of Technology
Elsevier B.V
2018
Abstract
According to the latest report from the World Health Organization, an estimated 265,000 deaths still occur every year as a direct result of burn injuries. A widespread range of these deaths induced by burn wound happens in low- and middle-income countries, where survivors face a lifetime of morbidity. Most of the deaths occur due to infections when a high percentage of the external regions of the body area is affected. Microbial nutrient availability, skin barrier disruption, and vascular supply destruction in burn injuries as well as systemic immunosuppression are important parameters that cause burns to be susceptible to infections. Topical antimicrobials and dressings are generally...
Calculation of the fuel composition and the thermo-neutronic parameters of the Bushehr's VVER-1000 reactor during the initial startup and the first cycle using the WIMSD5-B, CITATION-LDI2 and WERL codes
, Article Annals of Nuclear Energy ; Volume 57 , 2013 , Pages 68-83 ; 03064549 (ISSN) ; Pazirandeh, A ; Ghofrani, M. B ; Sadighi, M ; Sharif University of Technology
2013
Abstract
In this paper, the concentrations of fission products and fuel isotopes as well as the changes of the thermo-neutronic parameters of the Bushehr's VVER-1000 reactor were studied during the initial startup and the first cycle. In order to perform the time-dependent cell calculations and obtain the concentration of fuel elements, the WIMSD5-B code was used. Besides, by utilizing the CITATION-LDI2 code, the effective multiplication factor and the thermal power distribution of the reactor were calculated. A computer program (WERL code) was designed in order to perform accurate calculation of the temperature distribution of the reactor core. For this purpose, the Ross-Stoute, Weisman, and...
Design and manufacturing of a constant volume test combustion chamber for jet and flame visualization of CNG direct injection
, Article Applied Mechanics and Materials ; Volume 217-219 , 2012 , Pages 2539-2545 ; 16609336 (ISSN) ; 9783037855027 (ISBN) ; Ahmadisoleymani, S. S ; Abdullah, A ; Asgari, O ; Rezai, F
2012
Abstract
Constant volume transparent test combustion chambers are extensively used for investigating injection and fuel burning properties of various combustion engines. Their configuration depends on the engine type and the research purpose. Material of components, shape and dimensions of the chamber and its parts, ease of use, accessibility, sealing and safety of the assembly are the parameters needed to be considered in designing the test cell. This paper explains, structural design of a test combustion chamber and its optical windows using finite element analysis of ANSYS 12.0 software for bearing high pressure variations and thermal shocks of combustion. It was designed for conducting CNG direct...
Calculation, measurement and sensitivity analysis of kinetic parameters of tehran research reactor
, Article Annals of Nuclear Energy ; Volume 37, Issue 4 , April , 2010 , Pages 463-470 ; 03064549 (ISSN) ; Vosoughi, N ; Ghofrani, M. B ; Gharib, M ; Sharif University of Technology
2010
Abstract
Effective delayed neutron fraction βeff and neutron generation time Λ are important factors in reactor physics calculation and transient analysis. In the first stage of this research, these kinetic parameters have been calculated for two states of Tehran Research Reactor (TRR), i.e. cold (fuel, clad and coolant temperatures equal to 20 °C) and hot (fuel, clad and coolant temperatures of 65, 49 and 44 °C, respectively) states using MTR_PC code. In the second stage, these parameters have been measured with an experimental method based on Inhour equation. For the cold state, calculated βeff and Λ by MTR_PC code are 0.008315 and 30.190 μs, respectively. In the hot state, these parameters being...
Sensitivity analysis of kinetics parameters of Tehran Research Reactor (TRR)
, Article 17th International Conference on Nuclear Engineering, 12 July 2009 through 16 July 2009 ; Volume 5 , 2009 , Pages 419-423 ; 9780791843550 (ISBN) ; Vosoughi, N ; Nuclear Engineering Division, ASME; The Japan Society of Mechanical Engineers, JSME; The Chinese Nuclear Society, CNS ; Sharif University of Technology
Abstract
In this research, effective delayed neutron fraction (βeff) and neutron generation time (A) of the Tehran Research Reactor (TRR) are calculated for different uranium enrichments from 14.84 w/o to 96.56 w/o U 235 in two states of the TRR, (cold fuel, clad and coolant temperature of 20°C; and hot fuel, clad and coolant temperature of 65, 49 and 44°C, respectively) using the MTR-PC computer code. Comparative analysis shows that both βeff and Λ increase as fuel enrichment decreases. However, variation rate βeff is not the same in two conditions. βeff in the hot state is larger than those calculated in the cold state when fuel enrichment goes more than 83.91%, while the situation is reverse for...
Theoretical and experimental modeling of vortex engine in ramjet application
, Article 45th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 2 August 2009 through 5 August 2009, Denver, CO ; 2009 ; 9781563479762 (ISBN) ; Ghafourian, A ; Saidi, M. H ; Mozafari, A. A ; Sharif University of Technology
Abstract
A new experimental facility was designed, fabricated and tested to model and study the possibility of applying the bidirectional swirl flow on the combustion chamber of airbreathing subsonic ramjet engine. Appropriate intake was designed to convert axial external air to tangential swirl flow inside the combustion chamber. Inlets with appropriate angles conduct the swirl flow into the chamber and create bidirectional swirl flow field in the combustion chamber. This flow field has been modeled theoretically to determine the velocity field characteristics by previous researchers. Bidirectional swirl flow in liquid fuel ramjet engines has the proven advantage of keeping the combustion chamber...