Search for: depressurizations
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    Thrust termination dynamics of solid propellant rocket motors

    , Article Journal of Propulsion and Power ; Volume 23, Issue 5 , 2007 , Pages 1141-1142 ; 07484658 (ISSN) Tahsini, A. M ; Farshchi, M ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc  2007
    Thrust termination dynamics of a solid propellant rocket motor that is crucial to the performance of the rocket has been analyzed. Active thrust termination or reversing of a separating motor facilitate the staging process and enhance the performance of a multistage rocket. This can be achieved by opening a secondary nozzle located on the motor head and causing rapid depressurization of the motor chamber. The strong dependence of the solid propellant burning rate on the chamber pressure causes a transient nonlinear behavior that can result in premature dynamic extinguishments of the motor. It was confirmed that there is a maximum achievable level of equilibrium reverse thrust due to... 

    A risk-based decision making approach to determine fireproofing requirements against jet fires

    , Article Journal of Loss Prevention in the Process Industries ; Volume 26, Issue 4 , 2013 , Pages 771-781 ; 09504230 (ISSN) Badri, N ; Rad, A ; Kareshki, H ; Abdolhamidzadeh, B ; Parvizsedghy, R ; Rashtchian, D ; Sharif University of Technology
    API Publication 2218 is one of the most referred practices for fireproofing of onshore structural supports. Despite the extensive citation, it solely considers the effects of pool fire and rarely addresses jet fire outcomes. This absence of an explicit approach is common among all the other major references. Therefore, the basic objective of this paper is to introduce a new approach for determination of the necessity for fireproofing of structural supports against jet fires. For this purpose, the flame geometry and duration of jet fires are simulated for different leak sizes in identified fire potential sources. Then, following a worst-case analysis, those structures that may be impinged by... 

    Rapid depressurization dynamics of solid propellant rocket motors

    , Article 43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference, Cincinnati, OH, 8 July 2007 through 11 July 2007 ; Volume 8 , 2007 , Pages 7871-7879 ; 1563479036 (ISBN); 9781563479038 (ISBN) Tahsini, A. M ; Farshchi, M ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc  2007
    Transient internal ballistics of a solid propellant rocket motor during rapid depressurization due to opening of an auxiliary nozzle for active thrust termination has been considered in this work. Prediction of thrust termination and reversing dynamics is required for successful stage separation in multi-stage rockets. Quasi one-dimensional unsteady Euler equation with a transient propellant burning model that accounts for the effects of time rate of change of the chamber pressure on the burning rate have been used to simulate the internal ballistics of a rocket motor. The compressible convective flow solver used in this study is based on Roe's scheme. The effects of rapid chamber pressure... 

    Equilibrium and non-equilibrium gas–liquid two phase flow in long and short pipelines following a rupture

    , Article AIChE Journal ; Volume 63, Issue 7 , 2017 , Pages 3214-3223 ; 00011541 (ISSN) Nouri Borujerdi, A ; Shafiei Ghazani, A ; Sharif University of Technology
    John Wiley and Sons Inc  2017
    The two-phase flow following the blowdown of pipeline carrying flashing liquid is numerically investigated by using thermodynamic equilibrium and non-equilibrium models. Model equations are solved numerically by the finite volume method. The values of fluxes at cell boundaries are obtained by AUSM+-up. To obtain proper values for the coefficients of dissipation, both single phase liquid and two phase shock tube problems are investigated. The transient release from the pressurized pipeline is studied for two cases of long and short pipes. Comparison of the predictions against experimental data reveals non-equilibrium model performs a little better than equilibrium model in the prediction of... 

    A non-equilibrium relaxation model for fast depressurization of pipelines

    , Article Annals of Nuclear Energy ; Volume 111 , 2018 , Pages 1-11 ; 03064549 (ISSN) Nouri Borujerdi, A ; Shafiei Ghazani, A ; Sharif University of Technology
    Elsevier Ltd  2018
    In this paper, transient depressurization of high pressure pipelines containing initially subcooled liquid is simulated numerically by using thermodynamic non-equilibrium and choking condition model. The numerical method relies on finite volume. The convective terms of cell boundaries are discretized by Advection Upstream Splitting Method (AUSM+ - up) with a proposal of partially implicit approach for source terms. Different void fraction correlations are applied to simulate two phase shock tubes as well as the depressurization process. By comparison between the present results and previous experimental data, the best void fraction correlation is introduced. The results indicate that the... 

    Screening of Thermodynamic Models in Predicting Phase Behavior of Asphaltenic Crudes Applicable in Dynamic Deposition Models

    , M.Sc. Thesis Sharif University of Technology Naghdi Nasab, Mohammad Ali (Author) ; Taghikhani, Vahid (Supervisor)
    Prediction and prevention from asphaltene deposition is an essential topic in oil production systems that can enormously increase oil production costs. Many studies have been done to understand and predict the behavior of asphaltene-containing oils. Prediction and investigation of asphaltene precipitation are required to predict the asphaltene deposition problem. Changes in temperature, pressure, and composition can cause precipitation, and these changes are inevitable during production. This dissertation compares the thermodynamic models that can simulate asphaltene precipitation. Firstly, A comprehensive review was done to extract the maximum amount of experimental data from the literature... 

    Porous media approach in thermohydraulic analysis of high temperature reactors in pressurized/depressurized cooldown: An improvement

    , Article Progress in Nuclear Energy ; Volume 80 , 2015 , Pages 119-127 ; 01491970 (ISSN) Nouri Borujerdi, A ; Tabatabai Ghomsheh, S. I ; Sharif University of Technology
    Elsevier Ltd  2015
    The current study aims at introducing a 2D and fast-running code for the issues pertinent to design, analysis and safety in modular high temperature reactors. While the porous media approach is only applied to pebble bed type, the analysis in this paper covers both pebble bed and prismatic reactor. A time-dependent mass equation along with energy conservation equation for the cooling gas and a time-dependent energy conservation equation for the solid was solved. Appropriate series of constitutive equations (e.g. heat transfer coefficient, effective heat conductivity of solid, heat transfer coefficient, pressure drop etc.) has been recruited as well. In addition a finite-volume method is... 

    Activating solution gas drive as an extra oil production mechanism after carbonated water injection

    , Article Chinese Journal of Chemical Engineering ; Volume 28, Issue 11 , 2020 , Pages 2938-2945 Shakiba, M ; Ayatollahi, S ; Riazi, M ; Sharif University of Technology
    Materials China  2020
    Enhanced oil recovery (EOR) methods are mostly based on different phenomena taking place at the interfaces between fluid–fluid and rock–fluid phases. Over the last decade, carbonated water injection (CWI) has been considered as one of the multi-objective EOR techniques to store CO2 in the hydrocarbon bearing formations as well as improving oil recovery efficiency. During CWI process, as the reservoir pressure declines, the dissolved CO2 in the oil phase evolves and gas nucleation phenomenon would occur. As a result, it can lead to oil saturation restoration and subsequently, oil displacement due to the hysteresis effect. At this condition, CO2 would act as in-situ dissolved gas into the oil...