Space systems design (spacecraft, satellites, space stations and their equipment)
Mohammad Razmjooei; Mohammad Shahbazi; Fathollah Ommi
Volume 14, Issue 2 , June 2021, , Pages 1-26
Abstract
In this paper, the heat transfer and ablation thermal insulators in solid rocket motor are investigated. Therefore, by collecting and solving the thermal ablation equations, a computer program, using MATLAB software, is developed which can predict the thermal response of insulators in different operating ...
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In this paper, the heat transfer and ablation thermal insulators in solid rocket motor are investigated. Therefore, by collecting and solving the thermal ablation equations, a computer program, using MATLAB software, is developed which can predict the thermal response of insulators in different operating conditions and compare the performance of these insulators. The heat and mass transfer equations are considered in two dimensions in a solid body. We used the equations, finite volume method with implicit formulation for time dependency to solve equations. The reaction equation which written in the form of Arrhenius, is solved using Runge-Kutta method, and the density and the flux of the gas produced at each step are obtained. Also we represent a model for the rate of recession.
Space systems design (spacecraft, satellites, space stations and their equipment)
Alireza Mohammadi; Fathollah Ommi
Volume 13, Issue 4 , December 2020, , Pages 15-23
Abstract
This paper presents numerical study on spray characteristics and droplet distribution by using Lagrangian method in the discrete phase model of CFD. A two-fluid Eulerian method and Lagrangian approach is selected for modeling two phases turbulence flow in mixing chamber and atomization at outlet of nozzle ...
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This paper presents numerical study on spray characteristics and droplet distribution by using Lagrangian method in the discrete phase model of CFD. A two-fluid Eulerian method and Lagrangian approach is selected for modeling two phases turbulence flow in mixing chamber and atomization at outlet of nozzle while turbulence has been modeled by K-ɛ. In this study, water has been used instead of fuel and Nitrogen instead of atomization gas or oxidizer, while their ratio has been considered 0.32 to provide 26 degrees cone angle and this way, droplet‘s characteristic has been studied and compared with maximum entropy methods. Then droplet‘s diameter has been investigated by changing liquid and gas phase flow rateand based on that, we can optimize atomizer ‘s working condition with maximum efficiency with respect to its cone angle, droplet ‘s diameter and velocity and level of penetration by minimum need of experimental tests.
Space systems design (spacecraft, satellites, space stations and their equipment)
mohammad razmjooei; mohammad shahbazi; Fathollah Ommi
Volume 13, Issue 2 , June 2020, , Pages 13-35
Abstract
In this paper, the heat transfer and ablation thermal insulators in solid rocket motor are investigated. Therefore, by collecting and solving the thermal ablation equations, a computer program, using MATLAB software, is developed which can predict the thermal response of insulators in different operating ...
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In this paper, the heat transfer and ablation thermal insulators in solid rocket motor are investigated. Therefore, by collecting and solving the thermal ablation equations, a computer program, using MATLAB software, is developed which can predict the thermal response of insulators in different operating conditions and compare the performance of these insulators. The heat and mass transfer equations are considered in two dimensions in a solid body. We used the equations, finite volume method with implicit formulation for time dependency to solve equations. The reaction equation which written in the form of Arrhenius, is solved using Runge-Kutta method, and the density and the flux of the gas produced at each step are obtained. Also we represent a model for the rate of recession.
Fathollah Ommi; Dooman Poorrajab Sufinai; Davood Doomiri Ganji; Seyed Hossein Moosavi
Volume 13, Issue 1 , March 2020, , Pages 1-11
Abstract
In this research, it is attempted to determine the diameter and velocity distribution according to the flow characteristics of the upstream and without needing experimental measurements.Firstly, Fluent software has been used to simulate the turbulent flow of inside nozzle by k-? model to obtain the nozzle ...
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In this research, it is attempted to determine the diameter and velocity distribution according to the flow characteristics of the upstream and without needing experimental measurements.Firstly, Fluent software has been used to simulate the turbulent flow of inside nozzle by k-? model to obtain the nozzle turbulence energy at the nozzle outlet. Then, nonlinear growth rate analysis of instability is used to determine spray breakup length and the frequency of maximum instability and the mean diameter of primary breakup. Four equation maximum entropy model has been developed according to the inlet of upstream flow. Subsequently, the terms of momentum source as well as the energy of maximum entropy model has been determined using the results of simulated nozzle turbulence flow and instability analysis. In the following, first the results of maximum entropy model have been evaluated with the experimental input and then determined with upstream input. The obtained results which have been compared with experimental tests show well agreement.
Space Engineering
Mohammad N. Meibody; Hassan Naseh; Fathollah Ommi
Volume 12, Issue 4 , December 2019, , Pages 35-46
Abstract
Now, the required samples to achieve the specific precision of sensitivity analysis in design are performed based on trial and error methods. The purpose of this paper is to develop an approach for determining the number of the required sample to achieve the specific precision of sensitivity analysis. ...
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Now, the required samples to achieve the specific precision of sensitivity analysis in design are performed based on trial and error methods. The purpose of this paper is to develop an approach for determining the number of the required sample to achieve the specific precision of sensitivity analysis. Thus, in this paper, a new sensitivity analysis method is proposed based on the Progressive Latin hypercube Sampling (PLHS) and the convergence of the analysis results. For this purpose, a PLHS method has been developed. This cystic approach has led to a sensitivity analysis of accuracy, efficiency, and speed in a variety of models with a large number of large parameters and large changes. Sensitivity analysis has been performed on the design of a hydrazine monopropellant thruster catalyst bed model as a case study. The results of this study indicate that in the sensitivity analysis based on the PLHS, the minimum population required for sensitivity analysis with specified accuracy can be determined. This leads to lower processing costs in the sensitivity analysis process, especially in complex models.
mohammad shahbazi; mohammad razmjooei; Fatholah Ommi
Volume 12, Issue 2 , September 2019, , Pages 23-41
Abstract
In this research, the 3D grain burnback with quasi-one-dimensional internal ballistic in a solid rocket motor is simulated using the Level set theory and the utilization of Sections method, while achieving high accuracy in the simulation of green's post-back analysis time can also be significantly reduced. ...
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In this research, the 3D grain burnback with quasi-one-dimensional internal ballistic in a solid rocket motor is simulated using the Level set theory and the utilization of Sections method, while achieving high accuracy in the simulation of green's post-back analysis time can also be significantly reduced. By using Section method, 3D grains are divided to many 2D grain, then 2D Level set is utilized to analyse grain burnback. Finally, the burning port of 3D grains are calculated by means of Interpolation. Also, to predict the internal pressure of the motor and the burning rate, a numerical code is written and coupled with grain burnback programme.
Amirhossein Edalatpour; Fatholah Ommi; Zoheir Saboohi
Volume 12, Issue 1 , April 2019, , Pages 23-40
Abstract
Micro-propulsion Systems are low thrust engines that be used in space missions like keeping satellite in orbit and changing orbit. These engines have several kinds and liquid propellant micro-propulsion is used in this project. In two propellant micro-propulsion systems, various fuels and oxidizers can ...
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Micro-propulsion Systems are low thrust engines that be used in space missions like keeping satellite in orbit and changing orbit. These engines have several kinds and liquid propellant micro-propulsion is used in this project. In two propellant micro-propulsion systems, various fuels and oxidizers can be used. Kerosene is used as fuel and liquid oxygen is used as oxidizer in this project. First of all, a micro-propulsion is designed and analysis of combustion, heat transfer, nozzle exit flow and amount of performance’s parameters is done with RPA software. Similar to big engines, micro-propulsion systems have injectors, injection plate, combustion chamber and nozzle. Design of all of this parts will be explained. With manufacturing of designed model and perform hot fire test, accurate performance of engine is observed. Finally, performance’s parameters in hot fire test are compared with performance’s parameters in RPA.
Hadiseh Karimaei; Mostafa Hossein Alipour; F Ommi; Ehsan Movahednejad; Reza Sharifzadeh
Volume 10, Issue 4 , March 2018, , Pages 1-7
Abstract
A swirl injector is tested to investigate the instability of the liquid sheet emanating from it and determine the main microscopic characteristics of the spray. The injector, which is tested, was already approved by doing the characterization tests (macroscopic). Due to the fact that the PDPA systems ...
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A swirl injector is tested to investigate the instability of the liquid sheet emanating from it and determine the main microscopic characteristics of the spray. The injector, which is tested, was already approved by doing the characterization tests (macroscopic). Due to the fact that the PDPA systems to measure the spray characteristics are very expensive and high-tech, and therefore inaccessible for us , it is attempted to investigate the specifications and instability of the liquid sheet as much as possible, by photography. The liquid sheet emanating from the injector has perturbations on its surface which originate from inside the injector. Due to the aerodynamic interactions, these perturbations grow and eventually lead to break up the liquid sheet and form the ligaments. The growth of these unstable waves can be observed in the images. Also the breakup length can be measured using the images recorded. Also ligaments in the primary breakup zone and droplets were shown.
Javad Vaziri Naein Nejad; F. Ommi; Seyed Hossein Moosavi
Volume 10, Issue 1 , June 2017, , Pages 35-45
Abstract
The addition of proper-sized metal particles to the effervescent fuels increases the density of exhaust gases from rocket engines and the trust consequently. On the other hand, the addition of non-optimized metal particles causes combustion instability. Thus, the separation of proper-sized metal particles ...
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The addition of proper-sized metal particles to the effervescent fuels increases the density of exhaust gases from rocket engines and the trust consequently. On the other hand, the addition of non-optimized metal particles causes combustion instability. Thus, the separation of proper-sized metal particles is under consideration here. In this study, among different methods of separating the aluminum particles in the fuel, the performance of the conic cyclone separator has been studied and the numerical results are validated by the experimental data. With a specific particle diameter and speed, the less the angle between the cyclone body and the horizon, the higher would be the separation efficiency. In addition, for increasing the separation efficiency of aluminum particle, it is recommended to build the inlet section of cyclone at the lower point of cyclone body.
Ali Mehrabi; Fathallah Ommi
Volume 9, Issue 1 , May 2016, , Pages 59-72
Abstract
In this paper, an adaptive controller based on decentralized minimal control synthesis is designed n order to control an attitude of specific remote sensing satellite. The main design purposes are performing spinning, three axis and large angle maneuver as well as achieving a stable system and tracking ...
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In this paper, an adaptive controller based on decentralized minimal control synthesis is designed n order to control an attitude of specific remote sensing satellite. The main design purposes are performing spinning, three axis and large angle maneuver as well as achieving a stable system and tracking the reference attitude trajectory in the presence of uncertainties. In the design process, the effects of internal and external disturbances, nonlinearities in the satellite dynamic and the accurate model of actuators are regarded. Four reaction wheels with pyramidal structure are modeled as the actuators to accomplish an attitude maneuver. So the exact reaction wheels’ model with regarding the maximum voltage, current, allowable angular velocities and power of wheels is developed. The simulation results show an acceptable performance of controller in the presence of exacts actuators’ model, external and internal disturbances and uncertainties in the satellite parameters.
F. Ommi; A. Kargar; S. M. Hosseinalipour
Volume 2, Issue 1 , April 2009, , Pages 51-57
Abstract
Optimized injectors spray and consequently their proper fluid distribution is one of the most important factors determining the thrust force and combustion stability. Reaching a stable combustion with a high specific impulse needs a proper fuel distribution and atomization. Asymmetric distribution of ...
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Optimized injectors spray and consequently their proper fluid distribution is one of the most important factors determining the thrust force and combustion stability. Reaching a stable combustion with a high specific impulse needs a proper fuel distribution and atomization. Asymmetric distribution of fuel spray droplets lead to asymmetric spray cone and incomplete combustion that cause the chamber broken. Regarding to the numerous advantages of swirl double-based injectors, 25 number of this injector type are manufactured to be mounted on a circular injector plate. To ensure that they have enough accuracy, macroscopic spray characteristic of all injectors are measured and examined in cold test lab and PDA lab.Having checked the quality of each injector, two types of injector plates are designed and manufactured precisely. Having manufactured a circular and a hexagonally arranged injector plate, their spray characteristics are examined.Results show that the circular injector plate has satisfactory spray characteristics like droplet distribution and desirable spray cone and could be ready for warm test.
