Structure
hassan Naseh; Hadiseh Karimaei; mohammad lesani
Abstract
In this paper, the structural optimization of a space capsule has been discussed by approximating a thin-walled cylindrical shell with a certain length under the axial compression force and constant lateral pressure. Design variables include the outer diameter and cylinder thickness. The purpose of optimization ...
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In this paper, the structural optimization of a space capsule has been discussed by approximating a thin-walled cylindrical shell with a certain length under the axial compression force and constant lateral pressure. Design variables include the outer diameter and cylinder thickness. The purpose of optimization is to minimize the mass and maximize the frequency of the first vibration shape mode of the cylinder. The design constraints include the buckling load multiplier (buckling safety factor) above 1.5 and Von Mises stress below 100 MPa. In this article, first, according to the permissible limits of the design variables, a design of experiment (DOE) and then a sensitivity analysis was carried out to check the sensitivity of the objective functions and constraints to the design variables. After numerically solving the output values with the help of Ansys software and preparing the response surface, the optimal design point has been identified with the help of the two objectives optimization Genetic algorithm. Then, with the numerical simulation of the optimal point, the accuracy of the values obtained from the response surface method was checked and their accuracy was confirmed. The results show that at the selected design point, Von Mises stress becomes less than its allowed value, i.e. 100 MPa, and also the buckling load factor is more than twice its minimum allowed value. However, this point has the smallest distance from the origin and the optimum point has been chosen as the knee point
Propulsion
Hadiseh Karimaei
Abstract
The monopropellant thrusters of the situation control system are a requirement for the development and application of satellites and space capsules in space, which are high-tech and expensive. In this paper, the design and simulation of a pressure- swirl injector with full-cone spray as a fuel injector ...
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The monopropellant thrusters of the situation control system are a requirement for the development and application of satellites and space capsules in space, which are high-tech and expensive. In this paper, the design and simulation of a pressure- swirl injector with full-cone spray as a fuel injector of a monopropellant thruster are presented. For this injector, internal flow simulation was performed in order to predict its output flow characteristics including spray cone angle, output velocity distribution, mass flow rate, spray pattern, etc. For this purpose, VOF fluid volume method is used and the flow turbulence is simulated using the k-eps model. This type of injector is actually a combination of straight flow injector and swirl flow injector. Jet straight flow in the center of the injector and swirl flow along the injector wall are flowed. Both flow regimes are combined in the swirl chamber and the spray is formed as a full-cone. If the ratio of the outlets is selected correctly, the radial and environmental distribution of the liquid jet will be uniform. This injector is preferred to the capillary type (straight flow) and the swirl type. The pressure-swirl injector spray angle is larger than the capillary type, which improves the coverage of the catalyst bed, at the same time, spray angle is not as large as the swirl injector, which enlarges the radial dimensions of the decomposition chamber. Based on the results, it was ensured that the injector provides the desired mass flow rate (about 5.8 gr/s) at a certain design pressure difference (3 bar) and determines a suitable spray pattern. It also provides the desired spray angle (about 35).
