فصلنامه مواد پر انرژی
سال چهاردهم شماره 3 (پیاپی 43، پاییز 1398)

In this research, firstly, a one-dimensional steady state model for a catalytic fixed bed reactor is presented. All mass transfer, heat transfer and momentum equations are considered in this model, applying appropriate assumptions. The results of modeling predict temperature and concentration changes and also pressure drop along the reactor bed length. By applying the modeling, hydrazine catalytic reactor was designed. The design procedure includes thrust and specific impulse and continues with calculation of the bed diameter. Ammonia dissociation and the mass flux were calculated along the length of the bed. Finally, the reactor was designed and tested. In these tests, the maximum reactor temperature was 650 oC, the ammonia dissociation was 59% and the pressure drop was 1.3 bar, presenting a good coherency with the modeling data.

Grain design is the most important part of solid rocket motor design. In this paper, the goal is implementing and comparing various Artificial Neural Network metamodels in Finocyl grain design based on predetermined objective function with respect to thrust history or pressure history in order to satisfy various thrust performance requirements through an innovative design approach using genetic algorithm optimization method. The classical sampling method is used for design space filling. The level set method is used for simulating the evolution of burning surface in the propellant grain. An algorithm is developed beside the level set code that prepares the initial grain configuration using Pro/Engineer to export generated models to level set code. The zero dimensional method with considering the effect of erosive burning is used to perform internal ballistic analysis. The meta-model is used to surrogate the level set method in optimization design loop. The surrogate method is based on artificial neural network based on Multi Layer Perceptron with comparing various training algorithm and Radial Basis Function. Finally, a case study is done to verify the proposed algorithm. Observed results show that grain design method reduced the design time significantly and this algorithm can be used to design of any grain configuration.

PBXIH-135 thermobaric charge is an explosive with desirable mechanical and safety characteristics. In the present research, this PBX charge is prepared in 2 kg scale and its physical, mechanical, sensitivity and performance parameters were investigated. Prepared sample has density of 1.64 g/cm3 , hardness of 53 Shore A, tensional strength of 1.68 MPa and strain of 44%. Impact and friction sensitivity were 28 N.m and ≥36 kg.F respectively. Detonation velocity of PBXIH-135 was about 6700 m/s and its superiority in comparison with TNT in lead block test and dent producing in steel block by the same volume, were 1.13 and 1.33 respectively. As well as, field blast test showed that the PBXIH-135 has a significant advantage in terms of thermal parameters. Its TNT equivalency based on overpressure, measured at distances of 2.5 to 4.5 m, was around 1.23. Results also showed that increasing the distance of data acquisition, explosion impulse.of PBXIH-135 increases compared to TNT.

Aluminum based composites are manufactured in a variety of methods, such as mixing in liquid state, mechanical alloying and so on. Explosive welding is one of the modern ways of producing Aluminum based composite. Explosive welding is used for excellent bonding of similar and dissimilar materials with a wide variety of thicknesses, area dimensions and different thermal and mechanical properties. In this study, Aluminum plates were reinforced by steel wires by explosive welding. The steel wires are placed between two Aluminum plates and joint between plates and reinforcement were made by explosive welding process. The quality and morphology of the interface depend on standoff, the geometry of the welded plates, the properties of the metals, etc. In this paper, the appropriate parameters were determined using the numerical simulation and drawing of weldability window and layout of explosive welding was designed. The produced parts were examined by optical microscope. The simulation results showed that in the constant stand off by increasing the explosive ratio in constant standoff, velocities collision and dynamic collision angle increased. The metallography results showed that the composite obtained excellent bonding quality of interface without void and fracture.

A way to increase the specific impulse of solid propellants is using the energetic components such as energetic binder or energetic plasticizer in the propellant formulations. Hydroxy terminated poly butadiene (HTPB) is the one of pre-polymer which was specifically synthesized for its use as a binder in propellant. Incorporating PEG into HTPB chains increases the polarity of binder. In this study, in the first step, elastomers of HTPB/PEG blend are prepared and their mechanical and thermal properties are investigated. Then, the propellant based-on HTPB/PEG blend was prepared and its mechanical properties were compared to the propellant based-on HTPB binder. Incorporation of PEG into the binder, increases the stress and elongation of the propellant and also, influences its oxygen balance. In the solid propellant with 75% solid loading, theoretical and semi empirical specific impulse were increased to 7.9s and 6.9 respectively, by the addition of BuNENA.

The oxidation – reduction reaction of trinitrotoluene (TNT) with potassium permanganate solution and its decolorination rate are used as a quality control test in industry to verify the purity of TNT. The impurities such as other derivatives of TNT are due to increasing decolorination rate of potassium permanganate solution. On the other, nitrotoluene sulfonates are usually formed when sodium sulfite is added to TNT. The presence of sodium and sulfur in the TNT bulk is confirmed by using ICP technique. In this research, the kinetic of potassium permanganate reaction with pure TNT and nitrotoluene sulfonates (TNT and sodium sulfite) is studied using the absorption spectrometry in visible region and the rate constants and the reproducibility of the method are measured for determination of nitrotoluene sulfonates amounts. In the optimized concentrations of sulfuric acid (0.6 M) and potassium permanganate (0.6 mM), the results show 1.3 times increasing of reaction rate in the presence of nitrotoluene sulfonate. Introducing a simple, inexpensive and rapid method for quantifying nitrotoluene sulfonates are the advantages of the proposed method.