شهرام قنبری پاکدهی

The proximity of elastomers to fuel leads to fuel absorption and swelling. The solubility coefficient plays a role as an effective factor in the absorption of fuel by rubber and the swelling phenomenon. Inflation is a phenomenon of control penetration; which depends on the chemical nature of the polymer and solvent. The solubility coefficient of tetralin fuel was calculated ( ) using four methods the equilibrium swelling diagram, volumetric mass, light refractive index and enthalpy of evaporation. The presence of fuel exposed to the rubber leads to negative effects on its properties and causes a decrease in properties and a reduction in the useful life of the rubber part. By increasing the difference between the solubility coefficient of the fuel and the rubber, the swelling decreases and consequently reduces the loss of the properties of the rubber mixture. The NBR compound with filler swollen in tetralin fuel, a decrease in tension properties equal to 67%, strength 59% and for NBR compound non-filler decrease of tension 76% and strain 77% has been observed. Also, it has observed the energy of break for NBR compound with filler swollen 83% and NBR compound non-filler 88%.

In the present study, a space thruster system type monopropellant has been modeled and designed so as to create a Five- Newton thrust force(propulsion) and specific impulse of 220 seconds, with the usage of adjusting motion or changing the position of the satellite. This model consists of two major parts including a catalytic reactor with hydrazine feed, 15% nickel catalyst based on gamma alumina and a convergent-divergent nozzle. The catalytic reactor model is a fixed bed, one-dimensional, steady state and adiabatic with heterogeneous decomposition reactions. The process functions by performing two heterogeneous decomposition reactions of hydrazine and ammonia and converting to light gases (hydrogen and nitrogen) with high temperatures. Subsequently, the thrust force will be obtained by the evolution of the gas from bed and nozzle. The catalyst is made up of wet impregnation method and the required characteristics are specified by quantitative, qualitative and thermal analysis tests. The outcomes of modelling include mass, energy, kinetic, physical and chemical variables in the space propulsion. It is also considered as one of the important advantages of designing the measurement and predicting the variables. So as to determine the performance and validity of the model, indicators such as the thrust force, specific impulse, bed pressure drop and the minimum of ammonia decomposition has been scrutinized with the same kinetic and operating conditions in the designing and experimental model (in atmospheric conditions and static). The obtained results are consistent and have been verified.

Research in space thrusters has been one of the topics of interest to researchers in the world in recent years due to the need for satellites with high durability in orbit and controllability. If the propulsion system is not used in the structure of the satellite, after a short time, the life of the satellite will end due to the inability to attitude control and orbit adjustment. Therefore, the use propulsion system is inevitable. Among the thrusters used, the hydrazine catalytic thruster has a very favorable position. However, since hydrazine is carcinogenic, research is ongoing to replace the monopropellant. Finally, the liquid monopropellant based on ammonium dinitramide (ADN) has been introduced. Decomposition of liquid monopropellant requires a suitable catalyst to perform this process in the best possible way. In this article, a literature survey indicated that most catalysts used for the decomposition of liquid monopropellant based on ADN are copper, platinum, and copper-platinum supported on gamma-alumina dopped with lanthanum.

Due to low electrical conductivity of liquid fuels, electrostatic accumulation is a problem in production, transportation and storage of the fuels. Electrostatic accumulation more than ambient ionization energy leads to electrical spark which causes firing and/or fuel tank explosion. Therefore, the electrical conductivity is a key parameter in fuels or flammable solvents. In this research, the apparatus cell for electrical conductivity measurement of liquids was firstly manufactured based on DIN51412-1 standard. Due to some problems in standard cell such as dependency of electrical conductivity on sample volume, chemical leakage, high volume consumption of sample, difficult cleaning of the cell and carrying problems because of size and weight, a new cell was designed based on submerging method and manufactured. The new cell performance was calibrated with various solvents like toluene, hexane and also JP-8 and tetralin as aviation fuels. Then, the conductivity of each solvent and fuel was measured and compared via the standard and new cells in the presence of antistatic Stadis 450. The measuring error was less than 0.5%.

The engine cooling in first stage of satellite carrier rocket via kerosene fuel leads to increase the missile range. For increasing the heat transfer coefficient of the fuel, addition of nanoparticle is a preferred method. At constant velocity of nanofuel through the fuel flow passage in combustion chamber, evaluation of the coefficient depends on assessment of the effective parameters. These parameters are: density, specific heat capacity, thermal conductivity and viscosity of the nanofuel. In this article, the kerosene nanofuel was prepared by addition of carbon nanotube with surfactant oleyl amine to the kerosene fuel. Then, effect of volume fraction of carbon nanotube on the thermophysical properties of the fuel was studied in the range of 0 to 0.08 at 30 oC. Mouromtseff number (as a thermal performance index of a liquid fuel) was obtained more than 1 for the kerosene nanofuel with respect to base fuel, indicating the increasing the heat transfer coefficient for the kerosene nanofuel.

Liquid fuels usually have low electrical conductivity leads to accumulating in static electricity during transmission, mixing and spraying processes. This charge accumulation will spark and fire if it exceeds the air ionization energy. Therefore, one of the important parameters in fuels safety is their potential for static charge accumulation. In this manuscript, materials are classified into static electricity and the mode of generation, accumulation, discharge and distribution of electric charge in liquid fuels will be investigated. Then, solutions for static electricity control in low conductivity high energetic liquids presented. Finally, common methods of measuring the static electricity presented.

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.

1,5-Diazabicyclo[3.1.0]hexane (DABH) is aunusual and highly energetic derivative of diaziridine, because cis-diaziridines are thermodynamicallyless stable than the trans-isomers. Therefore, the investigation on DABH molecule has practical importance besides fundamental research. Three possible conformations of DABH were considered: boat, chair, and twist.According to the reports, DABH exists asboat conformation. The natural bond orbital (NBO) analysis has used for identification the most important stabilization factor in the boat conformation. DABH and its derivatives were found as promising liquid hypergolic compounds. The ignition delay time of DABH with nitrogen tetroxide is1 ms, and the ignition delay times of other alkyl substituted DABHCs are4−11 ms, which indicated the promising application of DABHCs as hypergolic propellants. In thisstudy, structure, molecular properties and also the synthesis process of 1,5-diazabicyclo [3.1.0] hexane and its derivatives are presented.

Dimethyl amino ethyl chloride hydrochloride (DMC) is a primary substance of dimethyl amino ethyl azide (DMAZ) fuel that is a suitable alternative for hydrazine derivatives in aerospace industries. In production processes of DMAZ (95% wt.) some amounts of unreacted DMC remains in the wastewater that due to its toxicity and corrosivity effects, determination of this compound is essential. In this research, an ion selective electrode was manufactured based on poly vinyl chloride (PVC) containing dithranol ionophore. Parameters such as membrane composition, pH effect, response time and selectivity of the electrode were investigated and optimized. Calibration curve on optimized conditions showed that the made electrode after 45 seconds for DMC cation measuring, within pH= 4.2- 4.8 range, has been responded with Nernstian slope of 58.14±0.22 (mV/dec) for concentration range of 1.2×10−5 to 5.6×10−2 M at 25 ºC. Detection limit and repeatability (RSD% for 10 -3 M of DMC concentration with 6 replicate runs) of the electrode were obtained as 1.8 × 10 -6 and 2.04 percent respectively. Finally after applying of this electrode in wastewater of DMAZ production, ion chromatography method was used for the results comparison and validation.

Metal-organic framework nanoadsorbents (MOFs) are a new type of nanoadsorbents with high adsorption capacity. They are interesting for investigators due to their unique characterizations such as very high porosity (more than 90% in pore volume), very high specific surface area (more than 4000 m2/g), different and simple methods for synthesis, adjustable pore diameter, low density, high biocompatibility, high mechanical and thermal stabilities, and finally low energy consumption for adsorbent reduction. Since the dewatering or dehumidification from liquids and gases is used extensively, the adsorbents are introduced and compared with commercial adsorbents such as zeoliths and silicagel. The results showed that the MOFs have high capacity in dewatering due to high stability in aqueous media, proper surface specifications and porosity.

Production ofdimethyl amino ethanol (DMAE) and effective parameters on efficiency and purity of the chemical were studied in this article. Dimethylation of ethanol amine using aqueous formaldehyde in the presence of formic acid was applied for production of DMAE. Results showed that four parameters such as outlet temperature of CO2 gas, reflux temperature, reflux time and extraction solvent were effective parameters. The best efficiency and purity were obtained under temperature of CO2 gas as 70 oC, reflux temperature as 100 oC and reflux time as 6 hours. Dichloromethane was selected as the best solvent for extraction process. Under those optimized conditions, production efficiency and purity were obtained as 70% and 98.5%, respectively.

Due to physico-chemical and performance properties of dimethyl amino ethyl azide (DMAZ), it is a good replacement liquid fuel for hydrazine group in space industries. After production of the fuel, it’s storage is a main parameter. It is necessary to determine the storage radius of the fuel for operators’ safety in storing zoon because of probable leakage. Calculating the storage radius of the fuel needs to diffusivity data of DMAZ in air. In this article, first of all, storage radius will be derived in general case according to the basic equation of mass transfer equation. Then, diffusivity of the fuel in air will be measured on the basis of Stefan tube method at atmospheric pressure. Storage radius of the fuel will be determined at different temperatures. At atmospheric pressure, results showed that the storage radius is 2.9 m, 3.2m, 3.7m and 4.2m with respect to temperatures of 15.95oC, 25.05oC, 39.45oC and 60.05oC.

Dimethyl amino ethyl azide (DMAZ) is a good replacement for hydrazine derivatives in aerospace industries. DMAZ is in organic phase with a concentration of at least 95%. It is necessary to purify DMAZ to high concentrations. Several routs have been suggested for this purpose، in which distillation is a practical and applied method. Thermal sensitivity of DMAZ leads to conducting the process in sub-atmospheric pressures. The previous tests showed 4kPa is an optimum pressure for the process. In this paper equilibrium data for DMAZ and water at 4kPa were obtained. Results were compared with proper software to determine the best equation of state. Finally، excess molar Gibbs energy of solution was derived on the basis of equilibrium data.

Dimethyl amino ethyl azide (DMAZ) is a good candidate fuel for hydrazine derivatives in aerospace industries. Due to thermal sensitivity of DMAZ, vacuum distillation is used as a preferred method for purification of the fuel. In this article, equilibrium behavior of binary solution of DMAZ and water at 4 kPa is investigated. The experimental equilibrium data were compared with different states equation (such as NRTL, WILSON, UNIQUAC and etc.) and with activity coefficient obtained from software simulations. Experimental results were in good agreement with UNIQUAC equation. Excess Gibbs energy was calculated using the data. Finally, it was concluded that the solution has positive deviation from ideal state. Results showed that the binary solution has an azeotrope at about 96 mole percent when total pressure is 4 kPa.

One of the effective factors in choosing a combination of rocket propulsion is ignition delay. In propulsion applications, optimizing the ignition delay time is very important. In liquid rocket, spontaneous combustion or hypergolic ignition is a very useful property to makes sure that the engine is turned on. Excessive delay leads the accumulation of non-reacted propellant in the combustion chamber before ignition and caused combustion instability which results in mechanical stresses imposed on the body and rocket hardware. On the other hand, the short ignition delay can damage the injector. In this paper, after definition of the ignition delay, its range and relation with hypergolic propellants, the importance of ignition delay and its measuring methods is investigated and the parameters affecting the ignition delay is presented.

Concentration of hydrogen peroxide from 35% to 98 wt% is performed via the methods such as vacuum distillation and cooling crystallization, but hydrogen peroxide with concentration of ≥90%, is very sensitive to impurities and may be decompose. Therefore, the solution should be quite pure before concentration process. Herein, separation of Magnesium (Mg) cation from the commercial hydrogen peroxide solution (35 wt%) by ion exchange method using strong acid cation resin Amberlite IR-120 H+ with styrene divinylbenzene copolymer matrix and sulfunic acid functional group is investigated. Effect of the amount of resin and contact time on the separation of cation is considered. The metal ion concentration in the original solution and the metal ions left unabsorbed were determined by Inductive Coupled Plasma Spectrometry technique. Experimental results obtained from the separation of Magnesium were compared with Freundlich, Langmuir and Jovanovic adsorption isothermal models. Results show that, these isotherm models only in a certain range of concentrations, are consistent with experimental results. Although, the Langmuir equation of adsorption isotherm gives the best results.

Dimethyl amino ethane azide (DMAZ) is a good replacement of hydrazine derivatives in aerospace industries. It is produced from the reaction between dimethyl amino ethyl chloride and aqueous sodium azide. DMAZ is formed in organic phase with a purity of at least 90%. High pure DMAZ is necessary for aerospace utilization. Thermal sensitivity of DMAZ leads the purification procedure to be performed at low temperatures. So, the Distillation at sub-atmospheric pressures is a good choice for this purpose. In this paper, effect of various parameters such as temperature and pressure on the distillation time and loss of material and final purity of DMAZ was studied in regular packed column, known as vigorous column, and optimized conditions were found.

Concentration of hydrogen peroxide to military grade (about 98 wt%) needs removal of impurities from hydrogen peroxide of commercial grade. In this research, separation of metallic impurities from hydrogen peroxide solution was studied and cations as Al, Fe, Pb, Zn and Cr were separated from commercial hydrogen peroxide using Amberlite IR-120 (strong cationic resin). The cations were separated in a vessel at constant stirring rate. The effects of pH, amount of resin, temperature and contact time on the separation process was studied. The amounts of metallic cations were measured by ICP method. For determination the amount of resin, certain concentrations of Mg2+ and Cr3+ were added to the solution and the results were followed. Results from separation of Cr3+ were compared with the Frendlich and Langmuir models and it has been shown that In a narrow limit of Cr3+ concentration, the models afford satisfactory results.

Hydrazine catalytic propulsion system is the most conventional system in satellite orbit control. Dimethyl amino ethyl azide (DMAZ) is a replacement candidate monopropellant for hydrazine in such systems. Catalyst IR/γ-Al2O3 has been reported for decomposition of DMAZ. However, there is no information about performance conditions of the catalyst. For prediction of decomposition ability of DMAZ by the catalyst, several catalysts with various amounts of IR were prepared and characterized. Then, a micro-reactor was designed to evaluate the catalytic activity. The prepared catalysts were tested and examined at various conditions. The results showed that the increase in temperature of catalytic bed and decrease in space velocity led to an increase in catalytic activity. Also, an optimum amount of 42% in IR showed maximum activity at 205 °C of catalytic bed and 2.82 hr-1 of space velocity.

Hydrogen peroxide in high concentrations (about 98%) is considered as an important energetic substance. In this paper, the methods for the separation of impurities and ions and concentrating of commercial solution of hydrogen peroxide is investigated. The results showed that the purification has been well done via the ion exchange and distillation techniques. Also vacuum distillation and then cooling crystallization are suitable methods for the concentration of hydrogen peroxide.

Filter masks are conventional protective devices for human respiratory system against chemical weapons. Due to the diffusion of some ultra high risk chemical agents through the masks, it is necessary to use the enclosed air breathing system. In other words, human exhalation can be applied with no need to use the contaminated ambient air. In this work, a new system containing three parts (dehumidifier and odorants remover, oxygen generation system (OGS) and COx remover) is proposed and tested which led to the production of 2.5ml/min of O2 from human exhalation. The key step in the system is conversion of CO2 to CO and O2 in OGS. OGS works on the principle of proper solid oxide electrolysis (such as Yttria Stabilized Zirconia or YSZ) which acts as oxygen ion conductor at elevated temperatures. The experiments showed that such system is steadily able to produce 300ml of O2 for at least 2 hours.