جستجوی مقالات مرتبط با کلیدواژه "calibration" در نشریات گروه "مواد و متالورژی"

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 high-expensive empirical analysis of blast waves motivates the researchers to investigate the explosion using numerical simulations. The literature shows that the computational fluid dynamics predicts the blast wave behavior accurately. Meanwhile, many methods such as the turbulence method, and the method of applying the explosion energy to the equations were presented to increase the accuracy of the numerical analysis. However, one of the most important factors in the results’ accuracy is the equation of state that describes the physical behavior of the explosion productions. The ideal-gas equation of state as the simplest equation of state was used in most of the previous researches. In this research the effect of using JWL and BKW, the real gas equations of state, on the results’ accuracy in comparison with the ideal-gas equation of state is investigated. To do this investigation, the problem of explosion close to a canopy is simulated. The numerical simulation of explosion phenomenon is done using the blastfoam solver of the openFoam open source code, and the results are compared with the previous studies. Finally, the constants of the BKW and JWL equations of state are calibrated using the empirical data.

One of the properties for liquid bipropellants is their hypergolicity. The required quantity for this purpose is ignition delay time (IDT). IDT is classified into two classes: physical and chemical. The chemical ignition delay time is the time interval between the contact of fuel droplet - oxidizer surface and appearance of the first flame. The most appropriate laboratory method for measuring the chemical ignition delay time is drop test. Considering the effective parameters on the ignition delay time (such as oxidizer to fuel ratio, temperature and pressure) and following the mechanical design, this system was manufactured with capability of temperature and the reaction chamber pressure adjustments. For calibration and standardization of the system, some liquid fuels (such as triethyl amine, unsymmetrical dimethyl hydrazine and Tonka-250 mixture) and some liquid oxidizers (such as strong nitric acid and conventional oxidizer AK27) were applied. Good repeatability and dispersity of the obtained results indicate the system accuracy.

One of the most important issues when working with energetic materials is their initiation. Of the various methods of energetic materials initiation in the military and civilian industries, shock initiation is of particular importance. Numerical and simulation study of the shock initiation of condensed phase explosives is related to models called burning rate models, which describe the conversion rate of unreacted materials to detonation products. Among the burning rate models that have been proposed for explosives so far, the Ignition and Growth (I&G) model is one of the most popular and widely used models. In this paper, the genetic optimization algorithm is coupled with an upgraded Fortran SIN simulator hydrocode. The calibration was based on minimizing the difference between the calculated pressure data and the experimental data obtained from manganin pressure gages in the shock initiation tests. The results of optimizing the I&G parameters for Comp-B demonstrates good accuracy of the algorithm; So that after calibration, the difference between the pressure history obtained from the calculations of this paper and the experimental data was about 15% and in this respect is about 6% more accurate than the results reported in previous reseorches.