International Journal of Engineering
Volume:15 Issue: 3, Oct 2002

The effect of chemical reactions on the blast initiation of detonation in gaseous media has been investigated in this paper. Analytical method is based on the numerical solution of onedimensional reactive Euler equations. So far, analyses on the blast initiation of detonation have modeled the combustion process as a one-step chemical reaction, which follows the Arrhenius rate law. Previous studies indicate that one-step model cannot predict single critical initiation energy. These results contradict with the experimental observation that a distinct value of critical initiation energy exists, below which no detonation occurs. Two-step chemical kinetics has been utilized in the present investigation. In two-step kinetics, first step is an induction step, while the chemical energy is released in second step via Arrhenius mechanism. With variation of activation energy in these two steps, the effect of induction length and energy release can be studied. This model predicts three regimes of blast initiation of detonation that have been observed in experimental observation. On the other hand, like one-step model, the present model cannot predict a limit for the initiation energy

The beverage industry has been a heavy producer of organic pollution. The major contaminants found in waste are biodegradable organic compounds, volatile organic compounds, toxic metals, and recalcitrant xenobiotics, suspend solids, nutrients (Nitrogen and Phosphor) Microbial pathogens and parasites. Activated sludge flocs contain a wide range of microorganisms such as bacteria, Fungi, yeast, viruses, and protozoa. In this study, we isolated some strains of yeasts from the factory sludge. More than 50 strains of yeast were selected. Among them 12 strains had a high removal of TOC.Yeast No. 11 (Y-11) has shown an overall efficiency of 87.5% in terms of TOC removal.

Biodesulfurization of coal has been carried out in batch culture of single strain and mixed culture of sulfur oxidizing bacteria. The pure cultures of Thiobacillus thiooxidans and Thiobacillus ferrooxidans utilized inorganic sulfur content of Malaysian coal. The chemolithotroph bacteria were able to grow on coal and metabolize the coal''s sulfur content. The batch cultures of coal with 3-5 percent sulfur were used for growing microorganisms. A few species of bacteria and fungi had potential to utilize coal complex media, which were isolated from coal rice hulls and pharmaceutical wastewater. Asperigillus niger and Thiobacillus species isolated from coal, fungi from rice hulls and Saccharomyces species from wastewater, all microorganisms capable to grow on coal. The main concern was the sulfur oxidizing bacteria were screened out from all non-sulfur reducing bacteria. In the Batch cultures, the biooxidation coal''s sulfur was affected by several parameters, such as pH, nutrients, agitation rate, growth stimulants and percentage coal. The trace amount of magnesium and cobaltions, 200 rpm agitation rate with initial pH of 2.6 for mixed culture of Thiobacillus thiooxidans and Thiobacillus ferrooxidans showed maximum growth rate and optimum batch operating conditions. The highest sulfur oxidation was obtained at the optimal Thiobacillus growth rate. More than 75 percent of sulfur was removed from coal. The biooxidation of coal, the kinetic model followed by Monod rate equation with specific growth rate, µmax = 4.8d-1 and rate constant. Ks =16.7 g/L.

Benzyl chloride is economically one of the most important starting materials for a large number of industrial syntheses. Far too much money is now spent to buy and import this valuable product. The production of benzyl chloride has been recognized as one of our national projects and budgeted by the National Iranian Petrochemical Organization in order to economize on the country’s foreign exchange. It is certain that obtaining a broad spectrum of scientific information must take priority. A part of this information consists of the kinetics of the reaction, resistance of the used materials, the proper gas-liquid ratio for efficient production, the best range of temperature, etc. Much attention has also been paid to the development of kinetic models, to the design of the reactor, the effects of agitators and inhibitors. The kinetics of thermal chlorination of toluene without catalyst in a semi-batch reactor in a temperature range of 80-100°C and a pressure range of 1-3atm has been investigated. The reactor had an approximate volume of 7 liters. It was equipped with condenser and electric heater and necessary measuring instruments. The reactor was made of SS-316. Since certain metallic impurities such as iron act as a catalyst for ring chlorination and self-condensation, their presence must be avoided. Consequently, a special resistant lining, PTFE, was used for coating the reactor interior. The rate of initial reactants conversion and the production of benzyl chloride in atemperature range of 80-100°C and a pressure range of 1-3atm with an optimized situation consideration and maximum efficiency of production have been determined.

For the purpose of exploring deformation characteristics of jointed rock masses, influence of joint inclination and confining pressure on the mechanical behavior of discontinuous rock a series of compression tests were conducted under satisfactory testing conditions on three types of sandstone from various locations. Three groups of jointed specimens were used in this research, including specimens containing saw cut planar joint, shear-surface joint and split breakage joint. The specimens were tested triaxially up to 70 MPa confined pressure. A 5 MN servo-controlled stiff testing machine was employed and a monitoring system was set up using a microcomputer controlled logger. The deformation characteristics of jointed specimens with saw cut joints were different in low and high confinements, however, in split breakage joints sliding behavior was the same in low and high confinements. Mohr envelope for 60° inclination in split breakage joints was above that of 45° in both saw cut and split breakage joints, i. e. a higher coefficient of sliding friction or a higher shear strength across the joint for this orientation.

(In this paper, the empirical equations that estimate hydraulic parameters for non-linear flow through coarse porous media are evaluated using a series of independent data collected in the laboratory. In this regard, three different relatively uniform soils ranging in size from 8.5 to 27.6 mm have been selected and three random samples drawn from each material. The physical characteristics such as size distribution, porosity, and shape factor have been measured for the 9 samples. In total, 9 permeameter tests have been conducted on the samples to create a set of reliable hydraulic gradientvs. bulk velocity data. Statistical measures have been used to compare the permeameter data with those predicted by the empirical equations. The study shows that McCorquodale et al. and Stephenson equations, which some subjective parameters related to the surface characters of the material, have been incorporated in their structures, can give good results. Also, equation developed by Adel who considers d15 as characteristic size of the media, shows acceptable performance. Other equations either underestimate or overestimate hydraulic gradient based on experimental work and analysis conducted in this study.

Single crystals and polycrystalline diamond films of several thicknesses were deposited using oxygen/acetylene combustion flame technique. The substrate used was pure polycrystalline molybdenum subjected to mechanical polishing. Quality and microstructural characteristic of diamond produced were investigated using X-Ray diffraction, Raman Spectroscopy, Scanning and Transmission Electron Microscopy. Results obtained revealed that a good quality single and polycrystalline diamond could be produced. However, a combination of various defects such as twins, dislocations and stacking faults are always present.

Abstract The influence of aluminum, within the range of 0.08 - 6.16 wt.%, on the microstructure and hardness of as-cast ductile cast iron has been studied. A number of irons of different composition have been made by green sand casting and gravity die casting of appropriate design to provide the experimental materials. It has been found that Al addition and higher cooling rates in permanent mould casting both promote pearlite formation in the as-cast irons. Detailed microscopic observation revealed that foreign particles (with a high concentration of Al, Si and Mg) within the graphite spherulites probably behaved as nucleation sites, and that Al addition can promote spheroidal graphite nucleation and growth. Furthermore, it was illustrated that spherulites with a fan-like structure consist of aggregates of graphite platelets and interplatelet regions.

This paper presents and analyses results from experimental and CFD work undertaken on a 24 kW domestic natural-draught gas fired boiler. The effect of chimney height on boiler flue gases is being considered to address the need for increasing concern over environmental safety as well as saving of energy. A multi-component analysis computer (DELTA 2000 CD) is used to analyze the flue gases. 3D numerical simulations are performed using the CFD-code Fluent. The theoretical results of partially premixed combustion incorporating the prompt NOx model compare well with measurements. The results show that the pollutant emissions and thermal behavior of natural-draught burners are sensitive to draught produced by the chimney and there is an optimum chimney height, which corresponds to the minimum air pollution emissions. The results also show that the level of NO exits the natural-draught boiler is lower than Environmental Protection Agency (EPA) standard for gas fired boilers and small-scale boilers are environmentally cleaner than large central heating boilers.

Effects of some important parameters like impactor effects, plug geometry and initiation points on bonding aluminum tubes to aluminum plugs were studied. The impact velocity and dynamic angle between tube and plug should be precisely managed to achieve an optimum bonding condition. A new explosive bonding technique with the use of two material impactors was proposed. Results are especially suitable for using high-speed explosive materials to bond welded parts having dissimilar properties. A welding window was first presented for bonding aluminum tube to aluminum plug with the help of the experimental data. Numerical simulation was then performed to understand the effect of impactor on flat and curved plugs:. However, due to limited data analysis systems used to register explosive welding parameters, it became evident that numerical analysis was necessary. The important findings were, therefore, explosion modeling and fast tube deformation. For low process duration time and fast deformation, the modeling is very difficult. At the same time, numerical analysis with Abaqus software was performed to investigate the bonding conditions. The calculated impact velocity of the tube and the dynamic angle between the tube and the plug were compared with the numerical results under the same conditions. It was shown that the numerical analysis was consistent with the predicted data. Eventually we concluded that in explosive welding, curved plugs were more advantageous than flat plugs. It can be recommended that due to having a connection surface in high-speed explosives, the use of plastic impactors is more favorable than using hypoelastic impactors.

An experiment set-up is used to study wall deposition rate of particles on a rough surface in a turbulent channel flow. Deposition velocities for three classes of particles, namely, spherical glass particles, irregular shape polymer particles, and fibrous silicon particles are studied. The particle concentration at the test section was measured with the aid of an isokinetic probe in conjunction with a digital image processing technique. The probe is made of sterile plastic and sticked to the sidewall of the wind tunnel. The deposition of spherical particles is found to increase with increasing in diameter. Also it is shown that the deposition velocity of spherical particles is affected by the surface roughness.

A passive false twist unit (spiral) has been developed to assist with the handling lowstrength slivers on a high speed-spinning machine with a high-speed feed. In the first trial, a falsetwist simulator device was constructed to determine whether the passive false twist unit can be usedon high speed feeding with different can distance from the feeding device. In the second trial, theeffects of using one or two false-twist units on rotor spun yarn properties with different draft ratioswere investigated. The experimental results show that the effect of double false-twist unit at 30° entryangle of sliver and two turns of sliver around the false-twist wire is significant on rotor spun yarnproperties. It is also found that to obtain the optimum operating conditions, single or double passivefalse twister units are needed for different conditions including the can distance from feed part anddifferent feed speeds.