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This study aims to present a basic mathematical model for investigating the structure of counter-flow non-premixed laminar flames propagating through uniformly-distributed organic fuel particles considering preheat, drying, vaporization, reaction and oxidizer zones.

Lycopodium particles and air are taken as biofuel and oxidizer, respectively. Dimensionalized and non-dimensionalized forms of mass and energy conservation equations are derived for each zone taking into account proper boundary and jump conditions. Subsequently, to solve the governing equations, an asymptotic method is used. For validation purpose, results achieved from the present analysis are compared with reliable data reported in the literature under certain conditions.

With regard to the comparisons, although different complex non-homogeneous differential equations are solved in this paper, acceptable agreements are observed. Finally, the impacts of significant parameters including fuel and oxidizer Lewis numbers, equivalence ratio, mass particle concentration, fuel and oxidizer mass fractions and lycopodium initial temperature on the flame temperature, flame front position and flow strain rate are elaborately explained.

An asymptotic method for mathematical modeling of counter-flow non-premixed multi-zone laminar flames propagating through lycopodium particles.

Chemical mechanical polishing (CMP) has attracted much attention recently because of its importance as a nano-scale finishing process for high value-added large components that are used in the aerospace industry. The paper aims to discuss these issues.

The characteristics of aluminum nanoparticles slurry including oxidizer, oxidizer contents, abrasive contents, slurry flow rate, and polishing time on aluminum nanoparticles CMP performance, including material removal amount and surface morphology were studied.

Experimental results indicate that the CMP performance depends strongly on the oxidizer, oxidizer contents, and abrasive contents. Surface polished by slurries that contain nano-Al abrasives had a lower surface average roughness (Ra), lower topographical variations and less scratching. The material removal amount and the Ra were 124 and 7.61 nm with appropriate values of the process parameters of the oxidizer, oxidizer content, abrasive content, slurry flow rate and polishing time which were H₂O₂, 2 wt.%, 1 wt.%, 10 ml/min, 5 min, respectively.

Based on SEM determinations of the process parameters for the polishing of the surfaces, the CMP mechanism was deduced preliminarily.

The widespread usage of magnetic nanoparticles (MNPs) requires their efficient synthesis during combustion process. This study aims to present a mathematical model for the oxidation of MNPs in a counter-flow non-premixed combustion system to produce MNPs, where the key sub-processes during the oxidation reaction are involved.

To accurately describe structure of flame and determine distributions of temperature and mass fractions of both reactants and products, equations of energy and mass conservations were solved based on the prevailing assumptions that three regions, i.e. preheating, reaction and oxidizer zones exist.

The numerical simulation was first validated against experimental data and characteristics of the combustion process are discussed. Eventually, the influences of crucial parameters such as reactant Lewis numbers, strain rate ratio, particle size, inert gas and thermophoretic force on structure of flame and combustion behavior were examined. The results show that maximum flame temperature can achieve 2,205 K. Replacing nitrogen with argon and helium as carrier gases can increase flame temperature by about 27% and 34%, respectively. Additionally, maximum absolute thermophoretic force was found at approximately 9.6 × 10–8 N.

To the best of authors’ knowledge, this is the first time to numerically model the preparation of MNPs in a counter-flow non-premixed combustion configuration, which can guide large-scale experimental work in a more effective way.

Low combustion completeness has been the main defect of hybrid rockets. The present study tries to address the problem by bringing up the setup of the precombustion zone, which do not increase the manufacture cost and complexity.

A precombustion zone can provide a space for the liquid oxidizer to vaporize before entering the combustion zone, and prevents the endothermic effect of liquid oxidizer which can block the chemical reaction as well as the fuel regression. Therefore, this design is expected to raise the combustion completeness. The numerical simulation focuses on the flow field inside a cylindrical hybrid combustor. The distribution of temperature, combustion mode, mass fraction of reactants, velocity, combustion completeness, and solid‐fuel regression rate are presented.

With the setup of prevaporized zone of appropriate length, the upstream separation bubble which is unobvious for the case with no prevaporized zone can increase the mixing of reactants, and then increases the combustion completeness. Besides, the radial temperature distribution is more uniform. But when the length of prevaporized zone exceeds about one fourth of the combustor length, due to no enough space for the reactants to react, the combustion completeness begins to decrease and the radial temperature distribution becomes uneven. Therefore, a prevaporized zone with about 24 per cent of the combustor length can have optimum combustion completeness in the present study.

This study provides a useful design to raise the combustion completeness of a traditional hybrid rocket. However, the manufacture cost and complexity are not increased. So the results can be a good reference for the hybrid rocket designers.

This paper aims to determine the regression rate using wax fuels for three different grain configurations and find a suitable grain port design for hybrid rocket application.

The design methodology of this work includes different grain port designs and subsequent selection of solid fuels for a suitable hybrid rocket application. A square, a cylindrical and a five-point star grained were designed and prepared using paraffin and beeswax fuels. They were tested in a laboratory-scale rocket with gaseous oxygen to study the effectiveness of solid fuels on these grain structures. The regression rate by static fire testing of these wax fuels was analyzed.

Beeswax performance is better than that of paraffin wax fuel for all three designs, and the five-slotted star fuel port grain attained the best performance. Beeswax fuel attained an average regression rate ≈of 1.35 mm/s as a function of oxidizer mass flux Gox ≈ 111.8 kg/m² s and for paraffin wax 1.199 mm/s at Gox ≈ 121 kg/m² s with gaseous oxygen. The local regression rates of fuels increased in the range of 0.93–1.194 mm/s at oxidizer mass flux range of 98–131 kg/m² s for cylindrical grain, 0.99–1.21 mm/s at oxidizer mass flux range of 96–129 kg/m2s for square grain and 1.12–1.35 mm/s at oxidizer mass flux range of 91–126 kg/m² s for a star grain. A complete set of the regression rate formulas is obtained for all three-grain designs as a function of oxidizer flux rate.

The experiment has been performed for a lower chamber pressure up to 10 bar.

Different grain configurations were designed according to the required dimension of the combustion chamber, injector and exhaust nozzle of the design of a lab-scale hybrid rocket, and input parameters were selected and analyzed.

The purpose of this paper is to show possible approaches which can be used for modeling complex flow phenomena caused by swirl burners combined with simulating coal combustion process using air- and oxy-combustion technologies. Additionally, the response of exist boiler working parameter on changing the oxidizer composition from air to a mixture of the oxygen and recirculated flue gases is investigated. Moreover, the heat transfer in the superheaters section of the boiler was taken into account by modeling of the heat exchange process between continuum phase and three stages of the steam superheaters.

An accurate solution of the flow field is required in order to predict combustion phenomena correctly for numerical simulations of the industrial pulverized coal (PC) boilers. Nevertheless, it is a very demanding task due to the complicated swirl burner construction and complex character of the flow. The presented simulations were performed using the discrete phase model for tracking particles and combustion phenomena in a dispersed phase, whereas the Eulerian approach was applied for the volatile combustion process modeling in a gaseous phase.

Applying the air- to oxy-combustion technology the temperature in the combustion chamber, decreased for investigated oxidizer compositions. This was caused by the higher heat capacity of flue gases which also influences on the level of the heat flux at the boiler walls. Simulations shows that increasing the O₂ concentration to 30 percent of volume base in the oxidizer mixture provided the similar combustion conditions as those for the conventional air firing. Moreover, the evaluated results give a good overview of differences between approaches used for complex swirl burners simulations.

Nowadays, the numerical techniques such as computational fluid dynamic (CFD) can be seen as an useful engineering tool for design and processes optimization purposes. The application of the CFD gives a possibility to predict the combustion phenomena in a large industrial PC boiler and investigate the impact of changing the combustion technology from a conventional air firing to oxy-fuel combustion.

This paper gives good overview on existing technique, approaches used for modeling PC boiler equipped with complex swirl burners. Additionally, the novelty of this work is application of the heat exchanger model for predicting heat loses in convective section of the boiler. This usually is not taken into account during simulations. The reader can also find basic concept of oxy-combustion technology, and their impact on boiler working conditions.

The purpose of this paper is to estimate the chamber pressure and flow behaviour in a vortex thrust chamber (VTC) during the cold flow with hydrogen and oxygen as propellants.

Experiments are carried out in a VTC with a different mixture ratio of hydrogen and oxygen. The pressures developed inside the VTC are measured. Numerical simulations are carried out to understand the flow patterns of fuel and oxidizer inside the VTC.

The chamber pressure is influenced by the type of injection of propellant and mixture ratio. Tangential injection of propellant is the key parameter for an increase of the chamber pressure of the VTC.

The pressure measurements are carried out in cold flow conditions without combustion happening in the VTC.

The practical implication is that when the combustion in the VTC ceases, the thrust generated due to the propellants in cold flow conditions can be assessed.

The VTC with the tangential injection of propellant generates higher chamber pressure.

The purpose of this paper is to investigate the effects of abrasive contents, oxidizer contents, slurry flow rate and polishing time in achieving a mirror-like finish on polished surfaces. Chemical mechanical polishing (CMP) is now widely used in the aerospace industry for global planarization of large, high value-added components.

Optimal parameters are applied in experimental trials performed to investigate the effects of abrasive contents, oxidizer contents, slurry flow rate and polishing time in achieving a mirror-like finish on polished surfaces. Taguchi design experiments are performed to optimize the parameters of CMP performed in steel specimens.

Their optimization parameters were found out; the surface scratch, polishing fog and remaining particles were reduced; and the flatness of the steel substrate was guaranteed. The average roughness (Ra) of the surface was reduced to 6.7 nm under the following process parameters: abrasive content of 2 weight per cent, oxidizer content of 2 weight per cent, slurry flow rate of 100 ml/min and polishing time of 20 min.

To meet the final process requirements, the CMP process must provide a good planarity, precise selectivity and a defect-free surface. Surface planarization of components used to fabricate aerospace devices is achieved by CMP process, which enables global planarization by combining chemical and mechanical interactions.

The purpose of this study is to describe the combustion of a magnesium particle falling into a hot oxidizer medium.

The governing equations, including mass, momentum and energy conservation equations, are numerically solved. Afterward, the influences of effective parameters on the temperature distribution and burning time are investigated. Artificial neural network (ANN) is applied to approximate the particle temperature as a function of time, diameter and porosity factor. To obtain the best arrangement of the ANN structure, an optimization process is conducted.

The results show that by considering variations of the particle size, the maximum temperature increases compared to the case in which the particle diameter is constant. Also, the ignition and burning times and the maximum temperature of the moving particle are lower than those of the motionless particle. Optimum network has the best values of regression coefficient and mean relative error whose values are found to be 0.99991 and 1.58 per cent, respectively.

In this study, particle size varies over the combustion process that leads to calculation of particle burning time. In addition, the effects of the motion and porosity of the particle are examined.

This study aims to present a method for conceptual design and simulation of hybrid propellant motors.

The design methodology is based on previous studies and thermo-physical governor relations, and also a computational code that was derived to simulate the performance of designed system.

Conceptual design algorithm for space hybrid propellant systems and method of performance simulation are findings of this study.

Results of this study are applicable for design process of space systems with hybrid propulsion. Also, simulation results can help the users to improve the performance weaknesses.

This study shows the implementation of present algorithm for a specified space mission and also study on variation of performance parameters.