The results of an experimental study of the combustion of aluminum particles in N2/O2 gas mixtures are presented and interpreted. This research focuses on measurement of flame speed and combustion velocity in aluminum particle dust cloud combustion. The dust dispersion technique uses an annular high-speed jet which disperses dust continuously supplied via a pistontype dust feeding system. Particles of one initial diameters of 18 micron were studied in this experiment. Flame speed as a function of dust concentration was determined during the laminar stage of flame propagation in dust-oxygen-nitrogen mixtures. It was found that increasing in O2 part (21% O2 to 25% O2) in N2/O2 gas mixtures leads to increasing in combustion velocity.

Sound is one of the forms of mechanical energy and the two main characteristics of sound are intensity or power and frequency or wavelength of sound.their performance against the incoming sound wave, industrial silencers can be divided into two general groups of resonating and absorption silencers, the main difference between these silencers is the release of sound energy from the channeling system, which is one of the common examples of the use of resonating type silencers, their use in It is the internal combustion engines that distinguish absorption silencers from the resonator type based on the fact that the main and visible part of the act of muting the sound is achieved by changing sound energy to heat energy.The goal of this article is to design a muffler based on the breaking of sound frequencies resulting from the movement of fluid in the exhaust output of vehicles, which leads to a reduction of at least 50 db of sound and gives the operator enough peace and concentration. In this article, after examining three types of mufflers, absorbent mufflers that use the properties of porous absorbent material to absorb passing sound and are the simplest form of mufflers, have been selected, analyzed and reviewed and are suitable for the OM457 engine of Idem Industrial Company. It designed for maximum inlet exhaust temperature is 520 and for the maximum kW power is 315 with the maximum discharge relative pressure of 185 mbar for homogenization with the standard atmosphere.

Introduction: An important variable in investigation of agility during puberty is the age of reaching peak high velocity, which like other agility indicators is under the effect of different factors such as physical condition and type. The purpose of present research was to examine relationship between somatotype and peak high velocity (PHV) among Iranian 7-10 years old boys.Methods: Participants were 313 7-10 year-old members of Basij talent identification centers in all Iran's provinces. Somatotype data were calculated using Heath-Cartr instruction and PHV was measured using Mirwald formula and were analyzed using Pearson correlation and multiple regressions.Results: Results of pearson correlation showed that PHV had a positive correlation with ectomorphy and negative correlation with endomrphy and mesomorphy. Total correlation between PHV and somatotype was 0.50 which explained 25% of PHV variance. Results of regression analysis showed ectomrphy and endomorphy were significant predictors of PHV but msomrphy was not a significant predictor of PHV.Conclusion: Endomorphy had a smaller part in predicting the PHV age, but mesomorphy was not a strong predictor, Moreover, ectomorphy following endomrophy had a strong predicting power. Studies in this area suggest that those who have greater ectomorphic characteristics are less agile and the physiologic requisites for their puberty develop later in their bodies. Therefore poor sport performance of ectomorphic children may result from their distance to PHV age so coaches and instructors should consider this measurement and somatotype.

In the present study, the effects of inlet velocity on characteristics of Repetitive Extinction-Ignition Dynamics are numerically investigated. Hydrogen-air mixture (with equivalence ratio=0.5) enters into a heated micro channel with a prescribed wall temperature. Low Mach number approach is considered for governing equations in numerical simulation and also detailed chemistry, and different mass diffusivity of species is utilized. The dynamic behavior is studied by two parameter, amplitude and frequency. The results show that the amplitude of repetitive extinction-ignition dynamics increases with increasing the inlet velocity, while the frequency has a descending-ascending behavior. For detailed study of this phenomenon the chemical reaction approach is used by considering the reaction rate parameter. The results illustrate that for high inlet velocitis the reactions tend to produce light species such as O, H and OH. The effects of inlet velocity on flame propagation velocity are also studied. For lower inlet velocities, flame stays longer in an extinction-ignition period in the channel, while increasing the inlet velocity causes the flame to extinguish faster.

The turbulent burning velocity of air- fuel mixture depends on the laminar burning velocity and turbulent aspects. The main factors influencing the laminar burning velocity are the fuel type, pressure, temperature and equivalence ratio of the mixture. In the current work, a constant volume spherical bomb and its related equipment are used to capture the experimental pressure-time data during combustion. The data is defined as input to a multi- zone thermodynamic model to calculate the laminar burning velocity. The velocity is evaluated for gasoline-air and natural gas (NG) -air mixtures at stoichiometric equivalence ratio and NG- gasoline- air mixtures with NG mass fraction of 25%, 50%, 75% and 100% at stoichiometric conditions with initial pressure and temperature of 500kPa and 333K, respectively. The obtained results of laminar burning velocity of gasoline- air in comparison with NG-air mixtures shows that the NG-air laminar burning velocity in the range of 5 to 20bar is higher than that of gasoline- air mixture. For dual fuel NG- gasoline it is observed that at the stoichiometric conditions and when the bomb pressure is lower than 20bar, the laminar burning velocities of 25% and 50% NG in dual case are lower than in the case of 100% NG.

The aim of this study is to investigate the effects of chemical kinetics and radiation model on the combustion of natural- gas- oxygen mixture using flamelet combustion model. For this purpose, C1_C3, DRM22 and GRI3.0 chemical kinetics mechanisms are combined with DO and P1 radiation models in the simulations. In addition, results with and without modelling radiative heat transfer are compared. The results of flamelet combustion model are also compared with the experimental data and PaSR combustion model. The most important advantage of using flamelet combustion model over the PaSR model is significant reduction in the cost of calculation. According to the obtained results, C1_C3 chemical mechanism predicts the temperature distribution in the furnace with highest accuracy and the predicted flame shape is a good match with that obtained using PaSR model. The flame length obtained using DRM22 and GRI3.0 chemical mechanisms, however, is very small. In addition, using P1 radiation model in comparison with DO leads to more computational errors in calculating the temperature distribution and the length of the high temperature region in the furnace, due to over- predicting the radiation losses.

One of the major goals for manufacturers of turbocharged spark ignited (SI) engines is to increase the knock resistance at high loads. In order to move out of knocking combustion, timing of the spark ignition is retarded, thus limiting the maximum pressure and temperature in the combustion chamber. This is an effective method to eliminate the knock. The negative effect of retarding spark timing is increasing the exhaust gas temperature. In order to reduce the exhaust gas temperature, rich mixtures are normally used. As a result, the fuel consumption increases. The cooled EGR can be used to solve this problem. Using the cooled EGR decreases the pressure and the temperature in the unburned zone. There are a number of different possible architectures, each with its specific characteristics. Main objectives of this study were to quantify the increase the knock resistance and to decrease the enrichment in order to the target stoichiometric operation over the full operating range. All the simulations were carried out in the GT-POWER Software on the EF7-TC engine.