---

A two dimensional numerical study is presented for steady state performance analysis of a catalytic radiant counter-diffusive burner. In these burners, the gaseous fuel enters from the rear of the burner and passes through the insulation and catalyst layers. The oxygen enters the catalyst layer from the burner surface and opposite to the fuel path. The reaction takes place over the catalyst layer. In this paper, the momentum, energy and species conservation equations in porous and non-porous media are solved using the finite element method in the COMSOL software. The simulations are based on proposed corrections on boundary conditions and combustion rate of methane equation. The simulation results compared with experimental measurements published in the literature for the same geometry and conditions which shows a considerable (10%) improvements. It is shown that diffusion of oxygen through the pad limits the catalytic combustion and controls the fuel conversion in the burner.

---

In the present study, fabrication and performance testing of a flameless catalytic pad has been investigated. The catalyst was prepared with 1g of H2PtCl6.6H2O solved in 0.5 liter solvent contains 50% water and 50% ethanol and sprayed on the alumina - silica fiber mat as the catalyst support. The wet pad was dried and calcined before usage. The performance of the heater was evaluated by design and fabrication of a test stand which was capable of measuring parameters such as temperature at surface and in depth of the catalyst layer, the amount of pollutants such as CO and NOx, flow rate and pressure of the fuel and surface air circulation in front of the pad. In addition, by placing the panel containing the pad in an environmental test chamber, the effect of different climate conditions in five cities of Iran, i.e., Borojerd, Khalkhal, Lavan, Mahshahr and Puladshahr were investigated. Average surface temperature of the pad was measured about 350°C. No NOx was detected and CO emission of the burner was measured up to 5ppm. In Khalkhal conditions with the lowest temperature and humidity, the highest temperature at surface was recorded and the maximum CO emissions in Mahshahr with the highest temperature and humidity was about 3ppm. It was shown that increasing the fuel flow rate increases the surface temperature and CO emissions. It was also shown that an increase of environment temperature and humidity, increases the surface temperature.

---

In recent years, Aerodynamic analysis of automobiles became one of the most important parameters which affect the power of the companies to be present in world markets. Therefore, they can be considered as one of the most important factors in aerodynamic design of vehicles. The formation of the vortex and consequently the pressure drop in the rear of the vehicle can increase the aerodynamic forces.
This paper investigates the methods for reduction of the vortices volume in the rear part of a sedan type vehicle by changing in geometry of the vehicles
. For this purpose, firstly in order to choosing the appropriate turbulence model and 3D simulation of incompressible flow around the Ahmed model (which its experimental results are available) was simulated using computational fluid dynamics. Then, the values of aerodynamic coefficients of a car model were studied by adding spoiler and creating curvature at its lateral surfaces. The results of this study indicated that the vortex volume formed at the rear of the vehicle can be simulated more precisely by using the Boundary-layer mesh around the model and analyzing the flow using the DES-SSTK-ω turbulence model Relative to the model K-ω-SST. Additionally, simultaneously use of the spoiler and the curvature of the lateral surfaces reduce fuel consumption and increase the stability of the vehicle due to a 26.3 % reduction in rear drag coefficient and a 5.2 % reduction in the lift coefficient, with respect to the simple car model.

---

Energy absorbers are used to absorb the kinetic energy of objects and convert it into another form, the most important of which are cylinder thin-walled tubes. In a thin-walled cylindrical absorber, the three parameters of diameter, thickness, and length affect the amount of energy absorption. In this research, to obtain the necessary information for designing an inexpensive energy absorber with high absorption capability, thin-walled cylinders with air pressure inside which the air inside condenses when collapsing have been investigated. In the current study, dynamic and axial loadings were chosen to have a higher match with reality. The simulation and analysis of the problem have been done by the finite element method and by applying Johnson-Cook coefficients to model the material's behavior. In the following, the graph of the total work done with time is extracted as the output of the problem, and its correctness has been proved by experimental tests. Then, different samples were modeled and based on them, the method of design of the experiment was applied. Using the results of the variance analysis, the absorber's optimal parameters have been designed by using the time evolutionary optimization algorithm. The results show that it is possible to reduce the weight of the absorber by creating internal density without lowering the absorbency.