فهرست مطالب m. ziabasharhagh

This paper introduces a novel approach to enhance the performance of a two-phase steam and air ejector through primary supersonic nozzle designs with uncircular cross-sections. Experimental tests evaluated the impact of these novel nozzle designs ،which included a star shape ،a simple square ،a square skewed in the direction of the nozzle axis ،a special sketch ،and a simple circular cross-section as the reference nozzle ،on the ejector's performance. The results indicated that the novel nozzles demonstrated the capability to enhance the ejector's entrainment ratio by up to 12% compared to the conventional circular cross-section reference nozzle. To validate and gain further insights into the novel nozzle designs ،computational fluid dynamics (CFD) simulations were also conducted. The integration of CFD simulations and experimental data showcased the potential of these uncircular cross-section nozzles to improve the ejector's performance. The findings offer promising opportunities for optimizing ejector configurations ، paving the way for more efficient and innovative solutions in various engineering applications.

Turbochargers are generally used in the combustion engine due to their capability to increase the specific power. This paper investigates the performance of the turbocharger turbine, which is mounted in a gasoline engine. Different working points, including close and open wastegate positions, are studied in a steady-state condition. The experimental test of this article has been performed on an engine test cell. The movement of the wastegate linkage in different working conditions of the engine was measured in the test cell. Furthermore, the static pressure was measured at the different positions of the turbine housing. Simulation results show that as the wastegate starts to open, maximum loading happens. However, increasing the wastegate opening angle will decrease the force, which is caused by the passing gas. It was found that at 2 degrees opening angle of the wastegate, there is an 80 kPa pressure difference between two sides of the wastegate valve. When the wastegate has a small opening angle, the pressure distribution on the flat surface of the valve is not symmetric, which means the gas does not provide a 360° flow distribution around the valve. Moreover, streamlines show that the high-speed flow passing bypass passage disturbs the flow exiting the turbine blades. Results show that the opening of the wastegate flap can reduce the turbine’s power. The 6 degrees opening of the wastegate causes a 30 percent power reduction. Moreover, the simulation results of the turbine’s map show that at the constant mass flow rate, the opening of the wastegate from the closed position to 6 degrees causes the pressure ratio to decrease 26 percent.

Porous media has interesting features in compared with free flame combustion due to the extended of the lean flammability limits and lower emissions. Advanced new generation of internal combustion (IC) engines are expected to have far better emissions levels both gaseous and particulate matter, at the same time having far lower fuel consumption on a wide range of operating condition. These criteria could be improved having a homogeneous combustion process in an engine. Present work considers simulation of direct fuel injection in an IC engine equipped with a chemically inert porous medium (PM), having cylindrical geometry that is installed in cylinder head to homogenize and stabilize the combustion process. A numerical study of a 3D model, PM engine is carried out using a modified version of the KIVA-3V code. Since there is not any published material for PM-engines in literature, the numerical results for combustion waves propagation within PM are compared with experimental data available in the literature for a lean mixture of air and methane under filtration in packed bed, the accuracy of results are very promising. For PM-engine simulation the methane fuel is injected directly through a hot PM which is mounted in cylinder head. Therefore volumetric combustion occurs as a result within PM and in-cylinder. The effects of injection timing on mixture formation, pressure and temperature distribution in both phases of PM and incylinder fluid together with combustion emissions such as CO and NO are studied in detail for an important part of the cycle.