M. H. Shojaeefard, I. Sohrabiasl, E. Sarshari,
Volume 1, Issue 2 (6-2011)
Abstract
Intake system design as well as inlet ports and valves configuration is of paramount importance in the optimal performance of internal combustion engines. In the present study, the effect of inlet ports design is investigated on OM-457LA diesel engine by using a CFD analysis and the AVL-Fire code as well. A thermodynamic model of the whole engine equipped with a turbocharger and an intercooler is used to obtain the initial and boundary conditions of the inlet and outlet ports of the engine cylinder which are necessary for performing the three dimensional CFD analysis. The intake stroke as well as the compression and power strokes are included in this three dimensional CFD model. As a mean of validation the performance of the engine model with the base configuration of the inlet ports is compared to the experimental data. Two new alternative configurations for the inlet ports are then investigated with respect to the turbulence levels of the in-cylinder flow and the combustion characteristics as well. Finally it is demonstrated that applying the new configurations results in circa 75% reduction in nitric oxide formation besides increase of 32% in the in-cylinder flow swirl.
A. Zandi, S. Sohrabi, M. Shams,
Volume 5, Issue 1 (3-2015)
Abstract
Cavitation and turbulence in a diesel injector nozzle has a great effect on the development and primary breakup of spray. However, the mechanism of the cavitation flow inside the nozzle and its influence on spray characteristics have not been clearly known yet because of the internal nozzle flow complexities. In this paper, a comprehensive numerical simulation is carried out to study the internal flow of nozzle and the cavitation phenomenon. The internal cavitation flow of the nozzle is simulated using the Eulerian-Eulerian two-fluid model. In this approach, the diesel liquid and the diesel vapor are considered as two continuous phases, and the governing equations of each phase are solved separately. Simulation method is validated by comparing the numerical results with experimental data and good correspondence is achieved. The effective parameters on the nozzle flow are investigated, including injection pressure, back pressure, inlet curvature radius of orifice, orifice iconicity and its length. Results clearly show the importance of nozzle geometrical characteristics and dynamic parameters on the internal nozzle flow. Discharge coefficient of nozzle and cavitation distribution in the nozzle are extremely dependent on these parameters, so the effect of cavitation on the primary breakup is not negligible.
Dr Moslem Mohammadi Soleymani, Benyamin Sohrabinejad, Dr Aliakbar Majidi Jirandehi,
Volume 14, Issue 2 (6-2024)
Abstract
In the automobile sector, stainless steel and resistance spot welding (RSW) are often used. In this work, RSW was used to join five samples of 316L stainless steel joints at currents of 15, 20, 25, 30, and 35 kA while the heat input parameters varied. The welded joints' microstructure, hardness, and mechanical properties were examined and evaluated. The base metal, heat-affected zone (HAZ), and weld areas' microstructures were all examined using optical microscopy. The mechanical characteristics of the joints were assessed using room-temperature tensile-shear testing and hardness testing. The microstructure findings revealed ferrite in many weld regions and an austenitic structure overall. In the samples with welding currents of 15, 20, 25, 30, and 35 kA, the average hardness of the weld zone was 329, 258, 251, 238, and 235 Vickers, in that order. The hardness of the weld zone exhibited an inverse connection with the welding current, as an increase in welding current resulted in a drop in the resistance spot welded area's hardness. Furthermore, when heat input increased, the hardness of the HAZ reduced and increased relative to the 316L steel. The joint strength of the RSW increased with increasing welding current, as demonstrated by the tensile-shear test results for all five welded samples with varying currents. As a result, the samples with 30 and 35 kA currents failed at the weld with a force greater than 3 kN, while the other samples with lower welding currents had a failure force of less than 2 kN.
