Amirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29377320240901Experimental and Numerical Study of a Supercritical Wing Performance at Low Reynolds Numbers Equipped with Different Winglet Planforms11527310.22060/ajme.2023.22145.6057ENParisaGhanooniDepartment of Aerospace Engineering, Amirkabir University of Technology, Tehran, IranMostafaKazemiDepartment of Aerospace Engineering, Amirkabir University of Technology, Tehran, IranMeisamHeydariDepartment of Mechanical Engineering, Polytechnic of Milan, Milan, ItalyMahmoudManiDepartment of Aerospace Engineering, Amirkabir University of Technology, Tehran, IranJournal Article20230202In the era of rapid technological developments, the green aircraft and winglets of an airplane play a crucial role in reducing fuel consumption and its ensuing pollution. In this regard, the novelty of this paper is to focus on investigating the effect of the different geometrical parameters of winglets planforms on improving the aerodynamic performance of a wing with a supercritical airfoil (NACA 641412) at lower Reynolds numbers (take-off and landing phase). These investigations were conducted experimentally in a wind tunnel by force measurements through an external force balance. The aerodynamic coefficients of CL and CL/CD were obtained for the clean wing and nine various winglet planforms at a wide range of angles of attack from -4° to 20° and Reynolds numbers from Re=0.99×105 to Re=1.98×105. Furthermore, to get better insight into the physics of the flow, the numerical simulation of specific cases was carried out. According to the force measurement and vorticity magnitude results, among single winglets of W1, W2, W3, and W4, the W1 winglet with vertical height and linear side showed a better performance in all Reynolds numbers with a maximum lift increment of 26%; also, the W7 winglet planform represented the best performance as in double winglets with a maximum lift-to-drag ratio increment of 40%.https://ajme.aut.ac.ir/article_5273_d193b787172c0fa500f373687f83e281.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29377320240901An Organic Rankine Cycle for Waste Heat of a Diesel Engine with Ethanol and Methanol Blends22533510.22060/ajme.2024.22229.6059ENYousefLotfiFaculty of Mechanical Engineering, University of Tabriz, Tabriz, IranSevdaAllahyariFaculty of Mechanical Engineering, University of Tabriz, Tabriz, IranMortazaYariFaculty of Mechanical Engineering, University of Tabriz, Tabriz, IranFarzadMohammadkhaniMechanical Engineering Department, Engineering Faculty of Khoy, Urmia University of Technology, Urmia, Iran0000-0003-3399-3099Journal Article20230224This paper refers to retrieve the lost heat of exhaust gas and working fluid of a turbocharged Diesel engine employing a Dual-Pressure Organic Rankine Cycle (DPORC). The efficiency and emission of Diesel compression ignition engine is studied by considering a one-dimensional two-zone thermodynamic model. In the proposed system, exhaust gas and intercooler waste heat have been utilized in the high and low pressure evaporators, respectively. The used cycle has the capability of reducing the irreversibility of heat transfer process in the evaporators and increasing the turbines’ power. Furthermore, hybrid fuels are used in the turbocharged Diesel engine to decrease the level of environmental pollutants. Accordingly, an exergy-based thermodynamic approach is employed to analyze a Diesel engine’s performance and its emissions. The proposed engine includes Diesel fuel mixed with methanol and ethanol with different volume fractions of 5% and 10%. The results indicate a reduction in power and maximum brake torque of the engine as well as a remarkable decrement in emission of pollutants such as NOx and CO (equal to 15%) by using the alcoholic compounds with Diesel fuel. Also, R123 is an appropriate coolant utilized in the DPORC for recovering the lost heat of the Diesel engine.https://ajme.aut.ac.ir/article_5335_e298ad44a986579d72492e80f93784df.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29377320240901Mathematical study on performance enhancement of solar updraft tower power plant by hot gas injection from an external source33533910.22060/ajme.2024.22382.6064ENMiladSetarehJundi-Shapur University of Technology, Dezful, IranMohammad RezaAssariJundi-Shapur University of Technology, Dezful, IranJournal Article20230504In this paper, a theoretical model for simulation of solar updraft tower power plant with the assumption of axisymmetric condition is developed to study the impact of hot gas injection at the chimney base as well as extraction a portion of hot gas after the turbine and re-entered it at the collector inlet. A new computational code is written by Matlab software and the effects of operational parameters are studied. Results show that the maximum power output is increased by 49.9% with increasing the extraction fraction from 0% to 40% at a wind velocity of 10 m/s. Besides, the obtained results show that the power output enhances as the mass flow rate of hot gas increases. As a result, the maximum power output at a hot gas mass flow rate of 30 kg/s is approximately 37% higher than the one at a hot gas mass flow rate of 10 kg/s. Results reveal that the optimum performance of SUTPP takes place at the ratio of pressure drop across the turbine to driving pressure potential in the range from 0.83 to 0.87. Furthermore, the power output in the presence of wind is investigated and the positive influence of wind on the SUTPP performance is illustrated. Results indicate that with increasing the wind velocity from 10 m/s to 30 m/s, the maximum power output is increased by 386.1%.https://ajme.aut.ac.ir/article_5339_fcc5012b3735be4c521050b32c01d446.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29377320240901Modeling the droplet break-up based on drawing the shape using velocity gradient and normal vector44535510.22060/ajme.2024.22348.6061ENSalehHeydarpoorTarbiat Modares UniversityNavid MFamilitarbiat modares university0000-0002-9499-1962Journal Article20230421The present study developed a model to deform a viscous droplet in a viscous matrix by a shear flow based on changing the normal vector. The initial cross-section was assumed to be a regular polygon with 1000 sides instead of a circle or ellipsoid, and also this model was independent of the initial polygon shape. Changing the normal vector and the length of each side of the droplet was a function of the velocity gradient. To calculate the velocity gradient over each side of the shape, the equations of tangential and normal stress, the conservation of mass equation, and the absence of mass transfer equation between two phases were solved simultaneously. By knowing the velocity gradient, normal vectors and the length of each side are calculated; therefore, the new shape can be plotted by drawing sides one after another. Then, four series of parameters were used for the simulation of the deformation of the droplet and its break-up. The results displayed that the time of the break-up, which this model predicts, coincides with the experimental results. On the other hand, the predicted shape of the droplet at the break-up has logically coincided with the experimental results in the middle range of the Capillary number ratio (1.4 Cac-2.6 Cac). This model could calculate the velocity gradient and velocity profile over and around the droplet.https://ajme.aut.ac.ir/article_5355_9d1771e1496723eac50a1d505ecae26a.pdf