This research investigates the aerodynamic performance and flow characteristics of a delta wing with 65° sweep angle and with coarse axial riblets,and then compares with that of a smooth-surface delta wing.Partic...This research investigates the aerodynamic performance and flow characteristics of a delta wing with 65° sweep angle and with coarse axial riblets,and then compares with that of a smooth-surface delta wing.Particle Image Velocimetry(PIV)were utilized to visualize the flow over the wing at 6 cross-sections upright to the wing surface and parallel to the wing span,as well as 3 longitudinal sections on the leading edge,symmetry plane,and a plane between them at Angles of Attack(AOA)=20°and 30°and Re=1.2×10~5,2.4×10~5,and 3.6×10~5.The effects of the riblets were studied on the vortices diameter,vortex breakdown location,vortices distance from the wing surface,flow lines pattern nearby the wing,circulation distribution,and separation.The results show that the textured model has a positive effect on some of the parameters related to drag reduction and lift increase.The riblets increase the flow momentum near the wing’s upper surface except near the apex.They also increase the flow momentum behind the wing.展开更多
Jet engine manufacturers and designers are seeking for lighter and smaller type of axial compressors.Improving the aerodynamic characteristics of blades is carried out by controlling the boundary layer.One way to cont...Jet engine manufacturers and designers are seeking for lighter and smaller type of axial compressors.Improving the aerodynamic characteristics of blades is carried out by controlling the boundary layer.One way to control the boundary layer is using tandem blades.Tandem-blade cascades are capable of using highly loaded stages for axial compressors because they provide more works than single-blade cascades.In other words,tandem blades help to achieve a specified total pressure ratio with less number of stages.Therefore,one of the most important problems for researchers is to optimize the aerodynamic parameters of tandem blades.Changing the geometrical parameters of blades is a method to achieve this purpose.In this work,the stagger and camber angle of each blade are first changed while the other geometrical parameters such as overall camber,total stagger angle,the axial overlap,percent pitch and chord ratio are fixed.Secondly,the overall camber angle of tandem blade is changed by increasing the difference between the stagger angle of the first and second blade while the type of two airfoils,axial overlap and percent pitch,overall chord length and overall stagger angle are fixed.The aerodynamic performances of the generated tandem-blade cascades are obtained using two-dimensional numerical solution of flow.For this,a viscous turbulent flow solver is used for solving the Navier-Stokes equations.In these simulations,inlet Mach number is fixed to 0.6.展开更多
The present study introduces an innovative aerodynamic redesign of an axial flow fan based on constant diffusion factor and radial equilibrium.All input design parameters such as mass flow rate,hub to tip ratio,aspect...The present study introduces an innovative aerodynamic redesign of an axial flow fan based on constant diffusion factor and radial equilibrium.All input design parameters such as mass flow rate,hub to tip ratio,aspect ratio,tip diameter and angular velocity are taken from NASA Rotor 67 as a conventional axial flow fan.A computer program is developed to extract the three-dimensional geometry of a fan and to estimate the span-wise distribution of parameters.The new designed fan flow field is investigated in detail by CFD tool at both design and off design conditions.Finally,a turbofan cycle analysis is conducted based on thermodynamic and gas dynamic principles to evaluate the fan performance in a turbofan engine in comparison to NASA Rotor 67.Achieving a higher total pressure ratio,meeting the target pressure ratio in lower rotational speed with higher efficiency,delivering more bypass air in a constant diameter and less fuel consumption for the same specific thrust force are the main advantages for the new design strategy in comparison to the conventional designed fans such as Rotor 67.However,efficiency reduction in fan over speed is the main disadvantage.展开更多
基金supported by the Brain Pool Program through the Korean Federation of Science and Technology Societies (KOFST), which is funded by the Ministry of Science, ICT and Future Planningprovided by the National Research Foundation of Korea (NRF) grant, which is funded by the Korean government (MSIT) (Nos. 2011-0030013, 2018R1A2B2007117 and NRF-2017K1A3A1A30084513)
文摘This research investigates the aerodynamic performance and flow characteristics of a delta wing with 65° sweep angle and with coarse axial riblets,and then compares with that of a smooth-surface delta wing.Particle Image Velocimetry(PIV)were utilized to visualize the flow over the wing at 6 cross-sections upright to the wing surface and parallel to the wing span,as well as 3 longitudinal sections on the leading edge,symmetry plane,and a plane between them at Angles of Attack(AOA)=20°and 30°and Re=1.2×10~5,2.4×10~5,and 3.6×10~5.The effects of the riblets were studied on the vortices diameter,vortex breakdown location,vortices distance from the wing surface,flow lines pattern nearby the wing,circulation distribution,and separation.The results show that the textured model has a positive effect on some of the parameters related to drag reduction and lift increase.The riblets increase the flow momentum near the wing’s upper surface except near the apex.They also increase the flow momentum behind the wing.
文摘Jet engine manufacturers and designers are seeking for lighter and smaller type of axial compressors.Improving the aerodynamic characteristics of blades is carried out by controlling the boundary layer.One way to control the boundary layer is using tandem blades.Tandem-blade cascades are capable of using highly loaded stages for axial compressors because they provide more works than single-blade cascades.In other words,tandem blades help to achieve a specified total pressure ratio with less number of stages.Therefore,one of the most important problems for researchers is to optimize the aerodynamic parameters of tandem blades.Changing the geometrical parameters of blades is a method to achieve this purpose.In this work,the stagger and camber angle of each blade are first changed while the other geometrical parameters such as overall camber,total stagger angle,the axial overlap,percent pitch and chord ratio are fixed.Secondly,the overall camber angle of tandem blade is changed by increasing the difference between the stagger angle of the first and second blade while the type of two airfoils,axial overlap and percent pitch,overall chord length and overall stagger angle are fixed.The aerodynamic performances of the generated tandem-blade cascades are obtained using two-dimensional numerical solution of flow.For this,a viscous turbulent flow solver is used for solving the Navier-Stokes equations.In these simulations,inlet Mach number is fixed to 0.6.
文摘The present study introduces an innovative aerodynamic redesign of an axial flow fan based on constant diffusion factor and radial equilibrium.All input design parameters such as mass flow rate,hub to tip ratio,aspect ratio,tip diameter and angular velocity are taken from NASA Rotor 67 as a conventional axial flow fan.A computer program is developed to extract the three-dimensional geometry of a fan and to estimate the span-wise distribution of parameters.The new designed fan flow field is investigated in detail by CFD tool at both design and off design conditions.Finally,a turbofan cycle analysis is conducted based on thermodynamic and gas dynamic principles to evaluate the fan performance in a turbofan engine in comparison to NASA Rotor 67.Achieving a higher total pressure ratio,meeting the target pressure ratio in lower rotational speed with higher efficiency,delivering more bypass air in a constant diameter and less fuel consumption for the same specific thrust force are the main advantages for the new design strategy in comparison to the conventional designed fans such as Rotor 67.However,efficiency reduction in fan over speed is the main disadvantage.
