为进一步理解节流盘对主次流轴向进气超紧凑燃烧室性能的影响,基于Cot t le超紧凑燃烧室原型结构,采用计算流体力学的方法探究了燃烧环内旋流涡流燃烧的组织原理以及节流盘对旋流涡流燃烧特性及出口温度特性的影响。结果表明:节流盘可...为进一步理解节流盘对主次流轴向进气超紧凑燃烧室性能的影响,基于Cot t le超紧凑燃烧室原型结构,采用计算流体力学的方法探究了燃烧环内旋流涡流燃烧的组织原理以及节流盘对旋流涡流燃烧特性及出口温度特性的影响。结果表明:节流盘可提高燃烧环内混气的离心加速度,加快火焰传播速度;节流效应导致的低压区可增大高温燃气径向迁移速度,增强高温燃气与核心流的掺混,改善燃烧室出口温度分布特性;燃烧环内存在涡流燃烧,节流盘可扩展燃烧涡的尺寸,提高火焰稳定性。展开更多
Fish are able to make good use of vortices.In a complex flow field,many fish continue to maintain both efficient cruising and maneuverability.Traditional man-made propulsion systems perform poorly in complex flow fiel...Fish are able to make good use of vortices.In a complex flow field,many fish continue to maintain both efficient cruising and maneuverability.Traditional man-made propulsion systems perform poorly in complex flow fields.With fish-like propulsion systems,it is important to pay more attention to complex flow fields.In this paper,the influence of vortices on the hydrodynamic performance of 2-D flapping-foils was investigated.The flapping-foil heaved and pitched under the influence of inflow vortices generated by an oscillating D-section cylinder.A numerical simulation was run based the finite volume method,using the computational fluid dynamics(CFD) software FLUENT with Reynolds-averaged Navier-Stokes(RANS) equations applied.In addition,dynamic mesh technology and post processing systems were also fully used.The calculations showed four modes of interaction.The hydrodynamic performance of flapping-foils was analyzed and the results compared with experimental data.This validated the numerical simulation,confirming that flapping-foils can increase efficiency by absorbing energy from inflow vortices.展开更多
Continuous vorticity panels were used to model general unsteady inviscid, incompressible, two-dimensional flows. The geometry of the airfoil was approximated by series of short straight segments having endpoints that ...Continuous vorticity panels were used to model general unsteady inviscid, incompressible, two-dimensional flows. The geometry of the airfoil was approximated by series of short straight segments having endpoints that lie on the actual surface. A piecewise linear, continuous distribution of vorticity over the airfoil surface was used to generate disturbance flow. The no-penetration condition was imposed at the midpoint of each segment and at discrete times. The wake was simulated by a system of point vortices, which moved at local fluid velocity. At each time step, a new wake panel with uniform vorticity distribution was attached to the trailing edge, and the condition of constant circulation around the airfoil and wake was imposed. A new expression for Kutta condition was developed to study the interference effect between two impulsively started NACA0012 airfoils. The tandem arrangement was found to be the most effective to enhance the lift of the rear airfoil. The interference effect between tidal turbine blades was shown clearly.展开更多
文摘为进一步理解节流盘对主次流轴向进气超紧凑燃烧室性能的影响,基于Cot t le超紧凑燃烧室原型结构,采用计算流体力学的方法探究了燃烧环内旋流涡流燃烧的组织原理以及节流盘对旋流涡流燃烧特性及出口温度特性的影响。结果表明:节流盘可提高燃烧环内混气的离心加速度,加快火焰传播速度;节流效应导致的低压区可增大高温燃气径向迁移速度,增强高温燃气与核心流的掺混,改善燃烧室出口温度分布特性;燃烧环内存在涡流燃烧,节流盘可扩展燃烧涡的尺寸,提高火焰稳定性。
基金Supported by the National Natural Science Foundation of China under Grant No.50579007,50879014the specialized research fund for the doctoral program of higher education under Grant No.200802170010
文摘Fish are able to make good use of vortices.In a complex flow field,many fish continue to maintain both efficient cruising and maneuverability.Traditional man-made propulsion systems perform poorly in complex flow fields.With fish-like propulsion systems,it is important to pay more attention to complex flow fields.In this paper,the influence of vortices on the hydrodynamic performance of 2-D flapping-foils was investigated.The flapping-foil heaved and pitched under the influence of inflow vortices generated by an oscillating D-section cylinder.A numerical simulation was run based the finite volume method,using the computational fluid dynamics(CFD) software FLUENT with Reynolds-averaged Navier-Stokes(RANS) equations applied.In addition,dynamic mesh technology and post processing systems were also fully used.The calculations showed four modes of interaction.The hydrodynamic performance of flapping-foils was analyzed and the results compared with experimental data.This validated the numerical simulation,confirming that flapping-foils can increase efficiency by absorbing energy from inflow vortices.
基金Sponsored by National Natural Science Foundation (No. 50279004)the National Hi-Tech. R&D Program of China (No. 2002aa516010)
文摘Continuous vorticity panels were used to model general unsteady inviscid, incompressible, two-dimensional flows. The geometry of the airfoil was approximated by series of short straight segments having endpoints that lie on the actual surface. A piecewise linear, continuous distribution of vorticity over the airfoil surface was used to generate disturbance flow. The no-penetration condition was imposed at the midpoint of each segment and at discrete times. The wake was simulated by a system of point vortices, which moved at local fluid velocity. At each time step, a new wake panel with uniform vorticity distribution was attached to the trailing edge, and the condition of constant circulation around the airfoil and wake was imposed. A new expression for Kutta condition was developed to study the interference effect between two impulsively started NACA0012 airfoils. The tandem arrangement was found to be the most effective to enhance the lift of the rear airfoil. The interference effect between tidal turbine blades was shown clearly.
