旋转蛇形通道内换热的非稳态实验

在旋转状态下,研究了涡轮内冷蛇形通道的非稳态换热特性.实验主要针对旋转状态下,通道内流量的变化和系统旋转速度的变化来进行的.结果表明:对于旋转通道的非稳态过程,换热系数的变化呈波动变化过程,且主要发生在实验参数变化的阶段.加速旋转时,角加速度力的作用会加强进气通道前缘面的换热,而降低后缘面的;减速旋转时,情况相反.而且,角加速度力的作用效果容易在旋转开始变化的时刻显现.当旋转速度在2个值之间往复时,换热系数变化呈现滞后环状,旋转速度越高滞后环越大.

Experiment of heat transfer within a rotating ribbed serpentine passage in unsteady cases

Experiments were conducted to study the heat transfer characteristics of a rotating ribbed square serpentine passage for unsteady cases. Abundant experimental data were obtained to investigate the variation of heat transfer coefficient at different engine working conditions, such as mass flux and rotational speed. For unsteady cases, the convective heat transfer was affected by the cross-stream secondary flow caused by unbalance distribution of the Corilis, the buoyancy and the angular acceleration forces. Effects of angular acceleration force increase heat transfer coefficients on leading surface and decrease the coefficients on trailing surface in radial outward passage flow for the accelerating rotation system; Reverse conclusions can be obtained for the case of decelerated rotation system. It is shown that the fluctuations of heat transfer coefficients occur mainly at the moment when the work conditions vary under unsteady cases. The fluctuations of heat transfer coefficients mainly occur at the moment when the work conditions change, though long exists of the walls temperatures variation. An interesting phenomenon was also observed that there exists a hysteresis of Nu number ratio when the variation of rotational speed completes a cycle.