旋转通道入口湍流度控制方法及验证

针对旋转通道实验,为了获得理想的旋转通道入口湍流度,更好地模拟实际涡轮叶片内冷通道的流动换热,提出了一种入口湍流度控制方法,并通过实验对该方法进行了验证和初步探索.实验中,在边长为40mm×40mm的方形通道中,放置了一层网丝直径d=3mm,网丝间距Mu=12mm的阻尼网,利用热线风速仪,得到了雷诺数为2 200~3 900范围内的阻尼网后下游湍流特性.研究发现:流体通过该阻尼网后,湍流度显著增大并沿流向逐渐衰减,相同点湍流度随阻尼网雷诺数增大而增大,气流在阻尼网后较短距离内就获得了5%的湍流度,这与实际涡轮叶片内冷通道流动湍流度相当;阻尼网雷诺数越小,流动越早进入横向均匀及各向同性湍流;通过经典公式对阻尼网后通道中心湍流度沿流向分布进行拟合,实验数据与曲线拟合较好.

Control method of inlet turbulent intensity in rotating channel and validation

In the experiments of rotating channels, in order to acquire an ideal inlet turbulent intensity in rotating channel and better simulate the flow and heat transfer in a inner-cooling channel of turbine, a control method of inlet turbulent intensity was proposed and implemented by experiment in current work. In a square channel of 40mm×40mm, a hot wire anemometry is used to measure the turbulent characteristics downstream of a grid which has a diameter of 3mm and mesh size of 12mm. The grid Reynolds numbers range from 2200 to 3900. It is shown that the turbulent intensity of flow after the grid increases significantly and then decreases along downstream direction. Its value on the same position increases as the grid Reynolds number increases. In a short length, the flow after the grid reaches a turbulent intensity of 5% which is equal to the value in a real turbine inner-cooling channel. Besides, it is revealed that the flow will be more likely to become homogeneous and isotropic at a lower grid Reynolds number. A classic formula was used to fit the data of turbulent intensity in central channel after grid along downstream direction. The experiment data fit well with the curves.