结冰风洞试验水滴直径选取方法

结冰风洞是开展飞机结冰研究的主要设备,确定合理的试验水滴大小,是选取结冰风洞试验条件的重要内容。为了研究结冰风洞试验水滴直径的选取原则,针对结冰风洞试验水滴的大小主要取决于试验速度的大小,在推导结冰风洞试验水滴直径选取公式的基础上,用数值方法预测并对比了不同试验速度对水滴大小选取效果及试验结果的影响。采用欧拉法数值计算了不同试验速度及相应试验水滴条件下,试验模型表面的水滴收集率,并与全尺寸物体表面的水滴收集率进行了对比。研究发现:对于小水滴,当参考速度较低时,试验速度与参考速度的比值不能取得太低,参考速度升高到一定程度之后,试验速度与参考速度的比值又不能取得太高;对于大水滴,当参考速度较低时,试验速度与参考速度的比值也不能取得太低,当参考速度升高到一定程度之后,试验速度和相应试验水滴直径的改变对模型表面的水滴收集率影响较小,试验速度与参考速度的比值在0.3～1.0之间变动,均可以在模型和全尺寸物体上得到一致的水滴收集率。

Selection of Water Droplet Diameter in Icing Wind Tunnel Test

The icing wind tunnel is the main facility for aircraft icing research. Water droplet diameter is one of the most important parameters of tests in an icing wind tunnel. Currently, the value of water droplet diameter is decided mainly by the test speed. To obtain the rule for selecting a reasonable droplet size, the formula for the selection of water droplet diameters in an icing wind tunnel test is derived in this article. Then the effect of speed on droplet size and test results is studied. Water droplet collection efficiency for different speeds and its corresponding droplet sizes on test models is computed with Eulerian method, which is then compared with the values on a full scale body. The result shows that, for small water droplets, when the reference speed is low, the ratio of the test speed to the reference speed should not be selected too small, and it should not be too large when the reference speed increases to a certain value. For large water droplets, when the reference speed is low, the ratio should not be selected too small either; however, when the reference speed increases to a certain value, the changes of test speeds and the corresponding droplet sizes do not affect the collection efficiency on the test model. The same collection efficiency on full scale bodies and test models can be obtained once the ratio of the test speed to the reference speed is in the range of 0.3 to 1.0.