Altitude Scaling of Ice Crystal Accretion
Altitude Scaling of Ice Crystal Accretion
复制标题
冰晶吸积的高度缩放
DOI：
10.2514/6.2013-2677
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
J. Macleod
中科院分区：
文献类型：
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作者：
T. Currie;D. Fuleki;D. Knezevici;J. Macleod
本文介绍了在加拿大国家研究理事会（NRC）的高空舱中进行的实验，作为发展高空定标律和程序的第一步，这种定标律和程序可能使航空发动机通过在海平面设施中进行的试验而获得在高空冰晶云中运行的合格证明。的主要目的是测试的假设，在压缩机内的吸积由于冰晶摄入发生时，当地的比freesthetic液态水含量（LWC）的总水含量（TWC）位于一个临界范围内的accretionsusceptible位置。如果这一假设是正确的，当地的LWC/TWC的比例是关键参数，必须在测试中匹配在低和高的压力，以匹配吸积。实验是在小型风洞中进行的，轴对称试验件由一个半球形头部和一个圆锥形后体组成，在一个固定的TWC下，在34.5 kPa和69 kPa的（绝对）压力下，在一系列LWC/TWC比范围内进行，以检验假设。通过改变湿球温度来改变LWC/TWC比。在分析预测产生匹配的LWC/TWC比的条件下，在两种压力下测量的吸积稳态体积和生长速率进行了比较。在所有情况下都取得了良好的一致性。在10- 25%范围内，LWC/TWC比率的吸积增长最大。额外的测试表明，湿球温度，这被确定为一个重要的变量在早期的研究中，除了其对LWC/TWC（即冰粒融化）的影响，对吸积增长的影响很小。还进行了测试，以确定是否吸积增长比例与TWC在恒定的LWC/TWC线性。这些测试证实，不仅在早期生长阶段的吸积生长速率与TWC成正比，而且吸积的最终尺寸也成正比。一个简单的半经验模型来预测这种行为。虽然大多数试验都是用45μ的冰粒中值体积直径进行的，但有些按比例缩放试验是用较大的冰粒重复进行的，这产生了较小的积冰。
This paper describes experiments performed in an altitude chamber at the National Research Council of Canada (NRC) as the first step towards developing altitude scaling laws and procedures that will possibly allow aero-engines to be certified for operation in ice crystal clouds at high altitude by testing in sea level facilities. The principal objective was to test the hypothesis that accretion within a compressor due to ice crystal ingestion occurs when the local ratio of freestream liquid water content (LWC) to total water content (TWC) lies within a critical range at an accretionsusceptible location. If this hypothesis is correct, the local LWC/TWC ratio is the key parameter that must be matched in tests at low and high pressures to match accretions. Experiments were conducted in a small wind tunnel with an axisymmetric test article, consisting of a hemispherical nose attached to a conical afterbody, at a fixed TWC over a range of LWC/TWC ratios at (absolute) pressures of 34.5 kPa and 69 kPa to test the hypothesis. The LWC/TWC ratio was varied by changing the wet bulb temperature. Accretion steady-state volumes and growth rates measured at the two pressures were compared at conditions which were analytically predicted to produce matched LWC/TWC ratios. Good agreement was achieved in all cases. Accretion growth was greatest for LWC/TWC ratios in the range 10-25%. Additional tests demonstrated that wet bulb temperature, which was identified as an important variable in earlier studies, had little influence on accretion growth beyond its effect on LWC/TWC (i.e. ice particle melting). Tests were also conducted to determine whether accretion growth scales linearly with TWC at constant LWC/TWC. Those tests confirmed that not only does the accretion growth rate in the early growth phase scale in direct proportion to TWC , but so does the final size of the accretion. A simple semi-empirical model for predicting this behavior is described. While most of the tests were conducted with an ice particle median volumetric diameter of 45μ, some of the scaling tests were repeated with larger particles, which produced smaller accretions.