大型结冰风洞云雾场适航应用符合性验证

Airworthiness application compliance verification of cloud flowfield in large icing wind tunnel

结冰风洞云雾场符合性是大型结冰风洞适航应用的基础。为验证3m×2m结冰风洞云雾场符合性,发展了基于SAE ARP5905的结冰风洞云雾场符合性验证方法,针对主试验段构型,开展了结冰云雾场符合性验证试验,获得了试验段内液滴尺寸和液态水含量拟合关系,考察了喷嘴水压、液滴尺寸、试验段气流速度和喷嘴数量对试验段液态水含量的影响,形成了主试验段结冰云雾控制包线。结果表明:主试验段内液滴尺寸分布具有显著的单峰分布特征,体积中值直径(MVD)模拟范围近似在10~75μm之间;试验段中心处液态水含量随着喷嘴水压和MVD的增大而增大,同时近似与试验段气流速度成反比,与喷嘴数量成正比;增大喷嘴水压和喷嘴数量会提高试验段内云雾液态水含量空间均匀性,但是增大气流速度却会减弱试验段内云雾空间均匀性;3m×2m结冰风洞主试验段结冰云雾控制包线可以覆盖大部分适航条例25部附录C结冰气象条件,但对低液态水含量结冰条件的模拟仍存在局限。

The compliance of the cloud flowfield of large icing wind tunnels is the foundation of their airworthiness application.To verify the compliance of the cloud flowfield of the 3 m×2 micing wind tunnel,a verification method based on SAE ARP5905 is firstly developed,followed by a verification test on the main test section,from which the fitting relationships of droplet sizes and liquid water content are obtained.In addition,the effect of the nozzle water pressure,droplet sizes,test section velocity and nozzle number on the test section liquid water content are examined.Finally,the icing cloud operating envelop is built for the main test section.Results show that the distribution of droplet sizes is unimodal and the simulation range is approximately from 10 to 75μm.Furthermore,the liquid water content in the center of the test section increases as the nozzle water pressure and Median Volume Diameter(MVD)increase,while approximately inversely proportional to the test section velocity and proportional to the nozzle number.Increased nozzle water pressure and nozzle number would enhance the spatial uniformity of the cloud liquid water content in the test section;however,increased test section velocity could reduce the spatial uniformity of the cloud.Moreover,although the icing cloud operating envelop of the 3 m×2 micing wind tunnel for the main test section could cover most of the icing atmospheric conditions listed in Appendix C,Part 25 of FAR,limitations still exist for simulations under low liquid water content conditions.