Scallop ice shape characteristics of swept wing based on large-scale icing wind tunnel experiment

Scallop ice is a special phenomenon that occurs during swept wing aircraft passing through icing clouds.It poses a great challenge for the icing safety assessment that the complex scallop ice shape feature and its mechanism are still unclear.In this work,a large-scale icing wind tunnel experiment of swept wing designed by NACA0012 airfoil is conducted in the Icing Wind Tunnel of China Aerodynamics Research and Development Center.The detailed three-dimensional ice shapes under 0°,15°,30°and 45°swept angles are obtained by laser scanning technology.The experimental results show that with the swept angle increasing from 0°to 45°,the 2D double ice horn structures show certain spanwise variation,and finally transform into complete scallop ice with ice thickness greatly enhanced in the stagnation line region.The empirical mode decomposition of the spanwise ice curve captures the high-frequency fluctuation on the scallop ice caused by the small-scale roughness element,while the trend with low frequency is not obvious.Based on the experimental data,a new complete scallop ice geometric model,named 5Points-5Lines-2Arcs(5P-5L-2A)model,is proposed,which can provide important basis for the quantitative description of complex scallop ice shape.

An anti-icing scaling method for wind tunnel tests of aircraft thermal ice protection system

The efficiency of the aircraft Ice Protection Systems(IPSs)needs to be verified through icing wind tunnel tests.However,the scaling method for testing the IPSs has not been systematically established yet,and further research is needed.In the present study,a scaling method specifically designed for thermal IPSs was derived from the governing equation of thin water film.Five scaling parameters were adopted to address the heat and mass transfer involved in the thermal anti-icing process.For method validation,icing wind tunnel tests were conducted using a jet engine nacelle model equipped with a bleed air IPS.The non-dimensional surface temperature and runback ice closely matched for both the reference and scaled conditions.The validation confirms that the scaling method is capable of achieving the similarity of surface temperature and the runback ice coverage.The anti-icing scaling method can serve as an important supplement to the existing icing similarity theory.

Design of a large-scale model for wind tunnel test of a multiadaptive flap concept

The design and application of morphing systems are ongoing issues compelling the aviation industry.The Clean Sky-program represents the most significant aeronautical research ever launched in Europe on advanced technologies for greening next-generation aircraft.The primary purpose of the program is to develop new concepts aimed at decreasing the effects of aviation on the environment,increasing reliability,and promoting eco-friendly mobility.These ambitions are pursued through research on enabling technologies fostering noise and gas emissions reduction,mainly by improving aircraft aerodynamic performances.Within the Clean Sky framework,a multimodal morphing flap device was designed based on tight industrial requirements and tailored for large civil aircraft applications.The flap is deployed in one unique setting,and its cross section is morphed differently in take-off and landing to get the necessary extra lift for the specific flight phase.Moreover,during the cruise,the tip of the flap is deflected for load control and induced drag reduction.Before manufacturing the first flap prototype,a high-speed(Ma=0.3),large-scale test campaign(geometric scale factor 1:3)was deemed necessary to validate the performance improvements brought by this novel system at the aircraft level.On the other hand,the geometrical scaling of the flap prototype was considered impracticable due to the unscalability of the embedded mechanisms and actuators for shape transition.Therefore,a new architecture was conceived for the flap model to comply with the scaled dimensions requirements,withstand the relevant loads expected during the wind tunnel tests and emulate the shape transition capabilities of the true-scale flap.Simplified strategies were developed to effectively morph the model during wind tunnel tests while ensuring the robustness of each morphed configuration and maintaining adequate stiffness levels to prevent undesirable deviations from the intended aerodynamic shapes.Additionally,a simplified design was conceived for the flap-wing interface,allowing for quick adjustments of the flap setting and enabling load transmission paths like those arising between the full-scale flap and the wing.The design process followed for the definition of this challenging wind tunnel model has been addressed in this work,covering the definition of the conceptual layout,the numerical evaluation of the most severe loads expected during the test,and the verification of the structural layout by means of advanced finite element analyses.

3D Ice Shape Description Method Based on BLSOM Neural Network

When checking the ice shape calculation software,its accuracy is judged based on the proximity between the calculated ice shape and the typical test ice shape.Therefore,determining the typical test ice shape becomes the key task of the icing wind tunnel tests.In the icing wind tunnel test of the tail wing model of a large amphibious aircraft,in order to obtain accurate typical test ice shape,the Romer Absolute Scanner is used to obtain the 3D point cloud data of the ice shape on the tail wing model.Then,the batch-learning self-organizing map(BLSOM)neural network is used to obtain the 2D average ice shape along the model direction based on the 3D point cloud data of the ice shape,while its tolerance band is calculated using the probabilistic statistical method.The results show that the combination of 2D average ice shape and its tolerance band can represent the 3D characteristics of the test ice shape effectively,which can be used as the typical test ice shape for comparative analysis with the calculated ice shape.

Wind Tunnel Test and Numerical Computation on Ice Accretion on Blade Airfoil for Straight-bladed VAWT

To invest the condition of ice accretion on the blade used for straight-bladed vertical axis wind turbine （SB-VAWT）, wind tunnel tests were carried out on a blade with NACA0015 airfoil by using a small simple icing wind tunnel. Tests were carried out at some typical attack angles under different wind speeds and flow discharges of a water spray with wind. The icing shape and area on blade surface were recorded and measured, Then the numerical computation was carded out to calculate the lift and drag coefficients of the blade before and after ice accretion according to the experiment result, the effect of icing on the aerodynamic characteristics of blade were discussed.

某风洞充气密封系统设计与应用研究

某风洞充气密封系统用于试验期间隔离大门内外气压环境或填充移动部件间隙,保证风洞回路最高可以模拟2万米高空以下气压环境;密封围带基体材料采用植入增强纤维的硅橡胶,围带截面为“凹”型带两侧固定基座,采用直线型带芯分段模压硫化成型,成功研制了适用于高低温环境、长寿命、高膨胀、大尺度环状充气密封围带;充气/放气气路、电磁阀和变送器等基于集成块安装设计;充气/放气控制系统采用PLC+电磁阀+真空发生器;系统通过Profinet接入风洞测控光纤环网,实现本地/远程自动化控制;解决了围带结构、气密泄漏、大尺度密封面平面度和金属气嘴结构设计等问题;系统应用效果好,自动化水平高,有较大推广应用价值。

飞机气动除冰系统试验研究

气动除冰技术具有能耗低、可靠性高的优点,广泛应用于小型商用飞机以及通用航空飞机。研究不同参数对气动除冰效果的影响,是飞机气动除冰系统设计和优化的基础。本文通过对气囊膨胀高度的研究,发现充气时间3 s、充气气压0.2 MPa是实现气囊最佳膨胀高度的条件。在此基础上,先后在地面冷环境以及结冰风洞中建立气动除冰系统试验平台,开展了不同参数对气动除冰效果的试验研究。试验结果表明,充气时间、充气气压、气囊宽度及结冰温度对除冰率均有一定程度的影响。并且,要想实现最好的气动除冰效果,靠近前缘驻点的气囊需达到一定宽度。此外,相较于霜冰,明冰的除冰效果更佳。

高速列车周围风雪运动特性及转向架区域积雪成因分析

采用基于Realizable k-ε模型的非定常雷诺时均方法(URANS)和离散相模型(DPM)研究高速列车底部转向架及其腔体区域的严重积雪问题。基于高速列车底部风雪两相流时空运动演化特性进行深入分析,并对转向架区域积雪成因进行归纳总结。研究结果表明:大量雪粒跟随转向架区域剪切层下方的高速气流流出转向架区域,部分雪粒在转向架中间区域和后端板附近跟随上扬气流向上扬起并撞击黏附在转向架和后端板迎风面,并在转向架底面形成大量积雪;仅有少量雪粒在后侧电机和后端板附近向上爬升至转向架上方,在后端板顶部相遇汇聚后在低速气流驱动下游离折返至前端板附近并重新汇入车底流场,悬浮雪粒在重力作用下沉积在转向架顶面,并在转向架上表面形成少量积雪。

低温试验室内小型风洞设计及结冰过程试验

在低温试验室中利用自搭建风洞设备提供水结冰所需的风速和温度条件,研究了极区风速、温度对水结冰速率的影响.结果表明:结冰池经历了整体快速降温和结冰两个阶段.在前一阶段对流换热占主体换热地位,风速影响大于温度影响;后一阶段随冰厚增加热传导占比逐渐上升,温度的影响也逐渐上升.结合温度变化与冰厚生长数据,计算得出降温速度与结冰速度,结合温度与风速分别进行曲面拟合,得到降温速度、结冰速度关于温度、风速的关系式.

面向适航验证的人工造雪晶核直径实验研究及应用

为了满足国产大飞机的适航试验需求,为扬雪、降雪试验提供规定密度与含水量的雪质,开展结冰风洞造雪实验,对不同工况下的人造雪进行采样和显微观察,利用图像识别算法进行数据分析,探究环境温度、风速、成雪距离、气水比等因素对冰晶生长的影响。结果表明:较大的环境过冷度有利于冰晶的快速生长,导致冰晶平均直径的减小,小于5℃的过冷度有利于冰晶均匀稳定生长;风速的降低与成雪距离的增加均可促进冰晶的直径增大;相比于气水比为1.1时,在气水比为1.2的工况下,较高的气相比例可以促进液滴的成核,然而过低的液相水比例会限制冰晶直径的增长。

大型结冰风洞双供水供气喷雾控制系统研制

双供水供气系统是保证结冰风洞实现过冷大水滴(Super-cooled Large Droplet,SLD)云雾模拟能力的关键,针对现有喷雾系统存在SLD云雾模拟能力不足、运行包线有待扩展等问题,研制了一套大型结冰风洞双供水供气喷雾控制系统。针对喷雾系统控制变量多、测量点数大等特点,基于工业以太网络建立分布式控制系统,制定了试验流程、方法与策略,建立了完善的双供水供气喷雾试验技术,并开展了系统调试与验证。试验结果表明,双路水压、气压控制精度均稳定在1%以内,达到了系统设计指标,该系统可为后续我国飞行器适航审定提供有力支撑。

0.75m×0.50m结冰风洞气动——热流场品质评估

结冰风洞气动—热流场品质是结冰风洞开展试验应用的先决条件,为评估0.75m×0.50m结冰风洞的气流场和热流场品质,依照SAE ARP 5905结冰风洞标准,对0.75m×0.50m结冰风洞的气流场和热流场开展符合性校测试验,考察试验段中心截面的气流速度场、方向场和温度场品质,获得试验段气流速度修正关系和气流总温修正关系。结果表明:试验段气流速度空间最大偏差小于±2%,且试验段气流速度空间均匀性会随着气流速度的增大而得到改善;试验段气流偏角空间最大偏差小于0.8°;气流总温在-20℃以内时,空间均匀性可达到±1℃,气流总温为-30℃时,空间均匀性可达±2℃;0.75m×0.50m结冰风洞的气动—热流场品质符合SAE ARP 5905要求。

高速列车转向架结冰特性风洞实验研究

风雪严寒环境导致转向架区域冰雪大量堆积,严重威胁高速列车行驶安全.为分析风雪严寒天气下转向架的结冰特性,采用包含简化车体和动力转向架的缩比模型,在中南大学轨道车辆积雪结冰风洞开展了高速列车转向架结冰实验研究.采用喷水系统模拟制动夹钳周围融水产生的喷水现象,以再现轮对甩水致转向架结冰过程.研究转向架区域动态结冰过程和整体结冰分布特性、各关键区域的结冰质量占比权重以及转向架结冰速率模型.研究结果表明:轮对甩出的水滴受紊乱流场作用扩散至转向架各个区域,在低温下结冰并随时间迅速发展,直至整个转向架区域被冰层覆盖;对于转向架舱,其后端板结冰严重,结冰质量占转向架舱结冰总质量的28%;对于转向架,构架和制动夹钳区域结冰分布最多,分别占转向架结冰总质量的34%和22%,空气弹簧、横梁和纵梁结冰分布较少,转向架呈现出底部结冰量大、结冰形状复杂的特性.随着结冰时间增加,各区域结冰速率不同,转向架舱、转向架的结冰总质量与结冰时间呈一次函数关系.研究获得的转向架结冰特性和结冰速率模型,可对一定运行时间内转向架结冰质量快速预测提供参考依据,对风雪环境下高速列车安全运行和转向架防除冰具有重要指导意义.

大型结冰风洞制冷系统蒸发压力预测与降温过程优化研究

构建了液氨蒸发器热力学仿真模型,进行了蒸发压力以及风洞降温的预测与验证。采用BP神经网络算法对试验数据和仿真数据进行训练,建立了氨制冷系统蒸发压力快速预测模型,分析了试验高度和试验风速对风洞降温速度的影响,提出了变风速降温控制方式,对比分析了不同降温控制过程的降温时间及系统能耗。结果表明:对于高空环境试验,先进行风洞减压再降温,可以有效缩短降温时间、减小系统能耗;试验风速75 m/s时风洞系统降温速度最快,高于75 m/s时可以通过降温过程变风速控制方法降低系统能耗。

3m×2m结冰风洞试验技术新进展(2020-2022年)

3 m×2 m结冰风洞是我国“十一五”国家重大科技基础设施,也是国际上尺寸最大的非季节性结冰风洞。自2013年建成以来,已经完成了70余项试验,有力支撑了我国飞机的自主研制和适航取证。本文首先介绍了3 m×2 m结冰风洞的组成和特点,其次重点阐述了2020年至2022年间风洞试验能力和试验技术的若干新进展,通过发展双闭环自适应温度控制技术、多路热气供气防除冰试验技术、冰形在线测量技术、发动机进气精确模拟技术、旋翼结冰与气动载荷同步测试技术等,使风洞的温度场模拟能力、热气防冰试验能力、冰形测量能力、进气模拟能力和直升机旋翼结冰试验能力得到增强,综合试验效率显著提升。最后,针对大型结冰风洞过冷大水滴试验面临的挑战,对下一步试验技术的发展进行了展望。

对称翼型前缘积冰粘结强度试验研究

当飞机在寒冷潮湿的环境中飞行时,机翼前缘有时会出现结冰现象威胁飞行安全。为了发展防冰和除冰技术,有必要对叶片翼型表面覆冰的粘结特性进行研究。本文设计并搭建了叶片翼型覆冰粘结力测量系统,提出了叶片翼型覆冰粘结强度的评估方法,记录和测量了不同条件下NACA0018翼型叶片段上的结冰分布和粘结强度。试验结果表明,结冰时间对冰粘结强度的影响较小。随着环境温度降低,叶片翼型表面冰粘结强度增加,但增长速率减小。此外,随着风速增加,叶片翼型表面冰粘结强度降低。本研究结果为深入探索叶片翼型覆冰粘结机理提供了参考。

超疏水/电热协同防/除冰策略在冰风洞中的实验研究

无人机结冰严重威胁飞行安全。无人机可供能量不足,因此需要一种节能的结冰防护策略。本文以一种内嵌电热膜与外喷涂超疏水涂层(Super‑hydrophobic coating and embedded electro‑thermal film,SHS‑EET)的一体化玻璃纤维复合翼型为研究对象,采用比例积分微分法(Proportional integral derivative,PID)调节表面温度和加热功率。在结冰风洞中开展试验验证了该策略的防/除冰性能。结果表明,没有热源的超疏水涂层不能避免积冰的形成。此外,SHS‑EET策略下除冰时间缩短了64.6%,能耗降低了72.3%。当表面温度低于10℃时,SHS‑EET实现了干防冰效果,对比电热膜布置在蒙皮内表面的玻璃纤维复合翼型(Fiberglass airfoil with underground electro‑thermal film,FG‑UET)只能实现湿防冰效果,能耗降低了27.5%。混合防/除冰策略有利于无人机结冰防护系统的发展。

低温痕量水条件下翼型表面结冰特性的数值模拟研究

相比于传统的风洞设备,低温风洞可以生成更高雷诺数的气流,而风洞降温过程中残留的痕量水蒸气可能会影响试验件气动参数的测量。痕量水结冰的热力学过程复杂,实验测试较为困难,其机理仍需深入研究。针对该问题,本文基于欧拉方法建立了空气⁃过冷水滴⁃冰晶多相流模型,仿真结果与文献中的实验数据吻合度较高,进一步采用该模型获得了低温风洞中水蒸气凝结液滴/冰晶撞击翼型的结冰过程,探究了气流中总的水含量、融化比、气流温度、压力、马赫数等参数对结冰过程的影响,并定量分析了结冰现象对翼型气动参数的影响,可为低温风洞的实际运行提供一定的理论参考。

轨道车辆冰雪风洞收缩段曲线对试验段流场特性的影响

采用基于SST k-ω的IDDES湍流模型研究轨道车辆冰雪风洞流道空气流动品质,并分析收缩段约束曲线对试验段内流场品质的影响。采用风洞流场校测的数据验证本文数值模拟方法的计算精度可靠性、网格尺度无关性和湍流模型适应性。研究结果表明:原始工况下,收缩段入口处由于拐角导流片导致流动分离,气流速度呈锯齿状分布;在试验段喷口前未发生明显流动分离,试验段速度均匀分布;喷口射流与周围的动量交换而导致速度较低,涡量增加,湍流度也较高。不同收缩段曲线工况中,维氏曲线在收缩段入口位置过快收缩,导致截面的速度均匀性较差,维氏曲线对一阶变量如速度、俯仰角、偏航角等变量影响较大,双三次曲线对二阶变量影响较大。综合考虑风洞收缩段气动外形关键参数设置,五次收缩段曲线对保证试验段流场品质效果最佳。

冰风洞过冷大水滴云雾水滴质量分布模拟

准确模拟过冷大水滴(Supercooled large droplet,SLD)云雾水滴质量分布是最新的结冰适航条款要求,也是当前冰风洞试验技术难点。以14CFR 25部附录O规定冻毛毛雨水滴累计质量分布曲线为目标,在冰风洞中开展过冷大水滴结冰条件模拟研究。基于水滴质量分布要求进行大水滴云雾与小水滴云雾匹配性分析,并在FL-61风洞喷雾系统现有条件下开展大水滴喷嘴喷雾性能测量,将生成的具有不同液态水含量(Liquid water content,LWC)和体积中值直径(Medium volume diameter,MVD)特征的云雾参数组合,在试验段中心位置生成了水滴质量分布曲线接近附录O规定的冻毛毛雨条件。研究结果表明,采用分别模拟相应水滴质量分布的大水滴和小水滴云雾,再进行组合喷雾能够较好地预测和指导在冰风洞中构造大水滴云雾,同时验证了在冰风洞内能够采用两种喷嘴模拟水滴质量为双峰分布云雾条件的可行性。