排水型遮罩式空速管設計與實驗研究

Design and experimental study on drained type of shielded total pressure tube

劉益仲(Liu, Y. C.) ； 歐陽駿塏(Ouyang, J. K.) ； 李沈達(Lee, S. D.) ； 徐榮男(Shyu, R. N.)

《航空安全及管理季刊》 4卷1期 (2017/01) Pp. 50-64

摘要

無人機在飛行進入積雨雲區或遇降雨天候時，易於空速管前端因液滴效應或雨水滲入等因素，使雨水進入空速管內部，經累積一段時間後，若雨水仍無法排出，則將會導致空速管所量測之全壓，因局部受到水滴阻塞而產生空速量測偏差。此時，若無人機內部之飛控電腦因感受到空速改變而產生自主姿態修調，易造成飛行不穩定或肇生可能的飛安事件；本試驗研究，主要探討三款由國家中山科學研究院-航空研究所自行設計開發之排水型遮罩式空速管，於受管頭噴水或管內浸水等實驗方法時之空速量測特性，用以模擬降雨天候對空速量測之影響，並對量測獲得之空速進行分析評估，所有實驗之穩定風場皆由航空所低速風洞相關儀器建立。由試驗結果可以發現，遮罩式空速軟管浸水後與未浸水之空速最大差異可達40knot，且軟管浸水後所測空速較不穩定，另於模擬下雨噴水試驗中發現，三款不同構型之遮罩式空速管於噴水期間所測得之空速差異皆高達20Knot 左右，於噴水停止後，所測得空速差異恢復為7Knot 內，足以證明此類遮罩式空速管設計，可有效防止雨水滲漏於空速軟管處所導致之空速不穩或空速誤差過大之飛安疑慮。本研究將可提供完善的技術文件於空速管設計及相關之實驗設計參考。

關鍵字

空速管 ； 無人機 ； 低速風洞 ； 全壓管

並列摘要

Unmanned Aerial Vehicle (UAV) operates under the weather conditions of cumulonimbus or heavy rainfall airspace, the head and inner of pitot tube may permeate the water due to the behaviors of water permeation or dropping effect. As the inner water in the pitot tube accumulated for a long time and could not be discharged, the air in the total pressure of pitot tube will be choked by the water and causes the measured error of the air speed in the flight condition. As the autonomous system of Flight Control Computer (FCC) in the UAV receives the wrong information of the air speed, the flight attitude of UAV will be changed due to wrong air speed and could cause the flight safety issues. The motivation of this paper studies the 3 types of shielded total-pressure tubes developed by ASRD-NCSIST, meanwhile the investigation of experimental methods including the inner hose of pitot tube with water permeation and spraying water on the head of pitot tube to simulate the weather conditions of heavy rainfall. All the experimental environment of steady flow field is created by the equipment of low-speed wind tunnel in ASRD-NCSIST. According to the experimental results, the maximum difference of air speed is reached to 40 knots as the inner hose of the shielded total-pressure tubes is chocked by the water, and also the measured quality of air speed in the chocked condition is unstable too. For the experiment of spraying water on the head of pitot tube also demonstrate that the maximum difference of air speed is reached to 20 knots as the spraying water device is operated and recovered at 7 knots as the device is stop. All the experimental results are sufficient to prove that the design of shielded total-pressure tubes in the present studies can effectively prevent the water permeated in the inner hose and reduce the unstable of air speed measurement to cause the flight safety issues. This study can well serve as reference technical document for pitot tube design and the related experiment.

並列關鍵字

Pitot tube ； Unmanned Aerial Vehicle ； Low-Speed Wind Tunnel ； Total Pressure Tube

參考文獻

Gracey, W.(1980).Measurement of Aircraft Speed and Altitude.John Wiley & Sons, Inc.

Richard, V. R., “Some Effects of Rainfall on Flight of Airplanes and on Instrument Indications”, NACA TN 803, April 1941.

Gracey, W.(1957).Wind-Tunnel Investigation of a Number of Total-Pressure Tubes at High Angles of Attack - Subsonic, Transonic, and Supersonic Speeds.NACA Report 1303.(NACA Report 1303).,未出版.

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