臺灣農藥常用扇形噴頭之流量、霧滴粒徑及飄散距離之研究

Study on Nozzle Flow Rate, Droplets Size Distribution and Its Drifting Ability of Various Fan Type Nozzles Used in Taiwan

黃郁容(Yu-Rong Huang) ； 徐榮志(Rong-Jhih Syu)

《臺灣農藥科學》 3期 (2017/12) Pp. 1-24

https://doi.org/10.6671/TPS/2017.003.01

摘要

臺灣農藥使用的扇形噴頭樣式及號碼種類繁多，並未有一致的規格，因此農民在選用時，僅能依照舊有習慣、經驗或農機行的建議選擇使用。本研究初步測試目前市面上有供應及使用的扇形噴頭，共7支小扇(直徑1.4 cm的噴片俗稱)、10支日扇(直徑1.4 cm且其上有黑色卡榫固定噴片方向者俗稱)及8支大扇(直徑1.8 cm又稱臺扇的噴片俗稱)，在7、15、20及25 kgf/cm^2等不同農民常用壓力下的霧滴粒徑，藉以瞭解其可能產生的飄散程度。結果顯示除了幾支號碼偏大的8號及大扇PL 1.0及偏小的HS H-4外，霧滴粒徑皆很相似，7 kgf/cm^2時Dv(50)(霧滴粒徑分布在50%相對應的霧滴粒徑大小)為77.19～101.5 μm，20 kgf/cm^2時約64.03～80.08 μm，若是相同扇型噴片之間(如：小扇噴片)，則差異更小。然而，在噴片上不同數字與孔徑的噴頭，確實有明顯流量的差異，將此25支噴頭以20 kgf/cm^2壓力下，依據適當流量區分為16個區間，結果顯示，小、日扇噴頭多位於流量0.85～1.75 L/min間，大扇流量較大，多位於1.50～4.00 L/min，其中有幾支小、日扇流量與大扇相似，例如小扇的HS H-5、日扇的PL D-5及大扇的PL D-3皆是屬於流量1.00 L/min區間，顯示目前市售的扇形噴頭是可以利用適當流量的區間分組，將不同廠牌間噴頭進行歸納以利噴頭選用，可作為噴頭規範的參考，然此一噴頭流量及霧滴數據，僅為市售噴片取樣測試，希望能先框出臺灣市售有在販賣及使用之扇型噴頭種類，作為背景資料收集，僅能代表此一測試結果，無法代表噴頭規格。再者，以日扇PL D-5進行3、7、25 kgf/cm^2模擬田間向下噴施時的飄散試驗，在下風處最尾端設置一與噴施點垂直高度等高並垂直擺放水試紙，量測越過8 m以後的霧滴飄散情況，結果顯示在風速達到4 m/s時，各種壓力下，飄散距離都會超過8 m以上。由相似溫、溼度條件下量測的3及25 kgf/cm^2數據顯示，不論在何種風速下，3 kgf/cm^2的霧滴飄散距離皆比25 kgf/cm^2的來得遠，如在風速2 m/s時，3 kgf/cm^2噴施最遠飄散距離為4 m，而25 kgf/cm^2則為3 m，而量測時溫度較高5～10℃左右的7 kgf/cm^2噴施時，飄散情況遠比其他兩個壓力測試下來得嚴重，風速在2 m/s以上其飄散距離就達7 m以上(7 kgf/cm^2時量測溫度約34～39℃，3及25 kgf/cm^2時約26～27℃)。綜合以上，從霧滴粒徑觀察噴頭在特定壓力下的飄散情況，需配合當時溫、溼度條件等環境因子作為評估，且未必同噴頭在高壓下，噴出的霧滴造成的飄散距離就會更遠，不同霧滴粒徑分布及霧滴比例在不同的環境條件下，也可能產生其他飄散的結果，後續須累積更多不同情況的噴施測試，或是借助電腦飄散評估軟體輔助，才能對霧滴造成的實際飄散沉降量與距離，有更完整且仔細的瞭解。

關鍵字

噴頭 ； 流量 ； 飄散 ； 霧滴粒徑

並列摘要

In this study, we tested 25 stainless steel fan nozzles that are used in Taiwan (including 7 types of small nozzles, 10 types of Japanese nozzles, and 8 types of large nozzles) in order to improve understanding of droplet size distribution under 3, 7, 15, 20, and 25 kgf/cm^2 of spray pressure. Most nozzles (exception of some smaller and larger size nozzles which named number 4 or 8 and 1.0) spray droplets have a similar size distribution; such as 77.17 ~ 101.5 μm and 64.03 ~ 80.08 μm under 7 kgf/cm^2 and 20 kgf/cm^2 of spray pressure, respectively. We tested and categorized nozzles into 16 groups according to their flow rate under 20 kgf/cm^2 of spray pressure. Most small nozzles and Japanese nozzles were classified in the 0.85 ~ 1.75 L/min group. Furthermore, large nozzles had a larger flow rate and belonged to the 1.50 ~ 4.00 L/min group. However, some different types of nozzles (i.e., HS H-5, small type; PL D-5; Japanese type, and PL D-3; large type) were found to have the same flow rate of 1.00 L/min. In order to evaluate the spray drift distance of the stainless steel fan nozzle used in Taiwan under typical field application conditions, we chose one commonly used nozzle PL D-5 for experiment. Specifically, these conditions included a downward spray pattern (the spray pattern that is most commonly used for ground crops) and spray pressures of 3, 7, and 25 kgf/cm^2, respectively. Our results revealed that (1) under all pressure conditions, sprays were able to drift more than 8 m when the wind speed was 4 m/s; and (2) 3 kgf/cm^2 of pressure was associated with longer spray drift distances than was 25 kgf/cm^2 of pressure at all 1~ 4 m/s wind speeds. For example, when the wind speed was 2 m/s, the spray drift at 3 kgf/cm^2 of pressure was more than 4 m, but when the pressure was 25 kgf/cm^2, the spray drift was only 3 m. We also found that, when test under higher temperatures and faster wind speeds (more than 2 m/s), the drift distance can reach over 7 meters when the spray pressure is 7 kgf/cm^2. Above all, evaluation of spray drift is a complicated issue; we should combine not only droplet size distribution but temperature, humidity, wind speed all parameters into consideration. In order to further improve understanding of spray drift, we recommend that future research focus on collecting more spray drift data for additional spray nozzles used in Taiwan and assist with the computer software used to predict spray drift distances for more completely evaluation of droplet spray drift.

並列關鍵字

spray nozzle ； flow rate ； spray drift ； droplet size