水刀是一種具有高精度的環保切割工具，使用水刀需配置切割槽，藉以承接切割過程中所產生的水、砂粒與碎屑，並吸收水刀切割後的水柱殘留能量。切割槽容量有限，需要不定期清除槽內的殘留物，以確保切割作業的安全性。切割槽內的砂粒與碎屑(簡稱殘留物)主要來自切割過程中高壓水柱內加入的磨料(石榴砂)以及被切割物產生的碎屑。目前清除切割槽殘留物的方式以人工挖取與泵浦抽砂兩種為主；人工挖取方法須先將水體放乾後再以人力挖除殘留物，費時費力；泵浦抽砂方法將切割槽內水與殘留物一併抽到指定的地方堆置進行沉降分離，此法卻相當耗費空間。有鑑於此，本研究提出結合抽砂泵浦及水力旋流排砂器(簡稱排砂器)的方法來清除切割槽的殘留物，提高殘留物與水體分離之效率，並節省空間使用。
本研究完成28組室內試驗研究(包含清水及渾水試驗各14組)，先探討排砂器不同模型尺寸配置(深寬比、底坡坡度、入流管管徑與底孔孔徑)對水砂分離效果的影響，然後探討泵浦在切割槽內的放置位置及泵浦回流出水口放置位置(6組)對清除切割槽殘留物的效果。試驗結果顯示排砂器能有效排除粒徑0.02 mm以上殘留物之固體顆粒，泥砂去除效率可達到99%。另外，將泵浦回流出水口位置安排在泵浦的正對面位置時，對於清除切割槽內殘留物有比較好的清除效果。試驗綜合結果顯示本研究所提出的排砂器與泵浦串聯的方法，可以縮短水砂分離的處理時間、增加水的再利用以及節省殘留物處理的操作空間。

SUMMARY
The objective of this paper is to improve the sediment removal operation of waterjet basins by applying a vortex-chamber-type (VCTSE) sediment extractor, enhancing the efficiency of pump operation. This experimental study contained three parts for relating a VCTSE sediment extractor, pump and waterjet basin. First, we used muddy water to test the efficiency of sediment removal under different experimental settings of a VCTSE sediment extractor containing bucket depth ratio (H/D), slope of angel (Sc), the diameters of inflow pipe (Di) and bottom orifice (Du). Results show that the experiment setting with H/D=1.4、Sc=35°、Di=2.4 cm and Du=0.5 cm could lead to sediment removal efficiency reaching 99%, being able to remove the sediment materials greater than 0.02 mm, and increase the 2 ~ 3 fold efficiency of sediment pumping. Second, we changed the condition of sedimentation in waterjet basin by placing the pump on different position to disturb the flow field, showing that the pump in front of the outlet can cause sediment materials concentrating around the pump and enhances the efficiency of sediment pumping. Third, experimental study combined with the VCTSE sediment extractor with pump operation show that VCTSE sediment extractor can maintain the sediment removal efficiency more than 90% in long term operation and its sediment concentration of bottom orifice averages 42.5 g/l.
Key words：vortex-chamber-type sediment extractor, sediment removal from water, waterjet cutting, sediment removal efficiency
INTRODUCTION
Waterjet is a kind of environmental protection cutting tools with great precision. Use of waterjet machines need a basin to absorb energy of waterjet after cutting and collects it consequent solid particles (denoted by sediment materials). In general, we need to remove the sediment materials within a waterjet basin to ensure the safety of the cutting operation because basin capacity is fixed. Sediment materials include the added abrasive of high-pressure waterjet and dregs produced by cutting. At present, sediment removal from waterjet basins has two ways. One is to drain the storage water and then we can remove the sediment materials from waterjet basin through artificial dredging as shown in Fig. 1a. The other one is to remove sediment materials from waterjet basins is by pumps (Fig. 1b). However, these methods usually need a lot of time and space to separate sediment materials from water during removal operation. Hence, this study proposed an innovative method that is to use a vortex-chamber-type sediment extractor (VCTSE) to improve the efficiency of removal operation and to save the use of space.
MATERIALS AND METHODS
In this study, we carried out a series of laboratory experiments to investigate the improvement of the sediment removal operation within a waterjet basin via a vortex-chamber-type sediment extractor (VCTSE). The experiments would be divide into three parts. First, we used muddy water to test the efficiency of sediment removal under different experimental settings of a vortex-chamber-type sediment extractor containing bucket depth ratio (H/D), slope of angle (Sc), the diameters of inlet pipe (Di) and bottom orifice (Du), as shown in Fig. 2. The muddy water is pumped from the water tank and is entrained into the vortex chamber through the inlet pipe, moving as a vortex flow inside the chamber. The water and sediments could be separated by the gravity and centrifugal force. Hence, the sediment-laden mixture flows though the bottom orifice flow with high sediment concentration, and the mixture flows through the upper outlet with low sediment concentration. Furthermore, to enhance the efficiency of sediment pumping operation. We changed the condition of sedimentation in waterjet basin by placing the pump on different position to disturb flow field, as shown in Fig. 3. Last, an experimental study combined with the VCTSE with pump operation to discuss how to promote this system of sediment removal operation.
RESULTS AND DISCUSSION
Results show that underflow sediment concentration of H/D=1.4 is higher than that of H/D=0.8 (and of Sc=35° is higher than that of Sc=0°, s shown in Figs. 4 and 5. These may result from the unblocked bottom orifice under high values of H/D and Sc=35° is higher than the repose angle of sediment. The underflow sediment concentration of Di=2.4 cm is higher than that of Di=1.6 cm and of Du=0.35 cm is also higher than that of Du=0.5 cm, Du=0.7 cm and Du=1 cm (Figs. 6 and 7). Small diameter of bottom orifice can help increase in underflow sediment concentration and ewe treat the diameter of bottom orifice as the first-order control on underflow sediment concentration.
Fig. 8 shows that trend in curve of fall velocity is faster than that in flow velocity when the sediment size is larger than 0.02 mm, indicating that the sediment particles can effectively settle to the bottom of vortex chamber and the VTCSE can efficiently remove the sediment particle size larger than 0.02 mm.
Fig. 9 shows the pump in front of the outlet can cause sediment materials concentrating around the pump and enhances the efficiency of sediment pumping. However, the range of sediment pumping is not enough still and we can change the condition of sedimentation in waterjet basin by other ways to enhance the disturbance of the flow field.
CONCLUSION
The experimental results show that its sediment removal efficiency can reaching 99%, being able to remove the sediment materials greater than 0.02 mm, and increase the 8 fold efficiency of sediment pumping at optimum result. Moreover, the vortex-chamber-type sediment extractor not only can effectively separate sediment from water but also enhance the sediment concentration of pumping. Hence, the VCTSE is suitable for the use of the sediment removal operation with a waterjet basin. Also, we changed the condition of sedimentation in waterjet basin by placing the pump on different position to disturb the flow field, showing that the pump in front of the outlet (case E) can cause sediment materials concentrating around the pump and enhances the efficiency of sediment pumping, improving the effect of pumps on sediment removal from a waterjet basin. Last, the experimental study combined with the vortex-chamber-type sediment extractor with pump operation was carried out, showing that the position of a pump could alter the conditions of sedimentation via disturbing the flow field within waterjet basin but its effect is still limited. In the future, the efficiency of sediment removal from a waterjet basin could be improved by changes in the position of pumps and the number of outlet pipes within a waterjet basin.

1.王順久、侯杰、邱秀云(1997)，「以流場分析初步探討排沙漏斗的輸沙機理」，新疆農業大學學報，第20卷，第3期，第12-16頁，中國大陸。
2.余新豔、邱秀云、劉芬、牧振偉、李琳(2008)，「渾水水力分離清水裝置溢流性能的影響因素實驗研究」，新疆農業大學學報，第31卷，第2期，第81-84頁，中國大陸。
3.李琳、邱秀云(2007)，「渾水水力分離裝置中水砂兩相湍流的數值模擬」，新疆農業大學水利學報，第38卷，第11期，第1279-1284頁，中國大陸。
4.李琳、邱秀云、龔守遠、劉芬(2007)，「渾水水力分離清水裝置弱旋流場特性研究」，水動力學研究與發展，第22卷，第4期，第520-528頁，中國大陸。
5.李琳、邱秀云、聶境、陶洪飛、崔瑞(2010)，「基於滴灌渾水水力分離裝置的水沙分離實驗研究」，水資源與水工程學報，第21卷，第6期，第37-40頁，中國大陸。
6.周著、邱秀云、侯杰、王順久(2001)，「漏斗式全沙排沙技術及其應用」，水科學進展，第12卷，第1期，第95-98頁，中國大陸。
7.林程翰(2009)，「懸板配置對高桶式旋流排砂器排砂效率影響之實驗研究」，國立成功大學水利及海洋工程學系碩士論文。(指導老師詹錢登)
8.邵學軍、王興奎(2005)，「河流動力學概論」，清華大學出版社，中國大陸。
9.邱秀云、肖俊、周著、侯杰(2006)，「渾水水力分離清水裝置清水流場特性實驗研究」，新疆農業大學學報，第29卷，第4期，第56-61頁，中國大陸。
10.侯杰、王順久、周著、王忠、欒文(2000)，「全沙排沙漏斗渾水流場特性及輸沙規律」，泥沙研究，第6期，第63-67頁，中國大陸。
11.唐毅、吳持恭、周著(1996)，「排沙漏斗水流結構及對輸沙過程的影響」，水動力學研究與發展A輯，第11卷，第2期，第181-187頁，中國大陸。
12.徐郁超(2014)，「高桶式旋流漏斗排砂器水流特性及泥砂去除效率之研究」，國立成功大學水利及海洋工程學系博士論文。(指導老師詹錢登)
13.郭新、張西正、徐曉瑩、郭春、陳明東、黃躍青、崔智慧(2009)，「水刀技術及其在醫學領域的應用」，醫療衛生裝備，第30捲，第七期，第34-36頁
14.楊致遠(2013)，「高桶式水力旋流漏斗排砂器泥砂去除效率之實驗研究」，國立成功大學水利及海洋工程學系碩士論文。(指導老師詹錢登)
15.詹錢登、羅偉誠、蔡長泰(2006)，「水力旋流漏斗排砂之實驗研究(1/2)」，經濟部水利署水利規劃實驗所。
16.詹錢登、羅偉誠、蔡長泰(2007)，「水力旋流漏斗排砂之實驗研究(2/2)」，經濟部水利署水利規劃實驗所。
17.詹錢登、羅偉誠、黃聰憲、徐郁超、張家榮(2008)，「水力旋流漏斗排砂之試驗研究」，水利署96年度委辦計畫成果發表會論文集，第357-370頁。
18.詹錢登、徐郁超、黃聰憲、羅偉誠(2008)，「導流墩對漏斗式排砂器內流場穩定效果之研究」，第十七屆水利工程研討會，逢甲大學，第C6.1-C6.9頁。
19.詹錢登、黃聰憲、徐郁超、羅偉誠(2008)，「漏斗式水力旋流排砂器排砂效率試驗研究」，第十七屆水利工程研討會，逢甲大學，第C22.1-C22.7頁。
20.詹錢登、阮光長、徐郁超、林程翰(2010)，「高桶式旋流排砂器排砂效率之實驗研究」，中華防災學刊，第2卷，第2期，第137-150頁。
21.詹錢登、徐郁超、林程翰、曾奕超(2011)，「懸板配置對高桶式旋流漏斗排砂器排砂效率之試驗研究」，農業工程學報，第57卷，第4期，第84-96頁。
22.詹錢登、徐郁超、黃聰憲(2014)，「導流墩配置對旋流漏斗排砂器內渦流穩定性影響之試驗研究」，台灣水利，第62卷，第1期，第44-55頁。
23.趙濤、陳偉東、邱秀云(2011)，「渾水水力分離清水裝置柱體高度對流場影響的數值模擬研究」，水動力學研究與發展，第26卷，第6期，第681-688頁，中國大陸。
24.劉麗萍、王祝煒(2000)，「高壓水設流切割技術及應用」，農業機械學報，第31卷，第5期，第117-119頁。
25.劉芬、邱秀云、陳偉東、李琳、趙濤(2007)，「渾水水力分離清水裝置的優化實驗研究」，新疆農業大學學報，第30卷，第2期，第81-86頁，中國大陸。
26.Athar, M., Kothyari U.C. and Garde R.J. (2002), “Sediment removal efficiency of vortex chamber type sediment extractor.” Journal of Hydraulic Engineering, ASCE, 128(12), 1051-1059.
27.Babu Rao, D., Baskey and Rawat,R.S.(2009), “Water jet cutter : An efficient toolfor composite product development.”National Conference on Scientific Achievements of SC & ST Scientists & Technologists, National Aerospace Laboratories, Bangalore-17,104-107
28.Birtu, C. and Avramescu,V.(2012), “Abrasive water jet cutting technique,equipment,performances.”Romanian Association of Nonconventional Technologies,40-46.
29.Bretney, E. cyclone.US Pstent No.453,105,May 26,(1891)
30.Chapokpour, J. and Farhoudi, J. (2011), “Turbulent flow measurement in vortex settling basin.” Iranica Journal of Energy & Environment, 2(4), 382-389.
31.Drissen, M.G.(1951), “Theory of flow in a hydrocyclone classier.” Rev. L-industries min. Spl.1951.4:449-461
32. Jan, C. D. and Nguyen, Q. T. (2010), ”Discharge coefficient for a water flow through a bottom orifice of a conical hopper.” Journal of Irrigation and Drainage Engineering, 136(8), 567-572.
33.Jan, C. D. and Nguyen, Q. T. (2011), “Discharge coefficient for bottom orifice of vortex chamber” Journal of Hydraulic Research, 49(3), 388-391.
34.Salakhov, F. S. (1975), “Rotational designs and methods of hydraulic calculation of load-controlling water intake structures for mountain rivers.” Proc. 9th ICID Congress, Moscow, Soviet Union, 151-161.
35.Tazibt, A., Parsy, F. and Abriak, N.(1996), “Theoretical analysis of the particle acceleration processin abrasive water jet cutting. ”Computational Materials Science 5 (1996) 243-254.
36.Thew, M.T, “Hydrocyclone redesign for liquid-liquid in a conventional hydrocyclone :an experimental research for optimum dimensions. ”Journal of Petroleum Science and Engineering, 1994.11:37-50.
37.Ziaei, A. N. and McDonough, J. M. (2007), “Using vorticity to define conditions at multiple open boundaries for simulating flow in a simplified vortex settling basin.” International Journal for Numerical Methods in Fluids, 54, 1-28.