مطالعۀ آزمايشگاهي عملكرد شير خودكار كنترل دبي در خطوط انتقال آب

Experimental study on Automatic Valve Control Performance in Water Pipelines

استفاده از لوله براي انتقال آب، به ­جاي شبكه­ هاي روباز، يكي از گزينه هاي انتقال آب است كه امروزه در حال گسترش مي­ باشد. اين نوع انتقال آب با لوله عموماً با فشار كمتر از 1/5 اتمسفر همراه است و به‌نام انتقال آب در خطوط لولۀ كم ­فشار شناخته مي­ شود. انتقال آب با لوله­ هاي كم فشار مي ­تواند تا حد زيادي از تلفات بي رويۀ آب آبياري جلوگيري كند. در اين تحقيق، عملكرد نوعي شيرفلكۀ خودكار تنظيم دبي براي تحويل حجمي آب به‌صورت آزمايشگاهي بررسي شده است. اين ابزار بدون استفاده از تمهيدات الكترونيكي و تنها با انجام برخي اقدام­ هاي مكانيكي مي­تواند براي تحويل آب به‌صورت حجمي در خطوط انتقال آب در شبكه ­هاي كم ­فشار استفاده شود. براي اين منظور، شير­هاي كنترل 5 و 10 ليتر بر ثانيه به‌ترتيب در محدودۀ فشار كاركرد 1 تا 10 متر و 3 تا 15 متر طراحي و ساخته شدند. با جايگذاري شيرفلكه­ ها در خطوط انتقال آب انتهاباز و انتهابسته، ضمن ايجاد نوسان­ هاي فشار در بالادست و پايين­ دست خط انتقال، عملكرد شير­هاي كنترل دبي در توزيع جريان به‌صورت آزمايشگاهي بررسي و نشان داده ­شد كه با وقوع نوسان هاي فشار در نقاط مختلف شبكه­ هاي انتها­باز و انتهابسته، ميانگين دبي عبور يافته از شيرهاي كنترل 5 و 10 ليتر بر ثانيه به‌ترتيب برابر با 5/4 و 9/9 ليتر بر ثانيه است. اين امر نشان مي­دهد كه شير­ خودكار كنترل دبي قادر است بدون حساسيت نسبت به تغييرات فشار در شبكه­هاي انتقال آب كم فشار، دبي تقريباً ثابتي به بهره­ برداران تحويل دهد.

Introduction Using pipelines instead of open channels for conveying water is getting much important recently. This type of pipe-water transfer, which is associated with a pressure below 15 meters, is known as low-pressure pipelines. Transfer of water through low pressure pipes can greatly prevent unnecessary losses of irrigation water. In this study, the application of a kind of volumetric water delivery structure known as discharge control valve was investigated. This instrument is used without implementing electronic facilities for water delivery in low pressurized pipe networks. For this purpose, two valves of the design discharges of 5 and 10 l/s are fabricated based on the design guidelines available in the literature. Their performances are experimentally tested in closed and open ended irrigation networks. The result showed that the valves of the design discharges of 5 and 10 l/s are not sensitive to pressure fluctuations in low pressurized networks and can deliver water with an almost constant discharge. Methodology This study presents an experimental approach of the application of discharge control valve for fairly water distribution in low pressurized irrigation networks. According to Table.1, four scenarios were defined to evaluate the performance of the flow control valves. Therefore, two experimental setups of open and closed ended networks were constructed in hydraulic laboratory of Imam Khomeini Intentional University, IKIU. Flow control valves of the design discharges of 5 and 10 l/s were installed in the water conveyance pipelines. Then, applying pressure changes at either upstream or downstream of the valves their performances were evaluated experimentally. Results and Discussion According to Table.2, it is concluded that the control discharge valves with the design discharge of 5 and 10 l/s can be used successfully to achieve the goal of volumetric water delivery. In all tested scenarios the delivered water deviates less than almost 10% compared to the associated design values. Consequently, an automatic discharge control valve can be implemented in a network to achieve a reasonable water uniformity which is irrespective to both sources and locations of the pressure fluctuations. Conclusions Fairly water distribution is an important issue in the irrigation section. In this research, the application of a flow control valve is investigated to improve uniform flow distribution in irrigation networks. Discharge control valves were installed in open and closed-ended pipe networks. According to the experimental results, it was found that the discharge control valves of the design discharges of 5 and 10 l/s deliver average discharges of 5.35 and 9.89 l/s respectively. The results indicated that the constructed control valves can be used effectively to deliver an almost constant discharge which is irrespective to the pressure fluctuations.