Place Graphic Here One of the major issues that prevent a large- scale dissemination of drip irrigation system is the requirement of high pumping pressure, which incurs a high cost of pumping and power systems. The high pressure is used to maintain the working condition of pressure-compensate emitters, which are installed at the outlets of drip irrigation system to compensate pressure loss and evenly distribute flows for each crop. Abstract Introduction Methodology Results A Bio-inspired Pressure Compensating Emitter for Low-Cost Drip Irrigation Systems Ruo-Qian Wang, Amos G Winter V Dept. of Mechanical Engineering, MIT ©Copyright, All Rights Reserved Contact: [email protected] Place Graphic Here Background Because of climate change, population growth, urbanization, and water pollution, the world is facing a water and food crisis. For example, the projected annual water usage of India for 2025 is 1020 km 3 , among which agriculture use contributes to 73% [1]. Drip irrigation is a potential solution • Save 30-70% water use compared to flood irrigation • Increase crop yields by 23-98% • Allow high-value crops to grow [2] High cost prevents large-scale applications • only 5% adoption of drip irrigation • high cost of ~$3000/acre with solar power • 90% of cost is power and pumping systems [2] A technological breakthrough is needed • Pumping power = pressure x flow rate • Current pressure demand is 3.5 bar [2] • Pressure compensating emitter (figure 1 & 5) needs ~1 bar [2] A bio-inspired design -30 -25 -20 -15 -10 -5 5 0 -5 -10 -15 -20 -25 -30 0.5 1 A / A0 Kp ∆P e) A new architecture of the pressure-compensate emitter is proposed using a flexible tube enclosed in a pressurized chamber similar to the design of a medical instrument called “Starling resistor”. This design enables the external pressure of the tube to correlate with the driving pressure, such that a higher driving pressure leads to a higher external pressure and consequently collapses the tube. The desirable feature that the flow rate is independent of the upstream pressure variation can be achieved with this new design at a lower driving pressure. This project is aimed to find the optimal combination of the design parameters that govern the physics behind the collapsible tube. A laboratory experiment has been conducted using rubber tubes with a variety of lengths, wall thicknesses and inner diameters. Then, an attempt to collapse the experimental results are made and empirical formula of activation pressure and regulated flow rate are given. Experiment Setup References [1] FAO. "Agriculture, food and water." (2003). [2] Information provided by Jain Irrigation Ltd. [3] Zimoch, et al. ”Bio-inspired, low-cost, self- regulating valves for drip irrigation in developing countries." IDETC (2013). Acknowledgement The authors would like to thank Jain Irrigation Inc. and MIT Tata Center for Research and Design for their support throughout the project. We are exploring a new drip emitter architecture consisting of an enclosed collapsible tube for pressure compensation. This novel architecture is based on a “Starling Resistor” – a means of restricting fluid flow by applying an external pressure to a flexible tube. Starling resistors are commonly found throughout the human body. An example is the bronchi in the lungs, which collapse and make a person wheeze when they exhale hard (see figure 4). [3] www.sultansurgicalcenter.com A series of experiments has been conducted to investigate the pressure compensation of collapsible tubes inside a pressurized chamber (figure 6), including four factors: • Tube length (L) • Wall Thickness (h) • Inner Diameter (D) • Materials (E) Pressure compensation • Flow rate increases with pressure before activation pressure • Flow rate is independent of pressure variation after activation pressure • The minimum activation pressure is ~ 0.2 bar (figure 7) Self-excited oscillation • Co-existing with pressure compensating • Potentially anti-clogging Hysteric effect Flow rate is higher in pressure increasing compared to pressure decreasing (arrows in figure 7) Figure 1 Pressure Compensating emitter Figure 2 Water and food crisis in India Figure 3 High pressure is needed in drip irrigation Figure 4 Collapsible tubes in respiratory airways Figure 5 Pressure compensation in commercial emitter Figure 6 Experimental Configuration Figure 7 Experimental results MIT GLOBAL ENGINEERING AND RESEARCH (GEAR) LABORATORY GEAR.MIT.EDU GEAR LAB GEAR LAB GEAR LAB G G G G P (bar)