This paper presents a novel pressure-compensating flow restrictor for low-cost/low-pressure drip irrigation systems. There are nearly one billion subsistence farmers in the developing world who lack the resources and opportunities to rise out of poverty. Irrigation is an effective development strategy for this population, enabling farmers to increase crop yields and grow more lucrative plant varieties. Unfortunately, as a large fraction of subsistence farmers live off the electrical grid, the capital cost of solar or diesel powered irrigation systems makes them unobtainable. This cost could be drastically reduced by altering drip irrigation systems to operate at a decreased pressure such that lower pumping power is required. The work presented here aims to accomplish this by designing a drip emitter that operates at 0.1 bar, 1/10 the pressure of current products, while also providing pressure-compensation to uniformly distribute flow over a field.
Our proposed pressure compensating solution is inspired by the resonating nozzle of a deflating balloon. First, a reduced order model is developed to understand the physical principles which drive the cyclic collapse of the balloon nozzle. We then apply this understanding to propose a pressure compensating emitter consisting of compliant tube in series with a rigid diffuser. A scaling analysis is performed to determine the ideal geometry of the system and the reduced order model is applied to demonstrate that the proposed design is capable of pressure compensation in the required operation range. Preliminary experiments demonstrating the collapse effect are presented, along with initial work to translate the concept to a robust physical device.