Hydraulic characteristic of chemigation by bypass flow across the pipe bend devices

Abstract

Chemigation is used to apply a wide variety of chemicals to many kinds of crops through different types of irrigation systems. The bypass flow chemical injector using the pipe bend devices is a simple pressure differential method. The hydraulic experiments of pipe bend devices with different shape and size crests were conducted using 30 mm internal diameter pipe bend devices without crest (bypass design No.1), with one 5 mm size crest on the outer wall (bypass design No.2), with one 10 mm size crest on the outer wall (bypass design No.3) and with two10 mm size crests on both inner and outer walls inside the pipe bend (bypass design No.4). Relations among the main pipe flow rate (Q), the bypass flow rate (q), the pressure difference without bypass flow (DH0) and the pressure difference with bypass flow (DH) between inside and outside of a pipe bend were investigated. The results show that the magnitudes of the parameters DH/Q2 and q/Q are ranked among different flow types as: No.4 > No.3 > No.2 > No.1, and they are also constant coefficients for bend pipe devices. Then, after a chemical tank or batch tank added in the bypass route, the chemical or fertilizer can be injected into irrigation systems by bypass flow across a pipe bend device at a constant flow rate, but the chemical content is being diluted with time as water flows into the tank and mixes with the original solution. In one irrigation system, the purpose of bypass flow rate can be reached using a pipe bend devices with and without different shape and size crests.