Fundamental Study on Pest Control Systems by High Pressure Type Sprinkler in the Orchard (4)

Uniform Spraying System by Discharge Pressure Control of Plunger Pump

Abstract

1. A practical system for uniform spraying by high pressure type sprinkler was researched. The fundamental experiments were done successfully. The discharge pressure p was programcontrolled to supply constant pressure to every sprinkler on each lateral pipe. The direction of flow was changed to a lateral under the condition that p became within the set pressure range.
Then p was changed a little according to the override characteristics of a pressure regulator, if the discharge rate of a pump changed. When spraying had began already, the change of p was corrected by re-regulation by a pressure regulator comparing p with the set pressure, so that spraying under the constant pressure was accomplished. It became clear that the accurate uniform spraying could be made in the orchard on the basis of the experimental results.
2. The pressure override characteristics of a pressure regulator and the step response to the rapid change of discharge rate of a pump was investigated. The pressure differences caused by the override characteristics were considerably large reaching about, 10kg/cm². The experimental results had a good agreement with the calculated when Qr<10l/min, but p became larger than the calculated value when Qr>10l/min. This might be caused by the reason that the pressure distribution on the ball valve became unequal because of the drop of pressure by the swirl around the valve seat. The response of p and x corresponded with the calculated results.
3. The pressure override characteristics should be improved if the pipeline with the closed end of the main pipe was used. For the direct type pressure regulator the improvement of override is limited by the structure of itself. However it was found by calculation that the pressure difference by the override characteristics was decreased to 7kg/cm² by setting the spring constant k to be 2kg/mm.