System design and performance analysis of travelling irrigators in relation to their power units

Abstract

Poor performance and mechanical failures of travelling irrigators are caused by improper overall system and power unit design. Power and winching units reviewed showed that water-motors and cable-winches are popular in travelling irrigator design. Theoretical power use analysis was developed for cable-tow irrigators and terms of power balance equations were measured by laboratory and field tests. Laboratory tests showed that the highest efficiency of the turbine power unit of a Turborain B 100 fixed boom travelling irrigator was 54 %, giving 1.9 kW power output and 4.7 Nm torque, in 2650 1/min flowrate. Equations were created by laboratory tests in order to assess the turbine, performance during field tests. Field testing procedure along one full run length was created for cable-tow travelling irrigators. Some indicative results were:

The rotating boom of Rotorainer 175 stalls in 60.8 km/hr wind speed with cable tension up to 18.7 kN, or 31.9 kN cable tension and wind speed up to 29 km/hr. The 0.77 % of 9.4 kW water power consumption from the hydrant was the effective power for motion. The highest application efficiency was 99 % with uniformity coefficient 89 %.

The Turborain B100 turbine was operating at 37 % efficiency using 12.4 % of the 7.5 kW water power from the hydrant, and the winching unit had 60 % efficiency at peak cable tension of 23.7 kN. The highest application efficiency was 94.8 % with uniformity coefficient 82.7 %.

The Southern Cross TCD 2000 small raingun had 6.7 kN peak cable tension being 18.9 % of the tension stalling the hydraulic piston. The effective power for motion was 0.63 % of the 10.7 kW water power consumption from the hydrant. The highest application efficiency was 87.4 % with uniformity coefficient 75.3 %.