Wind tunnel protocol for spray drift
assessment
Introduction
• The objective of wind tunnel protocol is to measure spray drift in a reproducible way in order to evaluate the relative drift potential of:
– different spray nozzles
– different operating parameters (Pressure, Height,…)
Introduction
• A normalisation process is underway at the international level: ISO/DIS 22856/1 within TC23/SC6. It defines:
– Typical wind tunnel design and layout (2*2m section, measurement section)
– Examples of measurement methods
– Wind turbulence and heterogeneity thresholds
– Wind tunnel instrumentation (humidity, wind speed, temperature)
Introduction
• Some major hurdles remain as the ISO/DIS
22856/1 protocol is designed for a static nozzle:
– The long axis of flat fan nozzle is set perpendicular to air flow, what is not representative of field drift
condition
– The blockage effect of droplet induced air-flow generate vortexes entraining driftable droplets resulting in a very specific pattern
– The collectors are prone to saturation due to local overdoses
Introduction
• The presentation intend to present the
protocol developed in Gembloux which is based on traversing
– an ISO/DIS 22856/1 wind tunnel
– a moving nozzle with controllable speed – fibre glass ground samples
Closed loop allows the use real formulations Speed up to 6 m/s Droplet filter Low turbidity Moving boom Large test section
The wind tunnel controllable parameters
• Wind speed 0 - 6 m/s (more with reduced wind homogeneity)
• Temperature (cooler and heater)
0.8m 6m Spray nozzle orientation Wind direction (2m/s) Nozzle displacement axis (2m/s)
WIND TUNNEL TEST SECTION
Ground collector
Standard settings : Wind speed = 2m/s RH = 80% T° = 20°C
P = 3 bar H=50cm
Glass fibre collectors Nozzle speed = 2m/s
parameters Mean CV (%) Wind (m/s) 2.026 0.814 Temp (°C) 19.684 0.137 RH (%) 79.797 0.100 P (bar) 3.093 0.393 FF 110 02 (LU)
Results repeatability
parameters mean CV (%) Wind (m/s) 1.825 1.162 Temp (°C) 19.207 0.185 RH (%) 78.858 0.177 P (bar) 2.892 0.281 DG 110 04
Results repeatability
parameters mean CV (%) Wind (m/s) 2.006 1.048 Temp (°C) 19.287 0.125 RH (%) 68.958 0.132 P (bar) 3.029 0.194 XR 110 04
Results repeatability
FF 110 02 (LU)
DG 110 04
Conclusion
• Repeatability is very satisfactory
• Small differences can be highlighted
• Other drift measurement methods can be used
• A Gaussian tilting plume model is
developed in order to predict drift of a moving nozzle
