Masters Theses

Date of Award

12-2003

Degree Type

Thesis

Degree Name

Master of Science

Major

Biosystems Engineering

Major Professor

Alvin R. Womac

Committee Members

John B. Wilkerson, William E. Hart

Abstract

A self-propelled sprayer with a 27-m boom was instrumented to measure inadvertent boom movement and acceleration during field operation to quantity application uniformity. The instrumentation system was developed to monitor boom end heights, accelerations, and sprayer longitudinal position along a track. Acceleration measures included longitudinal (x), vertical (y), and transverse (z) components at the sprayer vehicle rear, boom center, and at each boom end. A PC-based data acquisition system polled sensors at 2.5 kHz. Software-implemented, 2nd-order Butterworth band pass (0.1 to 15 Hz) filtering of raw data reduced signal noise. Y-accelerations at the boom center ranged from 1.5 to –0.8 g after filtering. Natural frequencies of the sprayer vehicle and boom ranged from 4 to 5 Hz in x, y, and z directions on a smooth track. A 20-cm track bump resulted in different sprayer and boom frequencies in the y direction (1 to 2 Hz), and in the x and z directions (5 to 6 Hz). The bump excitation increased the peak power level 12.86 dB for the y direction at both boom ends compared with the power levels from the smooth track. A 20-cm dip and an opposing 20-cm bump in the sprayer track had an insignificant effect in shifting primary natural frequency components in the y direction; however, the dip reduced natural frequency components (< 5 Hz) in the x and z directions at the boom center. A one-half sprayer tank load of water (1514 L) dampened vehicle vibration so that the water load changed the main natural frequency components (< 4.5 Hz) and reduced power levels (~55 %) in the y direction at the boom center.

Boom acceleration and height effects on spray deposit were determined for distinctly different track conditions, droplet spectra, and sprayer tank loads using the instrumented self-propelled sprayer with a 27-m boom at 12.8 km/h. Track configurations were smooth, 20-cm-high bump, and 20-cm-high bump and an opposing 20-cm-deep-dip. Droplet spectra included 255 and 588 um volume median diameters (Dv0.5) as determined by laser diffraction. Sprayer tank loads were either one-half capacity or empty. Results indicated three-dimension accelerations and boom end heights, for smooth, bump, and bump and dip tracks, ranging from 1.8 to –1.1 g, 14.3 to –6.7 g, and 20.7 to –11.0 g and 2.0 to 1.2 m, 2.6 to 0.5 m, and 3.5 to 0.4 m, respectively. Small droplets of 255 um (Dv0.5) resulted in a spray coverage range from 11 to 22 % with a maximum coefficient of variation (CV) of 55 %. Small droplets produced Pearson correlation coefficients between coverage and localized, instantaneous boom height ranging from –0.40 to –0.58. Large droplets of 588 um (Dv0.5) resulted in a spray coverage range from 9 to 18 % with a maximum CV of 39 %. Pearson correlation coefficients between large droplet coverage and localized, instantaneous boom height ranged from 0.49 to –0.62. Spray coverage significantly (P < 0.05) correlated with accelerations in 11 and 15 % of acceleration direction-test run combinations for 255 and 588 um (Dv0.5) droplets, respectively. Similarly, droplet density significantly (P < 0.05) correlated with accelerations in 26 and 22 % of combinations for 255 and 588 um (Dv0.5) droplets, respectively. Instantaneous boom heights less than 1.5 m maximized spray coverage and minimized variation in coverage for 255 um (Dv0.5) droplets. Boom height did not significantly affect spray coverage and droplet density of the 588 um (Dv0.5) droplets.

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