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Document Type

Thesis - University Access Only

Award Date

2000

Degree Name

Master of Science (MS)

Department

Agricultural and Biosystems Engineering

First Advisor

Darrell W. DeBoer

Abstract


Sprinkler irrigation is used to supplement natural rainfall on cultivated lands. In 1999 there were approximately 63.0 million irrigated acres in the United States of which 48.5% were under sprinkler irrigation (Irrigation Journal, 2000). Significant portions of these sprinkler systems are equipped with reduced pressure sprinkler heads, about 50% in South Dakota as an example. The reduced pressure sprinkler heads were introduced into the market in response to increasing energy costs during the 1970's. These designs tend to produce small application areas resulting in high application rates that could exceed the infiltration capacity of the soil and result in runoff. In 1988, Nelson Manufacturing introduced their ROTATORTM and SPINNERTM series low pressure sprinkler heads that had larger application areas than other reduced pressure sprinkler designs as those with spray plates. The Nelson design allows the system designer and the operator to configure each sprinkler for application rate, average drop size and application area.
The Midwest Plan Service publication Sprinkler Irrigation Systems (Scherer et al, 1999) lists factors to be considered in the selection of sprinkler packages for center pivot irrigation systems. The goal of system design is to apply water uniformly and efficiently. Application efficiency is a measure of how much of the irrigation application is available for the crop and is influenced by evaporation losses, wind drift, runoff and deep percolation. Application uniformity measures the evenness of the water application over the irrigated area. Sprinkler characteristics that influence application efficiency and uniformity include:
• Wetted diameter - reduced pressure sprinklers have smaller wetted diameters, resulting in higher application rates that are likely to exceed soil infiltration rates with resulting runoff.
• Droplet size - mean drop size is related to the nozzle diameter and discharge pressure, decreasing with increasing pressure and increasing with increasing nozzle diameter. Larger drops resist wind drift while increasing soil sealing potential that in turn reduces infiltration rates with resulting runoff. Soil crusting hampers seedling emergence. Smaller drops are susceptible to wind drift, which can be critical with chemigation.
• Nozzle pressure- drop sizes, application rates and wetted diameter are influenced by nozzle pressure.
Correspondence with Nelson Manufacturing (Vander Griend, 1994) showed their water application engineers were concerned with:
• efficiency of water application with emphasis on minimizing evaporative losses.
• application uniformity to minimize crop stress due to under or overwatering, especially in high value crops.
• in-crop performance with means to study application uniformity "with various sprinkler head spacings.
• wind resistance on how the application pattern is affected by wind.
• application intensity which affects soil sealing and surface runoff.
The Nelson engineering staff was also very interested in kinetic energy analysis.
Based on the communications with Nelson Mfg., this test program was initiated to obtain the data required for the application rate profiles and drop distributions that are needed for studies of kinetic energy associated with sprinkler water application. Data sets across a range of sprinkler configurations and operating parameters would be useful for the comparison of sprinkler configurations over a range of operating conditions.
This report documents the test procedures and summarizes the data obtained in a series of laboratory tests conducted with the Nelson ROTATORTM and SPINNERTM series of reduced pressure sprinklers. Data were obtained for a range of operating pressures, plate configurations, nozzle diameters and two discharge heights. Examples of application rate, drop distribution and kinetic energy analyses are presented to document the conversion of the data for technical use.

Description

Includes bibliographical references (44-47)

Format

application/pdf

Number of Pages

139

Publisher

South Dakota State University

Rights

Copyright © 2007 Micheal Monnens. All rights reserved

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