Simulation driven design improvement of the Marshall multispread fertiliser spreader (original) (raw)
With the rising cost of nitrogen based fertilisers caused by global energy price increases, and concerns surrounding the depletion of global phosphorus resources, efficient use of fertiliser is a major concern for modern Agriculture. Equipment used to apply fertiliser should be accurate and precisely calibrated as variations in the distribution of fertilisers can lead to reductions in crop yield, soil damage and environmental run-off which ultimately lead to loss of income to the farmer. In a competitive environment, a simulation driven design process can significantly reduce development time of agricultural machinery. This paper looks at the development of a numerical model that was used to improve the design of the Marshall Multispread fertiliser spreader. The model tracks fertiliser particles as they are loaded onto the spinner disc, are captured by the spinner vanes and then subsequently ejected over the field. Key design parameters such as spinner speed; particle loading position on the disc; the number of spinner vanes and their angle relative to the centre of the disc; particle drag coefficient and breakage thresholds and prevailing wind speed and direction are used as model inputs. Using particle motion and ballistic equations, the model outputs a map of the fertiliser distribution for a given paddock area which can be used as a comparison against industry based performance standards. A number of techniques were used to validate the model outputs including high speed photography, a bespoke collector device for measurement of angular distribution of particles as they leave the spinner disc and field based spread testing under controlled conditions. The sensitivity of the spreader’s performance to changes in wind speed and direction, fertiliser consistency and machine setup was analysed. Prototyping and Simulation of different spinner vane and chute designs was undertaken until the optimum machine configuration was achieved. As a result of this study a spinner design that is tolerant of variations that occur under real life spreading conditions was developed. The new Type D spinner design was placed into production in early 2012, achieving a 25% improvement in spread width over the previous configurations, allowing farmers to spread fertilisers at wider widths in the paddock, reducing labour and fuel costs, whilst maintaining accurate placement of fertilisers. The successfully completed design improvement demonstrates the value of numerical simulation techniques in the Agricultural Equipment design process.
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