Estimation of two-dimensional fertiliser mass flow distributions by recording granule impacts

A new method to simultaneously measure the horizontal and vertical distributions of the mass flow in the vicinity of the spinning disc of a centrifugal fertiliser spreader is presented. The method records granule impacts on a cylindrical vertical screen placed around the disc. The screen is covered with a paper band, a carbon film and a protective coat, so that granules hitting the screen produce impact marks on the recording paper band. A mathematical model is used to estimate the local impact density by correcting the bias due to overlapping impacts. Algorithms were developed to process the recording band, taking into account its location with respect to the spreading device. The distribution of the mass flow is studied for two fertilisers. The findings demonstrate that processing impact record clearly characterises the horizontal and vertical distributions of the mass flow for a compound fertiliser NPK and potassium chloride. For the horizontal distribution, comparisons are carried out with results deduced from a traditional compartmented ring. This new approach paves the way for the design of alternative tests and diagnostic tools to characterise centrifugal fertiliser spreading.