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

Abstract : This paper presents 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. The method consists in recording 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 granule shocks against 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 impact overlapping. Algorithms are here 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. Our findings demonstrate that processing impact record clearly distinguishes 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. The vertical distribution of the mass flow is also studied. This new approach paves the way for the design of alternative tests and diagnostic tools to characterise centrifugal fertiliser spreading.