Improving the Throwing Effectiveness of an Upward-cutting Forage Harvester

Abstract

An upward-cutting, cut-and-throw, forage harvester was previously shown to reduce specific energy requirements by 30 to 34%, but it also had a 27% shorter throwing distance than a conventional, cut-and-blow, forage harvester. The upward-cutting, cut-and-throw, forage harvester was modified to improve the throwing/blowing characteristics while maintaining the specific energy advantage. By increasing the open area in the sidewalls of the cutterhead housing, the air speed through the discharge spout was increased from 8.6 to 21.5 m/s, which significantly improved throwing distance. A video method was used to observe that cut material was engaged with the cutterhead knife for a significant fraction of a revolution, such that the crop left the cutterhead in a wide, nonconcentrated pattern. A throwing countersurface mounted below and perpendicular to the knife improved particle release. The throwing distance improved and the energy requirement increased with a smaller relief dimension from the countersurface to the knife tip. With a 9-mm relief, 9- and 12-knife cutterheads produced mean throwing distances 4 and 11% shorter, respectively, than a cut-and-blow harvester harvesting alfalfa; and 6 and 14% shorter, respectively, than a cut-and-blow harvester harvesting corn. The 9-knife cutterhead produced a throwing distance closer to that of the cut-and-blow harvester than the 12-knife cutterhead due to greater air velocity in the spout. With a 9-mm relief, 9- and 12-knife cutterheads resulted in specific energy requirements 21 and 24% lower, respectively, than a cut-and-blow harvester harvesting alfalfa; and 14 and 25% lower, respectively, than a cut-and-blow harvester when harvesting corn. The 12-knife cutterhead produced greater specific energy reductions than the 9-knife cutterhead due to lower peak cutting and mat compression loads.