Operational properties of forestry mulchers for cleaning field protection forest belts after sanitary cuttings

Experimental studies were conducted with forestry mulchers in field protection forest belts and clearings in the North-Eastern region of Bulgaria . Regression models were elaborated to determine the operating performance and fuel consumption of forestry mulchers with a rated power of 70 kW to 245 kW for site preparation of clearings with the amount of wood residues, shoots and bushes from 15 t/ha to 48 t/ha. The mode of influence of the mulcher rotor speed , the concentration of comminuted biomass and the mulching unit power on the performance and fuel consumption were established. When treating clearings with small biomass concentration of 15 t/ha, the productivity of the mulching units with a greater power of 245 kW is 0.392 ha/h, and of those with a smaller power of 70 kW it is 0.086 ha/h. This difference is even greater in clearings with a biomass concentration of 48 t/ha, where the operating productivity of 245 kW mulchers is 0.304 ha/h and that of 70 kW mulchers is 0.021 ha/h. Mulching units with greater power also have a lower relative fuel consumption per unit area. This fact is more pronounced in clearings with a larger amount of wood residues of 48 t/ha, where the fuel consumption of bigger units with a power of 245 kW is 155 l/ha, of units with a medium power of 160 kW it is 217 l /ha, and of units with a smaller power of 70 kW it is 335 l/ha. For treating clearings with relatively less wood residues and shrubs of 15 t/ha, depending on the rated power of mulching units, these fuel costs are respectively 86 l/ha, 122 l/ha and 214 l/ha. The optimal power and rotor revolutions of forestry mulchers when processing cuttings with different concentrations of woody biomass were determined.