Harvesting System Design and Performance - Engineering and Science of Biomass Feedstock Production and Provision - page 92

Fig. 5.6 A flail mower,
showing ( a ) side view and
( b ) types of flails commonly
used and their arrangement.
Adapted from [ 15 ]

The main sources of losses in flail mowers are uneven stubble heights and recut-
ting of the crop. The recutting of plant makes it difficult to be picked up. A push bar
in front of the mower reduces the losses by bending the crop away from the
machines. This action pushes the upper portion of plant stems out of the path of the
blade and thereby reducing the losses by eliminating recutting. The push bar also
puts pressure on the stems, which immobilizes them and allows cutting at a lower
velocity. The higher power requirements are due to friction of rotating parts, impact
cutting, and air pumping as crop is conveyed [ 16 ]. Horizontal axis mowers are now
falling into disuse due to poor cut quality. However, vertical axis mowers are becom-
ing popular due to their higher ground speed (see Table 5.3 ), robust construction,
and low maintenance requirements.

5.3.2 Conditioning

Conditioningisanoperationdesignedtoielddryhigh-moisturecrops.Various
conditioning methods, such as mechanical, chemical, and thermal, have been evalu-
ated for forage crops [ 22 ]. In mechanical conditioning, impellers or rollers are used
to crimp (Fig. 5.7a ) or crush the cut plants (see Fig. 5.7b ). The plant crushing or
crimping facilitates the moisture evaporation. Impeller or flail conditioners and
roller conditioners are the two main kinds of mechanical conditioners. Impeller
conditioners are used to condition whole stalks of a crop whereas rollers are used to
condition both whole stalks and chopped biomass. Impeller conditioners use