Optimising cane harvester extractor performance : SRDC final report BS65S
The three year project to optimise cane harvester extractor peformance was directed into three separate areas - evaluation of existing commercial or semi commercial cleaning system -development of an extractor hood design with improved aerodynamic properties - and - refinement of the design of the extractor chamber to improve cleaning performance. Initial testing of the Alfarm Mizzi harvester fitted with a pre-cleaning chamber to extend the length of the path for cleaning by the primary extractor proved inclonclusive, du to mechancial problems with the test harvester. However, it was observed that the precleaning chamber was ineffective at high feed rates and this problem has been partially addressed in the latest Joe Mizzi harvester by increasing the height of the chamber. Preliminary testing confirmed that cleaning performance of a vertical arm extractor was superior to a cross-arm mounted extractor and efficiency was affected by factors such as the deflector plate angle and blade tip clearance . The development of a protype 'lobster' shaped steel hood showed that air velocities in the extractor chamber were increased by widening the cross-section of the hood towards the outlet and providing a more streamlined shape. A prototype moulded polythlene hood was developed from the 'lobster' hood to facilitate manufacture of the tapered and smoothed shape. After refinement of the plastic hood in a further steel protype a final plastic hood mould was constructed with the extractor fan mounted on a vertical shaft supported by external steel legs. This hood is mounted on an extended steel barrel. Detailed testing of a range of extractor chamber configurations and inlet vent positions was carried out with results showing the following: improved cleaning and reduced cane loss with an additional rear vent directing air against the flow of cane from the chopper; similar improvements by introducing additional air into the bottom of the cleaning chamber by widening the base of the air inlet cone. It was noted that there needed to be a balance between the different locations for introducting air into the chamber to optimise separation of cane and leaf and trash without causing excessive cane loss. The final cleaning system development incorporated the plastic hood with extended steel barrel, additional air vent in the rear of the extractor chamber and a widened base on the air inlet cone. Field testing confirmed that this system garve superior cleaning and reduced cane loss compared to a standard steel hood with vertical arm extractor. It is recommended that the plastic hood, extended steel barrel and vertical extractor with support legs be developed as a retrofit option for pre-1996 Austoft 7000 harvesters. Commercial use is considered to be limited to wheeled harvesters due to excessive height of the extended barrel system on low loaders. There is also the option of developing a suitable folding system to lower the height for transport.