A natural flow or transverse combine harvester is a feature of a conventional combine while the axial flow is a feature of the new generation rotary combine. A hybrid combine harvester is a mixture of the conventional and rotary.

Conventional combine harvester versus rotary combine harvesters

A natural flow or transverse combine harvester is a feature of a conventional combine while the axial flow is a feature of the new generation rotary combine. A hybrid combine harvester is a mixture of the conventional and rotary.

1.    Natural flow: In conventional machines, the threshing must be done in one pass of the crop with a single rotation of the rotor. Hence, the crop must be thoroughly impacted and rubbed against the concave to get the maximum amount of grains out. In the process, there are higher chances of grain damage.

2.    Axial flow: The axial flow mechanism has two main key assemblies which are:

·       Stationary chamber or housing containing a concave element and a revolving rotor. Mounted on the rotor are impellers to move the crop. As the rotor turns, the impellers gather the crop and speed it to the rear in a helical path to the rasp bars. As the rotor turns more, the rasp bars rub the material repeatedly against the concave continuing the rearward spiral.

·       Separation area: The crop passes repeatedly over a separating gate where centrifugal force carries the grain through the gate and into the cleaning system. In the cleaning system, the grain is not rubbed against the concave hence little grain damage.

This high efficiency of the axial flow in combines permits the combining of high dense crops at high ground speed with less grain loss and damage.

The table below presents the five categorical differences between the natural flow and the axial flow:

Natural Flow

Axial Flow

Higher chances of grain damage

Low chances of grain damage

Single-pass threshing

Repeated threshing pass

High unthreshed grain loss

High threshed yield, low grain wastage

Straw walkers to separate grains from MOG (material other than grain)

Separation by centrifugal force

Low ground speed

Higher ground speed

Poor for grain with high moisture content

Works well with grains with high moisture content

 

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