Toward a Portable Cotton Harvester Machine, Necessitates and Design
By A. H. Haji
Cotton harvesting methods, affected by some parameters such as seeding type, product state at the time of harvesting and farmer affords are generally classified into two categories of manual and mechanized methods.
For example only in the case of a raw plant can a combine be used to harvest the product and otherwise the only way is to apply manual methods.
Considering some parameters as the popularity of non – mechanized planting methods in some traditional cotton producers like Iran, the manual harvesting is the general approach in these countries.
However the ever increasing demands for cotton and relatively high cost of the manual methods in comparison with its low efficiency have forced the traditional producers to improve their strategies against the resultant downturns.
At a glance the most important advantages and disadvantages of manual and mechanized methods can be noted as follows:
· Manual Methods
o Advantages: applicability regardless of plant type
o Disadvantages: high cost and low efficiency
· Mechanized Methods
o Advantages: much higher harvesting speed relative to manual methods
o Disadvantages: Lower product grade (harvesting impurities attached to cotton fibers), Relatively high price and maintenance cost of a cotton combine, Necessity of raw planting, Need for a chemical leaf shedder
An alternative for both manual and mechanized methods which presents the major advantages of these two methods and minimizes their deficiencies seems to be a portable harvesting machine.
But to increase the harvest worker what mechanism should be implemented? In other words where can a portable machine place in the manual harvesting process?
In concurrency with the fact that the major part of a harvest worker activities is due to the pulling of cotton fibers form the cotton boll, a suction mechanism sounds like the best solution. The principal characteristics of such mechanism can be outlined as follows:
· sufficient vacuum pressure in order to easy pulling of cotton fibers out of the boll
· satisfying portability conditions like weight, comfortability and safety conditions
· rapid discharge
In this project I have surveyed some previous works on the above idea and specifically investigated an indirect mechanism. This mechanism resembles the venturi mechanism in carburetor fuel type systems but with a higher flow rate which lets it generate a higher vacuum pressure. The major constraints on this mechanism were:
· the maximum power is 3HP
· the minimum vacuum pressure is 5kPa
· the maximum permitted sound level is 90dB
For solving the problem, first I applied both software (numerical) approach and analytical approach to reach an overall insight about the mechanism i.e. to construct a model for the venturi gas dynamics. Then having such model, I tried to optimize the design to satisfy the minimum pressure condition. This optimization included the fan selection and determination of venturi dimensions.