Two-phase pulsating flow analysis of air-milk in a milking robot

This project is done in close collaboration with Lely in Rotterdam.

The Lely Astronaut is a robot to fully automatically milk cows. This means that pre-treatment of the udders, attaching milking cups, milking of the cow and post-treatment of the udders is done without any involvement of the farmer. The milk is subtracted from the cow by means of a pulsating vacuum. The milk is transported from the teats to the jar by means of vacuum, and a bleed hole for air inlet is used to increase the flow rate.
 
In the current implementation, a bleed hole of 0.8 mm at the milk cup is used for air inlet. The air is separated from the milk in the milk jar. The air inlet should be minimized from a milk quality point of view, because mixing air with milk damages fat globules of the milk. The air inlet cannot be too small, because this decreases the milk flow rate and gives unstable vacuum under the teat. Currently, the optimal bleed hole size is not known. 
 
Objectives:
 
o   A representative model of pulsating air-milk flow from teat cup to milk jar (neglect intermediate components) to simulate milk flow rate, vacuum level under the teat and shear stress in the milk.
 
o   Quantify the relation between bleed hole size and milk flow rate, vacuum stability and shear stress on the fat globules.
 
o   Verify the model by experiments on average milk flow rate and vacuum stability

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