what is the principal of jet dyeing machine in textile dyeing ?

Answer 1

I can only give you info about carpet dying.

Jet dying is done after a complete roll of carpet has been tufted, usually 500 feet or so in length. Widths vary, 12', 13'6", 15'. Usually 700 +- sq yds.

The entire length is rolled out flat. Jets above spray dye onto the surface. This process is used most commonly on pattern goods.

Most carpet is "piece dyed". The roll of carpet is "Washed" through a huge vat of water and dye stuffs. Temperature of the water is heated continuously under controlled temp. Humidity must also be controlled at an even level, as best it can be. It will always vary as the outside humidity and temp changes.

Another method is "Stock Dyed Yarn".

Any yarn can be dyed in this manner, but most common are Polypropylene and Polyester.
Polypropylene cannot be dyed in any other manner. The yarn is dyed while in a liquid state, before cooling and extrusion. Finished Polypropylene will not absorb or accept dye. The color is completely through the fiber, much like a carrot.
Nearly impossible to stain, but has some shortcomings compared to other fibers.

Polyester can be piece dyed or stock dyed, as nylon can.
When piece dyed, the color is more like a radish. Dye penetrates the yarn to a limited depth.

Some Nylons are the strongest fiber, made from coal. Others from petroleum.

Newest process?
Some Nylon will soon be made from Corn Oil.