Low Liquor Jet Dyeing Heavy Cotton Duck Basics
Low liquor jet dyeing of heavy duck yields ten cent per metre savings but demands precise nozzle sizing and metered dosing to prevent unfixable rope creases.
Venturi Diameter
Hydrodynamic Geometry
The internal constriction dimension of a fluid jet nozzle governs the acceleration, static pressure drop and volumetric throughput of dye liquor driving a fabric rope. This mechanical dimension designated as venturi diameter controls the physical velocity and driving force exerted onto textiles moving inside closed jet dyeing vessels. Based on Bernoulli principles, narrowing the flow channel forces liquor to trade static pressure for fluid velocity.
The accelerated liquor stream transfers momentum to the fabric rope, propelling it through the transport pipe without mechanical nip rollers. Selecting this dimension dictates running rope speed, hydrodynamic shear and liquid exchange rates.
Nozzle Sizing
Orifice dimensions must match the specific cross-sectional bulk and linear weight of the moving fabric rope. An undersized venturi diameter squeezes the textile rope excessively, generating mechanical friction that induces rope bruising, fabric chafe marks and localized fiber pilling. Conversely, an oversized internal bore allows liquor to bypass the textile perimeter without transferring adequate kinetic drive, producing slow rope speeds, cloth slippage and internal machine tangles.
Heavy cotton terry fabrics require expansive nozzle clearances, while delicate microdenier synthetics demand reduced apertures to maintain transport velocity at low pump volumes.
Flow Kinematics
Fluid flow transitions within the converging and diverging sections of the nozzle determine dynamic processing pressures. Adjusting the venturi diameter alters the liquor flow velocity and system backpressure throughout the circulation system. Dyeing machines adjust operating speeds from one hundred to six hundred metres per minute based on the nozzle dimension paired with centrifugal pump speeds.
The dynamic pressure differential inside the constriction forces liquor into the fiber interior, driving dye penetration across heavy wovens. Machine manufacturers design interchangeable nozzle inserts, allowing dyehouse technicians to change internal dimensions when switching fabric qualities.
Operating Boundaries
Hydrodynamic propulsion terminates its utility when excessive nozzle pressure damages sensitive surface constructions or pulls lightweight knits out of dimensional shape. Measuring venturi diameter requires precision internal micrometer gauges, because progressive abrasive wear from processing fabrics gradually enlarges the throat dimension over years of production. Altering the nozzle dimension shifts system liquor flow curves, requiring manual recalibration of circulation flowmeters and pump frequencies.
The nozzle diameter provides hydrodynamic transport only, leaving total liquor ratio calculations to machine vessel volumes and total cloth weight. Clean nozzle surfaces avoid snagging fine filament loops on textured yarn knits.