Construction of a Pilot Headbox System and
Pressure Monitoring Apparatus for the Development of
High Speed Hydraulic Headboxes
Hye Jung Youn
and Hak Lae Lee
Department of Forest Products, College of Agriculture and Life Sciences, Seoul National
University, Suwon, 441-744, Korea
Corresponding author : page94@snu.ac.kr
ABSTRACT
To investigate the influence of the design and operating parameters of the headbox on
hydrodynamics,
a
pilot
headbox
system
and
pressure
monitoring
apparatus
were
constructed. The pilot headbox system consisted of a circulating water reservoir,
centrifugal pump, distributor, turbulence generator and slice. The distributor was designed
to function as a pressure attenuator. Flow rate to the headbox and MD and CD velocity
profiles in the slice zone were monitored using an ultrasonic flowmeter and Pitot tubes,
respectively. As the distance from the step diffusor increased, evener CD velocity profile
was observed. Wall effect increased with the increase of the velocity. Flow stability in
the headbox was evaluated by injecting a dye at the outlet of the distributor.
Application of theoretical analysis based on CFD in designing headboxes is briefly
discussed.
Introduction
Paper machine speed, which has increased substantially during last several decades, is
expected to increase continuously in the future even though the increase rate will a bit
diminish. Increase of paper machine width, however, does not appear to take place
within next ten years.
1-2)
To facilitate the increase of machine speed, many open draws
have been eliminated and diverse new concepts of compactness have been adopted in
designing today's paper machines. The philosophy of compactness in designing today's
paper machines can also be found in headboxes, which is one of the most critical parts
of a paper machine. Diverse research efforts have already been made to develop
headboxes which would provide excellent runnability and product quality.
The importance of headbox design for sheet properties including formation, fiber
orientation, MD and CD basis weight uniformity, etc has been acknowledged for many
years.
3-4)
With technological trends of increasing paper machine speed and reducing basis