Affiliations: Department of Mechanical Engineering, Faculty of
Engineering, King Mongkuts Institute of Technology, Ladkrabang(KMITL), Bangkok,
Thailand | Department of Mechanical Engineering, School of
Engineering, Tokai University, Japan
Abstract: The present paper describes a numerical prediction of optimum mixing
throat length for various drive nozzle positions of the central jet pump. The
flow pattern and pressure distribution in the pump for various positions of the
drive nozzle are investigated by three-dimensional numerical analysis using the
RNG k-ε turbulent flow model. Numerical analysis was carried out
for values of the nozzle throat ratio d/D of the jet pump of 0.5, 0.6 and
0.7, respectively. The static pressure in the flow field of the jet pump is
calculated for the following conditions: (1) drive nozzle position from the
entrance of the throat l/D=0∼2.0, (2) flow rate ratio M=0∼1.2, and
(3) Reynolds number Re=3.6×10^5. These calculations revealed
that (1) the optimum length of the mixing throat for l/D=0∼1.0 is Lm/D=2.0∼3.5,
(2) the length of the mixing throat for l/D=0 and M=0 (suction
flow rate ratio=0) is approximately Lm/D=3.5, and (3) the maximum
efficiency is obtained for d/D=0.6 at l/D=0.5. Moreover, the flow
pattern in the mixing throat is clarified through a spark tracing experiment.
The results obtained in the visualization experiment and the numerically
obtained mixing length agreed well.