Abstract
As an important over-current component of the waterjet propulsion system, the main function of a nozzle is to transform the mechanical energy of the propulsion pump into the kinetic energy of the water and eject the water flow to obtain thrust. In this study, the nozzle with different geometry and parameters was simulated based on computational fluid dynamics simulation and experiment. Numerical results show a good agreement with experimental results. The results show that the nozzle with a circular shape outlet shrinks evenly. Under the designed flow rate condition, the velocity uniformity of the circular nozzle is 0.26% and 0.34% higher than that of the elliptical nozzle and the rounded rectangle nozzle, respectively. The pump efficiency of the circular nozzle is 0.31% and 0.14% higher than that of the others. The pressure recovery and hydraulic loss of the circular nozzle are superior. The hydraulic characteristics of the propulsion pump and waterjet propulsion system are optimal when the nozzle area is 30% times the outlet area of the inlet duct. Thus, the shaft power, head, thrust, and system efficiency of the propulsion pump and waterjet propulsion system are maximized. The system efficiency curve decreases rapidly when the outlet area exceeds 30% times the outlet area of the inlet duct. The transition curve forms greatly affect thrust and system efficiency. The transition of the linear contraction shows improved uniformity, and the hydraulic loss is reduced. Furthermore, the hydraulic performance of the nozzle with a linear contraction transition is better than that of others.
Highlights
Waterjet propulsion is a type of special propulsion system that is different from a propeller.This device has been widely used in many high-speed ships because of its high propulsion efficiency, low noise and vibration, and simple transmission structure [1]
The main function of the nozzle, which is an important part of the waterjet propulsion system, is to transform the mechanical energy of the propulsion pump into the kinetic energy of the water and eject the water flow to obtain thrust
The hydraulic characteristics of the nozzle of the waterjet propulsion system were studied a combination of numerical simulationof and Different system grid values
Summary
Waterjet propulsion is a type of special propulsion system that is different from a propeller. The main function of the nozzle, which is an important part of the waterjet propulsion system, is to transform the mechanical energy of the propulsion pump into the kinetic energy of the water and eject the water flow to obtain thrust. Park et al [18] conducted a numerical simulation to obtain the complicated viscous flow feature of the waterjet and predict the performance of thrust and torque to obtain waterjet propulsion characteristics. Fluent 14.0 for the numerical simulation of four different nozzles and analyzed the effects of geometric and dynamic parameters of nozzles on the momentum thrust of the waterjet propulsion system of autonomous underwater vehicles. The influences of the nozzles with different geometric parameters on energy loss, efficiency, internal flow characteristics, and hydraulic performance of waterjet propulsion were investigated. A reasonable nozzle structure is conducive to improving the propulsion system efficiency and reducing energy consumption
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