The Effects Of Matching Between Two Stages On Characteristics Of Counter-rotating Water-jet Pump

The traditional water-jet propulsion system was used to be the rotating propeller propulsion and common axial-flow pump water jet propulsion,but the noise and anti-cavitation performance of propeller itself are poor,and the operating efficiency of ordinary axial-flow water-jet propulsion pump decreases rapidly under off-design conditions,which make against to the water-jet propulsion pump under multi-condition operation.In order to improve the performance and multi-condition adaptability of water-jet pump.In this paper,a counter-rotating axial-flow water-jet pump was designed for a underwater vehicle.The impellers with different axial clearances between the two impellers,secondary inlet angle and different speed ratios were numerically calculated under various working conditions,and their external characteristics and internal flow mechanism were analyzed.The main research contents are as follows:(1)The basic design parameters of the propulsion pump are calculated according to the relevant formula of the water jet propulsion principle.Then based on the velocity triangle,the hydrodynamic design of the counter-rotating water-jet pump studied in this paper was carried out by streamline method,and a three-dimensional model was established;(2)The counter-rotating pump is simulated under different working conditions,to analyze the streamline,static pressure distribution and velocity distribution of the middle shaft section under saddle area,design and large flow conditions.The flow field variation law of counter-rotating water-jet pump under different working conditions was obtained;(3)The axial clearance coefficient ? between first and secondary stage impeller is defined by refering to the range of axial clearance between guide vane and impeller and taking the outer diameter of the first impeller as a criteria,5 water-jet pump models with different axial clearance coefficient were designed to compared the external characteristics,internal flow and thrust characteristics under different working conditions;(4)In order to research the external characteristic under different incidence angle,the five groups of model which incidence angle is-4°?-2°?0°?2°?4° were established.The influence of the pressure load on the middle streamline with different inlet incidence angle model pump under design conditions was analyzed,and the influencerule of incidence angle on the flow field inside the secondary impeller under design conditions and saddle region conditions was compared.The variation trend of thrust performance of the five model pump was analyzed;(5)Pump and submarine are integrated into the whole basin,then control the rotational speeds of the front and rear impeller to 900 rpm,1200 rpm,1500 rpm,1800rpm and 2100 rpm respectively.The influence of the front and rear impeller speed matching on the external characteristics,internal flow and the distribution of the main vortex system of the water-jet pump in mooring condition and the thrust characteristics under the navigation state were studied in order to find the optimal speed ratio range and improve the efficiency of the water-jet propulsion pump under different operating conditions.