| The research in this article was carried out with the support of the National Natural Science Foundation of China(51779108).As a new type of propulsion,water jet propulsion has many advantages over traditional propulsion.It has excellent development potential in ships with high maneuverability.However,there is still a lack of research on the performance of water jet propulsion pumps under maneuvering conditions.In this paper,the combination of theoretical analysis and numerical simulation is used to study the internal flow of the water jet propulsion pump under different working conditions,and the internal flow characteristics and cavitation characteristics of the water jet propulsion pump under different forms of turning and acceleration Analysis to provide a certain reference for the performance optimization of water jet propulsion pumps.The main work and research results of this article are as follows:1.Summarizing the research status and development trend of water jet propulsion pump technology,water jet propulsion pump internal flow performance research and cavitation performance research in more detail.2.Firstly,the numerical simulation method of the internal flow of the water jet propulsion pump was described.Secondly,the internal flow of the water jet propulsion pump at four different speeds and four different speeds was numerically calculated.Finally,the internal flow and pressure pulsation of inlet flow channel,impeller inlet,impeller outlet and guide were analyzed.The results show that:(1)The thrust increases gradually with increasing speed and decreases gradually with increasing speed,the higher the speed,the faster the thrust increase,the thrust difference from 1800 to 2200 rpm is 2.4 times of that from 1000 to 1400 rpm.(2)There is a local high-pressure area in the lip of the lower inlet channel at different operating conditions.The high-pressure area increases with the increase of the speed and decreases with the increase of the speed.(3)There are more characteristic frequencies of pressure pulsation at the hub of impeller inlet at high speed.The amplitude of pressure pulsation in the middle of the outlet flow channel is large,and the characteristic frequency appears at 15 times the axial frequency.The main frequency of the pressure pulsation at the hub of guide vane outlet is the axial frequency,and the main frequency at the middle and rim of flow channel are the leaf frequency.3.The internal flow of water jet propulsion pump under turning condition was simulated by changing the angle of inflow.The internal flow distribution,turbulent kinetic energy and vorticity in the axial plane of intake channel and guide vane were studied when the turning angle is ± 10 °,± 20 ° and ± 30 °.Cavitation,vapor volume fraction and blade surface load were compared when the turning angle was ± 10 °,± 20 ° and ± 30 ° The results showed that:(1)the thrust decreases with the increase of turning angle,and the thrust of right turn was larger than that of left turn,and the maximum thrust difference was 9.14% of that of no turn;(2)compared with left turn,the pressure gradient on the axial surface of water jet propulsion pump was smaller and the vortex was less under the condition of right turn.(3)the cavitation in the impeller started from the outer edge of the impeller inlet,and developed to the middle of the blade with the increase of turning angle.The cavitation was concentrated on the turning blade,and the cavitation area in the right turn was smaller than that in the left turn.4.Considering the effect of the instantaneous acceleration of speed and speed on the performance of the water jet propulsion pump,the acceleration condition of the water jet propulsion pump was simulated by the method of UDF(self-defining function).The performance of thrust,pressure fluctuation,internal flow and cavitation in the water jet propulsion pump was compared when the acceleration time was 1s,and the performance of 0.5s,1s and 2S were analyzed The results showed that:(1)the thrust increased gradually with the increase of acceleration time;the thrust at the same time was lower than that at the linear acceleration,and the thrust at the linear acceleration was 1.41 times of that at the exponential acceleration.(2)the acceleration time and acceleration were different In this way,the law of pressure fluctuation at the impeller inlet,impeller outlet and guide vane outlet were basically similar.When the acceleration time was 0.5s,the main frequency at the impeller outlet was the blade frequency,and when the acceleration time was 1s and 2s,the main frequency at the impeller outlet changed to 7 times the shaft frequency,and the pressure fluctuation under the exponential acceleration was lower than that under the linear acceleration.(3)under the linear acceleration,the volume fraction of the vapor phase in the impeller was 27.3% higher than that under the exponential acceleration. |
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