Research On Operating Performance Of Marine Centrifugal Pumps

Compared with ordinary centrifugal pumps,the operating conditions of marine centrifugal pumps are more complicated due to the limitations of the cabin space,its operating environment and the special performance requirements of the ship.The current research on marine centrifugal pumps is basically not considered for the actual ship operating conditions such as roll and incline,which makes the practical application of existing results more limited.In order to get a better researching about the internal flow of the centrifugal pump on the real ship,the paper uses a marine pump rolling test bench developed by independent innovation to simulate the rolling and inclining motion of the marine pump under specific sea conditions,so as to study the operating characteristics of the pump under rolling and inclining conditions,and the numerical simulation method is used to explore the internal flow of the pump and its mechanism of action on the energy performance,pressure fluctuation and vibration of the marine pump.At the same time,in view of the small space and elbow of marine centrifugal pump,the effects of different inlet and outlet pipelines on pump performance and the pressure,velocity and pressure fluctuation of internal flow field under different inlet and outlet pipeline shapes are studied.The main research contents and creative conclusions are as followings:1.The research progress of current domestic and international marine pumps and their different inlet and outlet pipelines,as well as the research situations of centrifugal pump pressure fluctuation and vibration are summarized.The rolling model of marine pumps is also described.2.The marine pump inclining and rolling test device was designed and for the first time to achieve the simultaneous testing of energy performance,pressure fluctuation and induced vibration under the conditions of inclining and rolling marine pump.The performance test results show that:?1?As the inclining angle increases,the head gradually increases.Under different working conditions,the left-inclining and right-inclining head of model pump is higher than that of the normal working condition,and the maximum variation is 2.3%.?2?The influence of inclining on efficiency is relatively small,and with the increase of the inclining angle,the efficiency of left-inclining is higher than that of right-inclining under large flow rate.3.The experimental investigation on the pressure fluctuation characteristics and flow induced vibration characteristics of the model pump under different inclining angles was performed.The following 4 results were obtained:?1?The pressure fluctuation amplitude of monitoring points P₁ and P₂ in the second and fourth section of the volute increases with the increase of the left inclining angle and decreases with the increase of the right inclining angle in fluctuations.While the pressure fluctuation trends monitoring point P₃ in the six section of the volute and opposite to the tongue monitoring point P₄ are complex and similar.?2?With the increase of the inclining angle,the pressure fluctuation amplitude at the blade passing frequency and rotation frequency of each monitoring point increases overall.The maximum increment of pressure fluctuation amplitude at blade passing frequency is 27.49%,and that at shaft frequency is 29.14%.?3?When the left and right are inclined at the same angle,the amplitude of the vibration of each monitoring point changes greatly when inclined to the left,and the amplitude changes relatively small when inclined to the right.?4?The maximum vibration acceleration value of each monitoring point increases gradually with the increase of the left-inclining angle,and the maximum increment is 17.16%.However,as the right-inclining angle increases,it fluctuates within a small range,and the average amplitude is 4.50%.4.Taking a marine centrifugal pump with a specific speed of 78 as the research model,the effects of the inclining angle on the energy performance,internal flow and pressure fluctuation of the pump are studied by CFD method.The main conclusions were following:?1?with the increase of the inclining angle,the parameters such as head and power of the model pump increases as a whole.When the left-inclining and right-inclining of the pump is 25°,the maximum increase of the head is 1.30%and 1.90%respectively.?2?When the pump is inclined,the area of the low-pressure area in the inlet pipe becomes smaller,and there is an obvious vortex in the low-speed area at the outlet of the volute.?3?When the pump is operating at an incline,the amplitude of pressure fluctuation at the main frequency of each monitoring point in the pump increases,with an average increase of 8.1%.5.The pressure fluctuation and vibration test of marine centrifugal pump under different rolling angles and rolling periods show that:?1?With the increase of rolling angle,the peak value of pressure fluctuation in the pump increases gradually,with the maximum increment of 8.56%.Under different rolling periods,the amplitude of pressure fluctuation at the blade frequency of each monitoring point in the pump presents obvious regularity,and with the increase of rolling period,the peak value of pressure fluctuation increases initially and decreases afterwards,with the maximum change of17.63%.?2?As the increase of rolling angle,the vibration amplitude of the model pump increases gradually,with the maximum increment of 7.53%.With the increase of rolling period,except for the monitoring point M₁ at the pump outlet flange,the maximum vibration acceleration value of monitoring points decreases generally,with the maximum decrease of 9.14%.When the rolling angle is the same as the inclining angle,the vibration acceleration value of each monitoring point increases slightly under rolling,and the maximum value of M₆ at the monitoring point of motor base increases by 5.80%.6.The effects of inlet bend turning angle,turning radius and straight tube length on the performance parameters and internal flow field of marine centrifugal pump are studied by numerical simulation.The results can be concluded as follows:?1?With the increase of inlet bend turning angle?,the head and efficiency of the pump decrease gradually,with the maximum reduction of 0.8%and 3.2 percentage points separately.The pressure inside the elbow decreases gradually,while the pressure outside the elbow increases and the corresponding pressure difference between the inside and the outside increases.the pressure fluctuation amplitude at the monitoring point P₀ of the pump inlet flange decreases,and the maximum decrease is 27.3%.?2?As the increase of turning radius R,the head of the pump increases gradually,with a maximum increase of 1.2%.The efficiency increases with a maximum increase of 5.4 percentage points.The pressure value inside the elbow increases gradually,and the outside pressure value and the difference between the inside and outside pressure decreases.The pressure fluctuation amplitude of monitoring point P₀ at the inlet flange increases,with a growth of 67.8%.?3?With the increase of straight tube length L,the change of head and efficiency is small,increasing by0.4%and 1.2 percentage points respectively.The pressure and velocity values inside and outside the elbow are relatively stable,with small change.The pressure fluctuation amplitude of monitoring point P₀ at the inlet flange is larger,with an increase of 76.5%.7.The numerical simulation method is used to study the influence of 3 different types of outlet pipes on the energy performance of the model pump and the characteristics of pressure,velocity and pressure fluctuation in the pipe.The results show that:?1?With the increase of the turning angle?of the outlet bend,the pump head first decreases and then increases,with the minimum value at?=90?.The efficiency gradually decreases,with the maximum reduction of 3.8 percentage points.The pressure value of inside and outside of the elbow decreases first and then increases,and the change of the pressure difference between the inside and outside is opposite.The pressure fluctuation amplitude of the monitoring point P₅ at the pump outlet flange first increases and then decreases,reaching the maximum value at?=90?,with a variation of 2.5%.?2?As the increase of turning radius R,the head and efficiency of the pump increase gradually,with the maximum increase of 2.4%and 6.4 percentage points respectively.The pressure value inside the elbow increases gradually,while the pressure value outside decreases slightly and gently,and the pressure difference between the inside and outside of the elbow decreases.The pressure fluctuation amplitude at the main frequency of P₅ point at the outlet flange increases first and then decreases,with a small variation 0.4%.?3?When the length of outlet straight tube L increases,the head and efficiency increase first and then decrease,with the maximum increase of 1.8%and 1.5 percentage points respectively.The pressure value of inside and outside in the elbow increase slightly,while the pressure difference between inside and outside decrease,with small changes and tend to be stable.The pressure fluctuation amplitude of the monitoring point P₅ at the pump outlet flange decreases,decreasing by 3.0%.?4?Compared with the inlet bend,the three parameters of the outlet bend have a greater impact on the energy performance of the pump,and the turning radius and angle of the model pump outlet bend have a more significant impact on its energy performance than that of the length of outlet straight tube.