| Canned pump is widely used in petroleum,chemical,pharmaceutical and other production because of its non-leakage characteristics.And high temperature canned pump can be used to transport high temperature fluid above 200℃.However,the current high temperature canned pump is mostly in the form of single suction,which is restricted under high flow conditions due to its large axial force and cavitation margin,low efficiency and other reasons.For this reason,this project has developed an innovative high flow high temperature double suction canned pump,which is easy to balance the axial force and high efficiency,and has a large potential for promotion,so it has practical significance to systematically research such pumps.In this paper,we take the innovative high-flow high-temperature double-suction canned pump as the research object,establish an automated simulation optimization platform to explore the efficient pump hydraulic optimization design method,and carry out the optimization design of double-suction impeller under multiple working conditions to improve the pump performance and expand its high efficiency range.At the same time,numerical calculations of heat flow coupling are carried out for the cooling circulation system of high-temperature double-suction canned pump to study its flow characteristics,temperature distribution and convective heat transfer law,so as to provide some reference for the optimal design of the cooling circulation system.The main research contents and conclusions as follows.(1)Creo and ICEM are used to model and mesh the full flow channel of the high temperature canned pump,CFX is used to numerically calculate the model,and the high temperature double suction canned pump is tested and verified by a closed test bench.Ansys Workbench and Optislang are used to build an automatic optimization platform to optimize the double-suction impeller of the high-temperature double-suction canned pump in multiple operating conditions.Twenty-eight parameters were selected as input variables directly involved in the optimization,after which 300 samples were generated for sensitivity analysis by the advanced Latin hypercube sampling method,thus screening out eight variables with high sensitivity.Following that,a gradient-based quadratic Lagrange nonlinear programming method was used for iterative optimization,and the optimization results are verified numerically.The weighted efficiency of the pump was improved by 3.19% after optimization,so the optimization method was considered effective and efficient.(2)The pumps before and after optimization were simulated separately,and the results were compared and analyzed.The external characteristic curve shows that the optimized efficiency is overall higher than before the optimization under the condition that the head of design working condition is basically unchanged,and the high efficiency zone is obviously expanded.The internal flow field analysis shows that the flow field inside the impeller is significantly improved after optimization,most of the vortex and deliquescence are eliminated,and the low-pressure area at the inlet side of the blades are significantly reduced.The pressure pulsation analysis shows that the impeller pressure pulsation coefficient changes less before and after optimization,while the amplitude of pressure pulsation in the volute is significantly reduced after optimization.The analysis of non-constant radial force shows that the amplitude change is small,but the phase angle where the peak radial force is located is changed because the blade wrap angle becomes larger after optimization.The cavitation characteristics analysis shows that the optimization is not significant for it.In summary,the performance of the pump was significantly improved after optimization,especially for the flow field in the impeller and the pressure pulsation in the volute.(3)Numerical calculation of heat flow coupling is performed for the cooling circulation system and then analyzed its result.The analysis of the circulating flow and circulating system power loss reveals that the cooling circulation flow in the motor cavity is basically unchanged under different working conditions due to the narrow connection gap between the motor and the pump,so the power loss in the cooling circulation is also unchanged.It is calculated that the loss power is 2.268 KW,3.5% of the rated power of the canned motor pump,and the rotor shield sleeve and auxiliary impeller loss power ratio reaches more than 90% of the loss power.After analyzing the flow field in the cooling circulation system,it is found that after the liquid flow is pressurized by the two-stage auxiliary impeller,the highest pressure in the circulation system occurs at the outlet of the second-stage auxiliary impeller,and then the circulating liquid flows under the pressure for heat dissipation and lubrication.Moreover,as the pressure at the outlet of the volute decreases,the pressure in the cooling circulation system also decreases,and in the connection gap,the pressure in the motor chamber is balanced with the pressure transmitted from the volute outlet.The analysis of the temperature distribution within the cooling circulation system shows that the distinction between high and low temperatures on both sides of the connector gap is very obvious,and the maximum temperature is only 80.657℃ which is less than the required 100℃,indicating that the cooling circulation system is reasonably designed.The analysis of convective heat transfer of the circulation system shows that the surface heat transfer coefficient of the stator shield increases along the inlet to the outlet of the shield sleeve gap,because the liquid flow velocity increases gradually under the action of viscous force,while the surface heat transfer coefficient of the rotor shield is the opposite with that.And the surface heat transfer coefficient near the primary and secondary water inlets on the wall of the heat exchanger bundle is larger,while the other parts are smaller.Finally,the analysis of the pressure pulsation in the cooling circulation system revealed that the pressure pulsation decays rapidly after flowing through the inflow orifice,but to a lesser extent after moving away from the auxiliary impeller. |
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