Study On Anti - Cavitation Performance Of Centrifugal Methyl Ammonium Pump Based On

A ammonium carbamate pump is an key equipment to transfermethyl ammonium liquid back to the urea synthesis tower for recycling. It as a high-speed rotating equipment in the production of urea, its operation and service life will directly affect the entire urea production systems. However, whether at home or abroad, carbamate centrifugal pumps often happen cavitation phenomenon because of unreasonable designdesign or improper operation in the actual operation of the process, adversely affecting the normal operation of the carbamate pump, reducing the use of methyl bromide pump life.This paper starts research mainly around the cavitation phenomenon in the first-stage impeller of RON2×14centrifugal carbamate pump in the production of urea during operation. Through consulting the related literature at home and abroad, the progress of research and present situation of cavitation performance is analyzed and summarized, and understanding the system principles, methods and processes of tesearch flow problems by computational fluid dynamics. It is detailed analyzed that the feasibility and accuracy of applying CFD numerical simulation technology to.study cavitation performance in centrifugal pump. Firstly, the Pro/E software is used to get the3D model of the RON2x14centrifugal carbamate pump and the ANSYS ICEM CFD software is used to discrete computational domain. Secondly, a three dimensional flow through passage of this carbamate pump is simulated by the numerical simulation software-CFX. The first-stage impeller is optimized design based on the simulation results. And we finally achieve the purpose of improving the performance of pump cavitation under the the premise of stable performance curve and high efficiency. The main work and creativity results are:1) In the process of the RON2×14centrifugal carbamate pump three-dimensional solid modeling, grid conformal transformation method is used to get blade2D wooden-mold drawing, and then get wooden-mold cut line point coordinates (a working surface and a back surface), according to the impeller shaft plane projection drawing. Then importing these points into the Pro/E software, blade surfaces are created through a bottom-up modeling approach. In order to get high quality twisted blade surfaces, the Gaussian curvature and double curvature method are applyed to detect and correct the fairness of blade surfaces. Velocity method is operated to hydraulic design trapezoidal cross-section of the volute, then sweep blend is applied to create the volute and diffusion section of the fluid domain. It is the mainly considered object to use "patching method" to deal with parts of the tongue in the volute, in turn to ensure that the numerical simulation results of RON2×14type carbamate pump cavitation performance are more reliable.2) During the process of3D numerical simulation by using CFX software, the single-phase steady conditions are simulated and a steady flow field distribution and the cavitation performance prediction of the RON2x14pump are obtained. Moreover, we can obtain the pressure and velocity fields situation inside the pump. During the process of pressure fields analysis, we accurate predict the possible positions of the pump cavitation phenomenon,It indicate that the RON2×14carbamate centrifugal pump single-phase flow model by CFX software is veracity. On this basis, we creat the numerical simulation model of this carbamate pump cavitation process flow, in turn to visually show the location and extent of cavitation within the pump through the vapor volume fraction distribution.3) Based on the original model of single-phase unsteady numerical simulation results, targeted to optimize design of the first-stage impeller cavitation phenomenon, we establish the cavitation performance and efficiency of the impeller as the optimization objective, and use stable performance curve as constraints of optimization design. Then penalty function method is used to get the first-stage impeller structure parameter combinations of superb cavitation performance and efficiency. Theoretical calculation methods and CFD numerical simulation method are apply to analyze and compare cavitation performance and efficiency of the original model and optimized carbamate pump. The results show that the cavitation performance change from3.380m to2.952m improving12.7%, and the total energy loss reduce by4%. This indicate the correctness of the optimization results. In order to ensure the optimized carbamate pump steady operation, we select different running points in the stable operating conditions to numerical simulate, and by means of the Origin software to rendering performance characteristic curve, thus achieving the prediction assessment of the optimized carbamate pump performance based on numerical simulation.This paper constructs a wholly analysis system to improve pump cavitation performance, this analysis system is a combination of the CFD numerical simulation method, the multi-objective optimization design method based on Loss extremum method and the penalty function method based on Matlab. The system has certain reliability and good engineering practical value through theoretical calculations and numerical simulation analysis.