Optimum Design And Internal Flow Analysis On Super-low Specific-speed Centrifugal Pump's Impeller

Super-low specific-speed centrifugal pump is a part of centrifugal pumps, which is widely used in aerospace and petrochemical industries. It not only has the basic performance of centrifugal pump, but also has its special performance. First super-low specific-speed centrifugal pump has a long and narrow flow passage for its high head and low capacity, and the power absorbed by disc friction is too high, so the efficiency is very low; Secondly the diffusion of flow passage is so high, that the reserved flow often emerges at the inlet and outlet of impeller. Therefore the H ~ Q characteristic curve is often hump-shaped, and at the low-capacity operating condition the instability often occurs; Thirdly the centrifugal pump at high-capacity operating condition is easy to overload because the N ~ Q curve appears a rising trend. In present thesis, the actual design theories and methods for super-low specific-speed pump are introduced first, including "the increased flowrate design method", "the method of anti-hump on H ~Q characteristic curve ", "non-overload design method", "the design method of complex impeller" and so on. According to these methods, 5 types of impeller have been designed. This thesis also describes the numerical simulation of three-dimensional turbulent flow in super-low specific-speed impeller, points out the turbulence model and numerical solution for it, and gives the writer's view of the grid-generation. According to the distribution of pressure and velocity on the 5 types of impeller, it analyses and discribes the feature of internal flow in super-low specific-speed pump impeller. Comparing tow methods of efficency pre-estimation, it finds out the new method fit for super-low specific-speed pump. Acoording to the study and comparison on efficency and reliability, the thesis points out merits and faults of the 5 types of impeller, and draws a conclusion that the complex impeller and partly blocked-flow-passage impeller are fit for the impellers of super-low specific-speed centrifugal pump. A new type of very low specific speed pump—Roto-Jet pump is presented for low flowrate and high head transportation, which is introduced at the end of the thesis.It can be applied to petroleum and chemical engineering for equipment updating due to special design principal, configuration and remarkable performance. Numerical simulation and efficiency pre-estimation have been made to analyze performance of roto-jet pump impeller.