Design Of Supercharged Turbo Expander And Numerical Simulation Of Supercharger

Turbo expander is one of the essential equipments in the process of expander cycle for small scale gas liquefaction plant. Recently, with the development of liquefaction technology of natural gas in China, turbo expander obtains more and more attention. Since the supercharger can recover the output power of the original turbo expander, the refrigeration capacity of unit working medium for expander will be increased. Supercharged turbo expander has the advantages of compact structure, small volume, low weight, high efficiency and stationary performance under variant working conditions. It has been widely used in the domain of liquefied natural gas. So it is valuable to do some research on the supercharged turbo expander.Based on the structural characteristic of supercharged turbo expander, this paper shows the calculated process of expander and supercharger of one supercharged turbo expander, which is used in the process of nitrogen expander cycle. The calculation of expander is carried out by the MATLAB programming. The thermodynamic parameters and structural dimensions of every part have been determined.This paper presents the governing equations of three dimensional flow field and turbulent calculated model. Author particularly introduces the k -εturbulent model used in the study of this paper. The finite volume method is also introduced. All of these have supplied theoretical guideline for the simulation.In this thesis, the three dimensional viscous flow in the supercharger is simulated using the commercial CFD code FLUENT. In order to analyze the flow characteristics of supercharger impeller, vaneless diffuser and volute, single channel model and entire machine model are built for simulation. Single channel model is used to simulate the flow in the impeller. Based on the simulated results, the complex phenomenon of flow has been analyzed, including the separated flow, the secondary flow, wake and so on. In order to reduce the loss, the shape of leading blade is considered to change. The simulated results show that the elliptical leading blade can improve the blade performance. Finally, the calculated results of entire machine model are used to analyze the velocity and pressure in the vaneless diffuser. The flow in the volute is also analyzed and the tongue of volute has a large effect on the performance of flow.