AN AERODYNAMIC INVESTIGATION OF VANED DIFFUSERS FOR CENTRIFUGAL COMPRESSORS(Ⅰ)

摘要

An experimental and theoretical investigation was made of the flow in a vaned diffuser in order to determine means by which performance could be improved. Experimentation was carried out at the Gas Turbine Laboratory with a standard type of vaned diffuser designed by existing techniques. For aerodynamic simplification the exit flow from a rotating impeller was simulated with a ring of stationary nozzle blades. At the optimum inlet flow angle, sufficient data was obtained to establish the distributions of static and total pressure throughout the diffuser with inlet Mach numbers of 0.70 and 1.05. Diffuser efficiencies and pressure rise coefficients were evaluated and compared with vaneless diffuser perform¬ance figures measured upon removing the diffuser blades from the test section. Characteristics of the wall boundary-layer flow were determined by means of lamp-black and oil traces on the blades and sidewalls of the diffuser. A sig¬nificant loss in flow energy was found to result from cross-flow of boundary-layer fluid into the vaneless preliminary section and onto the pressure side of the diffuser blade.