The Axial Flow Compressor Casing Treatment And Its Mechanism

With the aid of CFD software NUMEC A, computational simulating is performed on an Axial-flow compressor for the study of casing treatment mechanism. Firstly, the simulating is performed on the objective compressor on three different rotating speeds, the result shows the simulating falls quite well agreement with the test, which means the simulating model is accountable for this study. The simulating studies are then carried out on three kinds of treated casings: the Circumferential Groove Casing, the Stepped Tip Gap, and the Self-recirculating Casing.Under the study of the Circumferential Groove Casing, an updated casing is designed against the already done designs. From the work, a series of theories about the circumferential groove working mechanism are testified, the main conclusion drawn is that, the position of the grooves is the most sensitive factor, that decides the effectiveness of this kind of casing. The criteria of the optimum position and depth of the grooves are also provided by the author.The theoretical analysis of the Stepped Tip Gap is done by contrasting it's effectiveness with the Circumferential Grooves, then the application suggestion on this structure is given based on the study, which is instructive to the realistic engineering design.As for the study of the Self-recirculating Casing, a self-designed configuration is . simulated, from the results its effectiveness on the subsonic compressors is verified. Analysis is carried out from the changes of the flow structures, the redistribution of flow mass and works, and so on, which gives us the insight into the mechanism of this kind of casing.