Exploration On Maximum Loading Design Techniques For Fan And Axial-Flow Compressor

Whether driven by great demands from national defense and civilian fields, or following internal evolution logic of aerodynamic theory and techniques of turbomachinery, high-loaded turbomachinery is always an important development trend, and then, striving hard to maximum loading design is permanent topic in researches on aerodynamic theory and design techniques of turbomachinery.Based on knowledge of flow mechanisms and design process for fan and axial-flow compressor, this dissertation firstly attempted to explain roundly what "maximum loading design" is and how to develop "maximum loading design". Preliminary explorations on maximum loading design techniques were developed through three aspects such as blade airfoil shape, radial matching between blade sections, and stage matching between blade rows. Main research work would be listed as follows:1. As to blade airfoil shape design, large turning angle blade (subsonic) and restricted separated blade (supersonic) are the two effort aspects. In the dissertation, a design method of large turning angle subsonic airfoil for use in stator hub section was developed. The method includes quasi-three-dimensional flow analysis, and blade contouring method which the dissertation focused on. Firstly, blade airfoil shape was contoured by adjusting metal angle distribution combined with special thickness distribution from a U.S. patent, and then the blade-to-blade flow was computed by solving the two-dimensional steady Navier-Stokes equations, finally, overall performance and internal flowfield characterization were obtained and analyzed.2. As to radial matching between blade sections, preliminary investigations were developed from three aspects such as stall margin customizing technique, control technology of tip clearance flow, prediction model and control technology of corner separate.a) On basis of reviewing on methods of achieving the goal of stall margin in design process of fan and axial-flow compressor, in conjunction of understandings on "Sweep/Dihedral", stall margin customizing technique was put forward; two-dimensional performance prediction method for stall margin customizing was developed, it can consider influences of radial stacking patterns of blade sections and axial distances between blade rows conveniently and rapidly.b) A simple model for tip leakage mixing loss of unshrouded blades for compressible flow was presented. The work drew ideas, was based on the theoretical analysis of the loss by Denton. Relationship for computing the loss is derived, in terms of blade surface static pressure, chordwise distribution of tip clearance, discharge coefficient and total pressure loss coefficient in the tip region. Parameter studies reveal average level and chordwise distribution of the above factors' contribution to the loss. Finally, combined with conclusions obtained above, explanations were given to various control technology of tip clearance flow.c) Based on the physical intuition of that the three-dimensional corner boundary layer is the conflux of both blade and end wall boundary layer, with assumptions of ignoring the cross flow effect and three-dimensionality of the nearby main flow, an equivalent two-dimensional corner boundary layer was put forward to predict the behavior of corner boundary layer. And then, a corner separate criterion was established using the boundary layer separate criteria. Finally, combined with conclusions obtained above, explanations were given to various control technology of comer separate.3. As to stage matching between blade rows, besides growing steady two-dimensional and three-dimensional methods which can could be dealt with by stall margin customizing technique, edge matching is a proper choice for guiding design to consider stage matching. Numerical investigations were presented in order to better understand the influences of edge matching on unsteady flow and performance of fan and axial-flow compressors, moreover, influences of edge matching on vibration and rotor/stator interaction noise were investigated preliminarily.