The Effect o f Diameter Ratio on the Performance of a Low, Stagger Axial-Compressor Stage

• Summary.-Low-speed tests have been carried out on a family of three single-stage compressors of different diameter ratios. The simple blade design tested showed considerable variations of performance as the diameter ratio was decreased from 0.65 to 0.35 but most of these variations are predictable by simple means and it is expected that they may be partially avoided by appropriate design methods. It is recommended that low-stagger constant ~3 stages of low diameter ratio should be designed on the basis of radial equilibrium after the inlet guide blades. In the interests of minimizing the loss of working range at low diameter ratios, at least the outer half of the blades should be designed as far below nominal conditions as other considerations allow. The performance of such stages is fairly well estimated by integration of the strip performances of the various sections of the blade, though further information is necessary to fully define the work-done characteristic. Evidence is shown that the establishment of radial equilibrium demands an axial distance which increases considerably with decreasing diameter ratio, and it is suggested that conditions upstream of a stator-blade row are influenced by conditions required for radial equilibrium downstream of that row.