trifugal stress. By regard to these parameters, stage-by-stage increases of temperature and hub-tip ratio allow increase of speed stage by stage. Rise of temperature delays compressibility effects and higher hub-tip ratio increases allowable critical centrifugal stress, which permit rotating by higher speed.
Increase of rotational speed expectedly widens velocities triangles, which raises differences between whirl components at entrances and exits of rotors Fig. 5. Increase of air outlet angle decreases pitch chord ratio (s/c), which increases blades number and decreases total drag coefficient. Such a situation makes also vector mean velocity closes in on the air axial velocity (reduction of δ), which raises blades row lift coefficient and decreases its drag coefficient. Total result of these changes is higher blades row efficiency (ηb ) defined as the ratio of the actual pressure rise to the theoretical pressure rise. Therefore, pressure loss affects this ratio directly and maintaining that into acceptable range additionally influences blades row efficiency Fig. 4.