# The Effect of Blade Angle Deviation on Mixed Inflow Turbine Performances
## 3 Results and Discussions  
The investigation of the deviation blade effect is based on the operation of the rotor in three rotation speeds (50%, 75%, and 100% of load), which represent successively 49,000 rpm, 73,500 rpm, and 98,000 rpm. Figure 16a shows that the output work is clearly proportional to the deviation angle for a 100% load and a negligible effect for 50% and 75% loads. The same influence is noted for the case of power (Figure 16b). This behavior is probably due to the rotor surface increase due to the deviation angle (Table 2). Therefore, the exchange surface is larger on one side, and on the other side, the flow adapts with the new blade curvatures. The analysis of Figure 17, which presents the expansion rate, shows that the deviation blade angle is not clear for a load of 50%; the expansion rate is proportional to the increase in the deviation angle for a 100% load; the opposite is just for a 75% load. The lowest expansion rate corresponds to \(-10^{\circ}\) for a 100% load, and the best expansion rates for value \(-35^{\circ}\) are noticed in the case of a 100% load. Figure 18 shows that the total kinetic energy at the exit rotor is compassionate by the variation of the blade deviation angle; it is essential for the cases of \(-10^{\circ}\), \(-15^{\circ}\), and \(-20^{\circ}\) for a rotation speed of 98,000 rpm. A slight influence in the opposite direction for the case of 73,500 rpm and an influence is not evident when 49,000 rpm has been detected. The variation of the relative Mach number along the axial direction of the flow for different deviation blade angles at a rotational speed of 50% is presented in Figure 19. It can be noticed that the gas seems to subsonic flow through a diverging-converging channel connection which causes a flow deceleration in the diverging part of the channel to a minimum relative Mach number located at the same axial distance from the entrance, equaling approximately 0.015 mm, followed by flow acceleration in the converging part of the channel. The variation of the relative Mach number between the exit and the rotor entrance is negligible for \(-10^{\circ}\) of deviation blade case, which implies a minimal degree of reaction. Figure 17: Expansion ratio for different deviation blade angles. Figure 18: Rotor exit total kinetic energy for different deviation blade angles. The variation is negatively confirmed for the other design cases by falling off the output work magnitude. The variation of the relative Mach number along the axial direction of the flow for different deviation blade angles at a rotational speed of 75% and 100% are successively presented in Figure 20a,b. It can be observed that (Figure 20b) the gas seems to subsonic flow through a converging-diverging channel connection and later through a convergent form which causes acceleration in the converging part of the channel to a maximum relative Mach number--followed by flow deceleration in the diverging part of the channel. All the relative Mach number curves intersect at an axial distance from the inlet within the interval 0.01-0.015 mm, reflecting a starting state of the flow deceleration. Then, there is an acceleration in the convergent blade channel from an axial length of 0.025 m until the exit rotor. The relative Mach number behavior is probably due to the formation of the boundary layer near the blades at several places, making it possible to vary the passage section of the flow, which will cause converging or diverging passages. The pressure distributions around the blade profiles become more uniform with a more significant pressure difference between the pressure side and the suction side, which results in higher loadings at a full rotational speed (Figure 21a-c)). Figure 19: Relative Mach number for different deviation blade angles at 50% rotation speed.