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An Investigation into the Flow of Rotating Orifices with Euler Angle and the Calculation Model of Discharge Coefficient Considering the Effect of Comprehensive Incidence Angle

As a typical flow element in an aero-engines, orifices play a vital role in the distribution and control of the mass flow rate within the secondary air system. In particular, rotating orifices with complex geometry (Euler angles) may significantly vary the discharge coefficients. Understanding the discharge coefficients of these orifices may guarantee a more reasonable distribution of the internal flow within the air system. This contributes to the safety, reliability, and structural integrity of the aero-engine under the all-inclusive line. In this paper, the flow state within the orifice and the discharge coefficient have been studied under the condition of different Euler angles (α0=0–30° and β0=0–30°) and rotational speeds (0–10,000 r/min). The comprehensive incidence angle is proposed to describe the combined effect of Euler angles and rotation. The correlation between the discharge coefficient and the comprehensive incidence angle is also given. At the same time, a general calculation model of the orifices is established considering the effect of the comprehensive incidence angle. The results indicate that the effects of the circumferential inclination angle, radial inclination angle, and rotation may be more clearly expressed by the comprehensive incidence angle. The larger discharge coefficient is obtained when the comprehensive incidence angle is close to 0, and under the fixed rotational speed and flow condition, the maximum discharge coefficient can be obtained by arranging the appropriate Euler angle for the orifice. Compared with the experimental results in the published literature, the calculation results of the model have an overall error of less than 6%. The calculation accuracy is high enough for the one-dimensional simulation of the secondary air system.