The flow characteristics of a tubed vortex reducer, which was used to reduce the pressure drop in an aeroengine air bleed system, were studied in this paper. Accurate prediction of the pressure drop in a rotating cavity with tubed vortex reducer installed is important, but the complex flow structure results in complicated local loss characteristic at the tube entrance, which is difficult to estimate. In this paper, a mathematical model for predicting the pressure drop in a rotating cavity with a tubed vortex reducer was established. For the first time, the effect of the local loss at the tube entrance under rotating conditions was considered, and a method of introducing the local loss factor was established based on a research method applied in traditional rotating orifices. Furthermore, the flow characteristics and the distribution of the static pressure in the tubed vortex reducer cavity were studied by the CFD method and experimental tests, and the pressure information inside the tubed vortex reducer was obtained by detailed experimental testing. This study reveals that the local loss characteristics at the tube entrance are mainly influenced by the incident angle; the closer the incident angle is to 0, the greater the speed coefficient is. The pressure drop at the tube entrance is important and represents approximately 10% of the total pressure drop. The mathematical model shows good accuracy for calculating the pressure drop, with an average error of approximately 2% compared to the experimental data.

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In the modern multi-shaft gas turbine engines, orifice is an important throttling element and the discharge coefficient of rotating orifices may vary considerably depending on the operating conditions, the geometry and surrounding environment. The influences of the rotating number and the pressure ratio on the rotating orifices flow characteristics are investigated in the present study. Besides, the effects of confined space, wall inclination angle (a) and the angle between the axis of orifice and the disk wall normal (ß) are also analyzed statistically. It is found that the rotating number has a significant effect on the discharge coefficient. As the rotating number increases from 0 to 0.6, the discharge coefficient reduces by about 47.88%. When rotating number is 0.74 and pressure ratio is 1.10, the discharge coefficient can be improved by 16.88% with a changes from 90° to 180°. The parameter, ß, affects discharge coefficient slightly in rotating condition. However, the maximum discharge coefficient is achieved with ß=0° in the static condition. The results also show that, a confined space weakens the effect of rotation, and changes the air flow direction in the inlet chamber, which also has a positive impact on the discharge coefficient. In the current research, it is found that there is a significant difference between the traditional empirical formulas used in the literature and the fitting result. By modifying the incidence angle and taking account of the influence of the angle of inclination, the maximum error was reduced from 56.79% to 3.16%