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Rotating holes are widely used in jet engine internal air systems as an important kind of throttling element. The flow characteristics of rotating holes are of great importance in the design of the internal air system. This paper aims to investigate the influence of pumping effect on the flow characteristics of axial rotating holes. Pumping effect refers to the flow phenomenon induced by a rotating plate which characterized by a radial outflow. There are altogether two types of holes considered in the paper: round hole and square hole. A 1/25 (14.4-degree) sector model is used to carry out the numerical investigation using the commercial software ANSYS CFX. In the simulation, the SST turbulent model is used. Meanwhile, a non-rotating method using the relative frame of reference is used. In the non-rotating method, an initial incidence angle is given at the inlet instead of setting the plate to be rotating, thus the pumping effect induced by the rotating plate can be eliminated. The non-rotating method results are compared with the conventional reference frame results to investigate the influence of pumping effect. The results show that due to the influence of the pumping effect-induced radial outflow, the theoretical two-dimensional incidence angle becomes three-dimensional, which has negative effects on the hole discharge coefficient. At the same time, due to a larger circumferential length, square holes will undermine the pumping effect, thus has a higher discharge coefficient than the round holes.

This paper reports on the flow (centrifugal = radially outward, centripetal = radially inward) through rotating radial orifices with and without preswirl in the flow approaching the orifice in the outer annulus. The aerodynamical behavior of flow through radial rotating holes is different from the one through axial and stationary holes due to the presence of centrifugal and Coriolis forces. To investigate the flow phenomena and the discharge coefficient of these orifices in detail, an existing test rig containing two independently rotating shafts (corotating and counter rotating) was used. To simulate conditions of real gas turbines, where the flow is often influenced by upstream components, various preswirl angles were used in the test rig. Measurements of the flow discharge coefficient in both flow directions through the orifices (centripetal and centrifugal), with and without preswirl generation in the outer annulus, are presented at various flow conditions (pressure ratios across orifices, Mach numbers of approaching flow) and for different geometric parameters (length to diameter ratios, sharp/rounded inlet edges). Flow effects that occur with preswirled flow are clarified. A comparison of the experimental data, for both flow directions, shows a similar behavior of the discharge coefficients with increasing shaft speeds. To supplement the experimental data and to better understand the experimental findings, numerical simulations were performed, which show a good agreement with the experimental results. Furthermore, an optimization model with complete automatic grid generation, computational fluid dynamics (CFD) simulation, and postprocessing, was built to enable large parametric studies, e.g., grid independence of the solutions. [ABSTRACT FROM AUTHOR]