Effects of Front Plate Geometry on Brush Seal in Highly Swirling Environments of Gas Turbine

Advanced brush seal technology has a significant impact on the performance and efficiency of gas turbine engines. However, in highly inlet swirling environments, the bristles of a brush seal tend to circumferentially slip, which may lead to aerodynamic instability and seal failure. In this paper, seven different front plate geometries were proposed to reduce the impact of high inlet swirl on the bristle pack, and a three-dimensional porous medium model was carried out to simulate the brush seal flow characteristics. Comparisons of a plane front plate with a relief cavity, plane front plate with axial drilled holes, anti-“L”-type plate and their relative improved configurations on the pressure and flow fields as well as the leakage behavior were conducted. The results show that the holed front plate can effectively regulate and control the upstream flow pattern of the bristle pack, inducing the swirl flow to move radially inward, which results in decreased circumferential velocity component. The anti-“L” plate with both axial holes and one radial hole was observed to have the best effect on reducing the swirl of those investigated. The swirl velocity upstream the bristle pack can decline 50% compared to the baseline model with plane front plate, and the circumferential aerodynamic forces on the bristles, which scale with the swirl dynamic head, are reduced by a factor of 4. This could increase the bristle stability dramatically. Moreover, the front plate geometry does not influence the leakage performance significantly, and the application of the axial hole on the front plate will increase the leakage slightly by around 3.5%.

FEATURES OF THE BEHAVIOR OF A SHOCK WAVE IN A CHANNEL WITH WALLS OF DIFFERENT STIFFNESS

Purpose of work. Determination of the terms of weakening the destructive action of a shock wave during its propagation in the channels of mining workings or long communication premises of industrial buildings in an emergency explosion. Methods. Using an analytical research method based on the main provisions of theory of combustion and explosion. Construction and analysis of the physical model of formation and distribution of a shock wave in the channel. Results. The problem of weakening of a shock wave during its propagation in long channels of mining workings or communication passageways of industrial buildings with a potentially explosive atmosphere is considered. It is shown that when an explosion in the channel is formed by a head shock wave with a flat front, dynamic pressure which significantly exceeds the pressure on the fronts of falling and reflected shock waves that form the head shock wave. A physical model of formation and distribution of a shock wave in a channel with walls of different rigidity is proposed. It is shown that if one of the walls of the channel is mobile or easily deformed, it leads to a violation of the geometry of the plane front of the head shock wave and its weakening. Moreover, the reconstruction of the plane front of the head shock wave can occur at a distance of not less than 6-8 channel width. On the basis of this observation, the need to arrange explosion-relief valves in channels of mining workings or communication premises of industrial buildings with a potentially explosive atmosphere is substantiated. Novelty. A physical model of the formation and propagation of a shock wave in a channel with walls of different stiffness is proposed. The necessity of equipping explosion-relief valves in the long communication channels of mine workings and buildings with increased explosion hazard to attenuate the shock wave is substantiated. Practical significance. Arrangement of expanders with explosion-relief valves with dimensions comparable to the channel diameter and intervals between them up to 8 channel diameters in long communication channels of mine workings and buildings with increased explosion hazard will lead to weakening of the shock wave and reduction of its destructive effect.