Brush seal is a novel contact seal in turbomachinery. Although this new type of seal has been adopted for many years, there are still some problems which should be investigated. One of the main problems is the determined pressure differential across a brush seal. Aerodynamic resistance, characterized by Euler number (Eu), is used to determine pressure differential of brush seals. Eu is a dimensionless quantity including a velocity term. Tube banks model is widely used in numerical simulation of brush seals. Various velocity values can be chosen by calculating Eu in a tube banks model. The present research analyzed the effect of different velocity values on Eu. Velocity choice in a tube banks model was preliminarily analyzed. Three different methods (Eu1, Eu2 and Eu3) for calculating Eu were presented. The results revealed that Eu1 decreases as the pressure differential increasing. Eu2 keeps almost unchanged or increase slightly with the growing of pressure differential, as well as Eu3. By comparing Eu1, Eu2 and Eu3 and considering practical application, Eu1 is qualified for measuring the aerodynamic resistance. © Springer Nature Singapore Pte Ltd 2019.

A two-dimensional model of staggered tube banks of the bristle pack with different pitch ratios was solved by computational fluid dynamics (CFD). The pressure distribution along the gap centerlines and bristle surfaces were studied for different upstream pressure from 0.2 to 0.6MPa and models. The results show that the pressure is exponentially rather than strictly linearly decreasing distributed inside the bristle pack. The pressure distribution is symmetry about the circle's horizontal line. The most obvious pressure drop occurred from about 60 degrees to 90 degrees. There is no stationary state reached between the kinetic energy and the static pressure when the upstream is larger than 0.3MPa.

The numerical model was established using the two-dimensional cross section of staggered tube bundle of bristles, and the flow field was numerically solved by Fluent. This work presents velocity of flow and the variation range of flow velocity under transient state at the-last bristles gap are much higher than those of the front row, which leads to severe wear of the last row of bristles; as the bristle row number increases, the leakage decreases rapidly, then decreases slowly; the leakage increases linearly with the increase of the pressure difference; the brush drag force slowly increases along the axial direction but increases significantly at the last row; the drag force increases linearly with differential pressure increasing. © Springer Nature Singapore Pte Ltd 2019.

In order to further study the pressure distribution in bristle seals, a uniformed two-dimensional closed staggered tube bundle model representing a bristle pack cross-section was proposed and the fluid flow through the bundle was solved by computational fluid dynamics(CFD) method. Accor-ding to the critical Reynolds number for boundary layer transition, a new method was proposed to decide the fluid flow regime in the bundle. The pressure and velocity distributions in the bundle were studied under various pressure differentials across the seal. The influences of distance between bristles and number of circumferential bristle rows on the pressure distribution were tackled. It is shown that the pressure distributions in the uniformed two-dimensional closed staggered tube bundle model agree well with the previous experimental data. The pressure distributions are like "V", while the velocity distributions are like the inverted "V". The pressure borne by the rear 1/3 part of the bristle pack is higher than that by the front 2/3 part. Moreover, the percentage of the pressure differential borne by the last 5 bristle rows increases with increasing total pressure differential. The pressure differential borne by the last bristle row is higher than that by a few rows in front of it. A reduced distance between bristles can allow the pressure to be distributed more even from one row to another. Bristles equally spaced can ensure an even pressure distribution rather well. Increasing the number of rows can also have the same effect. © 2018, Editorial Department of Journal of Drainage and Irrigation Machinery Engineering. All right reserved.

Aerodynamic resistance of a brush seal was mainly studied. The velocity distribution along three specified lines was presented. By considering the pressure differential, Reynolds number and Euler number (Eu) were modified. The effect of geometric arrangements and pressure differentials on Eu and leakage were analyzed. Two correlations were fitted based on the numerical results. The results reveal the velocity distribution is almost flat, asymmetric along the specified lines. The velocity increases and decreases almost linearly at centerlines. Eu decreases gradually less with the increase of pressure differential and trends towards a fixed value. A larger Eu indicates stronger resistance but not necessarily less leakage. Finally, two fitted correlations are developed and one is exponential to the row number fits better. © 2018 Elsevier Ltd