Experimental Investigation on the Influence of Geometrical Parameters on the Frictional Heat Input and Leakage Performance of Brush Seals

Hildebrandt, Manuel; Schwitzke, Corina; Bauer, Hans‐Jörg

doi:10.1115/gt2017-63423

Cited by 3 publications

(8 citation statements)

References 19 publications

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“…In order to quantify the influence of the external boundary conditions and the bore tolerances on the temperature measurement as well as the subsequent calculation of the heat input, a sensitivity analysis was carried out. The results of this analysis are summarized in [22].…”

Section: Evaluation Methodsmentioning

confidence: 99%

“…The values are averaged over the total rubbing time of 30 s each. In order to ensure comparability of the results, the values were normalized to the starting value of seal 2 at 0.1 mm (see the authors' previous publication [22], Figure 4). As expected, both the total power loss and the rotor heat input decrease with continuous testing.…”

Section: Generation and Distribution Of Rubbing Heatmentioning

confidence: 99%

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Contamination of Brush Seals by Oil and Salt and Its Impact on Rubbing and Hysteresis Behaviour

Hildebrandt¹,

Schwitzke²,

Bauer³

2019

IJTPP

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The literature already contains some experimental, analytical and numerical investigations on the rubbing and hysteresis behaviour of brush seals. What the investigations have in common is that they were carried out with new and uncontaminated seals, or that such a condition was assumed. The influence of contamination has not been explicitly investigated yet. Particularly in stationary gas and steam turbines, foreign substances can accumulate on and in the bristle package during steady-state operation. In the case of a rubbing event with a contaminated brush seal, e.g., during shutdown of the machine, the process is not expected to be comparable to that assumed in the presence of a new, uncontaminated seal. The present paper is dedicated to the question of the influence of contamination on the total frictional power loss generated during rubbing and the distribution of heat fluxes in friction contact. For this purpose, rub tests with two seals were carried out on the brush seal test rig of the Institute of Thermal Turbomachinery (ITS) in new conditions. Subsequently, the sealing packages were contaminated with oil or a salt mixture. After the treatment, the rub tests were repeated and compared with the previous tests. In addition, stiffness measurements were used to assess the degree of contamination. A strong influence on the rubbing behaviour by the contamination was detected. Contamination causes the flexibility of the bristle package to be greatly reduced. As a result, especially at the beginning of the first measurements, the total power losses and rotor heat inputs are strongly increased. This flexibility is partly regained in the course of the measurements. As expected, contamination also influences the hysteresis behaviour of the seal. A highly increased leakage rate after rubbing could be observed, because the bristles remained close to their deflected positions. In the case of the salted seal, however, an improvement in the leakage performance could be observed after several repeat tests.

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Section: Evaluation Methodsmentioning

confidence: 99%

Section: Generation and Distribution Of Rubbing Heatmentioning

confidence: 99%

Contamination of Brush Seals by Oil and Salt and Its Impact on Rubbing and Hysteresis Behaviour

Hildebrandt¹,

Schwitzke²,

Bauer³

2019

IJTPP

Self Cite

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show abstract

Section: Evaluation Methodsmentioning

confidence: 99%

“…During the investigations discussed in this paper, 19 thermocouples have remained intact. For further details of the rig, see [9].…”

Section: Cold Air Test Facility (Ifas)mentioning

confidence: 99%

Effects of the Back Plate Inner Diameter on the Frictional Heat Input and General Performance of Brush Seals

et al. 2018

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Reducing losses in the secondary air system of gas and steam turbines can significantly increase the efficiency of such machines. Meanwhile, brush seals are a widely used alternative to labyrinth seals. Their most valuable advantage over other sealing concepts is the very small gap between the sealing package and the rotor and thus reduced leakage mass flow. This small gap can be achieved due to the great radial flexibility without running the risk of severe detrimental deterioration in case of rubbing. Rubbing between rotor and seal during operation might occur as a result of e.g., an unequal thermal expansion of the rotor and stator or a rotor elongation due to centrifugal forces or manoeuvre forces. Thanks to the flexible structure of the brush seal, the contact forces during a rubbing event are reduced; however, the frictional heat input can still be considerable. Particularly in aircraft engines with their thin and lightweight rotor structures, the permissible material stresses can easily be exceeded by an increased heat input and thus harm the engine's integrity. The geometry of the seal has a decisive influence on the resulting contact forces and consequently the heat input. This paper is a contribution to further understand the influence of the geometrical parameters of the brush seal on the heat input and the leakage during the rubbing of the seal on the rotor. In this paper, a total of three seals with varied back plate inner diameter are examined in more detail. The experimental tests were carried out on the brush seal test rig of the Institute of Thermal Turbomachinery (ITS) under machine-relevant conditions. These are represented by pressure differences of 1 to 7 bar, surface speeds of 30 to 180 m/s and radial interferences of 0.1 to 0.4 mm. For a better interpretation, the results were compared with those obtained at the static test rig of the Institute of Jet Propulsion and Turbomachinery (IFAS) at the Technical University of Braunschweig. The stiffness, the blow-down and the axial behaviour of the seals as a function of the differential pressure can be examined at this test rig. It could be shown that the back plate inner diameter has a decisive influence on the overall operating behaviour of a brush seal.

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“…More recently, Raben et al developed a highly innovative approach for heat transfer measurement, by using rotor-integrated thermocouples [28]. For a large range of operating conditions, Hildebrandt et al recorded the temperature rise of two brush seals with different densities [29]. They used 24 thermocouples along the rotor circumference, close to the seal contact zone.…”

Section: Introductionmentioning

confidence: 99%

Experimental characterization of friction and heat generation of carbon fibre brush seals for aero-engines

Outirba

Hendrick

2020

Tribology International

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Brush seals have been extensively studied for the last thirty years as an advanced sealing solution for gas turbine engines. The research is always aimed towards the reduction of the leakage flow, that has direct repercussions on the specific fuel consumption, the thrust-to-weight ratio, and the emission of pollutants. In addition, the sealing device must cope with side effects related to higher interface speeds, rotordynamics issues, or durability. Brush seals main assets are their excellent leakage performance with low friction properties compared to other contact seals like lip seals, and their ability to withstand rotor radial excursion without permanent damage. However, proper design optimization cannot be performed without the inclusion of the tribological performance. This paper presents a parametric investigation of the friction properties of carbon fibre brush seals as a function of the fibre pack geometry and the rotational speed. Carbon fibre and commonly used metallic brush seals present fundamentally different behaviour in presence of differential pressure or rotational speed. This paper also proposes an alternative method to predict the brush seal torque, based on measurements with a torque sensor. Heat generation was also evaluated with a thermographic camera. Both methods ensured consistency between results.

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Experimental Investigation on the Influence of Geometrical Parameters on the Frictional Heat Input and Leakage Performance of Brush Seals

Cited by 3 publications

References 19 publications

Contamination of Brush Seals by Oil and Salt and Its Impact on Rubbing and Hysteresis Behaviour

Contamination of Brush Seals by Oil and Salt and Its Impact on Rubbing and Hysteresis Behaviour

Effects of the Back Plate Inner Diameter on the Frictional Heat Input and General Performance of Brush Seals

Experimental characterization of friction and heat generation of carbon fibre brush seals for aero-engines

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