Experimental Investigation on Leakage Loss and Heat Transfer in a Straight Through Labyrinth Seal

Abstract

Labyrinth seals are extensively used in turbomachinery to prevent high pressure gas from flowing into a region of low pressure. Because of thermal expansions and centrifugal forces, the actual seal clearance can vary based on engine conditions. Pressure ratio, Reynolds number, tip geometry, and seal clearance all affected the sealing performance. This paper deals with its influence on the leakage flow and heat transfer coefficient through a thirteen teeth straight through labyrinth seal. Three gaps were experimentally investigated using a stationary test rig. The experiments covered a range of Reynolds numbers between 5000 and 50000 and pressure ratios between 1.0 and 2.7. Cavity pressure measurements along the seal were also performed in order to characterize each constriction. In addition, 2D PIV measurements were made on the plane containing the seal teeth to obtain a high local resolution of the velocity distribution and the flow field within the seal. Experimental results show a strong influence of clearance on both leakage loss and heat transfer as well as on the development of the flow fields. A simplified model to calculate the leakage mass flow rate is presented and validated comparing its prediction capability with experimental data. In order to improve the agreement between numerical and experimental results a correction of published correlations is proposed.

Effect of Bending and Mushrooming Damages on Heat Transfer Characteristic in Labyrinth Seals

“…With the experimental data, a simple correction equation, which correlates Nu with Re, pitch width, and gap width, was proposed in their study. Recently, Micio et al, [10] experimentally investigated the leakage and heat transfer performance in the straight-through labyrinth seal with 13 fins. They found that their numerical results agree well with the test data with respect to the Nu distributions on seal stator surface while Nu on the rotor surface is overpredicted significantly.…”

“…Recently, Micio et al, [10] experimentally investigated the leakage and heat transfer performance in the straight-through labyrinth seal with 13 fins. By using the low-Re k-(ú turbulence model, the effects of sealing clearance, step position, and step height on the flow pattem and heat transfer coefficient distributions were investigated based on the experimental work of Willenborg et al,[9] [10] to investigate the heat transfer and windage heating effect in the rotational labyrinth seals with smooth and honeycomb lands. The local Nu distributions on both rotor and stator surfaces were measured at four different Reynolds numbers.…”

“…The mass flow rates and detailed flow fields in the labyrinth seals were measured at three different gap widths and a range of pressure ratios. However, almost all the studies mentioned above [3,[8][9][10][11][12][13][14] are mainly aimed towards the heat transfer characteristic of a labyrinth seal in its as-installed state (original design geometry). It shows that Nu on the stator surface exhibits dependent on gap width, and it increases with the increase of Re, With the development of efficient numerical codes, some researchers utilized numerical methods to investigate the heat transfer characteristic in labyrinth seals, Papanicolaou et al [12] adopted the conjugate heat transfer method combined with the low-Re k-E turbulence model to solve the wall heat transfer coefficient in the straight-through labyrinth seal based on the experimental work of Wittig et al [8], Their results indicate that, if proper numerical methods (such as the turbulence model and conjugate heat transfer method) were implemented, the numerical simulations would have reasonable accuracy in predicting the heat transfer characteristic in the labyrinth seals.…”

“…It shows that Nu on the stator surface exhibits dependent on gap width, and it increases with the increase of Re, With the development of efficient numerical codes, some researchers utilized numerical methods to investigate the heat transfer characteristic in labyrinth seals, Papanicolaou et al [12] adopted the conjugate heat transfer method combined with the low-Re k-E turbulence model to solve the wall heat transfer coefficient in the straight-through labyrinth seal based on the experimental work of Wittig et al [8], Their results indicate that, if proper numerical methods (such as the turbulence model and conjugate heat transfer method) were implemented, the numerical simulations would have reasonable accuracy in predicting the heat transfer characteristic in the labyrinth seals. Firstly, numerical methods (such as the turbulence model selection) were carefully verified based on the experimental data of Micio et al, [10], After the accuracy and reliability of the present numerical method have been demonstrated, the Nu distributions on the seal rotor and stator surfaces were computed and compared to the obtained experimental data at a range of Re and two different sealing clearances for the original design. Subsequently, Yan et al [13] numerically studied the flow and heat transfer characteristics in the stepped labyrinth seals with smooth and honeycomb lands.…”

“…However, for the labyrinth seal used in a gas turbine engine, some critical regions still remain that require more frequent inspection and repair due to frequent breakdowns. (a) break off (b)rub (c) mushrooming [4] on the rotor and stator surfaces [8][9][10][11]. and their opposite surface (i.e., rub groove) usually fall into this category.…”