0
Research Papers: Gas Turbines: Heat Transfer

Two-Phase Flow Heat Transfer and Pressure Drop in Horizontal Scavenge Pipes in an Aero-engine

[+] Author and Article Information
Michael Flouros, Francois Cottier, Markus Hirschmann

MTU Aero Engines AG,
Munich 80995, Germany

Georgios Iatrou, Kyros Yakinthos

Laboratory of Fluid Mechanics
and Turbomachinery,
AUTH,
Thessaloniki 54124, Greece

Contributed by the Heat Transfer Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received October 20, 2014; final manuscript received November 17, 2014; published online February 3, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(8), 081901 (Aug 01, 2015) (11 pages) Paper No: GTP-14-1586; doi: 10.1115/1.4029389 History: Received October 20, 2014; Revised November 17, 2014; Online February 03, 2015

In modern aero-engines, the lubrication system plays a key role due to the demand for high reliability. Oil is used not only for the lubrication of bearings, gears, or seals but it also removes large amounts of the generated heat. Also, air from the compressor at elevated temperature is used for sealing the bearing chambers and additional heat is introduced into the oil through radiation, conduction, and convection from the surroundings. The impact of excessive heat on the oil may lead to severe engine safety and reliability problems which can range from oil coking (carbon formation) to oil fires. Coking may lead to a gradual blockage of the oil tubes and subsequently increase the internal bearing chamber pressure. As a consequence, oil may migrate through the seals into the turbomachinery and cause contamination of the cabin air or ignite and cause failure of the engine. It is therefore very important for the oil system designer to be capable to predict the system’s functionality. Coking or oil ignition may occur not only inside the bearing chamber but also in the oil pipes which carry away the air and oil mixture from the bearing chamber. Bearing chambers usually have one pipe (vent pipe) at the top of the chamber and also one pipe (scavenge pipe) at the bottom which is attached to a scavenge pump. The vent pipe enables most of the sealing air to escape thus avoid over-pressurization in the bearing compartment. In a bearing chamber, sealing air is the dominant medium in terms of volume occupation and also in terms of causing expansion phenomena. The scavenge pipe carries away most of the oil from the bearing chamber but some air is also carried away. The heat transfer in vent pipes was investigated by Busam (2004, “Druckverlust und Wärmeuebergang im Entlueftungssystem von Triebwerkslagerkammern (Pressure Drop and Heat Transfer in the Vent System in an Aero Engine’s Bearing Chamber),” Ph.D. thesis, Logos Verlag, Berlin, Germany) and Flouros (2009, “Analytical and Numerical Simulation of the Two Phase Flow Heat Transfer in the Vent and Scavenge Pipes of the CLEAN Engine Demonstrator,” ASME J. Turbomach., 132(1), p. 011008). Busam has experimentally developed a Nusselt number correlation for an annular flow in a vent pipe. For the heat transfer predictions in scavenge pipes, no particular Nusselt number correlation exist. This paper intends to close the gap in this area. As part of the European Union funded research programme ELUBSYS (Engine Lubrication System Technologies), an attempt was done to simplify the oil system’s architecture. In order to better understand the flow in scavenge pipes, high speed video was taken in two sections of the pipe (vertical and horizontal). In the vertical section, the flow was a wavy annular falling film, whereas the flow in the horizontal section was an unsteady wavy stratified/slug flow. Heat transfer has been investigated in the horizontal section of the scavenge pipe, leaving the investigation on the vertical section for later. Thanks to the provided extensive instrumentation, the thermal field in, on, and around the pipe was recorded, evaluated, and also numerically modeled using ansys cfx version 14. Brand new correlations for two-phase flow heat transfer (Nusselt number) and for pressure drop (friction coefficient) in horizontal scavenge pipes are the result of this work. The Nusselt number correlation has been developed in such a way that smooth transition (i.e., no discontinuity) from two-phase into single phase flow is observed.

Copyright © 2015 by ASME
Your Session has timed out. Please sign back in to continue.

References

Busam, S., 2004, “Druckverlust und Wärmeuebergang im Entlueftungssystem von Triebwerkslagerkammern (Pressure Drop and Heat Transfer in the Vent System in an Aero Engine’s Bearing Chamber),” Ph.D. thesis, Logos Verlag, Berlin.
Flouros, M., 2009, “Analytical and Numerical Simulation of the Two Phase Flow Heat Transfer in the Vent and Scavenge Pipes of the CLEAN Engine Demonstrator,” ASME J. Turbomach., 132(1), p. 011008. [CrossRef]
Levy, S., 1999, Two-Phase Flow in Complex Systems, Wiley, New York, pp. 90–107.
Storek, H., and Brauer, H., 1980, Reibungsdruckverlust der adiabaten Gas-Flüssigkeit-Stroemung in horizontalen und vertikalen Rohren, VDI Verlag, Duesseldorf, pp. 8–9, Nr. 599/1980.
Yemada, T., and Dukler, A. E., 1976, “A Model for Predicting Flow Regime Transitions in Horizontal and Near Horizontal Gas–Liquid Flow,” AIChE J., 22(1), pp. 47–55. [CrossRef]
Tye, R. P., 1969, Thermal Conductivity, Vol. 1, Academic Press, London, p. 319.
Kanarachos, S., and Flouros, M., 2014, “Simulation of the Air–Oil Mixture Flow in the Scavenge Pipe of an Aero Engine Using Generalized Interphase Momentum Exchange Models,” WSEAS Trans. on Fluid Mech., 9, pp. 144–153.
Oshinowo, T., and Charles, M. E., 1974, “Vertical Two-Phase Flow, Part I. Flow Pattern Correlations,” Can. J. Chem. Eng., 52(1), pp. 25–35. [CrossRef]
Mandhane, J. M., Gregory, G. A., and Aziz, K., 1974, “A Flow Pattern Map for Gas–Liquid Flow in Horizontal Pipes,” Int. J. Multiphase Flow, 1(4), pp. 537–553. [CrossRef]
Baker, O., 1954, “Design of Pipelines for Simultaneous Flow of Oil and Gas,” Oil Gas J., 53, pp. 185–195. [CrossRef]
Aziz, A., Miyara, A., and Sugino, F., 2012, “Distribution of Two-Phase Flow in a Distributor,” J. Eng. Sci. Technol., 7(1), pp. 41–55.
Bratland, O., 2014, “Dr. Ove Bratland’s Flow Assurance Site”, Dr. Ove Bratland Flow Assurance Consulting, Banglamung, Thailand, http://drbratland.com/index.html
Incropera, F., DeWitt, D., Bergman, T., and Lavine, A., 2007, Fundamentals of Heat and Mass Transfer, 6th ed., Wiley, New York.
McAdams, W, H., 1954, Heat Transmission (Chemical Engineering), 3rd ed., McGraw-Hill, New York.
Rice, C. W., 1923, “Free and Forced Convection of Heat in Gases and Liquids—I,” Trans. Am. Inst. Electr. Eng., 42(12), pp. 653–706. [CrossRef]
Rice, C. W., 1924, “Free and Forced Convection of Heat in Gases and Liquids—II,” Trans. Am. Inst. Electr. Eng., 43(11), pp. 131–144. [CrossRef]
Cengel, C. A., 2002, Heat Transfer: A Practical Approach, Higher Education, 2nd ed., McGraw-Hill, New York.
Gnielinski, V., 1976, “New Equation for Heat and Mass Transfer in Turbulent Pipe and Channel Flow,” Int. J. Chem. Eng., 16, pp. 359–368.
Winterton, R. H. S., 1998, “Where Did the Dittus and Boelter Equation Come From?,” Int. J. Heat Mass Transfer, 41(4–5), pp. 809–810. [CrossRef]
Colburn, A. P., 1933, “A Method of Correlating Forced Convection Heat Transfer Data and a Comparison With Fluid Friction,” Trans. AIChE, 29, pp. 174–210.
Idel’chik, I. E., 1966, Handbook of Hydraulic Resistance, Coefficients of Local resistance and Friction, Begell House, New York.
Friedel, L., 1979, “Improved Friction Pressure Drop Correlations for Horizontal and Vertical Two-Phase Pipe Flow,” European Two-Phase Flow Group Meeting, Ispra, Italy, June 5–8, Paper No. E2.
ANSYS, 2011, ansys 14, ANSYS Inc., Canonsburg, PA, http://www.ansys.com
Ishii, M., and Zuber, N., 1979, “Drag Coefficient and Relative Velocity in Bubbly, Droplet or Particulate Flows, American Institute of Chemical Engineers,” AIChE J., 25(5), pp. 843–855. [CrossRef]
Ranz, W. E., and Marshall, W. R., 1952, “Evaporation From Drops, Part II,” Chem. Eng. Prog., 48, pp. 173–180.

Figures

Grahic Jump Location
Fig. 6

The flow regime in the vertical part of the scavenge pipe according to Oshinowo and Charles. The flow is an annular falling film flow (see also Fig. 4). The dots in the graph are measured points.

Grahic Jump Location
Fig. 7

The flow regime on the horizontal part of the scavenge pipe according to Mandhane and Baker. The flow is a slug–wavy stratified flow as observed (see also Fig. 5). The dots in the graph represent measured points.

Grahic Jump Location
Fig. 8

Two-phase flow regimes in horizontal pipes [12]. A flow pattern transitioning between a slug and a wavy stratified flow was witnessed (Fig. 5).

Grahic Jump Location
Fig. 9

Two-phase flow regimes in vertical pipes with downward flow [12]. A bubbly falling film/annular flow pattern was witnessed (Fig. 4).

Grahic Jump Location
Fig. 10

The metallic section of the scavenge pipe with instrumentation setup

Grahic Jump Location
Fig. 5

Wavy slug flow pattern in the horizontal section of the scavenge pipe

Grahic Jump Location
Fig. 4

(Wavy) annular flow pattern in the vertical section of the scavenge pipe

Grahic Jump Location
Fig. 2

The MTU rig facility

Grahic Jump Location
Fig. 1

The test facility for the heat transfer investigation in the horizontal part of the scavenge pipe having the length L. High speed cameras were used to visualize the flow at different sections.

Grahic Jump Location
Fig. 11

Details of the scavenge pipe instrumentation setup

Grahic Jump Location
Fig. 12

Comparison among the three Nusselt number correlations for lean air at a temperature of 100 °C. The inlet pressure is 5 bar.

Grahic Jump Location
Fig. 13

Comparison among the three Nusselt number correlations for pure oil flow at a temperature of 100 °C. The Flouros/Iatrou and the Colburn/Dittus–Boelter show similar behavior with increasing Re.

Grahic Jump Location
Fig. 14

Comparison between the Flouros/Iatrou and the Gnielinski correlations for flow transition from single into two-phase flow (air and oil) at 100 °C

Grahic Jump Location
Fig. 15

Pressure drop using the different correlations as a function of the mixture Reynolds number at an oil flow of 180 l/h

Grahic Jump Location
Fig. 16

Pressure drop using the different correlations as a function of the mixture Reynolds number at an oil flow of 360 l/h

Grahic Jump Location
Fig. 17

Pressure drop using the different correlations as a function of the mixture Reynolds number at an oil flow of 600 l/h

Grahic Jump Location
Fig. 18

Details of the computation domain. This includes all the flows inside and outside the pipe and also radial conduction through the pipe’s wall

Grahic Jump Location
Fig. 22

The typical plume for natural convection. The crosses indicate the locations of the thermocouples.

Grahic Jump Location
Fig. 23

The plume at two locations (planes) perpendicular to the flow axis X

Grahic Jump Location
Fig. 24

Nusselt number comparison among CFX results and the results from different authors for pure oil flow

Grahic Jump Location
Fig. 25

Nusselt number comparison among CFX results and the results from different authors for lean (pure) air flow

Grahic Jump Location
Fig. 19

Stratified flow simulated with CFX. The oil is mostly concentrated at the bottom of the tube.

Grahic Jump Location
Fig. 20

A magnification of the flow along the flow direction showing the oil and air distribution. Oil is accumulated at the bottom of the pipe.

Grahic Jump Location
Fig. 21

The wall temperature distribution along the flow direction (x-axis)

Grahic Jump Location
Fig. 26

Nusselt number results comparison for two-phase flow. Comparison between CFX and the Flouros/Iatrou correlation.

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In