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Research Papers

Reverse-Pass Cooling Systems for Improved Performance

[+] Author and Article Information
Benjamin Kirollos

Osney Thermofluids Laboratory,
Department of Engineering Science,
University of Oxford,
Parks Road,
Oxford OX1 3PJ, UK
e-mail: ben.kirollos@eng.ox.ac.uk

Thomas Povey

Osney Thermofluids Laboratory,
Department of Engineering Science,
University of Oxford,
Parks Road,
Oxford OX1 3PJ, UK
e-mail: thomas.povey@eng.ox.ac.uk

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 7, 2014; final manuscript received July 11, 2014; published online August 26, 2014. Editor: Ronald Bunker.

J. Turbomach 136(11), 111004 (Aug 26, 2014) (10 pages) Paper No: TURBO-14-1115; doi: 10.1115/1.4028161 History: Received July 07, 2014; Revised July 11, 2014

Total heat transfer between a hot and a cold stream of gas across a nonporous conductive wall is greatest when the two streams flow in opposite directions. This counter-current arrangement outperforms the co-current arrangement because the mean driving temperature difference is larger. This simple concept, whilst familiar in the heat exchanger community, has received no discussion in papers concerned with cooling of hot-section gas turbine components (e.g., turbine vanes/blades, combustor liners, afterburners). This is evidenced by the fact that there are numerous operational systems which would be significantly improved by the application of “reverse-pass” cooling. That is, internal coolant flowing substantially in the opposite direction to the mainstream flow. A reverse-pass system differs from a counter-current system in that the cold fluid is also used for film cooling. Such systems can be realized when normal engine design constraints are taken into account. In this paper, the thermal performance of reverse-pass arrangements is assessed using bespoke 2D numerical conjugate heat transfer models, and compared to baseline forward-pass and adiabatic arrangements. It is shown that for a modularized reverse-pass arrangement implemented in a flat plate, significantly less coolant is required to maintain metal temperatures below a specified limit than for the corresponding forward-pass system. The geometry is applicable to combustor liners and afterburners. Characteristically, reverse-pass systems have the benefit of reducing lateral temperature gradients in the wall. The concept is demonstrated by modeling the pressure and suction surfaces of a typical nozzle guide vane with both internal and film cooling. For the same cooling mass flow rate, the reverse-pass system is shown to reduce the peak temperature on the suction side (SS) and reduce lateral temperature gradients on both SS and pressure side (PS). The purpose of this paper is to demonstrate that by introducing concepts familiar in the heat exchanger community, engine hot-section cooling efficiency can be improved whilst respecting conventional manufacturing constraints.

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References

Eastop, T. D., and McConkey, A., 1986, Applied Thermodynamics, 4th ed., Longman Group, London. [PubMed] [PubMed]
Hale, C. A., Plesniak, M. W., and Ramadhyani, S., 2000, “Film Cooling Effectiveness for Short Film Cooling Holes Fed by a Narrow Plenum,” ASME J. Turbomach., 122(3), pp. 553–557. [CrossRef]
Kirollos, B., and Povey, T., 2013, “An Energy-Based Method for Predicting the Additive Effect of Multiple Film Cooling Rows,” ASME Paper No. GT2013-94934. [CrossRef]
Gomes, R. A., and Neihuis, R., 2013, “The Concept of Adiabatic Heat Transfer Coefficient and Its Application to Turbomachinery,” ASME Paper No. GT2013-94715. [CrossRef]
Crook, G., and Horlor, M., eds., 2005, The Jet Engine, 5th ed., Rolls-Royce Technical Publications, London.

Figures

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Fig. 1

Long plate (periodic) forward-pass, reverse-pass, and adiabatic cooling systems

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Fig. 2

Discretization for numerical solution with temperatures and heat flows

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Fig. 3

Temperature distributions of a long plate adiabatic cooling system Tw1 = Tw2

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Fig. 4

Temperature distributions of a long plate forward-pass system with point inlets

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Fig. 5

Temperature distributions of a long plate reverse-pass system with point inlets

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Fig. 6

External wall temperature distributions of long plate forward-pass system and reverse-pass systems with point inlets

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Fig. 7

Effect of wall thickness and wall conductivity on percentage coolant saving for both long plate forward-pass and reverse-pass systems with point inlets

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Fig. 8

Adiabatic film cooling effectiveness distributions

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Fig. 9

Effect of adiabatic film cooling effectiveness decay rate on percentage coolant saving for both forward-pass and reverse-pass long plate systems with point inlets

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Fig. 10

Periodic cooling systems with uniformly distributed inlets

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Fig. 11

Temperature distributions of a periodic forward-pass cooling system with uniformly distributed inlet

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Fig. 12

Temperature distributions of a periodic reverse-pass system with distributed inlet

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Fig. 13

Temperature distributions of a periodic middle pass system with distributed inlet

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Fig. 14

Percentage coolant saving of forward-pass and reverse-pass systems with point inlets and distributed inlets

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Fig. 15

2D representation of a baseline HPNGV SS and incorporation of a reverse-pass system. (a) Modified from Ref. [5].

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Fig. 16

SS baseline temperature distributions

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Fig. 17

SS reverse-pass temperature distributions

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Fig. 18

SS baseline and reverse-pass external wall temperature distributions

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Fig. 19

2D representation of a baseline HPNGV PS and incorporation of a reverse-pass system. (a) Modified from Ref. [5].

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Fig. 20

PS baseline temperature distributions

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Fig. 21

PS reverse-pass temperature distributions

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Fig. 22

PS baseline and reverse-pass external wall temperature distributions

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