Research Papers

Aeroderivative Mechanical Drive Gas Turbines: The Design of Intermediate Pressure Turbines

[+] Author and Article Information
Alberto Scotti Del Greco

Baker Hughes, a GE company,
Via F. Matteucci 2,
50127 Florence, Italy
e-mail: alberto.scottidelgreco@bhge.com

Vittorio Michelassi

Baker Hughes, a GE company,
Via F. Matteucci 2,
50127 Florence, Italy
e-mail: vittorio.michelassi@bhge.com

Stefano Francini

Baker Hughes, a GE company,
Via F. Matteucci 2,
50127 Florence, Italy
e-mail: stefano.francini@bhge.com

Daniele Di Benedetto

Baker Hughes, a GE company,
Via F. Matteucci 2,
50127 Florence, Italy
e-mail: daniele.dibenedetto@bhge.com

Mahendran Manoharan

GE Aviation, John F. Welch Technology Centre,
Bangalore, India
e-mail: mahendran.m@ge.com

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Turbomachinery. Manuscript received December 11, 2018; final manuscript received March 6, 2019; published online March 28, 2019. Assoc. Editor: Kenneth Hall.

J. Turbomach 141(8), 081007 (Mar 28, 2019) (11 pages) Paper No: TURBO-18-1354; doi: 10.1115/1.4043120 History: Received December 11, 2018; Accepted March 06, 2019

Gas turbines engine designers are leaning toward aircraft engine architectures due to their footprint, weight, and performance advantages. Such engines need some modifications to both the combustion system, to comply with emission limits, and turbine rotational speed. Aeroderivative engines maintain the same legacy aircraft engine architecture and replace the fan and booster with a higher speed compressor booster driven by a single-stage intermediate turbine. A multistage free power turbine (FPT) sits on a separate shaft to drive compressors for liquefied natural gas (LNG) applications or generators. The intermediate-power turbine (IPT) design is important for the engine performance as it drives the booster compressor and sets the inlet boundary conditions to the downstream power turbine. This paper describes the experience of Baker Hughes, a GE company (BHGE) in the design of the intermediate turbine that sits in between a GE legacy aircraft engine core exhaust and the downstream power turbine. This paper focuses on the flow path of the turbine center frame (TCF)/intermediate turbine and the associated design, as well as on the 3D steady and unsteady computational fluid dynamics (CFD)-assisted design of the IPT stage to control secondary flows in presence of through flow curvature induced by the upstream TCF.

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Fig. 1

Turbine layout for a typical 2.5 shaft aeroderivative engine

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Fig. 2

Grid sensitivity analysis: stator and rotor loss coefficient versus grid size

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Fig. 3

The three IPT flow paths: average exit radius increases from A to B (inlet and outlet annulus areas are the same for the three cases)

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Fig. 4

Hub curvature distributions. Peak curvature location is upstream the throat for all the three cases.

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Fig. 5

Stator ideal Mach number distributions at 5% (bottom) and 95% (top) span for the three cases of Fig. 3

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Fig. 6

Stator (left) and rotor (right) efficiencies for the three cases of Fig. 3

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Fig. 7

IPT total-to-total efficiency for the three cases of Fig. 3

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Fig. 8

Blade-to-blade throat distance along the span of stator (left) and rotor (right) for design 1 (free-vortex) and 2 (decambered endwalls)

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Fig. 9

Distributions of airfoil tangential shift for IPT vane (left). On the right, the degrees of reaction along the span for free-vortex design (1), decambered endwalls (2), and vane leaning solution (3).

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Fig. 10

Spanwise distribution of vane discharge flow coefficient CF defined as per Eq. (2)

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Fig. 11

Near suction side streamlines for three designs. The dotted lines indicate and compare the secondary flow penetration at the hub trailing edge of the blade.

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Fig. 12

Spanwise distributions of stator and rotor loss coefficient for the three designs

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Fig. 13

IPT total-to-total efficiency trends associated with free-vortex design (1), optimized decambered endwalls (2), and vane leaning solution (3)

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Fig. 14

View of the TCF struts and IPT nozzle

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Fig. 15

Stagnation pressure visualization at the nozzle inlet and exit

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Fig. 16

Vanes isentropic Mach number distributions at midspan. The dashed line refers to the single vane model and the shaded area represents the minimum to maximum envelope of the integrated TCF+IPT model.

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Fig. 17

IPT inlet distortions in terms of p00/T00 relative to flat profile (reference). ESP and EWP are families of endwall strong or weak profiles, respectively. The dashed line is the expected design distribution.

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Fig. 18

Impact of inlet distortion on FF (dashed) and efficiency (solid). All the variations are % with respect to the flat reference profile. The abscissa represents the endwall value respect to profile average.

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Fig. 19

Spanwise profiles of the IPT stator flow coefficient for different inlet profiles

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Fig. 20

Stator inlet (left) and stator exit (right) spanwise profiles of the mass flow rate for EWP and ESP

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Fig. 21

Stator (left) and rotor (right) kinetic losses for ESP and EWP

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Fig. 22

Qualitative sketch of the overall computational domain when cavities are directly gridded

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Fig. 23

IPT stage spanwise distributions of the exit flow angle (a), blade row efficiency (b), and flow rate (c)

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Fig. 24

IPT exit contour of blade-row efficiency (a), without source terms, (b) with source terms, (c) with resolved cavities

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Fig. 25

Comparison between the steady and time-averaged unsteady IPT spanwise distribution of exit flow angle (a), rotor efficiency (b), and flow rate (c)

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Fig. 26

Entropy contours at the blade exit predicted by the steady (left), time-averaged unsteady (center), instantaneous unsteady (right) CFD approach with endwall source terms

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Fig. 27

Efficiency curves as estimated by CFD and mean-line code Qualitative blade loadings in different regimes of speed ratio are also reported



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