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Research Papers

Aerodynamic Performance of Novel Lightweight Turbine Blade

[+] Author and Article Information
Yoji Okita

Corporate Research & Development,
IHI Corporation,
Yokohama 235-8501, Japan
e-mail: youji_ookita@ihi.co.jp

Kozo Nita

Aero-Engine & Space Operations,
IHI Corporation,
Tokyo 196-8686, Japan

Seiji Kubo

Corporate Research & Development,
IHI Corporation,
Yokohama 235-8501, Japan

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received June 28, 2016; final manuscript received December 7, 2016; published online February 28, 2017. Editor: Kenneth Hall.

J. Turbomach 139(7), 071005 (Feb 28, 2017) (7 pages) Paper No: TURBO-16-1134; doi: 10.1115/1.4035604 History: Received June 28, 2016; Revised December 07, 2016

The primary contribution of this research is to clarify the aerodynamic performance of a novel lightweight turbine blade with internal cooling passage and external film cooling, which is invented aiming at drastic weight reduction of a cooled blade. With a considerably thinner airfoil, a significant separation region is formed along the pressure side, and therefore, aerodynamic performance with such a flow field should be investigated. First, the lightweight-cooled airfoil is designed. In the design process, a conventional thick airfoil is first defined as a baseline. With the baseline airfoil, only the mid and rear parts of pressure side profile are redesigned to thin the airfoil without any change in the suction side geometry. The airfoil geometry is optimized so as not to bring significant aerodynamic loss increase. In this numerical optimization, the airfoil shape is gradually changed and evaluated step-by-step. In every step, an adjoint variable method is used to seek better airfoil shape, and then, the generated new shape is evaluated with full Reynolds-averaged Navier–Stokes (RANS) calculation. This iteration is repeated until any further recognizable weight reduction cannot be obtained without sensitive pressure loss increase and/or the airfoil shape reaches some geometrical constraints. The resultant optimized airfoil is approximately 20% lighter than the baseline hollow airfoil without any noticeable change in aerodynamic loss in the numerical solution. Next, the optimized airfoil is tested in a high-speed linear cascade rig to verify its aerodynamic performance. The baseline airfoil is also tested for comparison. The rig is composed of six airfoil passages. The compressed air is supplied to the cascade and discharges to the atmospheric exhaust chamber. The air is also heated up to about 540 K upstream of the cascade. The cascade exit Mach number at the design point is 1.25, while in the experiment other several off-design conditions are also tested to check if there is any Mach number sensitivity. At the design point, the optimized lightweight airfoil shows less total pressure loss compared to the baseline airfoil. Also, at any other off-design Mach number conditions tested, the magnitude of the pressure loss is less with the lightweight airfoil. These results verify that the proposed airfoil does not only bring a considerable weight advantage but also compares favorably with the conventional airfoil in aerodynamic performance.

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Figures

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Fig. 1

Sketch of the conventional blade (baseline) and lightweight-cooled blade

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Fig. 2

Computational domain and mesh around the baseline blade in (a) overall view and (b) detailed view (left: leading edge and right: trailing edge)

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Fig. 3

General arrangement of the experimental apparatus

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Fig. 4

Schematic of the test section

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Fig. 5

Computational domain and mesh around the optimal lightweight blade in (a) overall view and (b) detailed view (left: leading edge and right: trailing edge)

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Fig. 6

Comparison of computed Mach number contours around the airfoil on the design condition between (a) baseline airfoil and (b) lightweight airfoil

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Fig. 7

Comparison of computed isentropic surface Mach number profiles on the design condition (Mex = 1.25)

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Fig. 8

Comparison of pitchwise distribution of computed pressure loss on the design condition (Mex = 1.25)

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Fig. 9

Comparison of measured isentropic surface Mach number profiles along the midspan on the design condition (Mex = 1.25) between (a) baseline airfoil and (b) lightweight airfoil

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Fig. 10

Comparison of pitchwise distribution of measured pressure loss at the midspan on the design condition (Mex = 1.25)

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Fig. 11

Comparison of pitchwise distribution of measured pressure loss at the midspan on all the conditions between (a) baseline and (b) lightweight airfoil

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