Loss generation in radial outflow steam turbine cascades

Recent trends in the electric energy market such as biomass, waste incineration or combined cycle power plants require innovative solutions in steam turbine design. Variable operating conditions cause significant changes in flow field surrounding the steam turbine last stage blades. Therefore, the enlargement of operating range for last stage blades presents new challenges in design of turbine cascades. Several turbine cascades were designed and analyzed by commercial and in-house software of CTU Prague. Selected profiles were experimentally validated in the high-speed wind tunnel for 2D cascade measurements of the Institute of Thermomechanics of the Czech Academy of Sciences which is equipped by an adjustable supersonic inlet nozzle, perforated inserts at side walls and adjustable perforated tailboard. Comparisons are presented of numerical results with optical and pneumatic measurements for a wide range of inlet and outlet Mach numbers for optimized hub and tip profile cascades.

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Application of Artificial Neural Networks in Investigations of Steam Turbine Cascades

Journal of Turbomachinery ◽

10.1115/1.3103923 ◽

2009 ◽

Vol 132 (1) ◽

Cited By ~ 4

Author(s):

Krzysztof Kosowski ◽

Karol Tucki ◽

Adrian Kosowski

Keyword(s):

Neural Networks ◽

Artificial Neural Networks ◽

Steam Turbine ◽

High Performance ◽

Cross Sectional ◽

Complementary Method ◽

Numerical Tests ◽

Flow Parameters ◽

Turbine Cascades ◽

Artificial Neural

We present the results of numerical tests of artificial neural networks (ANNs) applied in the investigations of flows in steam turbine cascades. Typical constant cross-sectional blades, as well as high-performance blades, were both considered. The obtained results indicate that ANNs may be used for estimating the spatial distribution of flow parameters, such as enthalpy, entropy, pressure, velocity, and energy losses, in the flow channel. Finally, we remark on the application of ANNs in the design process of turbine flow parts, as an extremely fast complementary method for many 3D computational fluid dynamics calculations. By using ANNs combined with evolutionary algorithms, it is possible to reduce by several orders of magnitude the time of design optimization for cascades, stages, and groups of stages.

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Comparative Experimental Investigation on Aerodynamic Performance of a Steam Turbine Cascades: Part II — Stator Vanes

Volume 5B: Oil and Gas Applications; Steam Turbines ◽

10.1115/gt2013-94815 ◽

2013 ◽

Author(s):

Lei Gao ◽

Qun Zheng ◽

Hang Chen

Keyword(s):

Pressure Gradient ◽

Steam Turbine ◽

Aerodynamic Performance ◽

Wake Region ◽

Uniform Loading ◽

Experimental Conditions ◽

Blade Height ◽

Comparative Experimental Investigation ◽

Turbine Cascades ◽

Loading Type

In this paper, the eighth and the ninth stage stator blades of a marine steam turbine are improved and the experimental research has been carried out on aerodynamic performance at 50% blade height of the original and the improved plane cascades. The experimental results indicate that both of the two original stator blades are uniform loading type, which are improved and designed as the aft-loaded. The results also show that, comparing with the original blade, the improved one can shorten the length of reverse pressure gradient, therefore the reverse pressure gradient is reduced and the adaptability of cascades to incidence variation is enhanced. Meanwhile, the thin trailing edge of aft-loaded blade not only increases the base pressure of the wake region, but also reduces the width of the wake region. In addition, the results reveal that the losses of modified blades are lower than the original ones under the experimental conditions of different exit Mach numbers and different angle of incidences.

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Comparative Experimental Investigation on Aerodynamic Performance of Steam Turbine Cascades: Part I — Rotor Blades

Volume 5B: Oil and Gas Applications; Steam Turbines ◽

10.1115/gt2013-94814 ◽

2013 ◽

Author(s):

Lei Gao ◽

Qun Zheng ◽

Hang Chen

Keyword(s):

Steam Turbine ◽

Large Degree ◽

Aerodynamic Performance ◽

Rotor Blades ◽

Aerodynamic Loss ◽

Transverse Pressure ◽

Comparative Experimental Investigation ◽

Last Stage ◽

Turbine Cascades ◽

End Wall

In this paper, the static aerodynamic performance of the second to last stage rotor blades of a marine steam turbine is experimentally investigated. The experiments have been carried out for both original blade (ORI R1) and modified blade (MOD R1) annular cascades. The experimental results indicate that the straight original blade is aft-loaded type, and there is a large degree of diffusion at the tip end wall. The improvement methods include adopting twist blades, adjusting the blade profile to reach the aft-loaded as much as possible at both end walls as well as combining with the cylindrical meridian lines. It has been found in the experiment that the transverse pressure gradient of the modified decreases at both end walls, so does the loss of the flow, especially it weakens the secondary flow at the tip end wall. The aerodynamic loss coefficient of improved blades has reduced by about 25%.

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