Gas Turbine Stationary Blade Tip Bending for Secondary Flow Loss Reduction

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Solution Overview

Problem

Conventional gas turbine blade structures experience increased pressure loss and reduced efficiency due to secondary flow generation caused by leakage of combustion gas from the tip clearance between rotor blades and the casing, leading to fluctuating stagnation lines and pressure distributions.

Innovation Solution

The blade structure features stationary blades with a border section at 80% of their height bent in the rotational direction of the rotor, and a concave portion in the end wall closer to the rotational direction, aligning stagnation lines and reducing pressure differences between the back and ventral surfaces, thereby minimizing secondary flow loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a tip clearance is provided between the rotor blade tip and the casing, then the rotor blade can rotate freely without contact, but combustion gas leaks from the tip clearance causing increased pressure loss

Engineering Contradiction:

Improverotor blade rotationVSAvoidpressure loss

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The patent converts the harmful leakage flow into a beneficial effect by designing the stationary blade with a bent section that actively utilizes the leakage flow's direction and pressure characteristics to control the stagnation line position, thereby reducing secondary flow loss and improving overall turbine efficiency

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Ease of manufacture

If the stationary blade has a constant cross-section, then the manufacturing is simple, but the leakage flow causes fluctuating stagnation lines and increased secondary flow loss

Engineering Contradiction:

Improvestationary blade fabricationVSAvoidsecondary flow loss

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent applies local quality by introducing a bent section specifically in the tip region of the stationary blade while maintaining a constant cross-section in the main body, thereby locally addressing the leakage flow issue without complicating the overall manufacturing process

Inventive Principle:

Principle #3Local quality

3Loss of energy

If the leading edge including angle at the tip portion is increased, then the pressure loss from leakage flow is reduced, but the blade structure becomes more complex

Engineering Contradiction:

Improvepressure lossVSAvoidblade structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent employs curvature by bending the stationary blade section in the rotational direction, creating a curved geometry that naturally guides the leakage flow and stabilizes the stagnation line, achieving pressure loss reduction through smooth curved surfaces rather than sharp angular changes

Inventive Principle:

Principle #14Spheroidality (Curvature)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This configuration effectively reduces secondary flow loss and enhances turbine efficiency by stabilizing pressure distribution and aligning stagnation lines in the rotational direction, improving the overall performance of the gas turbine.

Implementation Method 1

there is a difference between a pressure on the side of the back surface 74 thereof and a pressure on the side of the ventral surface 75 thereof, and the pressure on the side of the ventral surface 75 is higher than the pressure on the side of the back surface 74. Therefore, the combustion gas flowing on the side of the ventral surface 75 leaks from the tip clearance 90 and flows into the side of the back surface 74 as the leakage flow 93

Methodology Applied

Scientific EffectSecondary flow:

Implementation Method 2

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Data Source

PatentEP2103782B1Blade structure for gas turbine

Publication Date: 2014.11.26 MITSUBISHI HITACHIPOWER SYST LTD

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AI summary

To reduce secondary flow loss and to improved turbine efficiency, a section located radially outward of a border section 28 of a stationary blade 21 is bent in the rotational direction of a rotor. Thus, even if combustion gas leaks from a tip clearance between an end wall of a casing and a tip portion of a rotor blade, and a stagnation line 35 near a tip portion 22 is situated in the side of a back surface 24, because a section located radially outward of the border section 28 is bent in the rotational direction of the rotor, the stagnation line 35 is also situated toward the rotational direction of the rotor. Therefore, the stagnation lines 35 formed at various heights in the heightwise direction of the stationary blade 21 are generally aligned in the rotational direction of the rotor. Thus, fluctuation of pressure distribution in the heightwise direction of the stationary blade 21, of the combustion gas flowing into the stationary blade 21 can be reduced. As a result, secondary flow loss can be reduced and turbine efficiency can be improved.