Control Valve Turbulence Elements Shear Layer Stability

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Solution Overview

Problem

Control valves in steam turbines experience flow instabilities due to shear layers between wall jet and core flow areas, leading to critical resonance effects that can damage the valve structure, and existing solutions like flow straighteners result in significant flow losses reducing turbine output.

Innovation Solution

Incorporating volume flow turbulence elements interacting with the throttle edge area, which are arranged asymmetrically or unevenly in the circumferential direction, to improve mixing of the shear layer and reduce instabilities, thereby preventing or dampening undesirable resonance effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If flow straighteners are incorporated in the area of the valve seat to counteract resonance effects, then the shear layer instabilities are reduced, but significant flow losses occur that reduce turbine power output

Engineering Contradiction:

Improvecontrol valve structural integrityVSAvoidturbine power output

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent introduces turbulence elements that deliberately increase turbulence in the shear layer, converting what was previously a harmful instability into a beneficial mixing effect. The turbulence elements promote rapid mixing between the wall jet and core flow, which stabilizes the shear layer and prevents resonance, while maintaining acceptable pressure losses.

Inventive Principle:

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

Solution Approach 2:

The patent changes the flow regime parameters by introducing controlled turbulence through specific geometric elements in the shear layer. By adjusting the turbulence intensity and distribution, the patent transforms the flow characteristics to achieve stability without the energy penalties of traditional flow straighteners.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If the control valve operates in a throttled state, then flow control is achieved, but shear layer instabilities and resonance effects occur that can damage the valve structure

Engineering Contradiction:

Improveflow control capabilityVSAvoidshear layer resonance effects

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent introduces turbulence elements as intermediary structures in the shear layer that mediate between the wall jet and core flow. These elements act as a buffer that promotes stable mixing and prevents the development of harmful resonance effects, allowing the valve to operate in throttled states without structural damage.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If turbulence elements are added to the control valve to reduce shear layer instabilities, then resonance effects are prevented, but device complexity increases

Engineering Contradiction:

Improvecontrol valve stabilityVSAvoidvalve internal structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent divides the shear layer into multiple segments by introducing discrete turbulence elements at specific locations. These segmented elements create localized mixing zones that collectively stabilize the entire shear layer, achieving reliability without requiring a completely redesigned valve structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies turbulence elements only in the specific region where shear layer instabilities occur, rather than modifying the entire valve structure. This localized approach maintains simplicity in non-critical areas while addressing the stability issue precisely where needed.

Inventive Principle:

Principle #3Local quality

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 solution effectively reduces shear layer instabilities and maintains low pressure losses, enhancing the efficiency and preventing structural impairment of the control valve, thereby increasing the overall efficiency of the steam turbine.

Implementation Method 1

a characteristic flow pattern almost always forms in the flow chamber of the control valve, which is essentially characterized by the formation of a wall jet region with flow velocities that are considerably higher than the flow velocities of a core flow region of a volume flow. Therefore, the different flow velocities cause a shear layer between the wall jet region of the volume flow passing through the control valve and the core flow region of this volume flow

Methodology Applied

Scientific EffectShear layer mixing: Turbulence

Data Source

PatentEP3209866B1Control valve and turbine

Publication Date: 2019.03.06 SIEMENS AG

Figure 1
Figure 2~3

AI summary

The invention relates to a control valve (1) for controlling a gaseous volumetric flow rate, in particular a steam volumetric flow rate (2), comprising a valve housing (3), a valve seat (5), and a valve throttle element (6; 106; 206) which can be moved relative to the valve seat (5) along a movement axis (7). The valve housing (3) shapes the valve seat (5), and the movable valve throttle element (6; 106; 206) has a throttle edge region (10; 110; 210) which interacts with the valve seat (5). The control valve (1) has multiple volumetric flow rate swirl elements (15; 115; 215) which interact with the throttle edge region (10; 110; 210) and which prevent or at least reduce shear layer instabilities in a shear layer between a wall jet region of the gaseous volumetric flow rate and a core flow region of the gaseous volumetric flow rate.