Segmented Blade Tip Sealing Members for Turbine Leakage Reduction
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Solution Overview
Problem
In gas turbine engines, blade tip clearances lead to significant leakage of air or combustion gases from the high-pressure side to the low-pressure side, reducing efficiency and potentially decreasing stall margin, while existing designs aim to prevent blade-casing contact to avoid damage.
Innovation Solution
A rotor assembly with a blade tip sealing portion featuring a blade tip platform and a plurality of sealing members positioned at an angle perpendicular to the airflow, extending between the pressure and suction side edges, which can overlap and contact an abradable region on the casing to form annular channels, reducing leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If blade tip clearance is maintained to prevent blade-casing contact, then blade and casing damage is avoided, but leakage from high-pressure side to low-pressure side increases, reducing efficiency
Solution Approach 1:
The blade tip is segmented into multiple sealing members (e.g., three sealing members 144 spaced along the chord) that create multiple seal lines. Each sealing member forms an individual seal with the casing, and the combined effect of multiple segments significantly reduces leakage compared to a single seal, while maintaining the same tip clearance for damage prevention
Solution Approach 2:
An abradable region 155 is introduced as an intermediary material layer on the casing surface. This soft material allows the sealing members to lightly contact and form seals without transmitting high impact loads that would cause blade damage. The abradable region deforms elastically under contact pressure to maintain sealing while accommodating blade vibrations and clearance variations
2Loss of energy
If blade tip clearance is reduced to decrease leakage, then efficiency increases, but the risk of blade-casing contact and damage increases
Solution Approach 1:
The sealing members are pre-positioned on the blade tip platform at optimal locations and angles before operation. The abradable region is pre-formed on the casing surface with appropriate hardness and geometry. This preliminary preparation ensures that when the blade rotates, the sealing members automatically engage the casing at the correct clearance without requiring active control or adjustment during operation
Solution Approach 2:
The invention changes the physical parameters of the sealing interface by using multiple sealing members with specific spacing, angles, and dimensions. The abradable region has controlled hardness, thickness, and radial extent. These parameter optimizations allow the system to maintain larger clearances while achieving effective sealing, as the multiple seal lines and compliant material compensate for the increased gap size
3Loss of energy
If multiple sealing members are added to reduce leakage, then sealing effectiveness increases, but device complexity increases
Solution Approach 1:
The blade tip platform serves multiple functions: it provides the mounting surface for the sealing members, creates a seal line itself where it contacts the casing, and maintains the structural integrity of the blade tip. The sealing members simultaneously seal the clearance and can be designed to accommodate thermal expansion and vibrational movements. This multi-functionality reduces the need for additional separate components
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 significantly reduces or eliminates leakage across the blade tip clearance, enhancing the efficiency of fan, compressor, and turbine operations and increasing stall margin, while ensuring the blade does not contact the casing to cause damage.
Implementation Method 1
rotating the rotor to effect rub between the plurality of sealing members and the abradable region, wherein the rub causes a plurality of annular channels to be formed in the abradable region
Data Source
AI summary
A blade tip sealing portion forms the distal end of a rotor blade in a turbine engine to reduce or prevent leakage through the blade tip clearance. A rotor assembly comprises a casing, a rotor, and at least one rotor blade coupled to the rotor. The rotor blade comprises a root portion coupled to the rotor, a main airfoil body extending radially from the root portion, and a blade tip sealing portion. The blade tip sealing portion comprises a blade tip platform and a plurality of sealing members. The sealing members are positioned on the blade tip platform at an angle substantially perpendicular to an air flow across the blade tip platform and are spaced to effect overlap of adjacent sealing members in the direction of the air flow.