Axial Compressor Rotor Blade Deflection for Diffuser Pressure Recovery
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Solution Overview
Problem
In axial flow rotary machines, fluid separation occurs easily in the diffuser portion due to shearing between the fluid and the casing, leading to loss and reduced pressure recovery performance.
Innovation Solution
The implementation of rotor blades with varying deflection angles in the blade height direction, particularly larger angles on the hub and chip sides, to enhance fluid compression and reduce separation, along with a diffuser flow path design that expands the cross-sectional area towards the downstream side and incorporates stator vanes to manage fluid flow and reduce friction loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional rotor blade with uniform deflection angle is used, then the structure is simple, but fluid separation occurs easily in the diffuser portion due to shearing between fluid and casing
Solution Approach 1:
The rotor blade employs different deflection angles at different radial positions: a first deflection angle in the hub region, a second deflection angle in the intermediate region, and a third deflection angle in the tip region. This local differentiation optimizes fluid flow control at each position, preventing fluid separation in the diffuser portion while maintaining overall blade functionality.
2Length of moving object
If the diffuser length is shortened to reduce machine size, then the device becomes more compact, but pressure recovery performance deteriorates
Solution Approach 1:
The diffuser portion employs different expansion angles at different radial positions: a first expansion angle in the hub region and a second expansion angle in the tip region. This local differentiation allows the diffuser to achieve sufficient pressure recovery in a shorter axial length by optimizing the expansion characteristics at each radial position, thereby maintaining pressure recovery performance while reducing overall diffuser length.
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 design enhances pressure recovery performance by reducing fluid separation and friction loss, allowing for a shorter diffuser length and increased pressure recovery ratio, while maintaining stable pressure recovery even when the diffuser dimension is shortened.
Implementation Method 1
the deflection angle of the blade portion in the rotor blades of the final rotor blade row, that is, a relative angle between a flow direction of a fluid at an inlet of the blade portion and a flow direction of the fluid at an outlet of the blade portion, is larger on the hub side and the chip side than at the central portion in the blade height direction
Implementation Method 2
a diffuser flow path is formed so that a cross-sectional area of the flow path gradually increases toward a downstream side of a flow of the fluid. This diffuser flow path reduces a flow velocity of the compressed fluid to recover pressure
Implementation Method 3
a flow velocity distribution (a pressure distribution) in a radial direction of a rotating shaft is generated due to an influence of shearing between a fluid introduced into a diffuser portion and an inner surface of a casing
Data Source
AI summary
A rotor blade (22) provided in an axial flow compressor (1) including a rotating shaft, a casing (3), a diffuser portion (4) provided on a downstream side of the casing to communicate with a flow path (C) of the casing and form an annular shape and configured to define a diffuser flow path (DC) in which a cross-sectional area of the flow path expands toward the downstream side, a plurality of stator vane rows (10), and rotor blade rows (20) performing compression of a gas. A plurality of rotor blades are spaced apart from each other in a circumferential direction, and constitute a final rotor blade row (20A) positioned on a most downstream side among the rotor blade rows, and include a blade portion (25) having a larger deflection angle on a hub side and a chip side than at a central portion in a blade height direction.