Hybrid Compressor Axial-Centrifugal Stages Diffusion
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Solution Overview
Problem
Existing air compressor designs face inefficiencies and weight/cost challenges, particularly in small gas turbine engines, where centrifugal compressors are compact but less efficient due to supersonic velocities, and multi-stage axial compressors are more efficient but heavier and more complex.
Innovation Solution
A hybrid compressor design combining an axial-like stage with a centrifugal-like stage and an intermediate diffusion stage, where the axial-like stage has a pressure ratio less than 2:1 and the centrifugal-like stage exceeds 2:1, with a diffusion stage interposed to manage tangential velocity, allowing for higher efficiency and reduced weight and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a centrifugal compressor design is used, then compact size and low cost are achieved, but efficiency decreases due to supersonic velocities at impeller exit
Solution Approach 1:
The compressor is divided into multiple compression stages (first compression stage, second compression stage, third compression stage) with diffusion stages in between. This segmentation allows the total pressure ratio to be distributed across stages, preventing supersonic velocities in any single stage while maintaining compact overall size through the centrifugal architecture.
Solution Approach 2:
Diffusion stages are introduced as intermediary components between compression stages. These diffusion stages convert kinetic energy to pressure energy and reduce velocities before gas enters the next compression stage, preventing the supersonic conditions that would occur in a single-stage centrifugal compressor while maintaining the compact design.
2Loss of energy
If multi-stage axial compressor design is used, then efficiency is improved, but weight and complexity increase
Solution Approach 1:
The design merges the advantages of axial and centrifugal compressor architectures into a hybrid configuration. The centrifugal compressor uses axial-like blade arrays in the first stage and centrifugal-like vane arrays in subsequent stages, combining the efficiency benefits of axial compression with the compactness of centrifugal design, thereby reducing overall structural complexity compared to pure multi-stage axial compressors.
Solution Approach 2:
Different stages of the compressor employ different blade/vane configurations optimized for their specific functions. The first stage uses axial-like blades for initial compression, while subsequent stages use centrifugal-like vanes for higher pressure ratios. This local optimization allows each stage to operate efficiently without requiring the full complexity of a complete multi-stage axial compressor.
3Volume of moving object
If high pressure ratio is achieved in a single centrifugal stage, then compact size is maintained, but supersonic velocities increase losses
Solution Approach 1:
The single high-pressure-ratio centrifugal stage is segmented into multiple compression stages with intermediate diffusion stages. This segmentation reduces the pressure ratio and velocity increase in each individual stage, preventing supersonic velocities while maintaining the compact overall compressor size through the centrifugal architecture.
Solution Approach 2:
Diffusion stages serve as intermediaries between compression stages, converting kinetic energy to pressure energy and reducing gas velocities. This mediation prevents the accumulation of supersonic velocities that would occur in a single high-pressure-ratio stage, allowing the compressor to maintain compact size without the efficiency penalties of supersonic flow.
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 achieves improved efficiency and reduced weight by tolerating higher losses in high-loaded stages, enabling a compact, lightweight compressor with enhanced pressure ratio and operability, potentially replacing conventional centrifugal compressors in the same space with greater efficiency and compression.
Implementation Method 1
diffusion stage vanes inclined oppositely to the compression stages to decrease tangential velocity of gas exiting the first compression stage
Implementation Method 2
first compression stage comprising a circumferential array of blades extending from a rotor hub towards the shroud, the second compression stage downstream of the first and comprising a circumferential array of centrifugal-like compressor vanes
Data Source
AI summary
A hybrid gas compressor has at least one rotor and shroud which define a compressor gas path extending from an inlet to an outlet. The compressor includes at least two compression stages and one diffusion stage between the inlet and outlet, the compression stages including respective circumferential arrays of blades extending from the rotor and the diffusion stage including a circumferential array of vanes between the compression stages. Blade aerodynamic loadings may be controlled, particularly in the last stage, to provide desired compression characteristics across the compressor. A bleed outlet is optionally located between the inlet and outlet for bleeding from the gas path.