Counter-Rotating Compressor Eliminates Diffusers

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Solution Overview

Problem

Centrifugal compressors and mixed-flow compressor stages face significant aerodynamic losses due to the need for diffusers to reorient gas flow, which increases space requirements and reduces efficiency, and there is a desire to enhance the pressure ratio beyond standard impeller-diffuser configurations.

Innovation Solution

A compressor design featuring counter-rotating rotors, where a non-axial first rotor is followed by a co-axial second rotor rotating in the opposite direction, eliminating the need for diffusers by discharging fluid flow into an uninterrupted passage, thereby reducing radial and circumferential flow components and increasing pressure ratio.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If diffusers are used to reorient gas flow in centrifugal compressors, then the gas flow can be converted into pressure energy and oriented parallel to the center axis, but aerodynamic losses increase and compressor efficiency decreases

Engineering Contradiction:

Improvepressure energy conversionVSAvoidaerodynamic losses

Core Design Contradiction:

TemperatureVSLoss of energy

Solution Approach 1:

The patent extracts and removes the diffuser component from the compressor system. By using a counter-rotating rotor configuration, the system eliminates the need for diffusers to reorient flow, directly addressing the aerodynamic losses caused by flow turning in conventional designs

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent uses counter-rotating rotors where the second rotor rotates in the opposite direction to the first rotor. This inversion of rotation direction allows the second rotor to directly discharge fluid flow in the desired direction without requiring flow reorientation through diffusers, thereby reducing aerodynamic losses

Inventive Principle:

Principle #13The other way round (Inversion)

2Temperature

If diffusers are used to reorient gas flow, then the gas can be directed parallel to the center axis, but the compressor occupies considerable space

Engineering Contradiction:

Improvegas flow orientationVSAvoidcompressor space

Core Design Contradiction:

TemperatureVSVolume of stationary object

Solution Approach 1:

The patent removes the diffuser component from the system, eliminating the space it occupies. The counter-rotating rotor configuration achieves flow orientation without requiring the additional volume that diffusers would demand

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent combines the flow reorientation function into the rotor system itself. The counter-rotating second rotor performs both compression and flow direction control in a single integrated component, eliminating the need for separate diffuser sections

Inventive Principle:

Principle #5Merging (Combining)

3Stress or pressure

If standard impeller-diffuser configurations are used, then the compressor can operate, but the pressure ratio is limited

Engineering Contradiction:

Improvepressure ratioVSAvoidcompressor configuration

Core Design Contradiction:

Stress or pressureVSDevice complexity

Solution Approach 1:

The patent employs counter-rotating rotors where the second rotor rotates opposite to the first rotor. This configuration enables higher pressure ratios by utilizing the relative motion between counter-rotating blades to compress fluid more effectively, while maintaining a relatively simple two-rotor structure

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent divides the compression function into two separate rotating stages. Each rotor handles a portion of the compression task, with the first rotor performing initial compression and the second counter-rotating rotor performing additional compression and flow direction control, achieving higher overall pressure ratio

Inventive Principle:

Principle #1Segmentation

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 reduces aerodynamic losses, eliminates the need for diffusers or stators, and potentially doubles the work of a conventional impeller, enhancing the overall efficiency and pressure ratio of the compressor while reducing the complexity and weight of gas turbine engines.

Implementation Method 1

a second rotor disposed immediately downstream from the first rotor and being co-axial therewith about a longitudinal axis of rotation, the second rotor rotating in a direction opposite the non-axial first rotor

Methodology Applied

Scientific EffectCounter-rotating mechanism:

Implementation Method 2

Centrifugal compressors in some gas compression systems require diffusers to convert the gas accelerated by the impeller of the centrifugal compressor into pressure energy

Methodology Applied

Scientific EffectKinetic energy to pressure energy conversion:

Data Source

PatentUS10378551B2Counter-rotating compressor

Publication Date: 2019.08.13 PRATT & WHITNEY CANADA CORP

AI summary

A compressor is described which includes a non-axial first rotor, and a second rotor disposed immediately downstream from the first rotor and being co-axial therewith about a longitudinal axis of rotation. The second rotor rotates in a direction opposite the non-axial first rotor to discharge fluid flow into an uninterrupted passage between an outlet of the second rotor and one of a downstream combustor or a further compression stage. The uninterrupted passage is free of a diffusing passage. A gas turbine engine including such a compressor and a method of compressing fluid flow is also described.