Variable-Pitch Centrifugal Compressor Diffuser for Partial Load Efficiency

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Solution Overview

Problem

Turbomachine engines face challenges in maintaining constant compression rate and performance across varying load conditions, particularly at partial loads, due to mechanical stresses and efficiency degradation caused by existing variable timing systems in radial diffusers.

Innovation Solution

A centrifugal compressor diffuser with a first annular grid of variable timing blades and a second annular grid of fixed timing blades, where the blades are decentralized and coupled to reduce mechanical stresses and optimize aerodynamic efficiency, allowing for adaptive air flow management.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If variable pitch control is implemented in radial diffusers to adapt airflow, then airflow adaptation capability is improved, but mechanical stresses between rotating and static parts increase

Engineering Contradiction:

Improveairflow adaptation capabilityVSAvoidmechanical stresses

Core Design Contradiction:

Adaptability or versatilityVSStress or pressure

Solution Approach 1:

The diffuser blade assembly is segmented into multiple independent pitch-controlled blade rows, allowing localized adjustment of airflow angles without requiring entire diffuser sections to move, thereby reducing mechanical stresses while maintaining adaptability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements dynamic pitch adjustment of diffuser blades based on real-time operating conditions, enabling the system to adapt airflow characteristics continuously while optimizing mechanical load distribution across the structure

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If diffuser inlet and outlet diameters are varied to achieve pitch angle ranges, then airflow control range is improved, but compressor efficiency at partial load decreases

Engineering Contradiction:

Improveairflow control rangeVSAvoidcompressor efficiency

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

Different sections of the diffuser are designed with locally optimized blade geometries and pitch ranges tailored to specific operating conditions, allowing efficient airflow control at partial load while maintaining adequate control range when needed

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent optimizes diffuser blade parameters such as inlet angle, outlet angle, and pitch range to achieve the required airflow control while minimizing adverse effects on compressor efficiency across the operating envelope

Inventive Principle:

Principle #35Parameter changes

3Reliability

If compressor operates below maximum efficiency to achieve pumping margin, then pumping margin is improved, but overall engine efficiency degrades

Engineering Contradiction:

Improvepumping marginVSAvoidengine efficiency

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The diffuser system dynamically adjusts blade pitch to optimize the compressor operating point, enabling the system to maintain adequate pumping margin while operating closer to maximum efficiency across varying load conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

By adjusting diffuser blade pitch angles, the system modifies the compressor performance characteristics to achieve adequate pumping margin without requiring operation at significantly reduced efficiency points

Inventive Principle:

Principle #35Parameter changes

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 maintains high compressor efficiency and reduces mechanical stress, enabling turbomachines to operate efficiently across varying loads without significant pressure or speed deviations, thus ensuring sufficient pumping margin and improved partial load performance.

Implementation Method 1

diffusing air through a first annular grid of variable-pitch blades radially bordered by a second annular grid of the same number of fixed-pitch blades

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

centrifugal compressor, particularly for helicopter turboshaft engines or auxiliary power units (APUs)

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentEP2558728B2Method for adapting the air flow of a turbine engine having a centrifugal compressor and diffuser for implementing same

Publication Date: 2022.10.12 SAFRAN HELICOPTER ENGINES

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AI summary

The invention relates to a method for maintaining the efficiency and duty of a turbine engine compressor in order substantially to reduce the specific consumption Cs, while guaranteeing a high enough pumping margin with partial load. For this purpose, the invention proposes an optimised method for adapting the airflow to a variable demand for flow or mechanical or electric power in a centrifugal compressor of a turbine engine. The method includes diffusing the airflow (F) through a first annular blade ring (G1) having variable-pitch blades (24), radially bordered by a second annular blade ring (G2) having the same number of fixed-pitch blades (28) with an equivalent extension, guiding the radial extension diffusion by coupling the blades (24, 28) of the two blade rings. According to said method, each blade (24) of the first blade ring (G1) is spun off-axis.