Two-Stage Blood Pump Impeller Segmentation for Shear Stress Reduction

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Solution Overview

Problem

Conventional blood pumps face issues with high shear stress and turbulence, leading to red blood cell damage and inefficiency due to high rotational speeds and complex flow patterns, particularly in centrifugal and axial-flow designs with small annular gaps and long blade profiles.

Innovation Solution

A rotordynamic blood pump design featuring a two-stage impeller configuration with a mixed-flow stage and an axial-flow stage, along with stator vanes, which reduces the need for high rotational speeds and minimizes shear stress by optimizing flow paths and clearances, resulting in higher efficiency and lower blood damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the annular gap between rotor and stator is made small to maintain magnetic radial stiffness, then magnetic stability is improved, but shear stress and turbulence increase leading to red blood cell damage

Engineering Contradiction:

Improvemagnetic radial stiffnessVSAvoidshear stress and turbulence

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The pump is divided into multiple impeller stages (first stage and second stage) with different flow characteristics. The first impeller stage is configured for mixed-flow to generate initial pressure rise, while the second impeller stage is configured for axial-flow to provide additional pressure rise. This segmentation allows the system to achieve required pressure rise at lower rotational speeds, thereby reducing shear stress and turbulence in the narrow annular gap while maintaining magnetic stability.

Inventive Principle:

Principle #1Segmentation

2Stress or pressure

If rotational speed is increased to generate desired pressure rise and flow rates in a narrow annular gap, then pressure rise is improved, but turbulence and shear stress increase causing red blood cell damage

Engineering Contradiction:

Improvepressure riseVSAvoidturbulence and shear stress

Core Design Contradiction:

Stress or pressureVSObject-affected harmful factors

Solution Approach 1:

The pressure rise requirement is segmented across multiple impeller stages. The first impeller stage (mixed-flow) provides initial pressure rise, and the second impeller stage (axial-flow) provides additional pressure rise. This allows the system to achieve the desired total pressure rise at lower rotational speeds compared to a single-stage design, thereby reducing turbulence and shear stress in the narrow annular gap.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different impeller stages have different local flow characteristics optimized for their specific positions. The first impeller stage uses mixed-flow configuration suitable for generating initial pressure rise, while the second impeller stage uses axial-flow configuration for additional pressure rise. This local optimization of flow characteristics allows efficient pressure generation at lower speeds.

Inventive Principle:

Principle #3Local quality

3Strength

If centrifugal or mixed-flow pumps with shrouded impellers are used, then structural strength is improved, but disk friction loss and retrograde leakage flow increase lowering efficiency and potentially inducing hemolysis

Engineering Contradiction:

Improvestructural strengthVSAvoiddisk friction loss

Core Design Contradiction:

StrengthVSLoss of energy

Solution Approach 1:

The impeller is segmented into multiple stages with different configurations. The first impeller stage may use shrouded impeller for structural strength, while the second impeller stage uses unshrouded impeller to minimize disk friction loss and retrograde leakage flow. This segmentation allows the system to balance structural strength requirements with efficiency requirements in different sections of the pump.

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

The two-stage design achieves higher hydraulic efficiency, lower power consumption, and reduced blood trauma by operating at lower speeds, while maintaining the required pressure rise, thus providing a compact, efficient, and safe implantable blood pump.

Implementation Method 1

magnetically suspended and rotated without mechanical means

Methodology Applied

Scientific EffectMagnetic levitation: Maglev

Implementation Method 2

magnetically suspended systems

Methodology Applied

Scientific EffectMagnetic field: Magnetic Field

Implementation Method 3

centrifugal or mixed-flow blood pumps

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentUS10371150B2Blood pump with separate mixed-flow and axial-flow impeller stages, components therefor and related methods

Publication Date: 2019.08.06 HEARTWARE INC

AI summary

A rotordynamic pump for delivering continuous flow of fluids, such as blood, is provided. In one embodiment, the pump includes a stator housing having an inlet and an outlet. A rotor hub is disposed within the stator housing having a first, mixed-stage impeller and a second, axial-flow stage impellers. One or more stator vanes and extend radially inwardly from the stator housing. In one particular embodiment, the second stage impeller is disposed nearer to the outlet than to the inlet. The stator vanes may include a first set of stator vanes disposed between the first and second stage impellers, and a second set of stator vanes positioned between the second stage impellers and the outlet.