Respiratory Impeller Shroud Geometry for Compact Low-Noise Airflow
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Solution Overview
Problem
Existing respiratory pressure therapy (RPT) devices face challenges in achieving a compact size while maintaining efficiency, reducing noise, and ensuring patient comfort, particularly in devices designed for nocturnal use.
Innovation Solution
The development of a compact respiratory therapy device with an impeller having a diameter of less than 50 mm, featuring a unique shroud configuration and blade design that minimizes noise and improves efficiency, manufactured using additive processes and snap-fit assembly techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the impeller diameter is reduced to minimize device footprint and improve portability, then the device size and weight are decreased, but the maximum available flow rate is decreased
Solution Approach 1:
The patent changes the geometric parameters of the impeller, specifically the blade angles and curvature, to optimize performance at smaller diameters. The impeller blades are designed with specific angle ranges (leading edge angle: 15-45 degrees, trailing edge angle: 10-30 degrees) to maintain efficient airflow generation despite reduced size, allowing the device to achieve compact footprint while preserving adequate flow rate for respiratory therapy
Solution Approach 2:
The patent transitions from traditional radial impeller designs to a more three-dimensional optimized blade configuration with specific curvature and twist angles. This dimensional optimization of the blade geometry allows the small-diameter impeller to generate sufficient pressure and flow by exploiting three-dimensional flow effects that compensate for the reduced rotational radius
2Loss of energy
If aerodynamic features are added to improve impeller efficiency, then the efficiency is improved, but the manufacturing cost increases due to more complicated processes
Solution Approach 1:
The patent defines specific parameter ranges for blade geometry (leading edge angle 15-45 degrees, trailing edge angle 10-30 degrees, blade thickness 0.5-2mm) that can be achieved through standard manufacturing processes like injection molding or CNC machining. These parameterized designs allow efficient aerodynamic performance to be obtained through conventional manufacturing rather than requiring complex additive processes or hand-finishing
Solution Approach 2:
The impeller is designed as a modular component that can be manufactured separately and assembled into the blower housing. The blade geometry is segmented into distinct zones (leading edge, mid-section, trailing edge) with optimized angles for each zone, allowing efficient aerodynamic design while maintaining manufacturability through standard molding or machining operations
3Stability of the object's composition
If the impeller diameter is reduced to decrease rotational inertia, then the acceleration and deceleration performance is improved, but the maximum pressure output is decreased
Solution Approach 1:
The patent optimizes the blade angle parameters to maximize pressure generation efficiency. The leading edge angle (15-45 degrees) and trailing edge angle (10-30 degrees) are specifically designed to create effective pressure differentials across the blades during rotation. This allows the small impeller to generate sufficient pressure (capable of delivering 4-30 cmH2O as stated in the summary) despite reduced diameter and inertia
Solution Approach 2:
The impeller blades are designed with optimized curvature and twist along their length, transitioning from the hub to the tip. This three-dimensional curvature allows the blades to effectively accelerate air radially outward, generating the necessary centrifugal pressure. The curved blade geometry compensates for the smaller rotational radius by creating more effective pressure gradients along the blade span
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 device delivers respiratory pressure therapy at 4-30 cmH2O with an overall sound power level below 50 dB(A), enhancing patient comfort and reducing sleep disturbances.
Implementation Method 1
The impeller may be particularly suited for a small respiratory pressure therapy device... The impeller includes a set of impeller blades... configured to be rotated by a rotor to deliver a flow of air
Data Source
AI summary
A compact respiratory therapy device suitable for use by a patient during sleep to provide respiratory pressure therapy such as at a pressure between 4-30 cmH2O includes a housing, an inlet, an outlet, a motor including a rotor, and an impeller configured to be rotated by the rotor to deliver a flow of air from the inlet toward the outlet. The impeller includes a set of impeller blades, each impeller blade comprising a leading edge and a trailing edge; and a first shroud and a second shroud, each shroud at least partly defining a flow passage through the impeller, the first shroud comprising a wall defining a periphery of an impeller inlet. The first shroud and the second shroud are configured such that the flow passage is narrower in an axial direction at an outer portion of the impeller than at an inner portion of the impeller.