Ventilator Exhalation Valve Geometry for Lower Flow Noise
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Solution Overview
Problem
Existing exhalation valves in ventilation apparatuses produce noise due to periodic eddying and pressure fluctuations, which are acoustically perceptible as whistling or hissing, during exhalation events.
Innovation Solution
The exhalation valve incorporates a skirt that surrounds the counterpart surface and end surface, guiding the exhalation flow along a longer path and stabilizing flow conditions, reducing noise emissions by constraining the flow through an annular gap space and using a wave-shaped skirt rim to create different but uniform flow conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a plate-shaped valve body is used to block gas flow, then the valve function is achieved, but noise is generated due to periodic eddying and pressure fluctuations
Solution Approach 1:
The patent applies curvature by replacing the plate-shaped valve body with a dome-shaped valve body. This curved surface guides the respiratory gas flow more smoothly, preventing periodic eddying and pressure fluctuations that cause noise. The dome shape allows flow to follow a more uniform path across the valve opening, eliminating the harmful acoustic effects while maintaining the blocking function.
Solution Approach 2:
The patent introduces a new spatial dimension by adding a dome-shaped structure that extends vertically above the valve opening. This three-dimensional configuration allows the flow to be distributed more evenly across the opening area, preventing the formation of eddies and pressure fluctuations that occur with flat plate configurations.
2Productivity
If the valve body is moved away from the end surface to enlarge the annular gap, then flow resistance decreases, but pressure fluctuations occur causing noise
Solution Approach 1:
The dome-shaped valve body creates a curved flow path that maintains smooth flow even when the annular gap is enlarged. The curvature ensures that flow velocity is distributed uniformly across the gap, preventing the formation of eddies and pressure fluctuations that would otherwise occur with larger gaps in plate-shaped designs.
3Ease of operation
If a plate-shaped valve body deflects flow through 90 degrees, then flow control is achieved, but eddying occurs in the region between the valve body and end surface
Solution Approach 1:
The dome-shaped valve body replaces the sharp 90-degree deflection of a plate with a gradual curved transition. This allows the flow to change direction more smoothly, maintaining flow control capability while eliminating the abrupt flow separation that causes eddying and instability in the region between the valve body and end surface.
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 solution significantly reduces noise emissions, particularly in the operationally relevant volumetric flow range of 15 liters per minute, by minimizing pressure fluctuations and eddying, resulting in a quieter operation without compromising the valve's performance.
Implementation Method 1
a preloading device, which has a preload effect on the valve body in a lifting direction oppositely to the exhalation flow direction
Implementation Method 2
the plate-shaped valve body experiences flow impingement in an exhalation flow direction during an exhalation event, so that the respiratory gas pressure rises on the flow impingement side of the valve body while ambient pressure continues to exist on the negative side of the valve body
Implementation Method 3
The valve body of the known exhalation valve, constituting a plate-shaped valve body, deflects the respiratory gas flow incident upon it through approximately 90 degrees, so that when the valve body is sufficiently far from the end surface, the respiratory gas flows radially through the above-described annular gap
Implementation Method 4
Periodic eddying and local flow detachments can occur in this context in the region between the end surface and valve body, and can cause pressure fluctuations in the exhalation valve
Data Source
AI summary
An exhalation valve for a ventilator apparatus for at least partial instrumental respiratory assistance of a patient, includes a valve housing with a flow passage which extends along a passage trajectory defining a local axial, radial and circumferential direction and along which respiratory air can flow through the valve housing. The valve housing has a housing-side valve sub-formation with a closed end surface which extends around the passage trajectory and towards which a mating surface of a valve body, movable relative to the valve housing and facing the end surface, can be pretensioned by the pretensioning force of a pretensioning device in such a way that the mating surface, when subjected to respiratory gas in an exhalation flow direction counter to the pretensioning force of the pretensioning device, is removable.