Passive Bleed Valve Noise Attenuation in Gas Turbine
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Solution Overview
Problem
Aircraft engine pneumatic systems, particularly bleed pipes, often induce undesired noises and vibrations due to flow instabilities and resonating cavities, which can damage components and cause unpleasant cabin or external noises.
Innovation Solution
Incorporating a non-actuated, passive second valve with pivotable gates located at the bleed port, which opens due to pressure differentials to reduce the volume of closed-ended cavities and prevent noise phenomena, acting as a one-way valve to control airflow and mitigate tonal noise and vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a pipe is used to draw air from the bypass duct, then air can be fed downstream for other uses, but undesired noises and vibrations are induced
Solution Approach 1:
A passive valve is introduced as an intermediary component in the air extraction system. The valve includes a body with a flow passage and a movable element that selectively blocks or opens the passage. This intermediary device mediates between the bypass duct and the extraction system, allowing air to be drawn when needed while preventing flow instabilities and resonating cavity effects that cause noise and vibration.
Solution Approach 2:
The system changes the flow parameters by using a passive valve that responds to pressure differentials. When the downstream pressure exceeds the upstream pressure by a threshold amount, the movable element opens to allow flow. This parameter-based control prevents continuous flow instabilities and eliminates the conditions that generate tonal noise and vibrations while maintaining the ability to feed air downstream when required.
2Productivity
If air is drawn from the bypass duct, then downstream systems can be supplied, but flow instabilities and resonating cavities occur
Solution Approach 1:
The passive valve acts as a mediator that stabilizes the flow between the bypass duct and downstream systems. By introducing this intermediate control element, the system achieves stable air supply when needed while preventing the flow instabilities and resonating cavity effects that would otherwise occur during air extraction.
Solution Approach 2:
The passive valve operates autonomously based on pressure differential conditions without requiring external control signals. The movable element automatically opens when downstream pressure exceeds upstream pressure by a threshold amount and closes when the differential decreases, providing self-regulating flow stability that ensures consistent air supply to downstream systems while eliminating flow instabilities.
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 effectively attenuates noise and reduces vibrations by ensuring airflow only in the intended direction, preventing backflow and resonance, thus enhancing the operational stability and quietness of the aircraft engine.
Implementation Method 1
the non-actuated valve moving from the second closed configuration to the second open configuration following a pressure differential across the second valve greater than a pressure threshold
Implementation Method 2
opens due to pressure differentials to reduce the volume of closed-ended cavities and prevent noise phenomena
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
An aircraft engine (10), has: a duct (22) having an inlet, an outlet, and a bleed port (24) through a wall (21) of the duct (22); a bleed conduit (30) stemming from the duct (22); a first valve (33) connected to the bleed conduit (30) and having an open configuration and a closed configuration; and a second valve (34) connected to the bleed conduit (30) upstream of the first valve (33) and at or proximate the bleed port (24), the second valve (34) having a second open configuration and a second closed configuration, wherein when in the second closed configuration, the second valve (34) blocks fluid communication between the bleed port (24) and the first valve (33) such that a portion of the bleed conduit (30) between the first valve (33) and the second valve (34) is fluidly isolated from the duct (22), the second valve (34) being in the second open configuration when the first valve (33) is in the open configuration.