Uniform Flow Supply Duct Using Restrictor Plates
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Solution Overview
Problem
Ventilation systems in aircraft and other vehicles face challenges in achieving uniform air distribution due to the manifold effect, which causes non-uniform flow rates along supply ducts, leading to increased static pressure and noise, and existing solutions either increase costs, complexity, or compromise comfort and safety.
Innovation Solution
A supply duct design featuring a main compartment with uniformly spaced restrictor plates that maintain a constant cross-section and control pressure drops to ensure a consistent flow rate per unit length, using identical restrictor plates to balance pressure and flow across the duct.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the supply duct is lengthened to extend further into the compartment, then the air distribution coverage is improved, but the static pressure rises non-uniformly causing flow distribution problems
Solution Approach 1:
The patent applies local quality by varying the nozzle characteristics along the duct length. Specifically, nozzles in different sections have different flow coefficients (Cv values) - upstream nozzles have larger openings while downstream nozzles have smaller openings. This local variation compensates for the increasing static pressure along the duct, ensuring uniform flow distribution throughout the entire compartment.
Solution Approach 2:
The patent changes physical parameters of the nozzles along the duct length. The nozzle flow coefficient (Cv) is varied as a parameter to compensate for static pressure changes. By adjusting the nozzle opening size and geometry, the system maintains constant flow rate per unit length despite the changing pressure conditions along the duct.
2Stress or pressure
If the nozzle opening size is reduced to decrease static pressure rise, then the flow rate uniformity is improved, but more fan power is required and noise increases
Solution Approach 1:
Instead of uniformly reducing all nozzle openings, the patent applies local quality by making each nozzle's opening size specific to its location. Upstream nozzles maintain larger openings while downstream nozzles have smaller openings. This localized adjustment achieves pressure balance without requiring overall reduction in flow capacity, thus avoiding increased fan power requirements.
Solution Approach 2:
The patent converts the harmful effect of static pressure rise into a beneficial design feature. Rather than fighting against the pressure increase, the design uses it to inform the nozzle sizing strategy. The natural pressure gradient is leveraged to determine the optimal nozzle Cv values at each location, transforming a problem into a solution guide.
3Productivity
If different sized nozzle orifices are used in downstream portions, then the flow rate uniformity is improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent changes the nozzle flow coefficient parameter systematically along the duct. By establishing a mathematical relationship between nozzle Cv value and position along the duct, the design provides a clear manufacturing specification. This parameter variation can be implemented through standardized nozzle families with different Cv ratings, making manufacturing feasible while achieving flow uniformity.
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 achieves a uniform air flow rate along the duct, reducing noise and complexity while maintaining comfort and safety, and allowing for easier manufacturing and assembly by using identical parts and minimizing pressure variations.
Implementation Method 1
The restrictors are configured to create a pressure drop thereacross the main compartment that is equal to a rise in static pressure from the source to a point downstream
Implementation Method 2
This rise in static pressure in turn creates a larger pressure gradient across the outlet of the nozzle, resulting in more air flow out of the nozzle
Data Source
AI summary
A supply duct is provided for supplying a gaseous fluid at a constant flow rate per unit length of the duct. The supply duct includes a main compartment, at least one nozzle disposed in the main compartment, and a plurality of restrictors extending from an inner wall of the main compartment. The main compartment of the supply duct has a generally constant cross-section. Each nozzle in the main compartment defines an outlet to allow a gaseous fluid to flow out from the main compartment. Each restrictor is configured to produce a flow rate through the nozzle at the first end of the main compartment that is substantially equal to the flow rate through the nozzle at the second end of the main compartment. The restrictor may be, for example, a restrictor plate. A method of sizing restrictor plates is also provided.