Ram Air Fan Diffuser Perforated Cone Noise Reduction
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Solution Overview
Problem
At lower flight speeds or on the ground, the ram air pressure is insufficient to provide adequate airflow across heat exchangers in aircraft environmental control systems, leading to inefficient heat removal, and existing ram air fans generate noise and have weight and efficiency issues.
Innovation Solution
A diffuser for the ram air fan assembly featuring a perforated cone with a frustoconical shape and ring seals, which reduces air pressure and flow velocity, enhancing efficiency and noise reduction through diffusion and acoustic foam damping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a traditional ram air fan is used without a diffuser, then the fan structure is simpler and lighter, but the airflow efficiency is insufficient and noise is higher
Solution Approach 1:
The diffuser is divided into multiple segments including a conical diffuser section, a cylindrical section, and a perforated section. Each segment performs a specific function: the conical section diffuses airflow, the cylindrical section maintains flow, and the perforated section creates acoustic damping. This segmentation allows the complex diffuser to achieve superior airflow efficiency and noise reduction while maintaining manufacturability through modular construction.
2Reliability
If the aircraft flies at lower speeds or on the ground, then ram air pressure is insufficient for adequate heat removal, but increasing fan power to compensate increases weight and noise
Solution Approach 1:
The diffuser is positioned upstream of the fan inlet to pre-condition the airflow before it enters the fan. By diffusing and slowing the incoming air in advance, the system improves heat exchanger effectiveness without requiring additional fan power, thus avoiding increased weight while maintaining reliable heat removal at low flight speeds.
3Object-generated harmful factors
If the diffuser reduces flow velocity to reduce noise, then noise is reduced, but the airflow volume may decrease
Solution Approach 1:
The diffuser employs different structural characteristics in different zones: the conical section provides gradual diffusion to reduce velocity and noise, while the perforated section with acoustic foam provides localized noise damping. This local differentiation allows noise reduction in specific areas without compromising overall airflow volume, as each zone is optimized for its specific function.
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 diffuser improves airflow efficiency and reduces noise by diffusing air flow and utilizing acoustic foam to dampen vibrations, ensuring effective heat removal and operational efficiency even at low air pressures.
Implementation Method 1
The present invention is a diffuser for a ram air fan that helps direct a flow of air from a ram air fan rotor in such a way as to diffuse the fan air flow
Implementation Method 2
reduce noise generated by the aircraft... utilizing acoustic foam to dampen vibrations
Data Source
AI summary
A diffuser for a ram air fan assembly includes a perforated cone, an inlet ring seal, and an outlet ring seal. The perforated cone has a frustoconical shape symmetrical about an axis of the diffuser. The inlet ring seal is attached to, and axially disposed about, a first end of the perforated cone. The inlet ring seal includes a fan housing connection having a cylindrical shape. The outlet ring seal is attached to, and axially disposed about, a second end of the perforated cone. An average external diameter of the second end is greater than an average external diameter of the first end such that the perforated cone extends away from the inlet ring seal and radially outward from the axis of the diffuser.