Ejector-Diffuser Cabin Air Distribution Using Low Motive Pressure
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Solution Overview
Problem
Existing air distribution systems in spacecraft are inefficient due to high energy consumption, complexity, and cost, particularly in the need for high-pressure motive fluids and circular converging and diverging sections, which limit their effectiveness and increase mass.
Innovation Solution
A passenger cabin air distribution system utilizing an ejector-diffuser with a secondary inlet and a nozzle featuring an elongated slot-shaped opening to mix conditioned air with cabin air, maintaining low motive pressure and achieving efficient mixing with low backpressure, and optionally incorporating sensors for air quality monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fans are used to pass air throughout the passenger compartment, then air distribution is achieved, but energy consumption increases
Solution Approach 1:
The patent replaces the mechanical fan system with a passive ejector-diffuser system that uses fluid dynamics principles. The ejector nozzle converts pressure energy to kinetic energy, creating a jet that entrains and moves cabin air without mechanical moving parts, thereby eliminating fan energy consumption while maintaining air distribution functionality
Solution Approach 2:
The system uses pneumatic principles by utilizing high-pressure motive air from the ventilation system to drive the ejector nozzle. The pressurized air creates a jet flow that induces and transports additional cabin air through the diffuser, replacing mechanical propulsion with pneumatic-driven fluid dynamics
2Productivity
If multiple ducted cabin air intakes and multiple air distribution discharge points are used, then air distribution coverage is improved, but system mass and complexity increase
Solution Approach 1:
The patent combines multiple air intake functions into a single ejector-diffuser assembly. The device integrates the motive air inlet, induced air intake, mixing chamber, and discharge point into one compact unit, reducing the number of separate ducts and components while maintaining effective air distribution capability
Solution Approach 2:
The ejector-diffuser performs multiple functions simultaneously: it acts as an air intake device, a mixing chamber, a flow amplifier, and a discharge mechanism. This multi-functionality eliminates the need for separate dedicated components for each function, reducing overall system complexity and mass
3Productivity
If an orifice plate is used to provide restriction for proper airflow to avionics branch, then airflow control is achieved, but system complexity and cost increase
Solution Approach 1:
The patent controls airflow parameters by changing the geometric parameters of the ejector-diffuser components, specifically the nozzle area ratio and diffuser angle. By optimizing these geometric parameters, the system achieves proper airflow distribution to the avionics branch without requiring additional restrictive components like orifice plates
4Productivity
If high-pressure motive fluid is used in known ejector-diffusers, then airflow induction is achieved, but motive pressure requirements increase system complexity
Solution Approach 1:
The patent changes the pressure parameter by optimizing the nozzle area ratio to a specific range (0.2 to 0.5). This parameter optimization allows the ejector to achieve effective airflow induction with significantly reduced motive pressure requirements compared to conventional designs, making the system compatible with lower-pressure ventilation sources
5Productivity
If circular converging and diverging sections are used in ejector-diffusers, then flow efficiency is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent employs asymmetric rectangular cross-sections for the converging and diverging sections instead of symmetric circular shapes. This asymmetric rectangular geometry maintains the necessary flow convergence and divergence characteristics while being significantly easier to manufacture using standard sheet metal forming and fabrication processes
Solution Approach 2:
The patent modifies the curvature requirements by using rectangular sections with controlled corner radii instead of fully circular cross-sections. This approach maintains sufficient flow smoothness for efficiency while dramatically simplifying manufacturing, as rectangular ducts are standard in HVAC systems and require minimal specialized forming
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 system achieves efficient air distribution with reduced energy consumption and lower costs by using existing pressure differences, providing a more uniform and increased airflow with a lower absolute pressure ratio, enhancing air quality diagnostics and reducing system complexity.
Implementation Method 1
The motive fluid nozzle 410 is supplied with a motive fluid 411 having a high pressure. The motive fluid nozzle 410 creates an injected flow at a higher velocity and lower pressure.
Implementation Method 2
The mixed flow passes through the diverging outlet cone 465, which slows the mixture down and increases its pressure to a mixture 460 having a pressure greater than the pressure of the low-pressure inlet fluid 451.
Implementation Method 3
The motive fluid 411 expands to a pressure below a pressure of the low-pressure inlet fluid 451, which is drawn by the pressure differential through side opening 450 and combined with the motive fluid 411.
Data Source
AI summary
A passenger cabin air distribution system includes a ventilation system and an ejector-diffuser. The ventilation system is operable to provide a conditioned air. The ejector-diffuser is positioned to receive a flow of the conditioned air from the ventilation system. The ejector-diffuser includes an induction unit and a diffuser section. The induction unit includes a secondary inlet in communication with a cabin air from a passenger cabin and is configured to mix the flow of the conditioned air with an induced flow of the cabin air into a mixed air. The diffuser section includes a discharge to eject the mixed air to the passenger cabin. The diffuser section is shaped to provide for efficient mixing with low backpressure in order to maintain the low motive pressure in the nozzle.