Bleed Air Heat Ejector Mixing via Vortex Generators
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Solution Overview
Problem
Traditional bleed air heat ejectors in aircraft environmental control systems often produce air that is excessively hot, requiring careful mixing with ambient air to achieve uniform heating, but they can still fail to provide optimal temperature uniformity.
Innovation Solution
A bleed air heat ejector design featuring a housing with a dispenser and vortex generators, secondary jets, and angled primary jets to enhance mixing of bleed and ambient air, creating a venturi effect that promotes swirl and converging flows for improved temperature uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional bleed air ejectors are used to heat the cabin, then hot bleed air can be provided, but the exit air temperature becomes excessively hot and temperature uniformity deteriorates
Solution Approach 1:
The single large mixing chamber is segmented into multiple smaller chambers with multiple apertures distributed throughout. This segmentation allows for distributed injection of bleed air into the ambient air stream, creating multiple localized mixing zones that collectively achieve uniform temperature distribution across the entire outlet, preventing excessive hot spots while maintaining overall temperature uniformity
Solution Approach 2:
Different regions of the mixing chamber are designed with different aperture distributions and orientations. Apertures are strategically positioned and angled to create localized flow patterns that promote thorough mixing in specific zones. This local optimization ensures that each region contributes to overall temperature uniformity, with particular attention to areas that would otherwise develop temperature stratification
2Temperature
If more ambient air is mixed with bleed air to reduce exit temperature, then temperature uniformity improves, but the heating efficiency decreases
Solution Approach 1:
The system pre-mixes bleed air with ambient air in controlled proportions within the mixing chamber before delivery to the cabin. By establishing the correct mixture ratio in advance through the aperture distribution design, the system achieves uniform temperature output without requiring excessive ambient air intake, thereby maintaining heating efficiency while ensuring temperature uniformity
Solution Approach 2:
The system utilizes pneumatic principles to leverage the high-velocity bleed air stream to draw in and mix with ambient air through the apertures. The kinetic energy of the bleed air creates a suction effect that pulls ambient air through the apertures and mixes it thoroughly, achieving efficient mixing without requiring additional power input or excessive ambient air volumes
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 superior mixing and heat output with a lower exit temperature, providing more uniform air flow compared to traditional systems.
Implementation Method 1
The inner passage can define a venturi with a throat
Implementation Method 2
A plurality of vortex generators can be mounted in the inner passage downstream of the apertures in the inner chamber, wherein the vortex generators are configured to promote mixing of bleed and ambient air
Implementation Method 3
The secondary jets can be angled to direct converging flows into the inner passage. It is also contemplated that the secondary jets can be angled to direct tangential flows into the inner passage for circumferential swirl about the inner passage
Data Source
AI summary
A bleed air heat ejector includes a housing defining an inner passage extending in an axial direction from an inlet of the housing to an outlet of the housing, wherein the inlet is configured to channel ambient air into the housing, and wherein the outlet is configured to channel mixed heated and ambient air out of the housing. A dispenser is mounted in the housing between the inlet and the outlet. The dispenser includes an inner chamber configured to receive heated air from a bleed line. The dispenser includes a plurality of apertures therein for issuing heated air from the inner chamber into the inner passage of the housing to form a flow of mixed ambient and bleed air. The apertures of the inner chamber can be angled primary jets, vortex generators can be included, and/or secondary jets can be included to promote mixing of bleed and ambient air.