Converging-diverging nozzle for supersonic fire suppressant dispersion
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Solution Overview
Problem
Efficient dispersion of dry chemical fire suppressants in cluttered aircraft engine nacelles and auxiliary power units is challenging due to rapid settling and adherence to surfaces, as standard cone nozzles result in quickly expanding sprays that mix with ambient air, leading to inadequate airborne agent concentrations.
Innovation Solution
A converging-diverging nozzle with a cone having axial segments of varying angles and a convex transition between them, which accelerates the suppressant flow from sub-sonic to supersonic speeds, ensuring better mixing and penetration by converting stored energy into kinetic energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a standard cone nozzle is used, then the spray expands rapidly, but the agent mixes quickly with ambient air and settles on surfaces
Solution Approach 1:
The cone is divided into multiple axial segments with different cone angles. The first segment has a steeper angle for initial rapid expansion, while subsequent segments have progressively smaller angles to control the expansion rate and maintain agent concentration in the airflow.
Solution Approach 2:
Different portions of the cone have different geometric properties (cone angles). The upstream portion has a steeper angle to accelerate flow quickly, while the downstream portions have progressively flatter angles to sustain supersonic flow and prevent premature mixing with ambient air.
2Length of moving object
If the spray expands rapidly, then penetration distance increases, but the agent adheres to surfaces in cluttered zones
Solution Approach 1:
The nozzle creates a dynamic supersonic flow regime that changes the physical state of the agent delivery. By achieving supersonic speeds through the converging-diverging passage, the agent is delivered with sufficient kinetic energy to penetrate cluttered zones while maintaining airborne concentration longer before settling.
3Productivity
If compressed gas is used to carry the agent, then the agent is delivered through the piping system, but the agent settles quickly in the designated fire zone
Solution Approach 1:
The nozzle changes the flow parameters by converting subsonic compressed gas flow into supersonic flow through the converging-diverging geometry. This parameter change (Mach number increase) extends the airborne duration of the agent by reducing settling velocity and maintaining higher kinetic energy in the dispersed particles.
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 nozzle achieves high velocity outputs that efficiently distribute fire suppressants, reducing settling on surfaces and ensuring effective mixing with ambient air, thereby improving dispersion in cluttered fire zones.
Implementation Method 1
A source of suppressant that is a mixture of powder and gas, and the inlet of the nozzle is fluidly coupled to the source of suppressant. The source of suppressant is pressurized to 800-10,000 psi and pressure at the outlet is atmospheric pressure or less.
Implementation Method 2
the suppressant flow in the throat region along the first segment of the cone approaches Mach 1, and the suppressant flow along the second segment of the cone is greater than Mach 1
Data Source
AI summary
A fire suppressant system, including: a nozzle having a passage wall that defines a converging-diverging passage, having: an inlet, an outlet downstream of the inlet, and a throat region that includes a converging portion and a diverging portion; a cone within the passage, having an upstream apex located within the diverging portion and a downstream end located within the passage and adjacent to the outlet, the cone has a radial outer wall that defines an exhaust passage with the passage wall, and the cone has a plurality of axial segments with differing segment cone angles, including: a first segment at the upstream apex of the cone that has a first cone angle such that the exhaust passage narrows along the first segment; and a second segment that is adjacent to the first segment and that has a second cone angle such that the exhaust passage expands along the second segment.