First-Stage Pressure Reducer Bushing to Prevent Adiabatic Cooling Jamming
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Solution Overview
Problem
Existing self-contained breathing apparatus (SCBA) systems face reliability and safety issues due to extreme cooling caused by adiabatic expansion of breathing gas in the first stage pressure reducer, especially in extreme temperature environments.
Innovation Solution
A first stage pressure reducer design that incorporates a bushing disposed coaxially with the piston bore and around the piston, which separates the piston from the piston bore, reducing contact and thus minimizing the impact of adiabatic cooling. The bushing is isolated from the higher-pressure region by a sealing element, reducing longitudinal forces and preventing jamming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the piston directly contacts the piston bore during pressure reduction, then the pressure reducer can maintain structural simplicity, but the adiabatic cooling causes extreme cooling of components resulting in reliability and safety issues
Solution Approach 1:
A bushing is introduced as an intermediary component between the piston and the piston bore. The bushing is disposed coaxially with the piston bore and around the piston, arranged to engage the piston and inhibit direct contact between the piston and piston bore. This intermediary element protects the piston from the harmful effects of adiabatic cooling while maintaining the pressure reduction function.
Solution Approach 2:
The pressure reducer is divided into distinct functional zones: a higher-pressure region for receiving high-pressure gas, a lower-pressure region for receiving reduced-pressure gas, and a piston bore connecting these regions. The piston moves reciprocally through the piston bore to transfer gas between regions, allowing pressure reduction while isolating components from extreme cooling effects.
2Productivity
If the piston moves reciprocally through the piston bore to transfer gas, then pressure reduction function is achieved, but adiabatic cooling causes extreme cooling of reducer components
Solution Approach 1:
The bushing is extracted from the higher-pressure region by the sealing element, which is arranged between the higher-pressure region and the bushing. The sealing element isolates the bushing from the higher-pressure region and inhibits fluid ingress flow along the ingress path defined between the external surface of the piston and the internal surface of the piston bore. This extraction protects the bushing from the harmful high-pressure gas and adiabatic cooling effects.
3Force
If the bushing is isolated from the higher-pressure region by a sealing element, then longitudinal forces on the bushing are reduced, but the device complexity increases
Solution Approach 1:
The sealing element acts as a mediator between the higher-pressure region and the bushing. It isolates the bushing from the higher-pressure region and inhibits fluid ingress flow, thereby reducing the longitudinal forces acting on the bushing. The sealing element is configured to seal against the piston, preventing high-pressure gas from contacting the bushing.
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 effectively decouples adiabatic cooling from the performance of the pressure reducer, enhancing the reliability and safety of the SCBA system by preventing component jamming and maintaining operational efficiency across a wide range of temperatures.
Implementation Method 1
a sealing element arranged between the higher-pressure region and the bushing, the sealing element configured to isolate the bushing from the higher-pressure region
Implementation Method 2
the expansion (i.e., reduction of pressure) of breathing gas in the first stage pressure reducer causes a significant degree of adiabatic cooling
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
There is disclosed a first stage pressure reducer (20) for a breathing apparatus comprising: a body (210) defining a cavity (211), the cavity (211) having a higher-pressure region (212) configured to receive higher-pressure gas from a gas source, a lower-pressure region (214) configured to receive lower-pressure gas from the higher-pressure region (212), and a piston bore (260), the piston bore (260) connecting the higher-pressure region (212) and the lower-pressure region (214); a piston (220) configured to move reciprocally through the piston bore (260), and further configured to transfer gas from the higher-pressure region (212) to the lower-pressure region (214); a bushing (240) disposed coaxially with the piston bore (260) and around at least a portion of the piston (220), the bushing (240) arranged to engage the piston (220) and inhibit contact between the piston (220) and the piston bore (260); and a sealing element (230) arranged between the higher-pressure region (212) and the bushing (240), the sealing element (230) configured to isolate the bushing (240) from the higher-pressure region (212). Also disclosed is a self-contained breathing apparatus comprising a first stage pressure reducer (20).