Hermetic Split Valve Bellows for Supercritical CO2 Flow Control
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Solution Overview
Problem
Existing split valves in thermal management systems for vehicles, such as aircraft, face challenges in maintaining the supercritical state of carbon dioxide (sCO2) due to insufficient sealing, which can lead to contamination and pressure drops, affecting the thermal efficiency of the system.
Innovation Solution
The use of hermetically sealed split valves with metallic bellows and intermediate fluid chambers pressurized with inert gas to reduce pressure differentials and prevent contamination, along with the sCO2 acting as the hydraulic fluid to minimize exposure to atmosphere and reduce leakage risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional split valves are used in thermal management systems, then fluid flow regulation is achieved, but sealing insufficiency leads to contamination and pressure drops
Solution Approach 1:
The valve body is divided into multiple sealed chambers (first chamber, second chamber, third chamber) separated by bellows and seals. This segmentation allows independent sealing zones for sCO2 and hydraulic fluid, preventing contamination while maintaining flow regulation functionality.
Solution Approach 2:
A piston acts as an intermediary element between the sCO2 chamber and hydraulic fluid chamber. The piston transmits hydraulic pressure to regulate the valve while being isolated by seals and bellows, preventing direct contact and contamination between the two fluids.
2Reliability
If metallic bellows are used to hermetically seal the valve, then contamination is prevented, but stress on the bellows increases
Solution Approach 1:
Inert gas is introduced as an intermediary medium in the second chamber between the sCO2 chamber and atmosphere. This inert gas cushion reduces pressure differentials across the bellows, preventing direct exposure to atmospheric pressure swings and reducing stress on the metallic bellows while maintaining hermetic sealing.
Solution Approach 2:
The second chamber is pressurized with inert gas to create a protective atmosphere that isolates the metallic bellows from direct pressure differentials between sCO2 and atmosphere. This inert environment reduces mechanical stress on the bellows while maintaining the hermetic seal integrity.
3Ease of operation
If sCO2 is exposed to atmosphere through valve mechanisms, then hydraulic actuation is enabled, but leakage risks and contamination increase
Solution Approach 1:
The valve is segmented into distinct sealed chambers: first chamber for sCO2, second chamber for inert gas, and third chamber for hydraulic fluid. This segmentation enables hydraulic actuation functionality while preventing direct exposure and leakage between sCO2 and atmosphere through multiple sealing barriers including bellows and piston seals.
Solution Approach 2:
The piston and inert gas act as intermediaries that enable hydraulic actuation while isolating sCO2 from atmospheric exposure. The piston transmits hydraulic force through sealed interfaces, and the inert gas cushion maintains pressure balance, allowing operational control without compromising sealing integrity.
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
This solution ensures the sCO2 remains in a supercritical state, maintaining thermal efficiency and extending the lifespan of the split valves by reducing stress on the bellows and preventing contamination, thus enhancing the overall performance of the thermal management system.
Implementation Method 1
a first bellows (218) hermetically sealing the fluid chamber (206) such that the sCO2 is prevented from blending with the hydraulic fluid or the atmosphere
Implementation Method 2
The inclusion of the second fluid chamber (222) pressurized with an inert gas reduces a pressure differential between the sCO2 and an atmosphere adjacent to the split valve
Implementation Method 3
the sCO2 acts as the hydraulic fluid to minimize exposure to atmosphere and reduce leakage risks
Data Source
AI summary
Example split valves for regulating a first flowrate and a second flowrate of a fluid within a closed loop systems are disclosed herein. An example split valve includes an electrohydraulic servo valve coupled to a first piston via a first hydraulic flowline and a second hydraulic flowline, the first piston to include a piston shaft, a first head, and a second head, the first hydraulic flowline to output a first pressure of a hydraulic fluid, the second hydraulic flowline to output a second pressure of the hydraulic fluid, a bellows fixed to at least one of the first head or the second head, the bellows to hermetically seal the fluid from the hydraulic fluid, and a control system connected to the electrohydraulic servo valve, the control system to adjust the first flowrate and the second flowrate of the fluid through a first fluid chamber.