Hermetic Split Valve 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 contamination and pressure leaks, which affect the thermal efficiency and operational effectiveness of the system.
Innovation Solution
The implementation of split valves with hermetic seals, including bellows and intermediate fluid chambers pressurized with inert gas, to prevent contamination and maintain high pressures, along with the use of sCO2 as a hydraulic fluid to actuate the piston, ensuring the sCO2 remains in a supercritical state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional split valves are used to regulate fluid flow, then flow control is achieved, but contamination and pressure leaks occur affecting supercritical state maintenance
Solution Approach 1:
A bellows component is introduced as an intermediary element that hermetically seals the piston chamber, preventing direct contact between the hydraulic fluid and the sCO2 fluid. This intermediary structure eliminates contamination pathways while maintaining flow control functionality.
Solution Approach 2:
The bellows creates a hermetic seal that maintains an inert environment around the piston, preventing external contaminants from entering the sCO2 fluid path. This hermetic sealing ensures the fluid remains free from contamination that would degrade its supercritical properties.
2Productivity
If split valves are used to control fluid flow paths, then thermal management control is improved, but pressure drops occur reducing system efficiency
Solution Approach 1:
The bellows acts as a mediator that transmits hydraulic pressure to the piston without allowing pressure leakage into the sCO2 fluid path. This intermediary mechanism ensures pressure is maintained in the supercritical fluid while enabling flow control.
Solution Approach 2:
The hermetic seal created by the bellows maintains a pressure-stable inert environment for the sCO2 fluid, preventing pressure drops that would occur with conventional valve designs. This ensures the fluid remains in the supercritical state during flow regulation.
3Reliability
If hermetic seals with bellows are implemented to prevent contamination, then supercritical state maintenance is improved, but device complexity increases
Solution Approach 1:
The bellows is constructed as a flexible hermetic seal that expands and contracts with piston movement while maintaining the seal. This flexible shell design provides contamination protection without requiring complex rigid sealing mechanisms, reducing overall structural complexity.
Solution Approach 2:
The bellows utilizes pneumatic principles to maintain hermetic sealing through pressure differential, where the sealed chamber maintains pressure balance to prevent leakage. This pneumatic approach simplifies the sealing mechanism compared to mechanical contact seals.
4Use of energy by moving object
If sCO2 is used as hydraulic fluid to actuate piston, then thermal efficiency is maintained, but pressure control precision is challenged
Solution Approach 1:
The bellows serves as an intermediary that isolates the sCO2 hydraulic fluid from the sCO2 thermal fluid paths, preventing contamination while allowing pressure actuation. This separation maintains the purity of both fluid paths for optimal thermal efficiency and pressure control.
Solution Approach 2:
The system utilizes phase and pressure parameter changes of sCO2 to enable both hydraulic actuation and thermal management functions. By carefully controlling pressure and temperature parameters, the sCO2 maintains supercritical state for efficient heat transfer while providing adequate hydraulic pressure for piston actuation.
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 effectively prevents contamination and pressure drops, maintaining the sCO2 in a supercritical state, thereby enhancing the thermal management system's efficiency and operational reliability.
Implementation Method 1
The bellows hermetically seal the fluid chamber such that the fluid within the fluid chamber is sealed from contamination
Implementation Method 2
The electrohydraulic servo valve pressurizes the sCO2 and the pressurized sCO2 acts as a hydraulic fluid to actuate a piston
Implementation Method 3
The inclusion of the intermediate fluid chamber pressurized with an inert gas provides a cascading pressure that maintains the sCO2 in a supercritical state
Implementation Method 4
Some thermal management systems that include sCO2 flowing through a thermal transport bus typically keep the sCO2 above a minimum temperature (e.g., 305 Kelvin (K), etc.) and a minimum pressure (e.g., 1150 pound-force per square inch (psi), etc.) to maintain the supercritical fluid state of the carbon dioxide
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; one or more bellows fixed to at least one of the first head or the second head, the one or more bellows to hermetically seal the fluid from a 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, the first piston to be located in the first fluid chamber.