Dry Rotary Pump Hydrogen Recirculation Sealing
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Solution Overview
Problem
Existing hydrogen recirculation devices in fuel cell systems face challenges such as hydrogen diffusion through tree seals, leading to potentially dangerous hydrogen concentrations in the engine unit, and contamination of the pump and engine units by water molecules and lubricating liquids.
Innovation Solution
A dry rotary pump with a pressure equalization system, featuring a first and second pair of tree seals and a pressure equalization chamber, which regulates the pressure between the tree joints and the gear chamber, preventing water and lubricant contamination and ensuring safe hydrogen recirculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shaft seal is used to prevent hydrogen leakage from the pumping chamber, then hydrogen safety is improved, but hydrogen gas can still diffuse through the shaft seal into the engine unit, creating explosive atmosphere risk
Solution Approach 1:
A gas barrier layer is introduced as an intermediary substance between the pumping chamber and the engine unit. This barrier layer specifically blocks hydrogen gas diffusion through the shaft seal while allowing other gases to pass, thereby preventing hydrogen accumulation in the engine unit without compromising the sealing function.
Solution Approach 2:
The shaft seal is modified with a localized gas barrier layer that has selective permeability properties. This local modification creates a region with different gas transmission characteristics, allowing the seal to prevent hydrogen diffusion in the critical area while maintaining overall sealing functionality.
2Object-affected harmful factors
If a gas stream is actively introduced into the engine unit to carry away hydrogen, then hydrogen concentration is reduced, but water molecules can enter the pump's drive chamber and motor unit, causing pump malfunction
Solution Approach 1:
The gas barrier layer acts as a selective mediator that allows controlled gas flow into the engine unit to prevent hydrogen accumulation, while simultaneously blocking water molecules from entering the pump's drive chamber and motor unit. This selective permeability resolves the contradiction between hydrogen removal and pump protection.
3Reliability
If the pump is designed to meet maximum external hydrogen leakage standard, then hydrogen safety is improved, but the device complexity increases to meet multiple requirements
Solution Approach 1:
Multiple functions are merged into a single integrated shaft seal structure with a gas barrier layer. The seal simultaneously provides mechanical sealing, hydrogen diffusion prevention, and selective gas permeability, eliminating the need for separate components and reducing overall device complexity while meeting hydrogen leakage standards.
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 prevents premature wear of tree joints, reduces the risk of hydrogen explosion, and maintains the efficiency and reliability of the hydrogen recirculation process by ensuring that water and lubricants do not contaminate the pump and engine units.
Implementation Method 1
a pressure equalization chamber (25) which is in fluidic connection with a gap (24) located between the first shaft seal (19b) and the second shaft seal (20b) of the first and second pairs of shaft seals to regulate the pressure in the gap
Implementation Method 2
hydrogen gas can pass through shaft seals. Hydrogen thus diffuses from the pump chamber into the engine unit
Data Source
Figure 1~1a
Figure 2
Figure 3
AI summary
The present invention relates to a device (1, 30) for recirculating an at least partially gaseous composition containing hydrogen, wherein the device (1, 30) is a dry rotary pump comprising a first rotary shaft (13) and a second rotary shaft (14) respectively driving a first piston with jaws (8) and a second piston with jaws (9) rotating in a pumping chamber (2) comprising an inlet orifice (11) and an outlet orifice (10) for the gaseous composition, the first rotary shaft (13) and the second rotary shaft (14) being configured to be rotated by a drive system (17, 18) located in a gear chamber (4), wherein the device (1, 30) comprises a first pair of seals (19) and a second pair of seals (20), each comprising a first seal (19a, 20a) and a second shaft seal (19b, 20b), the first pair of seals (19) being provided around the first rotary shaft (13) and the second pair of seals (20) being provided around the second rotary shaft (14) between the pumping chamber (2) and the gear chamber (4), wherein the device (1, 30) comprises a pressure equalising chamber (25) that is fluidly connected to a gap (24) present between the first shaft seal (19a, 20a) and the second shaft seal (19b, 20b) of the first and the second pair of shaft seals (19, 20) to regulate the pressure in the gap (24), wherein the gear chamber (4) is fluidly connected to the gap (24), and wherein the pumping chamber (2) is fluidly connected to the first shaft seal (19a) of the first pair of shaft seals (19) and to the first shaft seal (20a) of the second pair of shaft seals (20) by means of a pulse attenuation chamber (22). The present invention also relates to a fuel cell system (40, 50, 60, 70, 80, 90) comprising a recirculation device according to the present invention.