Fuel Cell Air Compressor Hub Channels for Axial Force Balance
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Solution Overview
Problem
Turbomachines used to supply air to fuel cell systems face inefficiencies due to high axial forces requiring large axial bearings, which lead to significant power loss and additional cooling needs, diverting a portion of compressed air and reducing system efficiency.
Innovation Solution
The turbomachine incorporates air channels in the hub portion to balance axial forces on the compressor wheel, reducing power loss in axial bearings and cooling requirements, while also using air channels to cool bearings and the electric motor, potentially recovering energy through an internally ventilated axial bearing disk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the compressor wheel speed is limited to 100,000-125,000 rpm due to control and strength constraints, then the electric motor remains controllable and structurally sound, but the compressor outlet pressure becomes insufficient and requires larger compressor wheel diameters
Solution Approach 1:
The patent changes the pressure distribution parameter by introducing air channels that supply compressed air to the rear side of the compressor wheel, creating a pressure balance that compensates for the reduced peripheral speed effect, allowing adequate outlet pressure at lower speeds
2Force
If larger axial bearings are used to handle high axial forces from large diameter compressor wheels, then the bearing capacity is sufficient, but the power loss increases significantly with axial bearings accounting for 2/3 of total bearing losses
Solution Approach 1:
The patent applies a counterbalancing pressure force by directing compressed air through channels to the rear side of the compressor wheel, creating a pressure differential that counteracts the axial thrust force, thereby reducing the load on axial bearings and minimizing energy losses
3Reliability
If foil air bearings are used to keep the system oil-free, then the fuel cell system remains contamination-free, but air friction losses occur requiring additional cooling air that diminishes system efficiency
Solution Approach 1:
The patent converts the harmful axial thrust force into a beneficial effect by using it to drive air flow through the air channels to the rear side of the compressor wheel, which simultaneously balances the axial forces and provides cooling to the bearing and motor without requiring additional cooling air
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 design enhances the efficiency of the turbomachine by minimizing power loss and cooling air requirements, increasing robustness against external accelerations, and potentially recovering energy from the cooling process.
Implementation Method 1
at least one air channel is formed in the hub portion, by means of which air channel a compressor inlet is connected to an annular space on the side of the compressor wheel facing away from the compressor inlet, thus ensuring that substantially the same air pressure is present on both sides of the compressor wheel
Implementation Method 2
the cooling air is usually diverted downstream of a charge-air cooler of the fuel cell system
Implementation Method 3
the cooling air can be fed to the turbomachine
Data Source
AI summary
The invention relates to a turbomachine (1) for supplying air to a fuel cell system, comprising at least one compressor wheel (3) conjointly connected to a shaft (2), and an electric motor (4) for driving the shaft (2), the compressor wheel (3) being connected via a hub portion (5) to a preferably hollow-cylinder-shaped shaft portion (6) of the shaft (2). According to the invention, at least one air channel (7, 8) is formed in the hub portion (5), by means of which air channel a compressor inlet (9) is connected to an annular space (10) on the side of the compressor wheel (3) facing away from the compressor inlet (9) such that substantially the same air pressure is present on both sides of the compressor wheel (3). The invention further relates to a method for operating a turbomachine (1).