Hydrogen Engine Braking via Supercharger Speed and Restriction
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Solution Overview
Problem
Hydrogen internal combustion engines (H2 ICE) with reduced compression ratios face significant reductions in braking power, which is essential for safe and effective braking.
Innovation Solution
The implementation of a supercharger that operates at a higher speed during engine braking mode, combined with a restriction mechanism to increase the pressure ratio across the supercharger, enhances the available braking power by increasing cylinder pressure during intake events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the compression ratio is reduced to prevent auto-ignition in hydrogen engines, then safety is improved, but braking power is significantly reduced
Solution Approach 1:
The supercharger compresses air before it enters the cylinder during the intake stroke, pre-pressurizing the air charge. This preliminary compression action increases the cylinder pressure during braking operations without requiring a higher engine compression ratio, thereby maintaining safety while improving braking power.
Solution Approach 2:
The system changes the pressure parameter of the air charge by using a supercharger to compress air to higher pressures before intake. This parameter change allows the engine to achieve sufficient braking power with a reduced compression ratio, resolving the contradiction between safety and braking performance.
2Reliability
If the compression ratio is reduced to prevent auto-ignition, then safety is improved, but the braking power matches only 25-30% of traditional engines
Solution Approach 1:
The supercharger performs preliminary compression of air before it enters the cylinder, ensuring that the air charge is already pressurized during the intake stroke. This preliminary action compensates for the reduced compression ratio effect, maintaining effective braking performance while preserving safety.
Solution Approach 2:
By changing the pressure parameter through supercharging, the system achieves sufficient cylinder pressure for effective braking despite the reduced compression ratio, thereby maintaining both safety and braking effectiveness.
3Power
If a supercharger operates at higher speed during braking mode, then braking power is increased, but energy consumption increases
Solution Approach 1:
The supercharger's rotational speed is dynamically adjusted based on operating conditions. During braking operations, the supercharger operates at higher speed to increase braking power. During normal propulsion, it operates at lower speed to reduce parasitic energy consumption. This dynamic operation resolves the contradiction between braking power and energy efficiency.
Solution Approach 2:
The supercharger operates at high speed only during periodic braking events rather than continuously. This periodic high-speed operation provides sufficient braking power when needed while minimizing overall energy consumption during propulsion phases.
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 approach significantly increases the braking power of H2 ICE engines, addressing the limitations of reduced compression ratios and providing a more effective engine braking solution.
Implementation Method 1
adding, during the first intake stroke, additional air into the cylinder with an air compressor; compressing the air in the cylinder during a compression stroke by the piston; and releasing the compressed air from the cylinder
Implementation Method 2
In the engine braking mode, the supercharger operates at a second rotational speed to deliver air to the intake manifold and a restriction is provided to increase a pressure ratio across the supercharger
Data Source
AI summary
A method of operating a system including a hydrogen internal combustion engine and a supercharger between a normal operating mode and an engine braking mode. In the normal operating mode, the supercharger operates at a first rotational speed to deliver air to an intake manifold of the engine. In the engine braking mode, the supercharger operates at a second rotational speed to deliver air to the intake manifold and a restriction is provided to increase a pressure ratio across the supercharger.