Split Cycle Engine Exhaust Valve Timing for Braking
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Solution Overview
Problem
Existing split-cycle internal combustion engines face challenges in optimizing engine braking power and reliability due to thermal limitations, particularly in the combustion cylinder, which can lead to material distortion and altered injections under high pressure.
Innovation Solution
The exhaust valve is opened 180° earlier than normal in engine brake mode, and the combustion cylinder is modified to cooperate with the compressor cylinder by allowing air flow from the exhaust line, optimizing the braking power and cooling the combustion chamber to prevent thermal overload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the exhaust valve is opened 180° earlier in engine brake mode, then the braking power is enhanced and thermal load is reduced, but the valve timing complexity increases
Solution Approach 1:
The valve timing system is made dynamic by switching between normal firing timing and engine brake timing (180° advanced exhaust valve opening) based on operating mode. This allows the system to optimize braking power when needed while maintaining normal operation otherwise, resolving the contradiction between enhanced braking capability and operational complexity.
Solution Approach 2:
The exhaust valve timing parameter is changed by 180° advancement during engine brake mode. This parameter change enables the combustion cylinder to cooperate with the compressor cylinder, allowing compressed air to flow directly to the exhaust line and enhancing braking power while managing thermal load.
2Power
If the combustion cylinder cooperates with the compressor cylinder to discharge compressed air directly to exhaust line, then the braking power is optimized and cooling is improved, but the thermal management complexity increases
Solution Approach 1:
The combustion cylinder and compressor cylinder are merged in function during engine brake mode, with compressed air from the compressor cylinder flowing directly through the combustion cylinder to the exhaust line. This merging eliminates the need for separate thermal management systems for each cylinder, optimizing braking power while managing thermal load through the existing exhaust pathway.
Solution Approach 2:
A continuous flow of compressed air is maintained from the compressor cylinder through the combustion cylinder to the exhaust line during engine brake mode. This continuous action ensures constant cooling of the combustion chamber and sustained braking power, preventing thermal overload without requiring intermittent cooling interventions.
3Reliability
If the continuous flow of cold air is maintained through the engine, then the thermal load is evacuated and reliability is improved, but the energy loss increases
Solution Approach 1:
The cold air flow that would normally represent an energy loss is converted into a beneficial cooling mechanism during engine brake mode. The continuous flow of cold air from the compressor cylinder through the combustion cylinder to the exhaust line evacuates thermal load effectively, improving reliability while the energy 'loss' is actually utilized for thermal management.
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 enhances braking power and engine reliability by dissipating compression work through continuous air flow, keeping temperatures within structural limits, thus preventing material distortion and ensuring stable engine operation.
Implementation Method 1
the compressor cylinder passes through the combustion cylinder reaching directly the exhaust line. This ensures that the air coming from the compressor cylinder is discharged before any positive work can be carried out during the expansion of the combustion cylinder.
Implementation Method 2
The lack of this constant flow of air which, initially cold sucked and brought by compression even at 700°C, evacuates the thermal power and leads the engine head to operate beyond its structural limits
Data Source
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AI summary
Split-cycle internal combustion engine comprising at least one compressor cylinder (H) associated with a relating piston and a relating head, at least one combustion cylinder (E) associated with a relating piston and a relating head, equipped with at least one admission valve (IN) and one exhaust valve (EX) of the combustor piston (E), first control means of said at least one admission valve and second control means of said at least one exhaust valve, wherein the piston of the combustion cylinder is associated with a crankshaft by means of a crank mechanism and wherein when the engine is in a firing condition said second control means are arranged to cause a first opening event of the at least one exhaust valve in a first predetermined angular position (EXF) of the crankshaft and wherein when the engine is in the engine braking condition said second means are arranged to reposition said first event in a second predetermined angular position (EXB, EXB_1) out of phase by about 180 degrees with respect to said first angular position.