Miller Cycle Engine Air-Path Reversion Management
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Solution Overview
Problem
Miller Cycle engines face issues with residual heat in the combustion chamber causing higher air/fuel mixture temperatures, reducing charge air cooler efficiency, and leading to unintentional detonation and delayed gas flow due to recirculated exhaust gases, which oppose the intake stroke flow direction.
Innovation Solution
Injecting compressed air into the intake port during the compression stroke when the intake valve is open to reduce the amount of air/fuel mixture reverted to the intake manifold, cool the charge air, and reverse the momentum of the air/fuel mixture, thereby enhancing mixing and atomization and improving engine responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the intake valve is kept open during the first portion of the compression stroke in a Miller Cycle engine, then the compression ratio is increased and thermodynamic efficiency is improved, but residual heat in the combustion chamber causes higher air/fuel mixture temperatures which reduces charge air cooler efficiency and may cause unintentional detonation
Solution Approach 1:
The system performs preliminary cooling of the air charge before it enters the combustion chamber during the intake stroke. The charge air cooler is activated in advance to reduce the temperature of the incoming air, preventing the air/fuel mixture from becoming too hot during the compression stroke when the intake valve is open, thereby avoiding detonation while maintaining the Miller Cycle efficiency benefits.
Solution Approach 2:
The patent introduces an intermediary cooling system (charge air cooler) between the air source and the combustion chamber. This intermediary component actively removes heat from the air charge, mediating the temperature issue caused by the Miller Cycle operation and preventing harmful thermal effects while preserving the desired compression ratio benefits.
2Adaptability or versatility
If recirculated exhaust gases are present during the reversion event, then they may be expelled back into the intake manifold, but they oppose the intake stroke flow direction causing delayed gas flow and reduced engine responsiveness
Solution Approach 1:
The system inverts the approach to handling recirculated exhaust gases by using a reversion event controller that actively manages the intake valve timing and position. Instead of allowing exhaust gases to naturally oppose the intake flow, the controller orchestrates a controlled reversion event where the intake valve is manipulated to reverse the flow direction, thereby eliminating the opposing flow effect and improving gas flow speed and engine responsiveness.
3Reliability
If the air/fuel mixture is compressed for only the final 25% of the compression stroke due to the intake valve being closed, then detonation risk is reduced, but the compression ratio is limited compared to Miller Cycle engines
Solution Approach 1:
The system performs preliminary cooling of the air charge before compression begins. By pre-cooling the air through the charge air cooler during the intake stroke, the air/fuel mixture enters the compression stroke at a lower temperature, which increases the safe compression ratio that can be achieved without causing detonation. This preliminary action removes the thermal constraint on compression ratio while maintaining reliability.
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 reduces charge air cooler degradation, decreases the risk of detonation, and accelerates gas flow into the combustion chamber, leading to more immediate torque responses and increased engine efficiency.
Implementation Method 1
the air may be compressed by a compressor and routed through a charge air cooler to cool the air before it is supplied to an intake manifold
Implementation Method 2
an air injector positioned in an intake port upstream of an engine cylinder and downstream of a compressor and charge air cooler
Data Source
AI summary
Methods and systems are provided for injecting air from a compressed air source into an intake port of a Miller Cycle engine. In one example, a method may comprise positioning an intake valve, coupled to a cylinder of a four-cycle internal combustion engine, in an open position during a portion of an intake stroke through a portion of a compression stroke of a piston reciprocating within said cylinder. The method may additionally comprise supplying air to said intake valve from a first source, and injecting air against said intake valve from a second source while said intake valve is open during said compression stroke.