Internal Combustion Engine Intake Airflow Reversal for Mode Switching
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Solution Overview
Problem
Internal combustion engines face challenges in efficiently switching between combustion modes with different manifold pressures, particularly in evacuating excess air in the manifold when transitioning from a higher to a lower pressure mode, which affects combustion stability and NOx emissions.
Innovation Solution
A system that includes a controller for an internal combustion engine with an intake air charging system, allowing for temporary airflow reversal to equalize pressure differences between intake and exhaust valves, utilizing a turbocharger or compressor with variable geometry to manage pressure changes during mode switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the engine switches from a combustion mode using higher manifold pressure (charged or boosted) to a combustion mode using lower manifold pressure (ambient or throttled), then the engine can operate in different combustion modes (e.g., HCCI to SI), but the excess air in the manifold cannot be evacuated quickly enough, causing prolonged high pressure that affects combustion stability and NOx emissions
Solution Approach 1:
The patent applies the inversion principle by reversing the normal airflow direction through the intake air charging system. Instead of air flowing only from the charger to the manifold, the system creates a temporary reverse flow that pulls excess air out of the manifold quickly. This is achieved by controlling the charger to create a pressure differential that reverses airflow, enabling rapid evacuation of excess air during mode transitions from high-pressure (charged/boosted) to low-pressure (ambient/throttled) combustion modes.
2Reliability
If the engine operates in HCCI mode with boosted intake pressure to extend the operating range, then the combustion stability and thermal efficiency improve, but the ability to quickly switch to SI mode and evacuate excess air deteriorates
Solution Approach 1:
The patent applies preliminary action by preparing the intake air charging system in advance for rapid mode switching. The controller is configured to activate the airflow reversal function before the actual mode switch occurs, pre-establishing the pressure differential and reverse flow path. This ensures that when the transition from HCCI to SI mode is needed, the excess air evacuation is already initiated and can proceed at maximum speed, thus maintaining both combustion stability and rapid mode switching capability.
3Loss of time
If the manifold pressure is reduced quickly during mode switching, then the excess air evacuation is accelerated, but the pressure control becomes difficult and combustion stability may be compromised
Solution Approach 1:
The patent applies feedback control by continuously monitoring manifold pressure and adjusting the intake air charging system accordingly. The controller receives real-time pressure data and dynamically modifies the charger operation to maintain optimal pressure differentials during the evacuation process. This feedback mechanism ensures that the pressure reduction is controlled and gradual enough to maintain combustion stability while still achieving rapid excess air evacuation. The system adjusts the reverse flow intensity based on actual pressure readings, preventing overly aggressive pressure changes that could destabilize combustion.
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
Enables rapid and efficient evacuation of excess air in the manifold, stabilizing combustion and reducing NOx emissions by effectively managing pressure changes during mode transitions, thereby extending the engine's operating range and improving thermal efficiency.
Implementation Method 1
controlling said intake air charging system to cause a temporary airflow reversal thereby equalizing a pressure difference between said intake valve and said exhaust valve
Implementation Method 2
equalizing a pressure difference between said intake valve and said exhaust valve
Implementation Method 3
the intake pressure can be boosted by means of a turbocharger or a compressor
Data Source
AI summary
The invention relates to an internal combustion engine provided with at least one cylinder and comprising a fuel injection system, an intake air charging system for supplying air under pressure to an air intake manifold, a controller for controlling the fuel injection system, a spark ignition system and the intake air charger. The control unit is adapted to switch the engine from a first combustion mode using a higher manifold pressure to a second combustion mode using a lower manifold pressure, and further adapted to control the intake air charging system to cause a surge in the intake air, in order to evacuate the higher manifold pressure. The invention further relates to a method for controlling the internal combustion engine and a vehicle provided with such an internal combustion engine.