Variable Supercharger and EGR Control for Premixed Compression Ignition Engines
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Solution Overview
Problem
Existing control apparatuses for premixed compression self-ignition combustion engines struggle to maintain stable combustion on the high-revolution/high-load side, leading to a limited operational range and increased combustion noise due to the inability to effectively control ignitability and fuel supply in varying external environments.
Innovation Solution
A control apparatus that includes a temperature sensor, revolution number sensor, load sensor, variable supercharger, and external EGR mechanism, with a control unit that adjusts supercharging pressure and EGR gas amount based on intake air temperature and engine load to enhance ignitability and reduce combustion noise, using a variable valve timing mechanism to optimize valve closure timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the amount of fuel supply is increased to meet load requirements on the high-revolution/high-load side, then the power output is improved, but the available amount of internal EGR gas decreases in inverse proportion, making it difficult to ensure sufficient ignitability and perform control according to external environment
Solution Approach 1:
The patent introduces an external EGR mechanism as an intermediary to supplement the insufficient internal EGR gas. The external EGR system recirculates exhaust gas through the intake passage, providing additional EGR gas that mixes with the fresh charge. This mediator allows the engine to maintain adequate EGR levels even when fuel supply is increased for high load conditions, thereby ensuring sufficient ignitability while meeting power requirements.
2Power
If the amount of fuel supply is increased on the high-revolution/high-load side, then the load requirement is met, but the temperature in the combustion chamber rises due to rise in intake air temperature, causing combustion noise to increase due to sudden combustion
Solution Approach 1:
The patent converts the harmful effect of high intake air temperature into a beneficial control parameter. By introducing external EGR gas, which is cooler than the compressed charge, the system reduces the overall combustion chamber temperature. This temperature moderation prevents sudden combustion and reduces combustion noise, while still allowing high load operation through increased fuel supply.
3Temperature
If the sealing period is prolonged to prevent temperature drop in the combustion chamber during cold conditions, then the temperature stability is improved, but the operational range allowing premixed compression self-ignition combustion is limited on the high-revolution/high-load side
Solution Approach 1:
The patent implements dynamic control of the sealing period duration based on operating conditions. Rather than using a fixed prolonged sealing period, the system adjusts the sealing period length according to the specific operating point (revolution speed, load, temperature). This dynamic adjustment allows the engine to maintain temperature stability when needed while extending the operational range to high-revolution/high-load conditions where shorter sealing periods are appropriate.
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
The solution enlarges the operational range for premixed self-ignition combustion towards the high-revolution/high-load side, ensuring stable combustion and reducing combustion noise by dynamically adjusting supercharging pressure, EGR gas amount, and valve timing in response to temperature changes.
Implementation Method 1
a supercharger of a variable supercharging pressure type which is disposed in an intake passage
Implementation Method 2
an external EGR (exhaust gas recirculation) mechanism for recirculating part of exhaust gas in an exhaust passage as an external EGR gas to the intake passage
Implementation Method 3
compressing a mixture of a fuel and an oxygen-containing gas in a combustion chamber to cause combustion thereof through self-ignition
Data Source
AI summary
At high temperature, namely, when the temperature of intake air is higher than a predetermined normal temperature range, an ECU (25) controls a variable valve timing mechanism (24) such that the timing for closing an exhaust valve (9) is adjusted to a retard side, thereby reducing the amount of high-temperature internal EGR gas to avoid the occurrence of pre-ignition. At intermediate load and high load, the ECU (25) makes the retard amount of the timing for closing the exhaust valve (9) larger than that at low load, thereby reducing the amount of internal EGR gas. At intermediate load and in an intermediate-revolution range or a high-revolution range, the rotating speed of an electric motor (16) is increased to raise a supercharging pressure exerted by a supercharger (17). At high load and in the high-revolution range, the electric motor (16) for the supercharger (17) and an EGR control valve (22) are controlled such that the supercharging pressure rises and the amount of external EGR gas increases as the temperature of intake air detected by a temperature sensor (26) rises.