SPCCI Engine Control via Variable Intake Valve Timing
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Solution Overview
Problem
The challenge is to stabilize SPCCI combustion in engines to maximize fuel efficiency, as existing configurations struggle with varying combustion start timing due to external factors and difficulty in controlling transient operations, especially at different engine speeds and loads.
Innovation Solution
A control system that adjusts the intake valve's open and close timings and phase, along with spark plug ignition, to create a lean gas-fuel environment and maintain a stoichiometric air-fuel ratio, ensuring stable SI and CI combustion by retarding intake valve timings at higher engine speeds and advancing them at lower speeds, while managing the exhaust valve timing to prevent excessive burnt gas recirculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the intake valve timings are kept constant, then the engine structure is simple, but the combustion start timing varies greatly due to external factors and transient operations
Solution Approach 1:
The patent applies dynamics by making the intake valve timing variable instead of fixed. The intake phase-variable mechanism dynamically adjusts the open and close timings of the intake valve based on engine operating conditions (engine speed and load), allowing the system to adapt to changing conditions and stabilize combustion start timing across different operating ranges.
Solution Approach 2:
The patent changes the timing parameters of the intake valve (open timing and close timing) based on engine speed and load conditions. By varying these parameters dynamically, the system maintains stable combustion start timing despite external factors and transient operations, resolving the contradiction between reliability and fixed configuration.
2Reliability
If burnt gas is left in the cylinder to stabilize flame propagation, then SI combustion stability improves, but flame propagation slows down and CI combustion timing is delayed
Solution Approach 1:
The patent applies partial action by controlling the amount of burnt gas remaining in the cylinder to an optimal level rather than maximizing it. The intake phase-variable mechanism adjusts timing to retain sufficient burnt gas for stable flame propagation while preventing excessive accumulation that would slow combustion. This balances stability requirements with speed requirements.
3Temperature
If the open timing of intake valve is advanced to increase burnt gas recirculation, then in-cylinder temperature increases for stable CI combustion, but excessive burnt gas slows flame propagation
Solution Approach 1:
The patent changes the intake valve timing parameters (open timing and close timing) based on engine operating conditions. By dynamically adjusting these parameters, the system optimizes the balance between in-cylinder temperature (needed for CI combustion stability) and combustion speed (affected by burnt gas accumulation), resolving the contradiction between temperature and speed requirements.
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 configuration ensures stable SPCCI combustion across a wide range of engine speeds, improving fuel efficiency by maintaining a suitable air-fuel ratio and reducing combustion noise, thereby enhancing the engine's operational controllability and thermal efficiency.
Implementation Method 1
a spark plug configured to ignite mixture gas containing the fuel injected by the injector and air
Implementation Method 2
combust a portion of the mixture gas by spark-ignition using a spark plug... after forcibly combusting a portion of the mixture gas through flame propagation caused by spark-ignition
Implementation Method 3
Homogeneous-Charge Compression Ignition (HCCI) combustion in which gasoline fuel mixed with air is combusted by self-ignition inside a sufficiently compressed combustion chamber
Implementation Method 4
The in-cylinder temperature increases as pressure inside the cylinder (in-cylinder pressure) increases
Implementation Method 5
the remaining mixture gas is combusted by self-ignition (CI combustion)... combust the remaining mixture gas by self-ignition (CI combustion)
Implementation Method 6
an intake valve configured to open and close the intake port... controls the intake phase-variable mechanism to form a gas-fuel ratio (G/F) lean environment in which burnt gas remains inside the cylinder
Implementation Method 7
an exhaust valve configured to open and close the exhaust port
Data Source
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AI summary
A compression-ignition engine control system is provided, which includes an intake phase-variable mechanism and a controller. The controller controls the intake phase-variable mechanism to form a gas-fuel ratio (G/F) lean environment in which burnt gas remains inside a cylinder and an air-fuel ratio is near a stoichiometric air-fuel ratio, and controls the spark plug to spark-ignite the mixture gas to combust in a partial compression-ignition combustion. The controller controls the intake phase-variable mechanism to retard, as an engine speed increases at a constant engine load, an intake valve close timing on a retarding side of BDC of intake stroke and an intake valve open timing on an advancing side of TDC of exhaust stroke, and controls the intake phase-variable mechanism so that a change rate in the intake valve open timing according to the engine speed becomes larger in a high engine speed range.