Engine Combustion Mode Switching via SPCCI Control
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Solution Overview
Problem
Existing engine systems face challenges in seamlessly switching between Homogeneous Charged Compression Ignition (HCCI) and Spark Ignition (SI) combustion modes due to the difficulty in instantly changing the gas fuel ratio (G/F) within the engine cylinder, leading to instability and abnormal combustion.
Innovation Solution
The introduction of a third combustion mode, SPark Controlled Compression Ignition (SPCCI), which allows for a middle G/F ratio between HCCI and SI, enabling seamless mode switching by adjusting the G/F and using spark ignition timing to control compression ignition, thereby enhancing combustion stability and reducing abnormal combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the combustion mode is switched between HCCI and SI corresponding to engine load changes, then the thermal efficiency is improved, but the combustion stability deteriorates due to difficulty in instantly changing the G/F ratio
Solution Approach 1:
The patent divides the traditional two-mode combustion system (HCCI and SI) into three distinct combustion modes: HCCI mode for low load, SPCCI mode for medium load, and SI mode for high load. This segmentation allows for more granular control of the G/F ratio across different operating conditions, enabling stable combustion transitions without the instability caused by abrupt mode switching in the conventional two-mode system.
Solution Approach 2:
The patent introduces dynamic control of the G/F ratio through the SPCCI mode, which allows continuous adjustment between the HCCI and SI operating points. By retarding the injection timing in SPCCI mode, the system can dynamically adapt the G/F ratio to match varying engine load demands, thereby maintaining combustion stability during transitions that would otherwise be unstable in a fixed two-mode system.
2Adaptability or versatility
If the G/F ratio is changed to match the switching target combustion mode, then the combustion mode switching is achieved, but the response time increases making instant switching difficult
Solution Approach 1:
The patent prepares the system for mode switching by establishing the SPCCI mode as an intermediate state that can be reached from both HCCI and SI modes. The control unit is configured to recognize when transition conditions are met and proactively adjusts the injection timing to enter SPCCI mode, reducing the overall transition time compared to direct mode switching that would require larger, more time-consuming G/F ratio changes.
Solution Approach 2:
The SPCCI mode acts as an intermediary state between HCCI and SI combustion modes. By introducing this intermediate mode with retarded injection timing, the system creates a transitional pathway that bridges the gap between the two extreme modes, allowing for smoother and faster transitions without the need for abrupt, time-consuming G/F ratio adjustments required in direct mode switching.
3Reliability
If the G/F ratio is adjusted for HCCI combustion, then the combustion stability is improved, but the abnormal combustion increases due to overly rapid combustion
Solution Approach 1:
The patent changes the injection timing parameter to retard it in SPCCI mode compared to HCCI mode. This parameter change slows down the combustion rate by delaying the fuel injection relative to the compression stroke, thereby reducing the overly rapid combustion characteristic of HCCI while maintaining the combustion stability benefits of the controlled G/F ratio. This allows the system to operate in SPCCI mode with stable combustion without the harmful overly rapid combustion of pure HCCI.
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 solution allows for stable combustion across various engine loads, improving thermal efficiency and reducing abnormal combustion occurrences by promptly changing the G/F ratio and utilizing spark ignition timing to control compression ignition in the SPCCI mode.
Implementation Method 1
the spark plug ignites the mixture gas inside the cylinder and the mixture gas combusts by flame propagation
Implementation Method 2
the mixture gas is combusted by the CI combustion, more accurately, by HCCI (Homogeneous Charged Compression Ignition) combustion
Data Source
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AI summary
An engine system is provided, including a controller which controls devices of an engine at a given engine speed so that, when a demanded engine load is a first load, a mass ratio (G/F) of intake air inside a cylinder (containing fresh air and burnt gas) to fuel is a first G/F and mixture gas inside the cylinder combusts by flame-propagation, when the demanded load is a second load (< the first load), the G/F is a second G/F (> the first G/F) and an injection center-of-gravity is at a timing such that the entire mixture gas combusts by CI combustion, and when the demanded load is between the first and second loads, the G/F is at a third G/F (between the first and second G/Fs) and the injection center-of-gravity is at a later timing such that at least part of the mixture gas combusts by the CI combustion.