Compression Ignition Gasoline Engine EGR Control for Octane Variations
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Solution Overview
Problem
Compression ignition gasoline engines face challenges in maintaining homogeneous charge compression ignition (HCCI) combustion when fuels with different octane numbers are used, leading to variations in ignition timing and combustion stability.
Innovation Solution
A compression ignition gasoline engine equipped with a fuel injection valve, an EGR device for high-temperature EGR, and an octane number determination unit, which controls the EGR rate to adjust for fuels with varying octane numbers by increasing the EGR rate in partial load operating ranges when a non-prescribed octane number is detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If HCCI combustion is performed with fuel having different octane numbers, then the engine can operate with various fuel types, but the ignition timing varies significantly from intended timing
Solution Approach 1:
The patent changes the EGR rate parameter based on the detected octane number of the fuel. When regular gasoline (lower octane number) is detected, the EGR rate is increased to raise the in-cylinder temperature, thereby compensating for the lower ignitability and maintaining consistent ignition timing across different fuel types
Solution Approach 2:
The patent implements a feedback control mechanism where the octane number determination unit detects the fuel's octane number, and the combustion control unit adjusts the EGR rate accordingly. This closed-loop feedback system ensures that ignition timing remains stable despite variations in fuel properties
2Reliability
If the EGR rate is increased to suppress ignition timing variation, then combustion stability is improved, but combustion noise may increase
Solution Approach 1:
The patent dynamically adjusts the EGR rate based on the detected octane number rather than using a fixed high EGR rate. This dynamic adjustment allows the system to achieve combustion stability with the minimum necessary EGR, thereby reducing combustion noise 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 solution effectively suppresses ignition timing variations due to different octane numbers, ensuring stable HCCI combustion across various fuel types by creating a high-temperature environment that minimizes low-temperature oxidation reactions, thereby maintaining consistent engine performance without the need for expensive fuel octane sensors.
Implementation Method 1
an EGR device for performing high-temperature EGR of introducing burnt gas generated in the cylinder into the cylinder at a high temperature
Implementation Method 2
HCCI combustion is combustion, which occurs by spontaneous reaction of fuel (gasoline) with oxygen in a high-temperature and high-pressure environment
Data Source
AI summary
A compression ignition gasoline engine includes a fuel injection valve for injecting fuel containing gasoline as a main component into a cylinder; an EGR device operative to perform high-temperature EGR of introducing burnt gas generated in the cylinder into the cylinder at a high temperature; an octane number determination unit for determining whether fuel injected from the fuel injection valve has a prescribed octane number; and a combustion control unit for controlling the fuel injection valve and the EGR device in such a way that HCCI combustion occurs within the cylinder. The combustion control unit controls the EGR device, in at least a partial load operating range in which HCCI combustion is performed, in such a way that the EGR rate increases, as compared with a case where fuel is determined to have a prescribed octane number, when fuel is determined not to have a prescribed octane number.