Gasoline Direct-Injection Engine Pre-Injection Combustion Control
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Solution Overview
Problem
Gasoline direct-injection engines face challenges in retarding self-ignition combustion timing without causing misfire, especially at high compression ratios, leading to increased vibration noise and potential soot generation due to excessive in-cylinder temperature fluctuations.
Innovation Solution
A gasoline direct-injection engine with a geometric compression ratio of 15:1 or higher employs a pre-injection to maintain in-cylinder temperature within a predetermined range through partial oxidative reactions, allowing for extended retardation of self-ignition combustion timing while reducing pressure increase rates and preventing excessive temperature increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the ignition timing is retarded to reduce pressure increase rate and vibration noise, then the NVH level is reduced, but the in-cylinder temperature decreases and misfire occurs
Solution Approach 1:
The patent applies preliminary action by performing a pre-injection of fuel before the main injection timing. This pre-injected fuel undergoes oxidative reaction during the compression stroke, generating heat that maintains the in-cylinder temperature after CTDC. This preliminary heat generation enables the main combustion to be retarded without causing misfire, as the temperature is sustained by the prior oxidative reaction of the pre-injected fuel.
2Use of energy by moving object
If the compression ratio is increased to improve thermal efficiency, then the thermal efficiency is improved, but the pressure increase rate increases and vibration noise increases
Solution Approach 1:
The pre-injection performs oxidative reaction in advance during the compression stroke, generating heat that maintains temperature after CTDC. This allows the engine to utilize high compression ratio (15:1 or higher) for improved thermal efficiency while the controlled temperature maintenance enables retardation of main combustion timing to reduce pressure increase rate and vibration noise.
Solution Approach 2:
The patent changes the injection timing parameter by introducing a pre-injection phase before the main injection. This creates a two-stage fuel injection process where the first stage (pre-injection) occurs during compression to generate oxidative heat, and the second stage (main injection) occurs after CTDC for controlled combustion. This parameter change enables decoupling of compression ratio benefits from vibration noise penalties.
3Stress or pressure
If the ignition timing is retarded excessively to reduce pressure increase rate, then the pressure increase rate is reduced, but the in-cylinder temperature becomes too low for reliable ignition
Solution Approach 1:
The pre-injection performs oxidative reaction as a preliminary action during the compression stroke, generating heat that maintains the in-cylinder temperature after CTDC. This preliminary heat generation compensates for the temperature drop that would normally occur with excessive ignition timing retardation, allowing the pressure increase rate to be reduced while maintaining sufficient temperature for reliable main combustion ignition.
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 enables self-ignition combustion to be retarded without misfire, reduces vibration noise, and prevents soot generation by maintaining in-cylinder temperature within a controlled range, ensuring sufficient torque production and efficient engine operation across varying engine loads.
Implementation Method 1
by injecting an amount of the fuel that causes an oxidative reaction without resulting in a hot flame reaction
Implementation Method 2
causing the self-ignition combustion of the fuel after the compression top dead center
Data Source
AI summary
A gasoline direct-injection engine is provided. The engine causes a self-ignition of a fuel injected into a cylinder by an injector and at least containing gasoline. The engine includes a controller for controlling the fuel injection by the injector. A geometric compression ratio of the engine is 15:1 or higher. The controller causes the injector to perform a pre-injection for keeping a variation of an in-cylinder temperature after a compression top dead center within a predetermined temperature range by injecting an amount of the fuel that causes an oxidative reaction without resulting in a hot flame reaction. The controller causes the injector to perform a main injection for causing self-ignition combustion of the fuel after the compression top dead center while the variation of the in-cylinder temperature is kept within the predetermined temperature range, by injecting the fuel after the pre-injection.