Compression-Stroke Fuel Injection for Engine Knock Control

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Solution Overview

Problem

Existing engines face issues with knock due to early combustion of gas mixtures caused by temperature and pressure in the combustion chamber, limiting compression ratios and thermal efficiency.

Innovation Solution

A control method that involves obtaining a characterizing temperature in the combustion chamber and injecting fuel during the compression stroke using a preset rule, allowing the fuel to spontaneously combust, thereby avoiding knock and enabling higher compression ratios.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If compression ratio is increased to enhance thermal efficiency, then thermal efficiency is improved, but engine knock occurs due to early combustion of gas mixtures

Engineering Contradiction:

Improvethermal efficiencyVSAvoidengine knock

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The invention changes the combustion mode from traditional spark ignition to compression ignition by controlling the injection timing and amount of fuel. By injecting fuel directly into the combustion chamber during the compression stroke and utilizing the high temperature and pressure conditions, the fuel spontaneously combusts without causing knock, thereby enabling higher compression ratios and improved thermal efficiency

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention performs preliminary injection of fuel into the combustion chamber before the end of the compression stroke. This allows the fuel to mix with the compressed air and be heated to spontaneous combustion temperature, ensuring controlled combustion occurs at the optimal moment without causing premature knock

Inventive Principle:

Principle #10Preliminary action

2Use of energy by moving object

If compression ratio is increased, then thermal efficiency is improved, but compression ratio is limited to below 15 due to knock

Engineering Contradiction:

Improvethermal efficiencyVSAvoidcompression ratio

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

By changing the combustion mode to compression ignition with direct fuel injection, the invention removes the knock limitation that previously capped compression ratios at below 15. The system now achieves compression ratios above 15 by controlling fuel injection timing and amount, allowing the compression process to proceed to higher ratios without harmful knock, thereby improving thermal efficiency

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If traditional combustion mode is used, then engine operation is simple, but knock occurs due to temperature and pressure effects on gas mixture

Engineering Contradiction:

Improvecombustion controlVSAvoidengine knock

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The invention introduces a fuel injection system as an intermediary mechanism between the compressed air-fuel mixture and the combustion process. By precisely controlling when and how much fuel is injected, the system mediates the combustion process to occur through spontaneous ignition rather than premature ignition, eliminating knock while maintaining operational simplicity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention utilizes the heat and pressure generated during the compression stroke itself to spontaneously ignite the injected fuel, rather than requiring an external spark or flame source. This self-service combustion approach eliminates the knock problem while keeping the control system relatively simple

Inventive Principle:

Principle #25Self-service

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 method effectively prevents engine knock, allowing for compression ratios above 15, enhancing thermal efficiency, and ensuring smooth engine operation.

Implementation Method 1

The fuel in the combustion chamber is heated and spontaneously combusts

Methodology Applied

Scientific EffectCompression heating: Adiabatic Heating

Implementation Method 2

The fuel in the combustion chamber is heated and spontaneously combusts

Methodology Applied

Scientific EffectSpontaneous combustion: Combustion

Data Source

PatentUS20250320838A1Engine control method, engine, vehicle, and computer-readable storage medium

Publication Date: 2025.10.16 BYD CO LTD

AI summary

An engine control method comprises: acquiring a characterizing temperature characterizing the temperature in a combustion chamber; and when an engine is in a compression stroke, controlling, according to a preset rule, a fuel injection system to inject fuel into the combustion chamber, wherein the fuel in the combustion chamber is heated and spontaneously combusted, and input parameters of the preset rule comprise the characterizing temperature.