Cetane Improver Fuel for HCCI Knock Limit

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Solution Overview

Problem

Internal combustion engines operating in low temperature combustion modes, such as HCCI, face limited high load limits due to knocking issues, which restrict their speed-load range and efficiency, and conventional gasoline fuels are not readily reactive enough to overcome these limitations.

Innovation Solution

Using a fuel composition of gasoline with a Research Octane Number (RON) greater than 85 combined with one or more cetane improvers, such as 2-ethylhexyl nitrate or di-tert butyl peroxide, to increase the high load knock limit and enhance combustion reactivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-generated harmful factors

If conventional gasoline fuel is used in low temperature combustion mode, then emissions are reduced and efficiency is improved, but the high load knock limit is significantly lower than in conventional engines

Engineering Contradiction:

ImproveemissionsVSAvoidhigh load knock limit

Core Design Contradiction:

Object-generated harmful factorsVSPower

Solution Approach 1:

The invention changes the chemical composition parameters of the fuel by adding cetane improvers (such as di-tert-butyl peroxide or 2-ethylhexyl nitrate) to conventional gasoline. This modifies the fuel's reactivity characteristics, allowing the engine to operate at higher loads without knocking while maintaining low temperature combustion benefits. The cetane improvers increase the fuel's cetane number, which enhances compression ignition capability and raises the knock limit.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the speed-load operating range is expanded in HCCI engines, then productivity is improved, but combustion stability and knock control become more difficult

Engineering Contradiction:

Improvespeed-load operating rangeVSAvoidcombustion stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The cetane improver acts as an intermediary substance that mediates between the conflicting requirements of expanded operating range and combustion stability. By adding this chemical intermediary to the fuel, the engine achieves broader speed-load operation while the cetane improver continuously regulates combustion timing and prevents knock across the expanded range, maintaining stability throughout.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 addition of cetane improvers to gasoline significantly increases the engine's high load knock limit, allowing it to operate at higher loads and reducing NOx emissions without the need for additional aftertreatment systems, thus enabling the use of conventional gasoline in advanced combustion engines.

Implementation Method 1

ignition is normally initiated via compression; however, a spark plug can be used to assist

Methodology Applied

Scientific EffectCompression ignition: Combustion

Implementation Method 2

one or more cetane improvers, such as 2-ethylhexyl nitrate or di-tert butyl peroxide

Methodology Applied

Scientific EffectChemical reaction of cetane improvers: Chemical Bonding

Data Source

PatentUS9562206B2Method for increasing the high load (knock) limit of an internal combustion engine operated in a low temperature combustion mode

Publication Date: 2017.02.07 CHEVRON USA INC

AI summary

Disclosed herein is a method for increasing the high load (knock) limit of an internal combustion engine operated in a low temperature combustion ignition mode, the method comprising operating the engine with a fuel composition comprising (a) gasoline having a Research Octane Number (RON) greater than 85 and (b) one or more cetane improvers.