Fuel Cooled Injector Tip Circumferential Gap Cooling

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Solution Overview

Problem

In diesel dual fuel engines, the tip of the fuel injector reaches intolerable temperatures due to reduced diesel fuel flow during high load operations, leading to increased carboning and potential damage, as conventional cooling methods are inadequate.

Innovation Solution

A fuel injector design incorporating a circumferential gap and drain gap system that utilizes low pressure diesel fuel to cool the injector tip, with a control module managing fuel flow to maintain optimal temperatures, including idling the engine before shutdown to allow cooling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If reduced diesel fuel flow is used during high load dual fuel operation, then natural gas substitution ratio increases, but fuel injector tip temperature becomes intolerable

Engineering Contradiction:

Improvenatural gas substitution ratioVSAvoidfuel injector tip temperature

Core Design Contradiction:

Adaptability or versatilityVSTemperature

Solution Approach 1:

The fuel injector system is segmented into two separate fuel flow paths: a high-pressure path for diesel pilot fuel injection and a low-pressure path for cooling fuel circulation. This segmentation allows the cooling function to be independently controlled without interfering with the injection function, enabling high natural gas substitution ratios while maintaining acceptable injector tip temperatures through dedicated cooling fuel flow

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Low-pressure cooling fuel acts as an intermediary substance that absorbs heat from the fuel injector tip through the circumferential gap, preventing direct heat transfer to the injector components. This intermediary cooling fuel enables the system to tolerate high natural gas substitution ratios by mediating the thermal load on the injector tip

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by moving object

If reduced diesel pilot fuel flow is used, then thermal efficiency is maintained, but carboning increases and injector damage occurs

Engineering Contradiction:

Improvethermal efficiencyVSAvoidcarboning and injector damage

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The low-pressure cooling fuel path converts the potentially harmful effect of reduced diesel pilot fuel flow (which causes carboning and overheating) into a beneficial cooling mechanism. The cooling fuel circulating through the circumferential gap absorbs excess heat that would otherwise cause carboning and damage, allowing the system to maintain high thermal efficiency through reduced pilot fuel while preventing the associated harmful effects

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The cooling fuel is introduced into the circumferential gap before the high-temperature combustion gases can cause excessive carboning and damage to the injector tip. This preliminary cooling action prevents the accumulation of carbon deposits and thermal damage by maintaining the injector tip temperature within acceptable ranges throughout dual fuel operation

Inventive Principle:

Principle #10Preliminary action

3Temperature

If conventional cooling methods are used, then injector tip temperature reduction is attempted, but cooling effectiveness is inadequate during high load dual fuel operation

Engineering Contradiction:

Improvefuel injector tip temperatureVSAvoidcooling effectiveness

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The cooling system provides localized cooling precisely where it is most needed - at the fuel injector tip and combustion shield interface. The circumferential gap is positioned to create a cooling film exactly at the hot spot region, concentrating the cooling effect where high load dual fuel operation causes the most severe thermal conditions, thereby achieving reliable temperature control

Inventive Principle:

Principle #3Local quality

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 reduces the operating temperature of the fuel injector tip, minimizing carboning and extending the lifespan of the injector by allowing increased substitution of natural gas with reduced diesel pilot fuel, while preventing damage from high temperature shut downs.

Implementation Method 1

routing the low pressure diesel fuel from the flow path through a circumferential gap extending about a tip of the fuel injector between an outer surface of the injector nozzle housing and an inner surface of a combustion shield adjacent the injector tip

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Data Source

PatentUS9897053B2Fuel cooled injector tip

Publication Date: 2018.02.20 CUMMINS INC

AI summary

A fuel injector is provided comprising an outer housing, a nozzle housing disposed within the outer housing, a flow path between the outer housing and the nozzle housing, the flow path being coupled to a low pressure fuel source, and a circumferential gap in flow communication with the flow path and extending about a tip of the fuel injector between an outer surface of the nozzle housing and an inner surface of a combustion shield adjacent the injector tip. The circumferential gap is in flow communication with a drain gap between the outer housing and a bore for receiving the fuel injector, the drain gap routing the low pressure fuel away from the injector tip.