Dual Fuel Engine Load Shedding Control

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Solution Overview

Problem

Dual fuel internal combustion engines face difficulties during load shedding events, as natural gas cannot be quickly cut off, leading to uncombusted fuel entering the exhaust and aftertreatment systems, causing unintended combustion and potential damage.

Innovation Solution

Implementing control techniques that reduce the flow of gaseous fuel and adjust liquid fuel delivery to mitigate uncombusted fuel in the exhaust system, including methods like terminating gaseous fuel flow, maintaining liquid fuelling to burn-off residual gas, retarding injection timing, and modulating valve actuation to manage torque output.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If natural gas flow is maintained during load shedding event, then continuous fuel supply is ensured, but uncombusted fuel enters exhaust system causing unintended combustion and damage

Engineering Contradiction:

Improvecontinuous fuel supplyVSAvoidunintended combustion in exhaust system

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The control system detects the load shedding event and terminates natural gas flow before uncombusted fuel can reach the exhaust system. This preliminary action prevents the harmful effect of unintended combustion while maintaining reliability by ensuring smooth transition to diesel-only operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent extracts the natural gas fuel supply from the combustion process during load shedding events by terminating its flow. This separates the gaseous fuel delivery from the liquid fuel delivery, allowing independent control of each fuel type to prevent exhaust system damage while maintaining engine operation.

Inventive Principle:

Principle #2Taking out (Extraction)

2Object-affected harmful factors

If natural gas flow is terminated quickly, then unintended combustion in exhaust system is prevented, but uncombusted fuel already in intake system may still enter exhaust

Engineering Contradiction:

Improveunintended combustion in exhaust systemVSAvoidresidual fuel clearance time

Core Design Contradiction:

Object-affected harmful factorsVSLoss of time

Solution Approach 1:

The control system maintains diesel fuel injection continuity during the transition period after natural gas termination. This continuous liquid fueling ensures that any residual natural gas in the intake system is combusted in the cylinders, preventing it from reaching the exhaust system uncombusted and eliminating the time-related hazard.

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

Liquid diesel fuel acts as an intermediary that combusts residual natural gas in the intake system. The diesel fuel serves as a mediator between the terminated natural gas supply and the exhaust system, ensuring complete combustion of mixed fuel before exhaust gases are produced.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Power

If liquid fuel rate is reduced during load shedding, then torque output is controlled, but insufficient fuel may leave uncombusted gas in exhaust

Engineering Contradiction:

Improvetorque output controlVSAvoiduncombusted gaseous fuel in exhaust

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The control system dynamically adjusts the liquid fuel injection rate parameter during load shedding events. By modifying this parameter, the system achieves torque control while maintaining sufficient fueling levels to ensure complete combustion of any residual gaseous fuel, preventing exhaust system contamination.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The control system uses feedback from engine operating conditions to adjust liquid fuel delivery rates during load shedding. This feedback mechanism ensures that fueling is optimized to burn off residual gas while controlling torque output, balancing power management with exhaust system protection.

Inventive Principle:

Principle #23Feedback

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

Minimizes unintended energy release in the exhaust system, reduces emissions, and prevents damage to aftertreatment components by effectively managing fuel flow during load shedding events.

Implementation Method 1

Near the end of the compression stroke, diesel fuel is injected, just as it would be in a traditional diesel engine. The diesel fuel ignites, and the diesel combustion causes the natural gas to burn.

Methodology Applied

Scientific EffectCompression heating: Adiabatic Heating

Implementation Method 2

The diesel fuel ignites, and the diesel combustion causes the natural gas to burn. The dual fuel engine combusts a mixture of air and fuel in the cylinders to produce drive torque.

Methodology Applied

Scientific EffectCombustion: Combustion

Data Source

PatentUS9228536B2Load shedding techniques for dual fuel engines

Publication Date: 2016.01.05 CUMMINS INC

AI summary

Systems and methods for controlling operation of dual fuel internal combustion engines in response to a load shedding event are disclosed. The control techniques mitigate the amount of uncombusted gaseous fuel passing into the exhaust and/or aftertreatment system and reduce the rate at which uncombusted gaseous fuel enters the cylinders to reduce engine torque output and/or speed in response to the load shedding event.