LNG Fuel Quality Prediction After Pressure Vessel Venting

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Solution Overview

Problem

Existing methods fail to accurately determine the changing composition of liquefied natural gas (LNG) in pressure vessels, leading to potential knock resistance issues and inefficient combustion in internal combustion engines due to varying fuel components, which can cause damage if the engine is operated with insufficient fuel quality.

Innovation Solution

A method to determine fuel quality by monitoring the discharge of gaseous components through a safety valve, predicting future fuel composition changes, and adjusting engine parameters accordingly to ensure safe operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the pressure vessel is regularly vented via safety device to prevent overpressure, then the pressure safety is improved, but the fuel quality deteriorates due to preferential discharge of gaseous components

Engineering Contradiction:
Improvepressure safetyVSAvoidfuel quality
Core Design Contradiction:
ReliabilityVSStability of the object's composition

Solution Approach 1:

The system performs preliminary determination of fuel quality parameters (methane content, energy content, knock resistance) before the safety valve discharge occurs. By predicting the future fuel composition based on current measurements and discharge forecasts, the system can prepare appropriate combustion parameters in advance, preventing knock resistance issues when the engine operates with altered fuel composition after venting.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors fuel quality parameters and uses this feedback to adjust combustion parameters dynamically. After safety valve discharge alters the fuel composition, the system receives feedback about the changed fuel quality and automatically adjusts engine operating parameters to maintain optimal combustion, preventing knock and ensuring efficient operation.

Inventive Principle:
Principle #23Feedback

2Adaptability or versatility

If the fuel composition varies in the pressure vessel, then the adaptability of the fuel system is improved, but the combustion efficiency deteriorates due to uncertain fuel properties

Engineering Contradiction:
Improvefuel composition variabilityVSAvoidcombustion efficiency
Core Design Contradiction:
Adaptability or versatilityVSProductivity

Solution Approach 1:

The system determines fuel quality parameters in advance before combustion occurs, creating a database of current fuel properties. This preliminary characterization allows the control system to pre-calculate optimal combustion parameters, ensuring that when combustion happens, the engine operates at peak efficiency despite composition variations in the pressure vessel.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts combustion parameters based on real-time fuel quality measurements. Rather than using fixed combustion settings, the system continuously adapts injection timing, injection quantity, and other combustion parameters to match the actual fuel composition, maintaining high combustion efficiency across varying fuel conditions.

Inventive Principle:
Principle #15Dynamics

3Device complexity

If no fuel quality determination is performed, then the device complexity is reduced, but the reliability of engine operation deteriorates due to potential knock resistance issues

Engineering Contradiction:
Improvemonitoring system complexityVSAvoidengine operation safety
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The system uses the existing safety valve discharge process itself as a source of information to determine fuel quality. By monitoring the discharge characteristics and using the natural venting process to provide samples of the fuel composition, the system determines fuel properties without requiring separate, complex sampling and analysis equipment, thus maintaining reliability while limiting complexity increase.

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

Enables predictive determination of fuel quality, preventing engine damage by adjusting combustion parameters based on real-time fuel composition analysis, ensuring safe and efficient engine operation.

Implementation Method 1

the fuel is, in particular, LNG or another liquefied gas which, due to its vapor pressure and boiling curve, requires the pressure vessel used for storing the fuel to be vented after a certain downtime

Methodology Applied
Scientific EffectVapor pressure: Vapour Pressure

Implementation Method 2

Due to its material properties, CH4, in particular, can be the first to evaporate from the mixture of various fuel components, or can evaporate in higher proportions

Methodology Applied
Scientific EffectEvaporation: Evaporation

Data Source

PatentEP3880952B1Method for determining a fuel quality
Publication Date: 2025.07.16 VOLKSWAGEN AG
  • EP3880952B1 patent drawingFigure 1~3

AI summary

The invention relates to a method for determining a fuel quality of a fuel (1), which is supplied to an internal combustion engine (2) in a gaseous form, wherein the fuel (1) is an at least partially liquefied fuel (1) that is stored in a pressure vessel (3), wherein, upon reaching a limit pressure, the pressure vessel (3) is released into the surroundings (5) by a safety device (4), whereby a gaseous component of the fuel (1) is removed from the pressure vessel (3), wherein the method comprises at least the following step: a) determining the fuel quality of the fuel (1) stored in the pressure vessel (3), taking into consideration at least one already achieved or ongoing discharge of a gaseous component of the fuel (1) via the safety device (4).