Cryogenic Fuel Delivery System for Internal Combustion Engines
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Solution Overview
Problem
Existing fuel delivery systems for cryogenically stored natural gas in internal combustion engines rely on fuel saturation pressure, which can lead to underperformance during transient conditions and require frequent venting, especially in larger vehicles with varying fuel demand.
Innovation Solution
A method and system that dynamically determine the required fuel supply pressure based on engine operating conditions, using a controller to activate a fuel pump and supply fuel from either the vapor or liquid space of the storage vessel, ensuring consistent fuel delivery through a hydraulic drive unit powered by an electric motor, and utilizing a heat exchanger to adjust fuel temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If fuel is stored as LNG in a cryogenic storage vessel and relies on saturation pressure for fuel delivery, then energy density is improved (four times that of CNG), but fuel delivery reliability deteriorates during transient conditions when saturation pressure drops below required levels
Solution Approach 1:
An electric motor is introduced as an intermediary component to drive the fuel pump independently of engine operating conditions. This mediator provides the necessary mechanical power to deliver fuel at required pressures even when LNG saturation pressure is insufficient, resolving the contradiction between high energy density storage and reliable fuel delivery during transients.
Solution Approach 2:
The traditional mechanical system relying on LNG saturation pressure to push fuel through the delivery system is replaced with an electrically-driven fuel pump system. This substitution allows active control of fuel delivery pressure independent of thermal conditions in the storage vessel, ensuring reliable operation during transient conditions while maintaining the high energy density benefits of LNG storage.
2Device complexity
If fuel is delivered using existing low pressure systems relying on saturation pressure, then system complexity is reduced, but fuel delivery consistency deteriorates during high load conditions when saturation pressure drops
Solution Approach 1:
A controller is implemented to monitor engine operating conditions and activate the electric motor-driven fuel pump when required fuel delivery pressure exceeds available saturation pressure. This feedback mechanism ensures consistent fuel delivery during high load conditions while maintaining simple passive operation during normal conditions, balancing complexity and performance.
3Reliability
If fuel is stored as CNG at ambient temperatures and high pressures, then fuel delivery reliability is improved, but energy density deteriorates (lower than LNG)
Solution Approach 1:
The electric motor serves as a mediator that enables reliable fuel delivery from LNG storage without requiring the high pressure conditions of CNG storage. This intermediary component allows the system to maintain the high energy density of LNG while achieving fuel delivery reliability previously associated only with CNG systems.
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 approach ensures reliable fuel delivery to internal combustion engines at the required pressure, reducing the need for frequent venting and improving engine performance during transient conditions by independently controlling the fuel pump operation and adjusting fuel temperature.
Implementation Method 1
utilizing a heat exchanger to adjust fuel temperature
Implementation Method 2
supplying fuel from the liquid space through a fuel pump driven by a hydraulic drive unit
Implementation Method 3
delivering fuel in a gaseous state from the vapor space through a vapor supply line
Data Source
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AI summary
A method and system is disclosed for delivering a cryogenically stored fuel in a gaseous state into the air intake system of a gaseous fuelled internal combustion engine. The method comprises measuring the pressure in the vapor space of the cryogenic storage vessel, comparing the measured pressure to a required fuel supply pressure and supplying fuel in gaseous state directly from the vapor space of the cryogenic storage vessel to the fuel delivery line that supplies fuel to the engine, when the pressure measured in the vapor space of the cryogenic storage vessel is equal to or higher than the required fuel supply pressure. The method further comprises activating a cryogenic pump to deliver fuel to the internal combustion engine from the liquid space of the cryogenic storage vessel when the measured pressure in the vapor space is lower than the required fuel supply pressure.