Self-Saturating LNG Delivery System with Nested Overflow Tank
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Solution Overview
Problem
Heavy-duty vehicle engines running on liquid natural gas (LNG) face reduced performance due to insufficient vapor pressure in the fuel tank, as LNG is often not saturated before storage, and existing solutions like pressure building circuits are inefficient for horizontal tanks and require additional space or weight with a second tank for CNG.
Innovation Solution
A cryogenic fluid storage and delivery system with a primary LNG tank and an overflow tank, where LNG is heated by vaporization and re-condensation to increase saturation pressure, using hydraulic pressure to maintain fuel delivery until saturation pressure is reached, allowing for continuous supply to the engine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a pressure building circuit utilizing gravity to feed liquid cryogen into an ambient vaporizer is used, then vapor pressure can be built above the liquid in the tank, but horizontal tank mounting results in small liquid head pressure and mobile applications cause vapor pressure to collapse quickly when the vehicle is in motion
Solution Approach 1:
The overflow tank is nested within the primary LNG tank, creating a compact two-tank system where the overflow tank serves as both a pressure regulation vessel and a saturation pressure builder. This nested configuration allows the system to maintain pressure without requiring external additions or complex external circuits.
Solution Approach 2:
The system changes the physical state parameters of LNG by controlling its temperature and pressure conditions. By allowing LNG to saturate in the overflow tank and then transferring it to the primary tank, the system transforms the LNG from an unsaturated state to a saturated state, maintaining adequate vapor pressure during vehicle operation.
2Stress or pressure
If a second tank for CNG is mounted on the vehicle to add vapor pressure above LNG, then the desired pressure can be achieved, but this adds weight and occupies space on the vehicle chassis
Solution Approach 1:
The overflow tank is integrated within the primary tank's existing structure rather than being mounted as a separate external component. This merging of functions allows the pressure regulation and saturation processes to occur within the existing tank footprint, avoiding additional weight and space requirements on the vehicle chassis.
3Stress or pressure
If LNG is transferred into the primary tank until completely full to create hydraulic pressure, then sufficient pressure can be provided to the use device, but the tank must be filled to a level that creates excessive hydraulic pressure
Solution Approach 1:
The regulator provides feedback control by monitoring the pressure in the primary tank and automatically opening or closing to maintain the desired pressure level. When pressure exceeds the set point, the regulator opens to release excess LNG to the overflow tank; when pressure drops, the regulator closes, automatically maintaining optimal pressure without manual intervention.
Solution Approach 2:
The system creates different pressure conditions in different locations: the primary tank maintains high hydraulic pressure for immediate fuel delivery, while the overflow tank maintains saturation pressure for long-term pressure building. This local differentiation allows each tank to serve its specific function optimally.
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 system ensures a continuous and efficient supply of LNG to the engine by leveraging hydraulic pressure initially and saturation pressure once achieved, maintaining optimal performance without the need for additional weight or space, overcoming the inefficiencies of prior methods.
Implementation Method 1
The gas then passes through a pathway that reenters into the primary tank. The gas re-condenses in this pathway, thereby adding heat to the LNG in the primary tank.
Implementation Method 2
A regulator allows excessive fluid caused by the LNG expansion to flow from the primary tank to the overflow tank via an overflow line. The pressure in the primary tank is now controlled hydraulically by the regulator's set pressure.
Data Source
AI summary
Described herein are at least systems and methods for cryogenic fluid delivery which utilize pumpless delivery of cryogenic fluid. The systems and methods utilize hydraulic pressure, saturation pressure, or a combination of both hydraulic pressure and saturation pressure to deliver cryogen to a use device, such as an engine.